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Sample records for mnas magnetocaloric compound

  1. Structural and magnetic study of the MnAs magnetocaloric compound

    Directory of Open Access Journals (Sweden)

    Nascimento Fabiana Cristina

    2006-01-01

    Full Text Available The temperature induced phase transition in MnAs is analyzed in this work using X ray Rietveld refinement. The results show the presence of the hexagonal phase (P6(3/mmc at room temperature and the first-order structural-magnetic transition to the orthorhombic phase (Pnma around 318 K was followed in detail. The MnAs magnetic characterization allowed to obtain the transition temperature and a maximum value of 47 J/(kg.K for the measured magnetocaloric effect for a magnetic field variation of 5 T.

  2. Magnetic transitions and magnetocaloric effect in MnAs0.9P0.1

    Institute of Scientific and Technical Information of China (English)

    Naikun SUN; Feng LIU; Yinbo GAO; Jinjun LIU

    2012-01-01

    The compound MnAs0.9P0.1 exhibits a multistep magnetic order-order transition from a helimagnetic γ-phase with Hα-type magnetic order to a ferromagnetic β-phase at 80 K and then to a helimagnetic α-phase at 203 K.The γ-β transition exhibits the characteristics of a first-order transition with a thermal hysteresis as large as 6 K,while the β-α transition is of second order with a thermal hysteresis smaller than 2 K and without magnetic hysteresis.With these two successive helimagnetism-related transitions,magnetic-entropy changes of -2.1 J/(kg·K) at 203 K for a field change from 0 to 5 T and 0.1 J/(kg.K) at 83 K for a field change from 0 to 1 T are obtained.Investigation of the magnetocaloric effect associated with a transition from Hα-type magnetic order to FM order may open a new route to explore candidates for magnetic refrigeration.

  3. First-Principles Prediction of Electronic, Magnetic, and Optical Properties of Co2MnAs Full-Heusler Half-Metallic Compound

    Science.gov (United States)

    Bakhshayeshi, A.; Sarmazdeh, M. Majidiyan; Mendi, R. Taghavi; Boochani, A.

    2016-12-01

    Electronic, magnetic, and optical properties of Co2MnAs full-Heusler compound have been calculated using a first-principles approach with the full-potential linearized augmented plane-wave (FP-LAPW) method and generalized gradient approximation plus U (GGA + U). The results are compared with various properties of Co2MnZ (Z = Si, Ge, Al, Ga, Sn) full-Heusler compounds. The results of our calculations show that Co2MnAs is a half-metallic ferromagnetic compound with 100% spin polarization at the Fermi level. The total magnetic moment and half-metallic gap of Co2MnAs compound are found to be 6.00μ B and 0.43 eV, respectively. It is also predicted that the spin-wave stiffness constant and Curie temperature of Co2MnAs compound are about 3.99 meV nm2 and 1109 K, respectively. The optical results show that the dominant behavior, at energy below 2 eV, is due to interactions of free electrons in the system. Interband optical transitions have been calculated based on the imaginary part of the dielectric function and analysis of critical points in the second energy derivative of the dielectric function. The results show that there is more than one plasmon energy for Co2MnAs compound, with the highest occurring at 25 eV. Also, the refractive index variations and optical reflectivity for radiation at normal incidence are calculated for Co2MnAs. Because of its high magnetic moment, high Curie temperature, and 100% spin polarization at the Fermi level as well as its optical properties, Co2MnAs is a good candidate for use in spintronic components and magnetooptical devices.

  4. Investigation on the magnetocaloric effect in TbN compound

    Energy Technology Data Exchange (ETDEWEB)

    Ranke, P.J. von, E-mail: von.ranke@uol.com.br [Instituto de Física, Universidade do Estado do Rio de Janeiro—UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil); Alvarenga, T.S.T.; Nóbrega, E.P.; Alho, B.P.; Ribeiro, P.O. [Instituto de Física, Universidade do Estado do Rio de Janeiro—UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil); Carvalho, A. Magnus G. [Divisão de Metrologia de Materiais (DIMAT), Instituto Nacional de Metrologia, Normalização e Qualidade Industrial (INMETRO), Duque de Caxias, RJ 25250-020 (Brazil); Sousa, V.S.R. de; Caldas, A.; Oliveira, N.A. de [Instituto de Física, Universidade do Estado do Rio de Janeiro—UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil)

    2013-09-15

    One of the biggest challenges in materials science is to understand the microscopic mechanisms responsible in storage and release material entropy. TbN compound, which presents non-degeneracy in ground state, was studied and the calculated magnetocaloric effect is in good agreement with the recent experimental data. Also inverse magnetocaloric effect and spin reorientation transition were predicted in TbN. The theoretical investigations were carried out using a Hamiltonian, which includes the crystalline electrical field, Zeeman and exchange interactions. - Highlights: • Theoretical description of the magnetocaloric effect in TbN. • Influence of the crystalline electrical field anisotropy on TbN. • Predictions of inverse and anomalous magnetocaloric effect in TbN.

  5. Negative magnetocaloric effect in Fe 1-x Rh x compounds

    OpenAIRE

    2007-01-01

    International audience; On increasing temperature, the Fe1-xRhx alloys present a transition from an antiferromagnetic to a ferromagnetic state, which induces a negative magnetocaloric effect (MCE). The magnetocaloric effect, in particular of the Fe0.49Rh0.51 alloy, was studied by direct measurements and accordingto specific heat measurements. Here, we report the recent results obtained on the annealed Fe0.48Rh0.52 compound we prepared by arc melting. The isothermal entropy change ΔS allowing ...

  6. Tuning the giant inverse magnetocaloric effect in Mn2−xCrxSb compounds

    NARCIS (Netherlands)

    Caron, L.; Miao, X.F.; Klaasse, J.C.P.; Gama, S.; Brück, E.

    2013-01-01

    Structural, magnetic, and magnetocaloric properties of Mn2-xCrxSb compounds have been studied. In these compounds, a first order magnetic phase transition from the ferrimagnetic to the antiferromagnetic state occurs with decreasing temperature, giving rise to giant inverse magnetocaloric effects tha

  7. Magnetocaloric effect in the metamagnet ErRhSi compound

    Science.gov (United States)

    Debnath, J. C.; Nair, Harikrishnan S.; Strydom, André M.; Ramesh Kumar, K.; Wang, Jianli

    2016-12-01

    The magnetocaloric effect is observed in the 1:1:1 compound ErRhSi, which is a metamagnet is reported in this paper. ErRhSi crystallizes in the orthorhombic space group Pnma, adopting the TiNiSi structure type, with lattice parameters a(Å) = 6.7903(5), b(Å) = 4.1881(3), and c(Å) = 7.3847(4). Our magnetic measurements confirm an antiferromagnetic phase transition at TN ≈ 8.5 K, also supported by the specific heat measurement. Crystal field effects of Er3+ are suggested by the inverse magnetic susceptibility data which do not conform to an ideal Curie-Weiss behaviour and also by the total entropy that attains Rln (2) at TN. Although the magnetic hysteresis indicates ErRhSi to be a soft magnet, several clear metamagnetic features are observed at 2 K. Magnetic entropy change ΔSM = - 8.7 J/kg-K is observed at about 9 K with the application of 5 T magnetic field. The corresponding adiabatic temperature change ΔTad is about 4 K. Large magnetocaloric effects suggest that this material is suitable for the low temperature magnetic refrigeration.

  8. Magnetocaloric effect in “reduced” dimensions: Thin films, ribbons, and microwires of Heusler alloys and related compounds: Magnetocaloric effect in “reduced” dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Khovaylo, Vladimir V. [National University of Science and Technology MISiS, Moscow 119049 Russia; ITMO University, St. Petersburg 197101 Russia; Rodionova, Valeria V. [National University of Science and Technology MISiS, Moscow 119049 Russia; Innovation Park and Institute of Physics & Technology, Immanuel Kant Baltic Federal University, Kaliningrad 236041 Russia; Shevyrtalov, Sergey N. [Innovation Park and Institute of Physics & Technology, Immanuel Kant Baltic Federal University, Kaliningrad 236041 Russia; Novosad, Val [Materials Science Division, Argonne National Laboratory, Argonne IL 60439 USA

    2014-08-19

    Room temperature magnetic refrigeration is an energy saving and environmentally-friendly technology which has developed rapidly from a basic idea to prototype devices. The performance of magnetic refrigerators crucially depends on the magnetocaloric properties and the geometry of the employed refrigerants. Here we review the magnetocaloric properties of Heusler alloys and related compounds with a high surface to volume ratio such as films, ribbons and microwires, and compare them with their bulk counterparts.

  9. Magnetic structure and phase formation of magnetocaloric Mn-Fe-P-X compounds

    NARCIS (Netherlands)

    Ou, Z.Q.

    2013-01-01

    This thesis presents a study of the crystal and magnetic structure, the magnetocaloric effect and related physical properties in Mn-Fe-P-X compounds. The influences of boron addition in (Mn,Fe)2(P,As) compounds have been studied. It is found that boron atoms occupy interstitial sites within the basa

  10. Magnetic structure and phase formation of magnetocaloric Mn-Fe-P-X compounds

    NARCIS (Netherlands)

    Ou, Z.Q.

    2013-01-01

    This thesis presents a study of the crystal and magnetic structure, the magnetocaloric effect and related physical properties in Mn-Fe-P-X compounds. The influences of boron addition in (Mn,Fe)2(P,As) compounds have been studied. It is found that boron atoms occupy interstitial sites within the

  11. Magneto-Caloric Effect of Gd5Si2Ge2Compounds under Different Processing Conditions

    Institute of Scientific and Technical Information of China (English)

    Zeng Hong; Yue Ming; Niu Peili; Zhang Jiuxing

    2004-01-01

    The magneto-caloric effect of Gd5 Si2Ge2 compounds produced by various techniques is investigated in terms of their magnetization behaviors in the magnetic field from 0 to 2.0 T.The studied materials include arc-melted, annealed and sintered alloys.The results demonstrate that the Gd5Si2Ge2 alloys obtained under different processing conditions possess distinct magneto-caloric effect due to their various microstructures.Proper annealing treatment can enhance the magneto-caloric effect of the alloy remarkably.While the sintered alloy bears relatively lower value of magnetic entropy change ( △ SM) than arc-melted one.The magnetic entropy change of the annealed Gd5 Si2Ge2 alloy arrives the arrives the maximum value of - △SM = 15.29 J· kg-1· K-1 for magnetic field change under 2.0 T in the present work.

  12. Study of the magnetocaloric properties of the antiferromagnetic compounds RGa2 (R = Ce, Pr, Nd, Dy, Ho and Er).

    Science.gov (United States)

    dos Reis, R D; da Silva, L M; dos Santos, A O; Medina, A M N; Cardoso, L P; Gandra, F G

    2010-12-08

    Magnetocaloric properties of antiferromagnetic RGa(2) (R = Ce, Pr, Nd, Dy, Ho and Er) compounds have been reported. These systems present an antiferromagnetic transition below 15 K and a field induced metamagnetic transition from the antiferromagnetic to ferromagnetic state. Our results show that the character of the magnetic field induced transition along the series affects the magnetocaloric properties. For the compounds with R = Ho, Dy and Er both negative and positive magnetocaloric effect (MCE) were observed above μ(0)ΔH = 2 T where the rate between negative and positive MCE contributions depends on how the magnetic transitions occur in these compounds. The evaluated values of maximum magnetocaloric properties of RGa(2) compounds are similar to other potential magnetic refrigerant materials reported in the literature.

  13. Observation of large magnetocaloric effect in equiatomic binary compound ErZn

    Science.gov (United States)

    Li, Lingwei; Yuan, Ye; Xu, Chi; Qi, Yang; Zhou, Shengqiang

    2017-05-01

    The magnetism, magnetocaloric effect and universal behaviour in rare earth Zinc binary compound of ErZn have been studied. The ErZn compound undergoes a second order paramagnetic (PM) to ferromagnetic (FM) transition at Curie temperature of TC ˜ 20 K. The ErZn compound exhibits a large reversible magnetocaloric effect (MCE) around its own TC. The rescaled magnetic entropy change curves overlap with each other under various magnetic field changes, further confirming the ErZn with the second order phase transition. For the magnetic field change of 0-7 T, the maximum values of the magnetic entropy change (-Δ SMmax ) , relative cooling power (RCP) and refrigerant capacity (RC) for ErZn are 23.3 J/kg K, 581 J/kg and 437 J/kg, respectively.

  14. Observation of large magnetocaloric effect in equiatomic binary compound ErZn

    Directory of Open Access Journals (Sweden)

    Lingwei Li

    2017-05-01

    Full Text Available The magnetism, magnetocaloric effect and universal behaviour in rare earth Zinc binary compound of ErZn have been studied. The ErZn compound undergoes a second order paramagnetic (PM to ferromagnetic (FM transition at Curie temperature of TC ∼ 20 K. The ErZn compound exhibits a large reversible magnetocaloric effect (MCE around its own TC. The rescaled magnetic entropy change curves overlap with each other under various magnetic field changes, further confirming the ErZn with the second order phase transition. For the magnetic field change of 0-7 T, the maximum values of the magnetic entropy change (−ΔSMmax, relative cooling power (RCP and refrigerant capacity (RC for ErZn are 23.3 J/kg K, 581 J/kg and 437 J/kg, respectively.

  15. Research Advance on Magnetocaloric Effect of La-Fe-M(Al, Si) Compounds

    Institute of Scientific and Technical Information of China (English)

    肖素芬; 陈云贵; 郝春; 吴金平; 涂铭旌

    2004-01-01

    Recent research progress on magnetocaloric effect of La-Fe-M(M=Al,Si)compounds was presented.La-Fe-M(M=Al,Si)compounds of high Fe content are excellent soft magnetic materials with NaZn13 structure.The Curie temperature of the compounds can be increased by substituting small amount of Co for Si,Al.The La(Fe1-yCoy)xSi13-x compounds with an appropriate ratio of Co and Si can produce giant magnetocaloric effect comparable to that for Gd5Si2Ge2 at room temperature.The La(FexSi1-x)13 doped with H can also produce giant magnetocaloric effect at room temperature,which is much greater than that for Gd.For La(FexSi1-x)13 compounds with low Si or high Si contents.The nature of phase transition near Curie temperature induced by temperature and magnetic field was described in detail.

  16. Metamagnetism-enhanced magnetocaloric effect in the rare earth intermetallic compound Ho5Ge4

    Science.gov (United States)

    Nirmala, R.; Morozkin, A. V.; Rajivgandhi, R.; Nigam, A. K.; Quezado, S.; Malik, S. K.

    2016-11-01

    Magnetic and magnetocaloric properties of polycrystalline Ho5Ge4 (orthorhombic, Sm5Ge4-type, Space group Pnma, No. 62, oP36) compound have been studied. This compound orders antiferromagnetically at ~24 K (TN). From the magnetization vs field isotherms obtained close to the magnetic transition temperature, magnetocaloric effect (MCE) has been estimated. The isothermal magnetic entropy change (ΔSM) reaches a maximum value of ~-27 J/kg-K at ~30 K for a field change of 140 kOe. A metamagnetic transition is observed in the field dependent magnetization data at temperatures below 20 K, for critical fields above 20 kOe, giving rise to a ferromagnetic order and hence a large MCE. The magnetic moment value at 2.5 K is ~8μB/Ho3+ in 90 kOe field.

  17. Inverse barocaloric effect in the giant magnetocaloric La-Fe-Si-Co compound.

    Science.gov (United States)

    Mañosa, Lluís; González-Alonso, David; Planes, Antoni; Barrio, Maria; Tamarit, Josep-Lluís; Titov, Ivan S; Acet, Mehmet; Bhattacharyya, Amitava; Majumdar, Subham

    2011-12-20

    Application of hydrostatic pressure under adiabatic conditions causes a change in temperature in any substance. This effect is known as the barocaloric effect and the vast majority of materials heat up when adiabatically squeezed, and they cool down when pressure is released (conventional barocaloric effect). There are, however, materials exhibiting an inverse barocaloric effect: they cool when pressure is applied, and they warm when it is released. Materials exhibiting the inverse barocaloric effect are rather uncommon. Here we report an inverse barocaloric effect in the intermetallic compound La-Fe-Co-Si, which is one of the most promising candidates for magnetic refrigeration through its giant magnetocaloric effect. We have found that application of a pressure of only 1 kbar causes a temperature change of about 1.5 K. This value is larger than the magnetocaloric effect in this compound for magnetic fields that are available with permanent magnets.

  18. Variations of magnetocaloric effect and magnetoresistance across RCuGe (R=Tb, Dy, Ho, Er) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sachin; Suresh, K.G., E-mail: suresh@phy.iitb.ac.in

    2015-10-01

    RCuGe (R=Tb–Er) compounds have been studied by structural, magnetic, magnetocaloric and magnetotransport measurements. All these compounds are iso-structural and show antiferromagnetic ordering below their Néel temperatures (T{sub N}). Except TbCuGe, all the studied compounds show large magnetocaloric effect (MCE), arising due to the field induced metamagnetic transition. They also show a sign reversal of magnetoresistance (MR) with change in temperature or field. The non-monotonic variation of the magnitude of MR is attributed to the competing effects of Lorentz force, changes in the spin disorder scattering and the spin fluctuations. - Highlights: • RCuGe (R=Tb–Er) compounds show low temperature antiferromagnetic ordering. • All compounds show field induced metamagnetic transitions. • These compounds show large magnetocaloric effect and magnetoresistance.

  19. Magnetic properties and magnetocaloric effect in TbCo2-xFex compounds

    Institute of Scientific and Technical Information of China (English)

    Zou Jun-Ding; Shen Bao-Gen; Sun Ji-Rong

    2007-01-01

    Magnetic properties and magnetocaloric effect in TbCo2-xFex compounds are studied by DC magnetic measurement. With increasing content of Fe, the entropy changes decrease slightly, though the Curie temperature is tuned from 231 K (x = 0) to 303 K (x = 0.1). Magnetic entropies of TbCo2 compound are calculated by using mean field approximation (MFA). Results estimated by using Maxwell relation are consistent with that of MFA calculation. It si shown that the entropy changes are mainly derived from the magnetic entropy change. The lattice has almost no contribution to the entropy change in the vicinity of phase transition.

  20. MnFe(PGe) compounds: Preparation, structural evolution, and magnetocaloric effects

    Science.gov (United States)

    Yue, Ming; Zhang, Hong-Guo; Liu, Dan-Min; Zhang, Jiu-Xing

    2015-01-01

    The interdependences of preparation conditions, magnetic and crystal structures, and magnetocaloric effects (MCE) of the MnFePGe-based compounds are reviewed. Based upon those findings, a new method for the evaluation of the MCE in these compounds, based on differential scanning calorimetry (DSC), is proposed. The MnFePGe-based compounds are a group of magnetic refrigerants with giant magnetocaloric effect (GMCE), and as such, have drawn tremendous attention, especially due to their many advantages for practical applications. Structural evolution and phase transformation in the compounds as functions of temperature, pressure, and magnetic field are reported. Influences of preparation conditions upon the homogeneity of the compounds’ chemical composition and microstructure, both of which play a key role in the MCE and thermal hysteresis of the compounds, are introduced. Lastly, the origin of the “virgin effect” in the MnFePGe-based compounds is discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 51171003, 51071007, and 51401002).

  1. The normal and inverse magnetocaloric effect in RCu2 (R=Tb, Dy, Ho, Er) compounds

    Science.gov (United States)

    Zheng, X. Q.; Xu, Z. Y.; Zhang, B.; Hu, F. X.; Shen, B. G.

    2017-01-01

    Orthorhombic polycrystalline RCu2 (R=Tb, Dy, Ho and Er) compounds were synthesized and the magnetic properties and magnetocaloric effect (MCE) were investigated in detail. All of the RCu2 compounds are antiferromagnetic (AFM) ordered. As temperature increases, RCu2 compounds undergo an AFM to AFM transition at Tt and an AFM to paramagnetic (PM) transition at TN. Besides of the normal MCE around TN, large inverse MCE around Tt was found in TbCu2 compound. Under a field change of 0-7 T, the maximal value of inverse MCE is even larger than the value of normal MCE around TN for TbCu2 compound. Considering of the normal and inverse MCE, TbCu2 shows the largest refrigerant capacity among the RCu2 (R=Tb, Dy, Ho and Er) compounds indicating its potential applications in low temperature multistage refrigeration.

  2. Magnetic properties and magnetocaloric effect in Tb{sub 3}Al{sub 2} compound

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hu, E-mail: zhanghu@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083 (China); Yang, Li Hong [Department of Physics, University of Science and Technology of Beijing, Beijing 100083 (China); State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Jing Yang; Wang, Zhe [School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083 (China); Niu, E. [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Beijing Zhong ke San Huan Research, No. 10 Chuangxin Rd., Changping District, Beijing 102200 (China); Liu, Rong Ming; Li, Zhu Bai; Hu, Feng Xia; Sun, Ji Rong; Shen, Bao Gen [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-12-05

    Highlights: • Domain-wall-freezing effect may occur at low temperature due to magnetocrystalline anisotropy. • The ΔT{sub ad} for Tb{sub 3}Al{sub 2} is 9.0 K under 50 kOe, comparable to that of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} compound. • The full width at half-maximum value of ΔT{sub ad} peak is much larger than that for La(Fe{sub 0.88}Si{sub 0.12}){sub 13}. - Abstract: Magnetic properties of intermetallic Tb{sub 3}Al{sub 2} compound have been investigated systematically by magnetization and heat capacity measurements. Tb{sub 3}Al{sub 2} compound undergoes a ferromagnetic–paramagnetic transition at Curie temperature T{sub C} = 190 K. Besides, another transition is observed around 86 K, which probably corresponds to a spin reorientation transition. In addition, a strong domain-wall-freezing effect may occur in low temperature range due to the high magnetocrystalline anisotropy, and thus resulting in the large intrinsic coercivity. Tb{sub 3}Al{sub 2} compound shows large magnetocaloric effect without hysteresis loss around T{sub C}, which is comparable to or even higher than those of some magnetocaloric materials in same temperature range. Furthermore, the full width at half-maximum value of adiabatic temperature change ΔT{sub ad} peak for Tb{sub 3}Al{sub 2} at 50 kOe is 55 K, more than three times of that (17 K) for typical magnetocaloric material La(Fe{sub 0.88}Si{sub 0.12}){sub 13}.

  3. Exchange bias in a mixed metal oxide based magnetocaloric compound YFe0.5Cr0.5O3

    Science.gov (United States)

    Sharma, Mohit K.; Singh, Karan; Mukherjee, K.

    2016-09-01

    We report a detailed investigation of magnetization, magnetocaloric effect and exchange bias studies on a mixed metal oxide YFe0.5Cr0.5O3 belonging to perovskite family. Our results reveal that the compound is in canted magnetic state (CMS) where ferromagnetic correlations are present in an antiferromagnetic state. Magnetic entropy change of this compound follows a power law (∆SM∼Hm) dependence of magnetic field. In this compound, inverse magnetocaloric effect (IMCE) is observed below 260 K while conventional magnetocaloric effect (CMCE) above it. The exponent 'm' is found to be independent of temperature and field only in the IMCE region. Investigation of temperature and magnetic field dependence studies of exchange bias, reveal a competition between effective Zeeman energy of the ferromagnetic regions and anisotropic exchange energy at the interface between ferromagnetic and antiferromagnetic regions. Variation of exchange bias due to temperature and field cycling is also investigated.

  4. Large magnetocaloric effect of GdNiAl{sub 2} compound

    Energy Technology Data Exchange (ETDEWEB)

    Dembele, S.N.; Ma, Z.; Shang, Y.F. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Fu, H., E-mail: fuhao@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Balfour, E.A. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Hadimani, R.L.; Jiles, D.C. [Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011 (United States); Ames Laboratory, US Department of Energy, Ames, IA 50011 (United States); Teng, B.H.; Luo, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2015-10-01

    This paper presents the structure, magnetic properties, and magnetocaloric effect of the polycrystalline compound GdNiAl{sub 2}. Powder X-ray diffraction (XRD) measurement and Rietveld refinement revealed that GdNiAl{sub 2} alloy is CuMgAl{sub 2}-type phase structure with about 1 wt% GdNi{sub 2}Al{sub 3} secondary phase. Magnetic measurements suggest that the compound is ferromagnetic and undergoes a second-order phase transition near 28 K. The maximum value of magnetic entropy change reaches 16.0 J/kg K for an applied magnetic field change of 0–50 kOe and the relative cooling power was 6.4×10{sup 2} J/kg. It is a promising candidate as a magnetocaloric material working near liquid hydrogen temperature (~20 K) exhibiting large relative cooling power. - Highlights: • Preferred orientation with axis of [010] was found in the GdNiAl{sub 2} compound. • The ΔS{sub Mmax} and the RCP are 16.0 J/kg K and 640 J/kg, respectively, for ΔH=50 kOe. • Relative low rare earth content in GdNiAl{sub 2} comparing with other candidates.

  5. Magnetocaloric effect in ErCo2 compound

    Institute of Scientific and Technical Information of China (English)

    Zou Jun-Ding; Shen Bao-Gen; Sun Ji-Rong

    2007-01-01

    The ErCo2 compound is prepared by arc-melting and its entropy changes are calculated using Maxwell relation.Its entropy change reaches 38 J/(kg·K) and its refrigerant capacity achieves 291 J/kg at 0-5 T. The mean field approximation is used to calculate the magnetic entropy of ErCo2 compound. Results estimated by using the Maxwell relation deviate from mean field approximation calculations in ferrimagnetic state; however, the data obtained by the two ways are consistent in the vicinity of phase transition or at higher temperatures. This indicates that entropy changes are mainly derived from magnetic degree of freedom, and the lattice has almost no contribution to the entropy change in the vicinity of phase transition but its influence is obvious in the ferrimagnetic state below TC.

  6. Magnetocaloric Effect in MnCo_(1-x)Al_xGe Compounds

    Institute of Scientific and Technical Information of China (English)

    Weiguang Zhang; O. Tegus; Yongli Wu; Yirgeltu; Huanying Yan; Song Lin

    2009-01-01

    The effects of substitution of Al for Co on magnetic and magnetocaloric properties of MnCo_(1-x)Al_xGe (x=0.00, 0.03, 0.05, 0.08, 0.10, 0.13, 0.15, and 0.20) compounds have been investigated by X-ray diffraction (XRD) and magnetization measurements. XRD exhibits that MnCo_(1-x)Al_xGe compounds crystallize in the orthorhombic TiNiSi-type structure for x0.03. Magnetic measurements show that the Curie temperature can be tuned between 286 and 347 K by changing the Co/Al ratio. The maximum magnetic entropy change determined from the isothermal magnetization measurement by Maxwell relation reaches 1.52 J/(kgK) for x=0.08 in a field change from 0 to 1.5 T around 310 K.

  7. Magnetic properties and magnetocaloric effect in quaternary boroncarbides compound ErNiBC

    Science.gov (United States)

    Zhang, Yikun; Wilde, Gerhard

    2015-09-01

    The magnetocaloric effect (MCE) of quaternary intermetallic compound ErNiBC has been investigated by magnetization and heat capacity measurements. The compound undergoes a paramagnetic (PM) to ferromagnetic (FM) transition at TC~5 K and the ground state of Er ion forms a Kramer's doublet state. The magnetic transition is found to be second order in nature. The maximum magnetic entropy change (-ΔSMmax) and adiabatic temperature change (ΔTadmax) of ErNiBC are 24.8 J/kg K and 8.6 K, respectively, for a magnetic field change of 0-50 kOe, and the corresponding refrigerant capacity (RC) is 312 J/kg.

  8. Magnetic properties and magnetocaloric effects in Tb6Co1.67Si3 compound

    Institute of Scientific and Technical Information of China (English)

    Shen Jun; Wang Fang; Li Yang-Xian; Sun Ji-Rong; Shen Bao-Gen

    2007-01-01

    Magnetic properties and magnetocaloric effects of Tb6Co1.67Si3 have been investigated by magnetization measurement. This compound is of a hexagonal Ce6Ni2Si3-type structure with a saturation magnetization of 187 emu/g at 5 K and a reversible second-order magnetic transition at Curie temperature TC = 186 K. A magnetic entropy change is found to be 330 J/kg for fields ranging from 0 to 5 T. The large RC, the reversible magnetization around TC and the easy fabrication make the Tb6Co1.67Si3 compound a suitable candidate for magnetic refrigerants in a corresponding temperature range.

  9. Magnetic properties and magnetocaloric effect in quaternary boroncarbides compound ErNiBC

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yikun, E-mail: zhangyk@epm.neu.edu.cn [Department of Material Science and Engineering, Shanghai University, Shanghai 200072 (China); Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Straße 10, D-48149 Münster (Germany); Wilde, Gerhard [Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Straße 10, D-48149 Münster (Germany)

    2015-09-01

    The magnetocaloric effect (MCE) of quaternary intermetallic compound ErNiBC has been investigated by magnetization and heat capacity measurements. The compound undergoes a paramagnetic (PM) to ferromagnetic (FM) transition at T{sub C}~5 K and the ground state of Er ion forms a Kramer's doublet state. The magnetic transition is found to be second order in nature. The maximum magnetic entropy change (−ΔS{sub M}{sup max}) and adiabatic temperature change (ΔT{sub ad}{sup max}) of ErNiBC are 24.8 J/kg K and 8.6 K, respectively, for a magnetic field change of 0–50 kOe, and the corresponding refrigerant capacity (RC) is 312 J/kg.

  10. Magnetocaloric effect in GdCu intermetallic compound

    Energy Technology Data Exchange (ETDEWEB)

    Oboz, M.; Talik, E.; Winiarski, A. [Institiute of Physics, University of Silesia, Katowice (Poland)

    2012-03-15

    A single crystal of GdCu of FeB-type was grown by the Czochralski method from a levitating melt and characterized using X-ray diffraction, dc -magnetization M(T) and ac -magnetic susceptibility (ac-{chi}). From ac and dc magnetic susceptibility a transition to the antiferromagnetic state has been found below T{sub N} = 37 K. The paramagnetic Curie temperature {theta}{sub p} and the effective magnetic moment {mu}{sub eff}were estimated assuming the Curie-Weiss law in the 100 to 300 K range and were found to be {theta}{sub p}=-37 K and {mu}{sub eff}=8.5 {mu}{sub B}. The last value is enhanced relatively to the free ion value of 7.94 {mu}{sub B} for Gd{sup 3+}. The calculated entropy changes {delta}S{sub m} for the examined compound amount to -1.22 J/K.kg, -0.6 J/K.kg and -0.09 J/K.kg at 7, 5 and 2 T respectively. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Progress Report 2011: Understanding compound phase transitions in Heusler alloy giant magnetocaloric materials

    Energy Technology Data Exchange (ETDEWEB)

    Stadler, Shane

    2011-12-13

    Our goal is to gain insight into the fundamental physics that is responsible for magnetocaloric effects (MCE) and related properties at the atomic level. We are currently conducting a systematic study on the effects of atomic substitutions in Ni2MnGa-based alloys, and also exploring related full- and half-Heusler alloys, for example Ni-Mn-X (X=In, Sn, Sb), that exhibit a wide variety of interesting and potentially useful physical phenomena. It is already known that the magnetocaloric effect in the Heusler alloys is fundamentally connected to other interesting phenomena such as shape-memory properties. And the large magnetic entropy change in Ni2Mn0.75Cu0.25Ga has been attributed to the coupling of the first-order, martensitic transition with the second-order ferromagnetic paramagnetic (FM-PM) transition. Our research to this point has focused on understanding the fundamental physics at the origin of these complex, compound phase transitions, and the novel properties that emerge. We synthesize the materials using a variety of techniques, and explore their material properties through structural, magnetic, transport, and thermo-magnetic measurements.

  12. Structural, atomic Hirschfeld surface, magnetic and magnetocaloric properties of SmNi{sub 5} compound

    Energy Technology Data Exchange (ETDEWEB)

    Nouri, K., E-mail: nouri@icmpe.cnrs.fr [C.M.T.R, I.C.M.P.E, CNRS, Université Paris Est Créteil, UMR 7182, 2-8 rue Henri Dunant, F-94320 Thiais (France); Laboratoire des Sciences des Matériaux et de l' Environnement, Faculté des Sciences de Sfax- Université de Sfax, BP 1171, Sfax, 3018 (Tunisia); Jemmali, M. [Laboratoire des Sciences des Matériaux et de l' Environnement, Faculté des Sciences de Sfax- Université de Sfax, BP 1171, Sfax, 3018 (Tunisia); Chemistry Departement, College of Science and Arts at Ar-Rass, Qassim University, P.O. Box53 (Saudi Arabia); Walha, S. [Laboratoire des Sciences des Matériaux et de l' Environnement, Faculté des Sciences de Sfax- Université de Sfax, BP 1171, Sfax, 3018 (Tunisia); Zehani, K. [C.M.T.R, I.C.M.P.E, CNRS, Université Paris Est Créteil, UMR 7182, 2-8 rue Henri Dunant, F-94320 Thiais (France); Ben Salah, A. [Laboratoire des Sciences des Matériaux et de l' Environnement, Faculté des Sciences de Sfax- Université de Sfax, BP 1171, Sfax, 3018 (Tunisia); Bessais, L. [C.M.T.R, I.C.M.P.E, CNRS, Université Paris Est Créteil, UMR 7182, 2-8 rue Henri Dunant, F-94320 Thiais (France)

    2016-07-05

    The SmNi{sub 5} intermetallic compound has been investigated by arc-melting. Powder X-ray diffraction analysis and Rietveld refinement revealed that the sample crystallized in the hexagonal CaCu{sub 5}-type structure P6/mmm space group with the following lattice parameters: a = 4.9203 (1) Å, c = 3.9662 (1) Å. These lattice parameters for the compound are in good agreement with previous theoretical result and experimental data. The EDX analysis has been performed to confirm the composition of this compound. The chemical bonding in SmNi{sub 5} was analyzed using atomic Hirshfeld surfaces, and this analysis supports the presence of the structural elements and the coordination of Sm (1a), Ni (2c) and Ni (3 g). This study indicates the different types of interatomic interactions between the Sm and Ni atoms and the weak interactions between Sm–Sm atoms were also observed along the c axis. The magnetic properties and magnetocaloric effect (MCE) have been established by the magnetization and isothermal magnetization of different temperature measurements. The magnetization curve as a function of temperature shows a magnetic transition from ferromagnetic to paramagnetic state at the Curie temperature T{sub C} = 29 K. We have studied the MCE phenomena in the vicinity of magnetic phase transitions in terms of magnetic entropy change. The temperature dependence of the magnetization, the magnetic entropy changeΔS{sub M}, as well as the relative cooling power around the second-order magnetic transition and the Arrott plots for the alloys are reported. - Highlights: • The SmNi{sub 5} intermetallic compound has been investigated by arc-melting. • The chemical bonding in SmNi{sub 5} was analyzed using atomic Hirshfeld surfaces. • The second order magnetocaloric material SmNi{sub 5} is investigated.

  13. Magnetic, thermal and magnetocaloric properties of non-stoichiometric TbMn{sub 0.33}Ge{sub 2} compound

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sachin; Suresh, K.G., E-mail: suresh@phy.iitb.ac.in

    2014-09-01

    Magnetic, heat capacity and magnetocaloric properties of non-stoichiometric TbMn{sub 0.33}Ge{sub 2} compound have been studied. Different measurements show that it undergoes three magnetic transitions at T{sub N}, T{sub 1} and T{sub 2}. The magnetocaloric effect has been estimated from magnetization data using Maxwell's relation. The existence of collinear and sine wave modulated components makes the magnetic structure complex at low temperatures. It is also found that this compound shows normal and inverse magnetocaloric effects in different temperature regimes.

  14. Giant magnetocaloric effect in antiferromagnetic DyVO{sub 4} compound

    Energy Technology Data Exchange (ETDEWEB)

    Midya, A., E-mail: arindam.midya@saha.ac.in; Khan, N.; Bhoi, D.; Mandal, P.

    2014-09-01

    We have investigated the magnetic and magnetocaloric properties of DyVO{sub 4} by magnetization and heat capacity measurements. χ(T) shows antiferromagnetic to paramagnetic transition at T{sub N}{sup Dy}∼3.5K. The compound undergoes a metamagnetic transition and exhibits a huge entropy change. The maximum values of magnetic entropy change (ΔS{sub M}), adiabatic temperature change (ΔT{sub ad}) and refrigerant capacity (RC) reach 26 J kg{sup −1} K{sup −1}, 17 K, and 526 J kg{sup −1}, respectively for a field change of 0–8 T. Moreover, the material is highly insulating and exhibits no thermal and field hysteresis, satisfying the necessary conditions for a good magnetic refrigerant material.

  15. Magnetocaloric effects in Fe4MnSi3Bxr interstitial compounds

    Institute of Scientific and Technical Information of China (English)

    Yongli WU; O.Tegus; Weiguang ZHANG; S.Yiriyoltu; B.Mend; Songlin

    2009-01-01

    The magnetic properties and magnetocaloric effect in Fe_4MnSi_3B_x compounds with x=0, 0.05, 0.10, 0.15, 0.20, 0.25 have been investigated. X-ray diffraction study shows that all these compounds investigated crystallize in the Mn_5Si_3-type structure with space group P6_3/mcm. Boron insertion in the host ternary silicide Fe_4MnSi_3 does not change the crystal symmetry, only leads to an increase of the lattice parameters, indicating the B atoms entered the interstitial sites. With increasing B content, the Curie temperature shifts to higher temperatures. The maximal magnetic-entropy changes of the Fe_4MnSi_3B_x compounds with x=0, 0.10 and 0.20 are about 1.8 J/(kg·K), 1.8 J/(kg·K) and 1.6 J/(kg·K), respectively, for a field change from 0 to 1.5 T.

  16. Metamagnetism-enhanced magnetocaloric effect in the rare earth intermetallic compound Ho{sub 5}Ge{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Nirmala, R., E-mail: nirmala@physics.iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Morozkin, A.V. [Department of Chemistry, Moscow State University, GSP-2, Moscow 119992 (Russian Federation); Rajivgandhi, R. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Nigam, A.K. [DCMP& MS, Tata Institute of Fundamental Research, Mumbai 400005 (India); Quezado, S.; Malik, S.K. [Departamento de F´ısica Teorica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59072-970 (Brazil)

    2016-11-15

    Magnetic and magnetocaloric properties of polycrystalline Ho{sub 5}Ge{sub 4} (orthorhombic, Sm{sub 5}Ge{sub 4}-type, Space group Pnma, No. 62, oP36) compound have been studied. This compound orders antiferromagnetically at ~24 K (T{sub N}). From the magnetization vs field isotherms obtained close to the magnetic transition temperature, magnetocaloric effect (MCE) has been estimated. The isothermal magnetic entropy change (ΔS{sub M}) reaches a maximum value of ~−27 J/kg-K at ~30 K for a field change of 140 kOe. A metamagnetic transition is observed in the field dependent magnetization data at temperatures below 20 K, for critical fields above 20 kOe, giving rise to a ferromagnetic order and hence a large MCE. The magnetic moment value at 2.5 K is ~8μ{sub B}/Ho{sup 3+} in 90 kOe field. - Highlights: • The intermetallic compound Ho{sub 5}Ge{sub 4} orders antiferromagnetically around 24 K. • Magnetic field-induced transition to ferromagnetic state is observed at temperatures below about 20 K. • Reasonably large magnetocaloric effect accompanies this metamagnetic transition.

  17. Phase transitions and magnetocaloric effects in intermetallic compounds MnFeX (X=P, As, Si, Ge)

    Institute of Scientific and Technical Information of China (English)

    O.Tegus; Bao Li-Hong; Song Lin

    2013-01-01

    Since the discovery of giant magnetocaloric effect in MnFeP1-xAsx compounds,much valuable work has been performed to develop and improve Fe2P-type transition-metal-based magnetic refrigerants.In this article,the recent progress of our studies on fundamental aspects of theoretical considerations and experimental techniques,effects of atomic substitution on the magnetism and magnetocalorics of Fe2P-type intermetallic compounds MnFeX (X=P,As,Ge,Si) is reviewed.Substituting Si (or Ge) for As leads to an As-free new magnetic material MnFeP1-xSi(Ge)x.These new materials show large magnetocaloric effects resembling MnFe(P,As) near room temperature.Some new physical phenomena,such as huge thermal hysteresis and 'virgin' effect,were found in new materials.On the basis of Landau theory,a theoretical model was developed for studying the mechanism of phase transition in these materials.Our studies reveal that MnFe(P,Si) compound is a very promising material for room-temperature magnetic refrigeration and thermo-magnetic power generation.

  18. Large reversible magnetocaloric effect induced by metamagnetic transition in antiferromagnetic HoNiGa compound

    Science.gov (United States)

    Wang, Yi-Xu; Zhang, Hu; Wu, Mei-Ling; Tao, Kun; Li, Ya-Wei; Yan, Tim; Long, Ke-Wen; Long, Teng; Pang, Zheng; Long, Yi

    2016-12-01

    The magnetic properties and magnetocaloric effects (MCE) of HoNiGa compound are investigated systematically. The HoNiGa exhibits a weak antiferromagnetic (AFM) ground state below the Ńeel temperature TN of 10 K, and the AFM ordering could be converted into ferromagnetic (FM) ordering by external magnetic field. Moreover, the field-induced FM phase exhibits a high saturation magnetic moment and a large change of magnetization around the transition temperature, which then result in a large MCE. A large -ΔSM of 22.0 J/kg K and a high RC value of 279 J/kg without magnetic hysteresis are obtained for a magnetic field change of 5 T, which are comparable to or even larger than those of some other magnetic refrigerant materials in the same temperature range. Besides, the μ0H2/3 dependence of well follows the linear fitting according to the mean-field approximation, suggesting the nature of second-order FM-PM magnetic transition under high magnetic fields. The large reversible MCE induced by metamagnetic transition suggests that HoNiGa compound could be a promising material for magnetic refrigeration in low temperature range. Project supported by the National Natural Science Foundation of China (Grant Nos. 51671022 and 51427806), the Beijing Natural Science Foundation, China (Grant No. 2162022), and the Fundamental Research Funds for the Central Universities, China (Grant No. FRF-TP-15-002A3).

  19. Towards tailoring the magnetocaloric response in FeRh-based ternary compounds

    Energy Technology Data Exchange (ETDEWEB)

    Barua, Radhika, E-mail: barua.r@husky.neu.edu; Jiménez-Villacorta, Félix; Lewis, L. H. [Department of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

    2014-05-07

    In this work, we demonstrate that the magnetocaloric response of FeRh-based compounds may be tailored for potential magnetic refrigeration applications by chemical modification of the FeRh lattice. Alloys of composition Fe(Rh{sub 1−x}A{sub x}) or (Fe{sub 1−x}B{sub x})Rh (A = Cu, Pd; B = Ni; 0 < x < 0.06) were synthesized via arc-melting and subsequent annealing in vacuum at 1000 °C for 48 h. The magnetocaloric properties of the FeRh-based systems were determined using isothermal M(H) curves measured in the vicinity of the magnetostructural temperature (T{sub t}). It is found that the FeRh working temperature range (δT{sub FWHM}) may be chemically tuned over a wide temperature range, 100 K ≤ T ≤ 400 K. While elemental substitution consistently decreases the magnetic entropy change (ΔS{sub mag}) of the FeRh-based ternary alloys from that of the parent FeRh compound (ΔS{sub mag},{sub FeRh} ∼ 17 J/kg K; ΔS{sub mag,FeRh-ternary =} 7–14 J/kg K at H{sub app} = 2 T), the net refrigeration capacity (RC), defined as the amount of heat that can be transferred during one magnetic refrigeration cycle, of the modified systems is significantly higher (RC{sub FeRh} ∼ 150 J/kg; RC{sub FeRh-ternary =} 170–210 J/kg at H{sub app} = 2 T). These results are attributed to stoichiometry-induced changes in the FeRh electronic band structure and beneficial broadening of the magnetostructural transition due to local chemical disorder.

  20. Structure and magnetocaloric effect in melt-spun La(Fe,Si)13 and MnFePGe compounds

    Institute of Scientific and Technical Information of China (English)

    YAN Aru

    2006-01-01

    The magnetocaloric properties of melt-spun La(Fe,Si) 13 and MnFePGe compounds were investigated. Very large value of magnetic entropy change |ΔS|=31 and 35.4J·(kg·K)-1 under 5 T were obtained at 201 K in LaFe11.8Si1.2 melt-spun ribbons and at around 317 K in Mn1.1Fe0.9P0.76Ge0.24 melt-spun ribbons, respectively. The large magnetocaloric effect results from a more homogenous element distribution related to the very high cooling rate during melt-spinning. The excellent MCE properties, the low materials cost and the accelerated aging regime make the melt-spun-type La(Fe,Si)13 and MnFePGe materials an excellent candidate for magnetic refrigerant applications.

  1. Giant rotating magnetocaloric effect induced by highly texturing in polycrystalline DyNiSi compound.

    Science.gov (United States)

    Zhang, Hu; Li, YaWei; Liu, Enke; Ke, YaJiao; Jin, JinLing; Long, Yi; Shen, BaoGen

    2015-07-10

    Large rotating magnetocaloric effect (MCE) has been observed in some single crystals due to strong magnetocrystalline anisotropy. By utilizing the rotating MCE, a new type of rotary magnetic refrigerator can be constructed, which could be more simplified and efficient than the conventional one. However, compared with polycrystalline materials, the high cost and complexity of preparation for single crystals hinder the development of this novel magnetic refrigeration technology. For the first time, here we observe giant rotating MCE in textured DyNiSi polycrystalline material, which is larger than those of most rotating magnetic refrigerants reported so far. This result suggests that DyNiSi compound could be attractive candidate of magnetic refrigerants for novel rotary magnetic refrigerator. By considering the influence of demagnetization effect on MCE, the origin of large rotating MCE in textured DyNiSi is attributed to the coexistence of strong magnetocrystalline anisotropy and highly preferred orientation. Our study on textured DyNiSi not only provides a new magnetic refrigerant with large rotating MCE for low temperature magnetic refrigeration, but also opens a new way to exploit magnetic refrigeration materials with large rotating MCE, which will be highly beneficial to the development of rotating magnetic refrigeration technology.

  2. Magneto-caloric effect in the pseudo-binary intermetallic YPrFe{sub 17} compound

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, Pablo [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Gorria, Pedro, E-mail: pgorria@uniovi.es [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Sanchez Llamazares, Jose L. [Division de Materiales Avanzados, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San Jose 2055, CP 78216, San Luis Potosi (Mexico); Perez, Maria J. [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Franco, Victorino [Departamento de Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Reiffers, Marian; Kovac, Jozef [Institute of Experimental Physics, Watsonova 47, SK-04001 Kosice (Slovakia); Puente-Orench, Ines [Institute Laue Langevin, 6 rue Jules Horowitz, 38042 Grenoble (France); Blanco, Jesus A. [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer YPrFe{sub 17} exhibits a broad {Delta}S{sub M}(T) associated with the ferro-to-paramagnetic phase transition (T{sub C} Almost-Equal-To 290 K). Black-Right-Pointing-Pointer We obtain |{Delta}S{sub M}| Almost-Equal-To 2.3 J kg{sup -1} K{sup -1} and RCP Almost-Equal-To 100 J kg{sup -1}for a magnetic field change of 1.5 T. Black-Right-Pointing-Pointer A single master curve for {Delta}S{sub M} is found when compared with other isostructural R{sub 2}Fe{sub 17} binary alloys. - Abstract: We have synthesized the intermetallic YPrFe{sub 17} compound by arc-melting. X-ray and neutron powder diffraction show that the crystal structure is rhombohedral with R3{sup Macron }m space group (Th{sub 2}Zn{sub 17}-type). The investigated compound exhibits a broad isothermal magnetic entropy change {Delta}S{sub M}(T) associated with the ferro-to-paramagnetic phase transition (T{sub C} Almost-Equal-To 290 K). The |{Delta}S{sub M}| ( Almost-Equal-To 2.3 J kg{sup -1} K{sup -1}) and the relative cooling power ( Almost-Equal-To 100 J kg{sup -1}) have been calculated for applied magnetic field changes up to 1.5 T. A single master curve for {Delta}S{sub M} under different values of the magnetic field change can be obtained by a rescaling of the temperature axis. The results are compared and discussed in terms of the magneto-caloric effect in the isostructural R{sub 2}Fe{sub 17} (R = Y, Pr and Nd) binary intermetallic alloys.

  3. Hyperfine interactions in MnAs studied by perturbed angular correlations of $\\gamma$-rays using the probe $^{77}$Br $\\rightarrow ^{77}$Se and first principles calculations for MnAs and other Mn pnictides

    CERN Document Server

    Gonçalves, J N; Correia, J G; Lopes, A M L

    2011-01-01

    The MnAs compound shows a first-order transition at T$_{c}$≈ 42$^{\\circ}$C, and a second-order transition at T$_{t}$ ≈120$^{\\circ}$C. The first-order transition, with structural (hexagonal-orthorhombic), magnetic (FM-PM) and electrical conductivity changes, is associated to magnetocaloric, magnetoelastic, and magnetoresistance effects. We report a study in a large temperature range from −196$^{\\circ}$C up to 140$^{\\circ}$C, using the $\\gamma\\!-\\!\\gamma$ perturbed angular correlations method with the radioactive probe $^{77}$Br→$^{77}$Se, produced at the ISOLDE-CERN facility. The electric field gradients and magnetic hyperfine fields are determined across the first- and second-order phase transitions encompassing the pure and mixed phase regimes in cooling and heating cycles. The temperature irreversibility of the 1st order phase transition is seen locally, at the nanoscopic scale sensitivity of the hyperfine field, by its hysteresis, detailing and complementing information obtained with macroscopic me...

  4. Magnetism and magnetocaloric effect in multicomponent Laves-phase compounds: Study and comparative analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ćwik, J., E-mail: cwikjac@ml.pan.wroc.pl

    2014-01-15

    This paper presents a review and results of comparative study of the influence of Gd on some physical properties of (R{sub 0.9}R′{sub 0.1}){sub 1−x}Gd{sub x}Co{sub 2} solid solutions with R=Dy, Ho and R′=Er, Ho and x varied from 0.05 to 0.15. Powder X-ray diffraction analysis performed at room temperature revealed that all studied solid solutions solidify with the formation of a Laves-phase MgCu{sub 2}-type structure (space group Fd−3m). The magnetization behavior and the magnetic transition are analyzed in terms of the Landau theory. The studies of magnetic properties and heat capacity showed that a relatively small Gd addition significantly increases T{sub C} of the compounds. The maximum percentage increase in T{sub C}, namely, ∼43% was observed for (Ho{sub 0.9}Er{sub 0.1}){sub 1−x}Gd{sub x}Co{sub 2}. However, the highest temperature was noted for the (Dy{sub 0.9}Ho{sub 0.1}){sub 0.85}Gd{sub 0.15}Co{sub 2} solid solution; it is T{sub C}=183.4 K. Below the ordering temperature, all samples are ferrimagnetically ordered; at high temperatures, they are Curie–Weiss paramagnets. Moreover, a small Gd addition eliminates the field-induced magnetic transition near T{sub C} and, as consequence, transforms the nature of magnetic transition from the first- to second-order. The magnetocaloric effect has been estimated in terms of both isothermal magnetic entropy and adiabatic temperature changes. The highest adiabatic temperature change ΔT{sub ad}=3 K and highest isothermal entropy change ΔS{sub mag}=12.1 J/kg K were observed for (Ho{sub 0.9}Er{sub 0.1}){sub 0.95}Gd{sub 0.05}Co{sub 2} at ∼90 K in magnetic fields of 2 T and 3 T, respectively. A decrease in the entropy change has been observed with increasing Gd content in all studied samples. The smallest values of ΔS{sub mag} were observed for the (Dy{sub 0.9}Ho{sub 0.1}){sub 1−x}Gd{sub x}Co{sub 2} solid solutions. Under an external field change of from 0 to 3 T, the maximum entropy change for (Dy{sub 0

  5. Magnetocaloric effect in M-pyrazole-[Nb(CN)(8)] (M = Ni, Mn) molecular compounds.

    Science.gov (United States)

    Fitta, Magdalena; Bałanda, Maria; Mihalik, Marian; Pełka, Robert; Pinkowicz, Dawid; Sieklucka, Barbara; Zentkova, Maria

    2012-12-19

    We report a study of magnetocaloric effect (MCE) in cyanido-bridged {[M(II)(pyrazole)(4)](2)[Nb(IV)(CN)(8)]·4H(2)O}(n) molecular compounds where M = Ni, Mn, pyrazole = C(3)H(4)N(2). The substances show a sharp phase transition to a long range magnetically ordered state, with ferromagnetic coupling between M and Nb sublattices in the case of the Ni-based sample 1 (T(c) = 13.4 K) and ferrimagnetic coupling for the Mn-based sample 2 (T(c) = 23.8 K). The magnetic entropy change ΔS due to applied field change ΔH as a function of temperature was determined by the magnetization and heat capacity measurements. The maximum value of ΔS at μ(0)ΔH = 5 T is 6.1 J mol(-1) K(-1) (5.9 J kg(-1) K(-1)) for 1 at T = 14 K and 6.7 J mol(-1) K(-1) (6.5 J kg(-1) K(-1)) for 2 at T = 25 K. MCE data at different applied fields have been presented as one universal curve, which confirms magnetic transitions in 1 and 2 to be of second order. The temperature dependences of the n exponent characterizing the dependence of ΔS on ΔH have been obtained. The n(T(c)) values, consistent with the shape of the magnetization curves, pointed to the 3D Heisenberg behaviour for 2 and some anisotropy, probably of the XY type, for 1. The (H/T(c))(2/3) dependence of the maximum entropy change has been tested in the ferrimagnetic Mn(2)-L-[Nb(CN)(8)] (L = C(3)H(4)N(2), C(4)H(4)N(2)) series.

  6. Magnetic and magnetocaloric properties of amorphous Y3Fe5O12 compound

    Science.gov (United States)

    Nóbrega, E. P.; Costa, S. S.; Alvarenga, T. S. T.; Alho, B. P.; Caldas, A.; Ribeiro, P. O.; de Sousa, V. S. R.; de Oliveira, N. A.; von Ranke, P. J.

    2017-01-01

    We report a theoretical model formed by two coupled magnetic sublattices of localized spins in the presence of an applied magnetic field to investigate the magnetic characteristics and magnetocaloric properties of amorphous yttrium iron garnet. The magnetic state equation is based on Handrich-Kobe´s theory, where the amorphization is taken into account by introducing fluctuations in the exchange parameters. Experimental results report that Y3Fe5O12 presents a structural phase transition from crystalline to amorphous caused by a variation of external pressure. This phase transition on Y3Fe5O12 leads to interesting results in the magnetic properties and magnetocaloric quantities.

  7. Magnetic and magnetocaloric properties of polycrystalline La0.48Ca0.52MnO3 compound at low temperature: Influence of glassy magnetic state

    Science.gov (United States)

    Das, Kalipada; Das, I.

    2017-04-01

    We report the magnetic, magnetocaloric and electrical transport properties of polycrystalline bulk La0.48Ca0.52MnO3 compound. In addition to earlier reported properties viz. charge ordering and antiferromagnetic ordering, we address the presence of glassy magnetic phase at low temperature (T magnetic and magnetocaloric properties reveal that, pronounced glassy behavior in this compound is due to presence of ferromagnetic clusters in the low-temperature region. In addition to that, analysis of low-temperature x-ray diffraction measurements indicate increasing crystallographic unit cell volume which is attributed to the enhancement of eg-electron bandwidth at low temperature.

  8. The physical mechanism of magnetic field controlled magnetocaloric effect and magnetoresistance in bulk PrGa compound.

    Science.gov (United States)

    Zheng, X Q; Wu, H; Chen, J; Zhang, B; Li, Y Q; Hu, F X; Sun, J R; Huang, Q Z; Shen, B G

    2015-10-12

    The PrGa compound shows excellent performance on the magnetocaloric effect (MCE) and magnetoresistance (MR). The physical mechanism of MCE and MR in PrGa compound was investigated and elaborated in detail on the basis of magnetic measurement, heat capacity measurement and neutron powder diffraction (NPD) experiment. New types of magnetic structure and magnetic transition are found. The results of the NPD along with the saturation magnetic moment (MS) and magnetic entropy (SM) indicate that the magnetic moments are randomly distributed within the equivalent conical surface in the ferromagnetic (FM) temperature range. PrGa compound undergoes an FM to FM transition and an FM to paramagnetic (PM) transition as temperature increases. The magnetizing process was discussed in detail and the physical mechanism of the magnetic field controlled magnetocaloric effect (MCE) and the magnetoresistance (MR) was studied. The formation of the plateau on MCE curve was explained and MR was calculated in detail on the basis of the magnetic structure and the analysis of the magnetizing process. The experimental results are in excellent agreement with the calculations. Finally, the expression of MR = β(T)X(2) and its application conditions were discussed, where X is M(H)/Meff, and Meff is the paramagnetic effective moment.

  9. The physical mechanism of magnetic field controlled magnetocaloric effect and magnetoresistance in bulk PrGa compound

    Science.gov (United States)

    Zheng, X. Q.; Wu, H.; Chen, J.; Zhang, B.; Li, Y. Q.; Hu, F. X.; Sun, J. R.; Huang, Q. Z.; Shen, B. G.

    2015-10-01

    The PrGa compound shows excellent performance on the magnetocaloric effect (MCE) and magnetoresistance (MR). The physical mechanism of MCE and MR in PrGa compound was investigated and elaborated in detail on the basis of magnetic measurement, heat capacity measurement and neutron powder diffraction (NPD) experiment. New types of magnetic structure and magnetic transition are found. The results of the NPD along with the saturation magnetic moment (MS) and magnetic entropy (SM) indicate that the magnetic moments are randomly distributed within the equivalent conical surface in the ferromagnetic (FM) temperature range. PrGa compound undergoes an FM to FM transition and an FM to paramagnetic (PM) transition as temperature increases. The magnetizing process was discussed in detail and the physical mechanism of the magnetic field controlled magnetocaloric effect (MCE) and the magnetoresistance (MR) was studied. The formation of the plateau on MCE curve was explained and MR was calculated in detail on the basis of the magnetic structure and the analysis of the magnetizing process. The experimental results are in excellent agreement with the calculations. Finally, the expression of MR = β(T)X2 and its application conditions were discussed, where X is M(H)/Meff, and Meff is the paramagnetic effective moment.

  10. Review of magnetic properties and magnetocaloric effect in the intermetallic compounds of rare earth with low boiling point metals

    Science.gov (United States)

    Ling-Wei, Li

    2016-03-01

    The magnetocaloric effect (MCE) in many rare earth (RE) based intermetallic compounds has been extensively investigated during the last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress on studying the magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal(s) (Zn, Mg, and Cd). Some of them exhibit promising MCE properties, which make them attractive for low temperature magnetic refrigeration. Characteristics of the magnetic transition, origin of large MCE, as well as the potential application of these compounds are thoroughly discussed. Additionally, a brief review of the magnetic and magnetocaloric properties in the quaternary rare earth nickel boroncarbides RENi2B2C superconductors is also presented. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374081 and 11004044), the Fundamental Research Funds for the Central Universities, China (Grant Nos. N150905001, L1509006, and N140901001), the Japan Society for the Promotion of Science Postdoctoral Fellowships for Foreign Researchers (Grant No. P10060), and the Alexander von Humboldt (AvH) Foundation (Research stipend to L. Li).

  11. Study of the magnetic phase transitions and magnetocaloric effect in Dy{sub 2}Cu{sub 2}In compound

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yikun, E-mail: ykzhang10@hotmail.com [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, Shanghai, 200072 (China); School of Materials Science and Engineering, Shanghai University, 200072 (China); Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Straße 10, D-48149, Münster (Germany); Xu, Xiao; Yang, Yang; Hou, Long; Ren, Zhongming [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, Shanghai, 200072 (China); School of Materials Science and Engineering, Shanghai University, 200072 (China); Li, Xi, E-mail: lx_net@sina.com [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, Shanghai, 200072 (China); School of Materials Science and Engineering, Shanghai University, 200072 (China); Wilde, Gerhard [Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Straße 10, D-48149, Münster (Germany)

    2016-05-15

    The magnetic properties and magnetocaloric effect (MCE) in Dy{sub 2}Cu{sub 2}In compound have been investigated. Dy{sub 2}Cu{sub 2}In undergoes two magnetic phase transitions, a paramagnetic to ferromagnetic (FM) at T{sub C} ∼ 49.5 K followed by a spin reorientation (SR) at T{sub SR} ∼ 19.5 K. For a magnetic field change of 0–7 T, the maximum values of the magnetic entropy change (−ΔS{sub M}{sup max}) are estimated to be 16.5 around T{sub C} and 6.7 J/kg K around T{sub SR} with a large relative cooling power (RCP) value of 617 J/kg. The modified Arrott plots and universal curves of the rescaled ΔS{sub M} confirmed that the magnetic phase transitions in Dy{sub 2}Cu{sub 2}In compound belongs the second order phase transitions. The present results may provide some clues to search for new magnetocaloric materials belonging to RE{sub 2}T{sub 2}X system. - Highlights: • Magnetic properties and magnetocaloric effect in Dy{sub 2}Cu{sub 2}In was studied. • The Dy{sub 2}Cu{sub 2}In undergoes 2 s order magnetic phase transitions. • A large reversible MCE was observed in Dy{sub 2}Cu{sub 2}In. • The origin of MCE and its potential application in Dy{sub 2}Cu{sub 2}In were discussed.

  12. Magnetic and magnetocaloric properties of DyMn2Si2 compound with multiple magnetic phase transition

    Science.gov (United States)

    dos Reis, D. C.; França, E. L. T.; de Paula, V. G.; dos Santos, A. O.; Coelho, A. A.; Cardoso, L. P.; da Silva, L. M.

    2017-02-01

    Structural, magnetic and magnetocaloric properties of the ternary intermetallic compound DyMn2Si2 are studied by X-ray diffraction and magnetization measurements. It is found that DyMn2Si2 crystalizes with tetragonal ThCr2S2-type structure and exhibits four successive magnetic transitions at low temperature, around 20 K, 31 K, 38 K and 82 K, named respectively as T1, T2, T3 and T4 transitions. Large values of magnetic field (>35 kOe) favor antiferromagnetic clusters and give rise to exchange bias effect. The different responses of T2 and T3 to field change, induces two non-identical isothermal entropy change (-ΔSM) peaks. The maximum values of -ΔSM occur in temperatures around T3 and reaches 8.2 J/kgK, for a magnetic field change of 50 kOe. Also, the presence of transitions T2 and T3 close to each other induces a table-like magnetocaloric effect (MCE) in a wide temperature range. Thus, the peculiar magnetic properties observed for DyMn2Si2 compound are interesting for low temperature magnetic refrigeration.

  13. Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds.

    Science.gov (United States)

    Wu, Rongrong; Shen, Feiran; Hu, Fengxia; Wang, Jing; Bao, Lifu; Zhang, Lei; Liu, Yao; Zhao, Yingying; Liang, Feixiang; Zuo, Wenliang; Sun, Jirong; Shen, Baogen

    2016-02-17

    Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RCeffe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials.

  14. Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds

    Science.gov (United States)

    Wu, Rongrong; Shen, Feiran; Hu, Fengxia; Wang, Jing; Bao, Lifu; Zhang, Lei; Liu, Yao; Zhao, Yingying; Liang, Feixiang; Zuo, Wenliang; Sun, Jirong; Shen, Baogen

    2016-02-01

    Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RCeffe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials.

  15. Critical dependence of magnetostructural coupling and magnetocaloric effect on particle size in Mn-Fe-Ni-Ge compounds

    Science.gov (United States)

    Wu, Rongrong; Shen, Feiran; Hu, Fengxia; Wang, Jing; Bao, Lifu; Zhang, Lei; Liu, Yao; Zhao, Yingying; Liang, Feixiang; Zuo, Wenliang; Sun, Jirong; Shen, Baogen

    2016-01-01

    Magnetostructural coupling, which is the coincidence of crystallographic and magnetic transition, has obtained intense attention for its abundant magnetoresponse effects and promising technological applications, such as solid-state refrigeration, magnetic actuators and sensors. The hexagonal Ni2In-type compounds have attracted much attraction due to the strong magnetostructural coupling and the resulted giant negative thermal expansion and magnetocaloric effect. However, the as-prepared samples are quite brittle and naturally collapse into powders. Here, we report the effect of particle size on the magnetostructural coupling and magnetocaloric effect in the Ni2In-type Mn-Fe-Ni-Ge compound, which undergoes a large lattice change across the transformation from paramagnetic austenite to ferromagnetic martensite. The disappearance of martensitic transformation in a large amount of austenitic phase with reducing particle size, to our best knowledge, has not been reported up to now. The ratio can be as high as 40.6% when the MnNi0.8Fe0.2Ge bulk was broken into particles in the size range of 5~15 μm. Meanwhile, the remained magnetostructural transition gets wider and the magnetic hysteresis becomes smaller. As a result, the entropy change drops, but the effective cooling power RCeffe increases and attains to the maximum at particles in the range of 20~40 μm. These observations provide constructive information and highly benefit practical applications for this class of novel magnetoresponse materials. PMID:26883719

  16. Magnetic properties and magnetocaloric effects in NaZn13-type La(Fe, Al)13-based compounds

    Institute of Scientific and Technical Information of China (English)

    Shen Bao-Gen; Hu Feng-Xia; Dong Qiao-Yan; Sun Ji-Rong

    2013-01-01

    In this article,our recent progress concerning the effects of atomic substitution,magnetic field,and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed.With an increase of the aluminum content,the compounds exhibit successively an antiferromagnetic (AFM) state,a ferromagnetic (FM) state,and a mictomagnetic state.Furthermore,the AFM coupling of LaFe13-xAlx can be converted to an FM one by substituting Si for Al,Co for Fe,and magnetic rare-earth R for La,or introducing interstitial C or H atoms.However,low doping levels lead to FM clusters embedded in an AFM matrix,and the resultant compounds can undergo,under appropriate applied fields,first an AFM-FM and then an FM-AFM phase transition while heated,with significant magnetic relaxation in the vicinity of the transition temperature.The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co,C,or H,and a strong magnetocaloric effect can be obtained around the transition temperature.For example,for the LaFe11.5Al1.5C0.2H1.0 compound,the maximal entropy change reaches 13.8 J·kg-1·K-1 for a field change of 0-5 T,occurring around room temperature.It is 42% higher than that of Gd,and therefore,this compound is a promising room-temperature magnetic refrigerant.

  17. Magnetic and Magnetocaloric Properties of High-Energy Ball-Milled Nanocrystalline CeMn2Ge2 Compound

    Science.gov (United States)

    Kaya, Melike; Dincer, Ilker; Akturk, Selcuk; Elerman, Yalcin

    2016-10-01

    CeMn2Ge2 nanopowders have been obtained by high-energy ball milling for 5 and 10 hours from bulk compound to investigate the effect of milling time on magnetic and magnetocaloric properties. CeMn2Ge2 nanopowders have been characterized by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, and magnetization measurements. The average grain size of the nanoparticles from XRD measurements is about 12.2 and 8 nm for 5-hour and 10-hour ball-milled samples, respectively. The investigations reveal that magnetic entropy change (∆ S m) can be altered by changing the particle size of the compound. Maximum ∆ S m is -2.45 and -1.30 J kg-1 K-1 for the 5- and 10-hour ball-milled nanopowders, respectively.

  18. Magnetic transition and large reversible magnetocaloric effect in EuCu1.75P2 compound

    Institute of Scientific and Technical Information of China (English)

    Huo De-Xuan; Liao Luo-Bing; Li Ling-Wei; Li Miao; Qian Zheng-Hong

    2013-01-01

    The magnetocaloric effect (MCE) in EuCul.75P2 compound is studied by the magnetization and heat capacity measurements.Magnetization and modified Arrott plots indicate that the compound undergoes a second-order phase transition at Tc ~ 51 K.A large reversible MCE is observed around Tc.The values of maximum magnetic entropy change (-△SMmax)reach 5.6 J.kg-1.K-1 and 13.3 J.kg 1.K-1 for the field change of 2 T and 7 T,respectively,with no obvious hysteresis loss in the vicinity of Curie temperature.The corresponding maximum adiabatic temperature changes (△Taadmax) are evaluated to be 2.1 K and 5.0 K.The magnetic transition and the origin of large MCE in EuCu1.75P2 are also discussed.

  19. Room-temperature Magnetocaloric Effect in (Co0.35Mn0.65)2P Compound

    Institute of Scientific and Technical Information of China (English)

    Naikun Sun; Da Li; Songning Xu; Zhenhua Wang; Zhidong Zhang

    2011-01-01

    The (Co0.35Mn0.65)2P compound, prepared by a mechanical alloying plus solid sintering process, exhibits a second-order transition from a ferromagnetic state to a paramagnetic one at Curie temperature of about 320 K with no clear thermal hysteresis. A magnetic-entropy change (△SM) value above 1.6 J·kg-1·K-1 for a 5 T field change is obtained in the whole temperature range of 292.5-352.5 K and the maximum value of the △SM is 2.3 J·kg-1·K-1 at 337.5 K. The study on the magnetocaloric effect of the (Co0.35Mn0.65)2P compound may be helpful for exploring good candidates for room-temperature magnetic refrigeration.

  20. Phase control studies in Gd{sub 5}Si{sub 2}Ge{sub 2} giant magnetocaloric compound

    Energy Technology Data Exchange (ETDEWEB)

    Belo, J.H. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Pereira, A.M., E-mail: ampereira@fc.up.pt [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Ventura, J.; Oliveira, G.N.P. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Araujo, J.P., E-mail: jearaujo@fc.up.pt [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Tavares, P.B.; Fernandes, L. [Departamento de Quimica and CQ-VR, Universidade de Tras-os-Montes e Alto Douro, 5001-801 Vila Real (Portugal); Algarabel, P.A. [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones Cientificas, 50009 Zaragoza (Spain); Magen, C. [Instituto de Nanociencia de Aragon-ARAID, Universidad de Zaragoza, 50009 Zaragoza (Spain); Morellon, L. [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones Cientificas, 50009 Zaragoza (Spain); Instituto de Nanociencia de Aragon, Universidad de Zaragoza, 50009 Zaragoza (Spain); and others

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer Study of time dependence of O(I) to M phase. Black-Right-Pointing-Pointer Determination of the optimal annealing time. Black-Right-Pointing-Pointer New method for phase amount estimation (O(I) and M). Black-Right-Pointing-Pointer Effect of annealing on the MCE. Black-Right-Pointing-Pointer Analysis of the nature of the magnetic transition through the Arrot plot representation. - Abstract: A systematic set of annealings on arc-melted synthesized Gd{sub 5}Si{sub 2}Ge{sub 2} sample was performed. Through powder X-ray diffraction (XRD) and magnetometry measurements we monitored the effect of varying the annealing time with constant temperature (T = 1473 K) on the formation of the monoclinic (M) crystallographic phase fraction, which is the one responsible for the giant magnetocaloric effect (GMCE) in this compound. The conversion of the orthorhombic O(I) crystallographic phase into M was achieved, resulting in a significant increase of the M mass fraction. Such conversion led to a change in the magnetic transition nature, evolving from a second to a first order transition for the as-cast and annealed samples, respectively. An optimal annealing time range for the M phase conversion was identified to be within 80-120 min at T = 1473 K followed by a rapid quenching to liquid N{sub 2}. Furthermore, an increase up to {approx}50% of the magnetocaloric effect was obtained for the sample annealed during 120 min.

  1. Influence of the materials magnetic state on the accurate determination of the magnetocaloric effect

    Directory of Open Access Journals (Sweden)

    Forchelet J.

    2012-06-01

    Full Text Available In this paper, we report a detailed study of the magnetocaloric effect (MCE in different first order magnetic transition (FOMT materials with different situation of the magnetic state (magnetic order. For this purpose, R-Co2, MnAs based compounds were considered in this study. The MCE is discussed in terms of Maxwell relation (MR and Clausius-Clapeyron (C-C equation. The deviation observed between both methods is discussed and analyzed. On the other hand, practically all the reported data of the MCE in the literature are associated to the applied external magnetic field and have not been corrected taking into account the demagnetization effect related to the materials shape. The obtained results demonstrate that this phenomenon can alter drastically the MCE values by cancelling out a large part of the external field, resulting in spurious values of the measured MCE. The effect of the demagnetization field on the magnetocaloric performances is also the subject of this paper.

  2. Magnetocaloric Refrigeration.

    Science.gov (United States)

    1987-03-01

    material having a magnetocaloric effect. Larger temperature spans require a cycle with some type of heat exchange. One such cycle is the Brayton cycle... heat capacity of the rare-earth metals, which had a small magnetocaloric effect at the higher temperatures. In order to optimize the small... magnetocaloric effect and minimize the heat capacities of the inactive rare- earth metals while they are being cooled to their Curie points, half the volume of

  3. Magnetocaloric effect in Gd6Co1.67Si3 compound with a second-order phase transition

    Institute of Scientific and Technical Information of China (English)

    Shen Jun; Li Yang-Xian; Dong Qiao-Yan; Wang Fang; Sun Ji-Rong

    2008-01-01

    The magnetic properties and the magnetic entropy change ΔS have been investigated for Gd6Co1.67Si3 compounds with a second-order phase transition. The saturation moment at 5 K and the Curie temperature TC are 38.1μB and 298 K, respectively. The AS originates from a reversible second-order magnetic transition around TC and its value reaches 5.2J/kg.K for a magnetic field change from 0 to 5T. The refrigerant capacity (RC) of Gd6Co1.67Si3 are calculated by using the methods given in Refs.[12] and [21], respectively, for a field change of 0-5 T and its values are 310 and 440 J/kg, which is larger than those of some magnetocaloric materials with a first-order phase transition.

  4. Evolution of magnetostructural transition and magnetocaloric effect with Al doping in MnCoGe1-xAlx compounds

    KAUST Repository

    Bao, Lifu

    2014-01-03

    The effect of Al doping in MnCoGe1-xAlx compounds has been investigated. The substitution of Al for Ge enhances Mn-Mn covalent bonding by shortening the distance of nearest Mn atom layers, and thus stabilizes the hexagonal structure. As a result, first-order magnetostructural transition between ferromagnetic martensite and paramagnetic austenite takes place for the optimized compositions (x = 0.01, 0.02). Accompanied with the magnetostructural transition, large magnetocaloric effect (MCE) is observed. More doping of Al(x = 0.03, 0.04) leads to the separation of magnetic and structural transitions and remarkable reduction of MCE. © 2014 IOP Publishing Ltd.

  5. Heterogeneous nucleation and heat flux avalanches in La(Fe, Si)13 magnetocaloric compounds near the critical point

    Science.gov (United States)

    Bennati, C.; Gozzelino, L.; Olivetti, E. S.; Basso, V.

    2016-12-01

    The phase transformation kinetics of LaFe11.41Mn0.30Si1.29-H1.65 magnetocaloric compound is addressed by low rate calorimetry experiments. Scans at 1 mK/s show that its first order phase transitions are made by multiple heat flux avalanches. Getting very close to the critical point, when the transition becomes of the second order type, the step-like discontinuous behaviour associated with avalanches is smoothed out and the thermal hysteresis disappears. This result is confirmed by magneto-resistivity measurements and allows to obtain accurate values of the temperature hysteresis (ΔThyst = 0.37 K) at zero external magnetic field and of the critical field (Hc = 1.19 T). The number and magnitude of heat flux avalanches change as the magnetic field strength is increased, showing the interplay between the intrinsic energy barrier between phases and the microstructural disorder of the sample.

  6. Rate dependence of the magnetocaloric effect in La-Fe-Si compounds

    Directory of Open Access Journals (Sweden)

    Sasso C.P.

    2013-01-01

    Full Text Available The dynamic magnetocaloric effect in La(FexCoySi1-x-y13 with x=0.9 and low Co content of y=0.015 was analysed by calorimetric measurements at constant magnetic field and constant temperature as well as magnetisation relaxation measurements. It is shown that the rate dependence of the measurement, which leads to an increased entropy hysteresis with increasing rate of the driving force (temperature or magnetic field, can be mainly attributed to a thermal contact resistance R between sample and thermal bath of the measurement setup.

  7. The Giant Magnetocaloric Effect

    Science.gov (United States)

    Pecharsky, Vitalij K.

    1998-03-01

    Since the discovery of the magnetocaloric effect in pure iron by E.Warburg in 1881, it has been measured experimentally on many magnetic metals and compounds. The majority of the materials studied order magnetically undergoing a second order phase transformation. The magnetocaloric effect, typically peaking near the Curie or the Néel temperature, generally ranges from 0.5 to 2 K (in terms of adiabatic temperature change) or at 1 to 4 J/kg K (in terms of isothermal magnetic entropy change) per 1 T magnetic field change. The giant magnetocaloric effect recently discovered in Gd_5(Si_xGe_1-x)4 alloys, where x refrigerant capacity, which is the measure of how much heat can be transferred from a cold to a hot reservoir in one ideal thermodynamic cycle, is larger than that of the best second order phase transition materials by 25 to 100%. When the Gd_5(Si_xGe_1-x)4 alloys are compared with other known materials, which show first order magnetic phase transition, such as Dy, Ho, Er, HoCo_2, NdMn_2Si_2, Fe_0.49Rh_0.51, and (Hf_0.83Ta_0.17)Fe_2+x, only Fe_0.49Rh_0.51 has comparable magnetocaloric properties. However, the first order magnetic phase transition in Fe_0.49Rh_0.51 is irreversible, and the magnetocaloric effect disappears after one magnetizing/demagnetizing cycle. A study of the crystal structure, thermodynamics, and magnetism of the Gd_5(Si_xGe_1-x)4 alloys, where 0 basic relations between the composition, the crystal structure, and the change in thermodynamics and magnetocaloric properties, which occur in the Gd_5(Si_xGe_1-x)4 system, and which brings about the giant magnetocaloric effect when x <= 0.5.

  8. Magnetocaloric effects in Mn1.35Fe0.65P1-xSix compounds

    Institute of Scientific and Technical Information of China (English)

    Geng Yao-Xiang; Tegus O; Bi Li-Ge

    2012-01-01

    The structural and magnetocaloric properties of Mn1.35Fe0.s5P1-xSix compounds are investigated. The Sisubstituted compounds,Mn1.35Fe0.65P1-xSix with x =0.52,0.54,0.55,0.56,and 0.57,are prepared by high-energy ball milling and the solid-state reaction.The X-ray diffraction shows that the compounds crystallize into the Fe2P-type hexagonal structure with space group P(6)2m.The magnetic measurements show that the Curie temperature of the compound increases from 253 K for x =0.52 to 296 K for x =0.56.The isothermal magnetic-entropy change of the Mn1.35Fe0.65P1-xSix compound decreases with the Si content increasing.The maximal value of the magnetic-entropy change is about 7.0 J/kg·K in the Mn1.35Feo.65Po.48Sio.52 compound with a field change of 1.5 T.The compound quenched in water possesses a larger magnetic entropy change and a smaller thermal hysteresis than the non-quenched samples.The thermal hysteresis of the compound is less than 3.5 K.The maximum adiabatic temperature change is about 1.4 K in the Mn1.35Feo.65P0.45Si0.55 compound with a field change of 1.48 T.

  9. Excellent magnetocaloric properties in RE2Cu2Cd (RE = Dy and Tm) compounds and its composite materials

    Science.gov (United States)

    Zhang, Yikun; Yang, Yang; Xu, Xiao; Geng, Shuhua; Hou, Long; Li, Xi; Ren, Zhongming; Wilde, Gerhard

    2016-09-01

    The magnetic properties and magnetocaloric effect (MCE) of ternary intermetallic RE2Cu2Cd (RE = Dy and Tm) compounds and its composite materials have been investigated in detail. Both compounds undergo a paramagnetic to ferromagnetic transition at its own Curie temperatures of TC ~ 48.5 and 15 K for Dy2Cu2Cd and Tm2Cu2Cd, respectively, giving rise to the large reversible MCE. An additionally magnetic transition can be observed around 16 K for Dy2Cu2Cd compound. The maximum values of magnetic entropy change (-ΔSMmax) are estimated to be 17.0 and 20.8 J/kg K for Dy2Cu2Cd and Tm2Cu2Cd, for a magnetic field change of 0-70 kOe, respectively. A table-like MCE in a wide temperature range of 10-70 K and enhanced refrigerant capacity (RC) are achieved in the Dy2Cu2Cd - Tm2Cu2Cd composite materials. For a magnetic field change of 0-50 kOe, the maximum improvements of RC reach 32% and 153%, in comparison with that of individual compound Dy2Cu2Cd and Tm2Cu2Cd. The excellent MCE properties suggest the RE2Cu2Cd (RE = Dy and Tm) and its composite materials could be expected to have effective applications for low temperature magnetic refrigeration.

  10. Hydrostatic pressure effect on magnetic phase transition and magnetocaloric effect of metamagnetic TmZn compound

    Science.gov (United States)

    Li, Lingwei; Hu, Guanghui; Qi, Yang; Umehara, Izuru

    2017-02-01

    The magnetocaloric effect (MCE) is an intrinsic thermal response of all magnetic solids which has a direct and strong correlation with the corresponding magnetic phase transition. It has been well recognized that the magnetic phase transition can be tuned by adjusting applied pressure. Therefore, we perform the high hydrostatic pressure magnetization measurements (up to 1.4 GPa) on a recently reported giant MCE material of TmZn. The results indicate that the Curie temperature of TC increases from 8.4 K at the ambient pressure to 11.5 K under the pressure of 1.4 GPa. The field-induced first order metamagnetic transition is getting weak with increasing pressure, which results in a reduction of MCE. The hydrostatic pressure effect on the magnetic phase transition and MCE in the metamagnetic TmZn is discussed.

  11. Large magnetocaloric effect of HoxEr1-xNi (0 ≤ x ≤ 1) compounds

    Science.gov (United States)

    Zheng, X. Q.; Zhang, B.; Wu, H.; Hu, F. X.; Huang, Q. Z.; Shen, B. G.

    2016-10-01

    A secondary magnetic transition (spin reorientation transition) below Curie temperature in ErNi was observed via different characterization techniques. Ho-substitution for Er atoms has a great impact on the magnetic property and magnetocaloric effect. The two magnetic transitions change close to each other with 10% of Ho-substitution at the Er site. It is also found that 10% of Ho-substitution contributes up to ˜14.9% of enhancement on the maximal magnetic entropy change (ΔSM) and ˜21.9% of enhancement on the maximal adiabatic temperature change (ΔTad). The maximum value of ΔSM and ΔTad for Ho0.1Er0.9Ni compound is as high as 34 J/kg K and 8.9 K, respectively, under a field change of 0-5 T. The relationship between the maximal ΔSM and the refrigerant temperature width (δTFWHM) for HoxEr1-xNi (0 ≤ x ≤ 1) compounds is analyzed. The enhancement of MCE for Ho0.1Er0.9Ni compound is considered to be resulted from the tendency of merging of spin reorientation transition and ferromagnetic to paramagnetic transition.

  12. Magnetocaloric pump

    Science.gov (United States)

    Brown, G. V.

    1973-01-01

    Very cold liquids and gases such as helium, neon, and nitrogen can be pumped by using magnetocaloric effect. Adiabatic magnetization and demagnetization are used to alternately heat and cool slug of pumped fluid contained in closed chamber.

  13. Large magnetocaloric effect and near-zero thermal hysteresis in the rare earth intermetallic Tb1-x Dy x Co2 compounds

    Science.gov (United States)

    Zeng, Yuyang; Tian, Fanghua; Chang, Tieyan; Chen, Kaiyun; Yang, Sen; Cao, Kaiyan; Zhou, Chao; Song, Xiaoping

    2017-02-01

    We report the magnetocaloric effect in a Tb1-x Dy x Co2 compound which exhibits a wide working temperature window around the Curie temperature (T C) and delivers a large refrigerant capacity (RC) with near-zero thermal hysteresis. Specifically, the wide full width at half maxima ({δ\\text{WFHM}} ) can reach up to 62 K and the RC value changes from 216.5 to 274.3 J Kg-1 when the external magnetic field increases to 5 T. Such magnetocaloric effects are attributed to a magnetic and structural transition from a paramagnetic and cubic phase to a ferromagnetic (M S along [1 1 1] direction) and rhombohedral phase or ferromagnetic (M S along [0 0 1] direction) and tetragonal phase.

  14. Phase Transitions and Magnetocaloric Properties in MnCo1−xZrxGe Compounds

    Directory of Open Access Journals (Sweden)

    Anil Aryal

    2017-01-01

    Full Text Available The structural, magnetic, and magnetocaloric properties of MnCo1-xZrxGe (0.01≤x≤0.04 have been studied through X-ray diffraction, differential scanning calorimetry, and magnetization measurements. Results indicate that the partial substitution of Zr for Co in MnCo1-xZrxGe decreases the martensitic transition temperature (TM. For x = 0.02, TM was found to coincide with the ferromagnetic transition temperature (TC resulting in a first-order magnetostructural transition (MST. A further increase in zirconium concentration (x = 0.04 showed a single transition at TC. The MST from the paramagnetic to ferromagnetic state results in magnetic entropy changes (-ΔSM of 7.2 J/kgK for ΔH = 5 T at 274 K for x = 0.02. The corresponding value of the relative cooling power (RCP was found to be 266 J/kg for ΔH = 5 T. The observed large value of MCE and RCP makes this system a promising material for magnetic cooling applications.

  15. Characterization of magnetocaloric effect, magnetic ordering and electronic structure in the GdFe{sub 1−x}Co{sub x}Si intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Wlodarczyk, P., E-mail: patrykw@imn.gliwice.pl [Institute of Non-Ferrous Metals, ul. Sowinskiego 5, 44-100 Gliwice (Poland); Hawelek, L. [Institute of Non-Ferrous Metals, ul. Sowinskiego 5, 44-100 Gliwice (Poland); University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40-008 Katowice (Poland); Zackiewicz, P. [Institute of Non-Ferrous Metals, ul. Sowinskiego 5, 44-100 Gliwice (Poland); Rebeda Roy, T. [SRM Research Institute, SRM University, Chennai 603203 (India); Chrobak, A. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40-008 Katowice (Poland); Kaminska, M.; Kolano-Burian, A. [Institute of Non-Ferrous Metals, ul. Sowinskiego 5, 44-100 Gliwice (Poland); Szade, J. [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40-008 Katowice (Poland)

    2015-07-15

    GdFeSi silicide is a strong ferromagnet with Curie temperature (T{sub c}) equal to 118 K. The substitution of cobalt for iron continuously suppresses ferromagnetism of the former compound, while it changes magnetic transition temperature nonlinearly. When the molar amount of cobalt reaches 0.4, the temperature of magnetic transition reaches minimal value i.e, 70 K. For larger amount of cobalt, magnetic transformation temperature rises well above 200 K and the antiferromagnetic interactions become dominant. In the present work we have found that the magnetic transformation temperature can be strictly correlated with the lattice constant c, which determines the distance between gadolinium layers as well as distance between neighboring gadolinium atoms in one layer. These results correspond to the change of amplitude of magnetocaloric effect which is being suppressed when the amount of cobalt increases. Adiabatic temperature change is equal to 2 K during the magnetic field cycle 0–1.7 T for pure GdFeSi, while no temperature change is observed during the same cycle for pure GdCoSi because of its antiferromagnetic character. - Highlights: • We have studied magnetocaloric properties of GdFe{sub x}Co{sub 1−x}Si intermetallic compounds. • It was found that when x is changing from 1 to 0, initially ferromagnetic compound becomes antiferromagnetic. • The highest magnetocaloric effect was found in pure GdFeSi (ΔT = 2 K at B = 1.7 T at T = 135 K)

  16. Conventional and inverse magnetocaloric effect in Pr{sub 2}CuSi{sub 3} and Gd{sub 2}CuSi{sub 3} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fang, E-mail: jfzw2001@163.com [Ning Bo University of Technology, Ning Bo, Zhe Jiang 315211 (China); Yuan, Feng-ying [Tian Jin University of Science and Technology, Tian Jin 300222,China (China); Wang, Jin-zhi; Feng, Tang-fu; Hu, Guo-qi [Ning Bo University of Technology, Ning Bo, Zhe Jiang 315211 (China)

    2014-04-01

    Highlights: • Two phase transitions in a narrow temperature range were observed and studied. • Both typical and inverse magnetocaloric effect were observed and discussed. • The inverse magnetocaloric effect was attributed to the spin-glass behavior. - Abstract: Magnetic properties and magnetocaloric effect (MCE) in Pr{sub 2}CuSi{sub 3} and Gd{sub 2}CuSi{sub 3} compounds were investigated systematically. Both Pr{sub 2}CuSi{sub 3} and Gd{sub 2}CuSi{sub 3} compounds experienced two phase transitions in a relatively narrow temperature range: first a paramagnet (PM)–ferromagnet (FM) second-order phase transition at 12 and 26 K and then a FM–spin glass (SG) transition at 6 K and 7.5 K, respectively. The magnetic entropy change (ΔS{sub M}) was calculated based on Maxwell relation using the collected magnetization data. The maximum of ΔS{sub M} for Pr{sub 2}CuSi{sub 3} and Gd{sub 2}CuSi{sub 3} compounds was 7.6 and 5 J kg{sup −1} K{sup −1}, respectively, at the applied filed change of 0–5 T. The shape of the temperature dependence of ΔS{sub M} (ΔS{sub M}–T) curve was obviously different from that of the conventional magnetic materials undergoing only one typical phase transition. In the left half part of ΔS{sub M}–T curve, ΔS{sub M} is not very sensitive to the applied field and they tend to intersect with the decrease of temperature. Both typical conventional and inverse MCE behavior were observed in Gd{sub 2}CuSi{sub 3}, which would be originated from the two transition features at the low temperatures.

  17. Tunable magnetocaloric effect around room temperature by Fe doping in Mn0.98Cr (0.02 - x)Fex As compound

    Science.gov (United States)

    Ipus, Jhon J.; Ribeiro, Paula O.; von Ranke, P.; Caraballo Vivas, R. J.; Carvalho, Alexandre M. G.; Coelho, Adelino A.; Franco, Victorino; Rocco, Daniel L.

    2017-08-01

    In this work, we present an investigation of the magnetic and magnetocaloric properties of Mn0.98Cr (0.02 - x)Fex As compounds with x = 0.002, 0.005 and 0.010. Our findings show that as Fe content increases the unit cell volume decreases, which indicates that Fe doping emulates the pressure effect on the crystalline structure. The transition temperature TC decreases as x increases and it can be set at approximate value of room temperature by changing the doping level. In addition, the magnetic entropy change ΔSM was determined using a discontinuous measurement protocol, and realistic values from the magnetocaloric effect presented by MnAs-type compounds under pressure (emulated pressure) could be obtained. The values of Δ SMMAX are very large, around -11 Jkg-1K-1 with ΔH = 15 kOe, which is higher than that observed for most compounds with TC around room temperature. However, ΔSM is confined to a narrow temperature range of 11 K. To overcome this drawback, the composition of a theoretical composite formed by our samples was calculated in order to obtain a table-shaped ΔSM curve. The simulated composite showed a high value of full width at half maximum δTFWHM of 33 K, which is much higher than that of single sample.

  18. Comparative analysis of magnetic and caloric determinations of the magnetocaloric effect in Mn0.99Co0.01As

    Directory of Open Access Journals (Sweden)

    Wang Gaofeng

    2014-07-01

    Full Text Available The results from direct and indirect determinations of the magnetocaloric parameters of Mn0.99Co0.01As have been analyzed. The isothermal entropy change (ΔST due to external magnetic field changes has been determined through direct measurements of the heat absorbed by the sample when the field is removed under isothermal conditions. It has also been calculated from isothermal magnetization and isofield heat capacity measurements. In addition to that, the adiabatic temperature change (ΔTS has been obtained from direct measurements and from isofield heat capacity measurements. The different results of both ΔST and ΔTS are compared. Due to the presence of a first-order phase transition, the studied sample exhibits giant magnetocaloric effect at room temperature. The observed maximum values, −ΔST,max = 32.1 J/kg·K and ΔTS,max = 17.7 K for a field change from 0 to 6 T, suggest that the Co-doped MnAs compounds are promising candidates for the preparation of useful materials for magnetic refrigeration near room temperature.

  19. Spin correlations in (Mn,Fe2(P,Si magnetocaloric compounds above Curie temperature

    Directory of Open Access Journals (Sweden)

    X.F. Miao

    2016-06-01

    Full Text Available The longitudinal-field muon-spin relaxation (LF-μSR technique was employed to study the spin correlations in (Mn,Fe2(P,Si compounds above the ferromagnetic transition temperature (TC. The (Mn,Fe2(P,Si compound under study is found to show itinerant magnetism. The standard deviation of the magnetic field distribution of electronic origin increases with a decrease in temperature, which is attributed to the development of spin correlations. The anomalously low magnetic fluctuation rate is suggested to be another signature of the spin correlations. The development of pronounced magnetic fluctuations is in agreement with the observed deviation of the paramagnetic susceptibility from Curie–Weiss behavior. Our study sheds light on the magneto-elastic transition and the mixed magnetism in (Mn,Fe2(P,Si compounds.

  20. Magnetic and magnetocaloric properties of Gd2In0.8X0.2 compounds (X=Al, Ga, Sn, Pb)

    Science.gov (United States)

    Tencé, Sophie; Chevalier, Bernard

    2016-02-01

    We show that it is possible to replace in Gd2In some amount of In by X=Al, Ga, Sn and Pb to obtain Gd2In1-xXx samples after melting. The magnetic and magnetocaloric properties of the Gd2In0.8X0.2 intermetallic compounds have been investigated through dc magnetization measurements. We evidence that the substitution of Al and Ga for In barely changes the Curie temperature TC but decreases the second magnetic transition temperature T‧ which corresponds to the transition from a ferromagnetic to an antiferromagnetic state. On the other hand, the substitution of Sn and Pb for In strongly increases TC and changes the nature or even suppresses the transition at lower temperature. This magnetic behavior gives rise to an interesting way to tune the Curie temperature near room temperature without diluting the Gd network and thus to modify the magnetocaloric effect in Gd2In1-xXx compounds.

  1. Magnetocaloric properties of the Gd_5Si_(2.05-x)Ge_(1.95-x)Mn_(2x) compounds

    Institute of Scientific and Technical Information of China (English)

    E.Yüzüak; I.Dincer; Y.Elerman

    2010-01-01

    The influence of the manganese-alloying on the structure and magnetocaloric properties of the Gd5Si2.05Ge1.95 compound was studied by X-ray powder diffraction and magnetization measurements.The Gd5Si2.05-xGe1.95-xMn2x(2x=0,0.03 and 0.08) compounds crystallized in the Gd5Si2Ge2-type monoclinic structure.In all X-ray powder diffraction patterns,a minor hexagonal Gd5Si3 phase was observed as a second phase.With increasing Mn content,the unit cell volume increased.For the compounds with x=0,0.03 and 0.08,the fi...

  2. Magnetocaloric Properties of (Gd1-xTbx)3Al2 Compounds Near Room Temperature

    Institute of Scientific and Technical Information of China (English)

    龙毅; 陈艳平; 万发荣

    2003-01-01

    Magnetic and thermal properties of the (Gd1-xTbx)3Al2 compounds were studied as potential magnetic refrigerant materials which are used in magnetic refrigeration near room temperature at low magnetic field. The compounds (Gd1-xTbx)3Al2 with x=0, 0.1, 0.2 and 0.3 exhibit a second-order magnetic transition. Curie temperature varies from 255 K for x=0.3 to 280 K for x=0. The maximum of the isothermal magnetic entropy change ΔS increases by substituting Tb element for Gd element. ΔSmax=18.9 kJ*m-3*K-1 for x=0.1 by changing the magnetic field from 0 to 1 T.

  3. Magnetic and magnetocaloric properties of the first-order phase transition in Sm0.5+ x Sr0.5- x MnO3 compounds

    Science.gov (United States)

    Thanh, Tran Dang; Linh, Dinh Chi; Manh, Tien Van; Nan, Wen-Zhe; Yu, Seong-Cho; Piao, Hong-Guang; Pan, Liqing

    2016-08-01

    In this work, we present a detailed study on the magnetic and the magnetocaloric properties of Sm0.5+ x Sr0.5- x MnO3 compounds with x = 0 - 0.1, which were prepared by using a solid-state reaction method. The x-dependent magnetic, as well as magnetocaloric, properties, including the magnetic phase transition, have been studied. The increase in Sm/Sr ratio plays an important role in controlling the Curie temperature ( T C ). We point out that all the samples undergo a first-order phase transition and exhibit a giant magnetocaloric effect. The magnetic entropy change (Δ S m ) of samples was calculated based on isothermal M( H, T) data. The maximum value of Δ S m (denoted as |Δ S max|) at around T C is found to be 2.6 - 8.9 J·kg -1·K -1 for Δ H = 30 kOe and depends on the value of x. We have also used the universal master curve method for the temperature dependences of Δ S m curves measured at different Δ H values, Δ S m ( T,Δ H), to distinguish the magnetic order in the samples. Interestingly, none of the Δ S m ( T,Δ H) curves for the samples follow the universal master curve, Δ S m ( T,Δ H)/Δ S max versus θ = ( T -T C )/( T r - T C ). As a consequence, a breakdown in the universal behavior of Δ S m ( T,Δ H)/Δ S max versus θ curve is another feature confirming a first-order phase-transition nature.

  4. Effect of rapid quenching on the magnetism and magnetocaloric effect of equiatomic rare earth intermetallic compounds RNi (R = Gd, Tb and Ho)

    Science.gov (United States)

    Rajivgandhi, R.; Arout Chelvane, J.; Quezado, S.; Malik, S. K.; Nirmala, R.

    2017-07-01

    Magnetocaloric effect (MCE) in RNi (where R = Gd, Tb and Ho) compounds has been studied in their arc-melted and melt-spun forms. The compound GdNi has the orthorhombic CrB-type structure (Space group Cmcm, No. 63) and the compound HoNi has the orthorhombic FeB-type structure (Space group Pnma, No. 62) at room temperature regardless of their synthesis condition. However, arc-melted TbNi orders in a monoclinic structure (Space group P21/m, No. 11) and when it is rapidly quenched to a melt-spun form, it crystallizes in an orthorhombic structure (Space group Pnma, No. 62). The arc-melted GdNi, TbNi and HoNi compounds order ferromagnetically at ∼69 K, ∼67 K and ∼36 K (TC) respectively. While the melt-spun GdNi shows about 6 K increase in TC, the ordering temperature of TbNi remains nearly the same in both arc-melted and melt-spun forms. In contrast, a reduction in TC by about 8 K is observed in melt-spun HoNi, when compared to its arc-melted counterpart. Isothermal magnetic entropy change, ∆Sm, calculated from the field dependent magnetization data indicates an enhanced relative cooling power (RCP) for melt-spun GdNi for field changes of 20 kOe and 50 kOe. A lowered RCP value is observed in melt-spun TbNi and HoNi. These changes could have resulted from the competing shape anisotropy and the granular microstructure induced by the melt-spinning process. Tailoring the MCE of rare earth intermetallic compounds by suitably controlled synthesis techniques is certainly one of the directions to go forward in the search of giant magnetocaloric materials.

  5. Magnetocaloric materials

    Energy Technology Data Exchange (ETDEWEB)

    Jeppesen, Stinus

    2008-10-15

    New and improved magnetocaloric materials are one of the cornerstones in the development of room temperature magnetic refrigeration. Magnetic refrigeration has been used since the 1930ies in cryogenic applications, but has since the discovery of room temperature refrigerants received enormous attention. This Ph.D. work has been mainly concerned with developing a new technique to characterize the magnetocaloric effect (MCE) and using this technique in the investigations on new and improved magnetocaloric materials. For this purpose a novel differential scanning calorimeter (DSC) with applied magnetic fields was developed for measuring heat capacity as function of magnetic field. Measurements using the developed DSC demonstrate a very high sensitivity, fast measurements and good agreement with results obtained by other techniques. Furthermore, two material systems have been described in this work. Both systems take basis in the mixed-valence manganite system La{sub 1-x}Ca{sub x}MnO{sub 3} well known from research on colossal magnetoresistance (CMR). The mixed-valence manganite crystallizes in the perovskite structure of general formula ABO{sub 3}. The first material system is designed to investigate the influence of low level Cu doping on the B-site. Six different samples were prepared with over-stoichiometric compositions La{sub 0.67}Ca{sub 0.33}Mn{sub 1.05}Cu{sub x}O{sub 3}, x=0, 1, 2, 3, 4 and 5%. All compositions crystallized well in the same perovskite structure, but the morphology of the samples changed drastically with doping. Investigation on the magnetocaloric properties revealed that small levels of Cu up to around 3% could improve the magnetocaloric performance of the materials. Furthermore, Cu could be used to tune the temperature interval without deteriorating the MCE, which is a much desired characteristic for potential use in magnetic refrigerators. A less comprehensive part of the work has been concerned with the investigation of doping on the A

  6. Magnetotransport properties and magnetocaloric effects of Mn1.95Cr0.05Sb0.95Ga0.05 Compound

    Institute of Scientific and Technical Information of China (English)

    Liu Xi-Bin; Zhang Shao-Ying; Shen Bao-Gen; Yao Jin-Lei; Wang Fang

    2004-01-01

    The magnetotransport properties and magnetocaloric effects of the compound Mn1.95Cr0.05Sb0.95Ga0.05 have been studied. With decreasing temperature, a spontaneous first-order magnetic phase transition from ferrimagnetic (FI) to antiferromagnetic (AF) state takes place at Ts=200K. A metamagnetic transition from the AF to FI state can be induced by an external field, accompanied by a giant magnetoresistance effect of 57%. The magnetic entropy changes are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation. Mn1.95Cr0.05Sb0.95Ga0.05 exhibits a negative magnetocaloric effect, and the absolute values of △Smax M (T, △H) are 4.4, 4.1, 3.6, 2.8 and 1.5 J/(kg.K) for magnetic field changes of 0-5T, 0-4T, 0-3T, 0-2T and 0-1T,respectively.

  7. Effect of microstructure and texture on the magnetic and magnetocaloric properties of the melt-spun rare earth intermetallic compound DyNi

    Science.gov (United States)

    Rajivgandhi, R.; Chelvane, J. Arout; Nigam, A. K.; Park, Je-Geun; Malik, S. K.; Nirmala, R.

    2016-11-01

    Magnetization measurements have been carried out on the melt-spun ribbon sample of the rare earth intermetallic compound DyNi (Orthorhombic, FeB-type, Space group Pnma) and its magnetic and magnetocaloric properties are compared with those of the arc-melted analog. The arc-melted DyNi orders ferromagnetically at around 61 K (TC) whereas the melt-spun DyNi orders ferromagnetically at about 47 K. The maximum isothermal magnetic entropy change, ∆Smmax , near TC of the arc-melted and the melt-spun DyNi is found to be -32.7 J/kg K and -22.4 J/kg K, respectively, for a field change of 140 kOe. For low magnetic field changes of ~20 kOe, the relative cooling power (RCP) is ~660 J/kg for the arc melted DyNi and ~460 J/kg for the melt-spun ribbon. The reduction in TC and magnetocaloric effect may be attributed to the microstructure-induced anisotropy developed during the melt-spinning process.

  8. Characterization and theoretical investigation of the magnetocaloric effect of La0.67Ba0.33Mn1-xSbxO3 compounds

    Science.gov (United States)

    Hassine, A. Ben; Dhahri, A.; Bouazizi, L.; Oumezzine, M.; Hlil, E. K.

    2016-05-01

    In this study, the structural, magnetic and magnetocaloric properties of the polycrystalline La0.67Ba0.33Mn1-xSbxO3 (x=0.01, x=0.03 and x=0.07) were consistently investigated. X-ray analysis revealed that the substitution of Mn by Sb produced no considerable structural change just the diffraction peaks of rhombohedric symmetry were obtained all the samples. The variation of the magnetization M versus temperature T, under an applied magnetic field of 1.5 T, shows a ferromagnetic-paramagnetic transition. The experimental results exhibit that with the increase of Sb substitution TC decreases from 326 K to 296 K. The prediction of magnetic entropy change, relative cooling power and specific heat for magnetic field variation were predicted with the help of a phenomenological model. A large magneto-caloric effect has been observed, the maximum of magnetic entropy change, | Δ S mmax|, reaches the highest value of 2.74 J kg-1 K-1 under a magnetic field of 1.5 T with an RCP value of 132.8 J kg-1 for La0.67Ba0.33Mn1-xSbxO3 (x=0.07) composition , which will be an interesting compound for application materials working as magnetic refrigerants near room temperature.

  9. Influence of bismuth on magnetism and magnetocaloric properties of LaFe11.6Si1.4 intermetallic compound

    Institute of Scientific and Technical Information of China (English)

    A Boutahar; K Zehani; L Bessais; H Lassri; EK Hlil

    2015-01-01

    Crystal structure, magnetic properties and magnetocaloric effects (MCE) of La1–xBixFe11.4Si1.6(x=0.0 and 0.1) compounds were investigated by X-ray diffraction and magnetization measurements. The La1–xBixFe11.4Si1.6compounds presented a cubic NaZn13 type structure. First, the magnetization behavior and the magnetic transition were analyzed in terms of Landau theory. Then, Bi sub-stitution for La in La1–xBixFe11.4Si1.6compounds led to a decrease in magnetic entropy change (maxM−ΔS) but an increase in Curie tem-perature (TC) significantly. The significant increase ofTC by Bi substitution from 202.5 to 256 K forx=0.0 andx=0.1 respectively was attributed to an increase in the Fe-Fe exchange interactions. Moreover, magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. The maximum values of (maxM−ΔS) of La1–xBixFe11.4Si1.6forx=0.0 and 0.1 compounds were found to be, re-spectively, 22.56 and 4.36 J/(kg·K) under an applied magnetic field change of 5 T. For the same applied magnetic field (µ0H=5 T), the relative cooling power (RCP) values were found to vary between 487 and 296 J/kg.

  10. Enhanced magnetocaloric effect material

    Science.gov (United States)

    Lewis, Laura J. H.

    2006-07-18

    A magnetocaloric effect heterostructure having a core layer of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, and a constricting material layer coated on at least one surface of the magnetocaloric material core layer. The constricting material layer may enhance the magnetocaloric effect by restriction of volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect heterostructure powder comprising a plurality of core particles of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, wherein each of the core particles is encapsulated within a coating of a constricting material is also disclosed. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with a constricting material is disclosed.

  11. Magnetocaloric effect and critical behaviour in Mn2-pyridazine-[Nb(CN)8] molecular compound under press.

    Science.gov (United States)

    Fitta, Magdalena; Bałanda, Maria; Pełka, Robert; Konieczny, Piotr; Pinkowicz, Dawid; Sieklucka, Barbara

    2013-12-11

    A comprehensive study of magnetocaloric effect (MCE) and critical behaviour in the ferrimagnetic Mn2–pyridazine–[Nb(CN)8] molecular magnet under hydrostatic pressure is reported. The pressure-induced structural changes provoke the strengthening of magnetic interaction between Mn and Nb centres. Consequently, an increase of critical temperature Tc is observed from 43 K for a sample at ambient pressure (A) to 52.5 K for a sample under a pressure of 1.19 GPa (AHP). The magnetocaloric effect was determined by the magnetization measurements. The application of a hydrostatic pressure of 1.19 GPa causes a decrease in the maximum value of magnetic entropy change ΔS, which for AHP is equal to 4.63 J mol−1 K−1 (7.73 J kg−1 K−1) at μ0ΔH = 5 T, while for A it is 5.36 J mol−1 K−1 (8.95 J kg−1 K−1) for the same magnetic field change. The temperature-dependent parameter n obtained for AHP, describing the field dependence of MCE, is consistent with other critical exponents determined from magnetization measurements. The critical exponents allow us to classify AHP to the 3D Heisenberg universality class, similar to the case of the non-pressurized sample.

  12. Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe2 (P,Ge intermetallic compounds

    Directory of Open Access Journals (Sweden)

    Wlodarczyk P.

    2016-09-01

    Full Text Available The magnetocaloric effect in the MnxFe2−xP1−yGey intermetallic compounds with the amount of Mn in the range of x = 1.05 to 1.17 and amount of Ge in the range of y = 0.19 to 0.22 has been studied. It was found that a higher Ge/P ratio causes an increase in Curie temperature, magnetocaloric effect at low field (up to 1 T, activation energy of structural transition and a decrease in thermal hysteresis, as well as transition enthalpy. Contrary to this observation, higher Mn/Fe ratio causes a decrease in Curie temperature, slight decrease of magnetocaloric effect at low magnetic field, and an increase in thermal hysteresis. Simultaneous increase of both ratios may be very advantageous, as the thermal hysteresis can be lowered and magnetocaloric effect can be enhanced without changing the Curie temperature. Some hints about optimization of the composition for applications at low magnetic fields (0.5 T to 2 T have been presented.

  13. Magnetic properties and magnetocaloric effect of Gd(Ni{sub 1-x}Fe{sub x}){sub 3} crystalline compound and powder

    Energy Technology Data Exchange (ETDEWEB)

    Bajorek, Anna; Chelkowska, Grazyna; Kwiecien, Marzena [August Chelkowski Institute of Physics, University of Silesia, Katowice (Poland); Haneczok, Grzegorz [Institute of Materials Science, University of Silesia, Katowice (Poland); Chrobak, Artur

    2009-04-15

    In the paper we present and discuss magnetic properties of the Gd(Ni{sub 1-x}Fe{sub x}){sub 3} crystalline compounds and their ball-milled powders in a context of the magnetocaloric effect (MCE). Moreover, based on the obtained results, powders and composites with non-magnetic (Cu) and magnetic (Fe) additions were prepared. Magnetic quantities such as the Curie temperature, the saturation magnetization and the MCE (as a magnetic entropy change) were determined for all examined samples. In the case of the bulk crystalline compounds a partial substitution of Ni by Fe atoms causes a decrease of the saturation magnetization as well as the MCE and an increase of the Curie temperature. Samples with x ranging from 0.1 to 0.15 show the best potential for room-temperature refrigeration. Pulverization of the tested compounds leads to formation of flake-like grains with thickness less than 1{mu}m. Such grinding causes a decrease of the Curie temperature (by about 10 K) as well as the MCE (by about 50%) in a comparison with the crystalline samples. In the case of the composite with magnetic addition an enhancement of the MCE was observed. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Neutron Diffraction Investigation of MnAs under High Pressure

    DEFF Research Database (Denmark)

    Andresen, A.F; Fjellvag, H; Lebech, Bente

    1984-01-01

    Powdered MnAs has been investigated by neutron diffraction in a pressure cryostat, at hydrostatic pressures up to 13 kbar and temperatures down to 4.2 K. It has been found that in the orthorhombic MnP type structure, which under pressure is retained at low temperature, a spiral magnetic structure...

  15. Feasibility Analysis of Establishing Multilateral Nuclear Approaches (MNAs in the Asian Region and the Middle East

    Directory of Open Access Journals (Sweden)

    Makiko Tazaki

    2014-12-01

    Full Text Available To establish frameworks for multilateral nuclear approaches (MNAs, we identified challenges and their possible solutions through case studies proposing to establish three different MNAs, comprising existing states in the Asian region and the Middle East, in accordance with twelve features deemed necessary for establishing MNAs. In all case studies, political instability of MNA member states and the region, as well as political conflicts between MNA member states and other states were seen as challenges hindering the establishment of MNAs. There are no simple measures to overcome such challenges, but additional case-by-case measures, including the direct involvement of international organizations, supplier states and nuclear weapon states, in MNAs, as well as the application of regional safeguards and regional systems of accounting for and control of nuclear material (RSAC within MNAs, may contribute toward mitigating the political challenges.

  16. Large low field magnetocaloric effect in first-order phase transition compound TlFe3Te3 with low-level hysteresis

    Science.gov (United States)

    Mao, Qianhui; Yang, Jinhu; Wang, Hangdong; Khan, Rajwali; Du, Jianhua; Zhou, Yuxing; Xu, Binjie; Chen, Qin; Fang, Minghu

    2016-01-01

    Magnetic refrigeration based on the magnetocaloric effect (MCE) is an environment-friendly, high-efficiency technology. It has been believed that a large MCE can be realized in the materials with a first-order magnetic transition (FOMT). Here, we found that TlFe3Te3 is a ferromagnetic metal with a first-order magnetic transition occurring at Curie temperature TC = 220 K. The maximum values of magnetic entropy change (Δ) along the crystallographic c-axis, estimated from the magnetization data, reach to 5.9 J kg−1K−1 and 7.0 J kg−1 K−1 for the magnetic field changes, ΔH = 0–1 T and 0–2 T, respectively, which is significantly larger than that of MCE materials with a second-order magnetic transition (SOMT). Besides the large ΔSM, the low-level both thermal and field hysteresis make TlFe3Te3 compound an attractive candidate for magnetic refrigeration. Our findings should inspire the exploration of high performance new MCE materials. PMID:27681203

  17. Effect of Al Substitution on Structural, Magnetic, and Magnetocaloric Properties of Er6Fe23−xAlx (x = 0 and 3 Intermetallic Compounds

    Directory of Open Access Journals (Sweden)

    M. Jemmali

    2017-05-01

    Full Text Available The structural, magnetic, and magnetocaloric properties of Er6Fe23−xAlx (x = 0 and 3 intermetallic compounds have been studied systematically. Samples were prepared using the arc furnace by annealing at 1073 K for one week. Rietveld analysis of XRD shows the formation of pure crystalline phase with cubic Fm-3m structure. Refinement results show that the unit cell volume decreases with increasing Al content. The Curie temperature Tc of the prepared samples was found to be strongly dependent on the aluminum content. This reduces magnetization and the ferrimagnetic phase transition temperature (Tc from 481 K (for x = 0 to 380 K (for x = 3, is due to the substitution of magnetic element (Fe by non-magnetic atoms (Al. With the increase of the Al content, a decrease in the values of magnetic entropy is observed. The magnitude of the isothermal magnetic entropy (|∆SM| at the Tc decreases from 1.8 J/kg·K for x = 0 to 0.58 J/kg·K for x = 3 for a field change 14 kOe. Respectively, the relative cooling power (RCP decreases with increasing Al content reaching 42 Jkg−1 for x = 0 to 28 Jkg−1 for x = 3.

  18. Large low field magnetocaloric effect in first-order phase transition compound TlFe3Te3 with low-level hysteresis

    Science.gov (United States)

    Mao, Qianhui; Yang, Jinhu; Wang, Hangdong; Khan, Rajwali; Du, Jianhua; Zhou, Yuxing; Xu, Binjie; Chen, Qin; Fang, Minghu

    2016-09-01

    Magnetic refrigeration based on the magnetocaloric effect (MCE) is an environment-friendly, high-efficiency technology. It has been believed that a large MCE can be realized in the materials with a first-order magnetic transition (FOMT). Here, we found that TlFe3Te3 is a ferromagnetic metal with a first-order magnetic transition occurring at Curie temperature TC = 220 K. The maximum values of magnetic entropy change (Δ) along the crystallographic c-axis, estimated from the magnetization data, reach to 5.9 J kg‑1K‑1 and 7.0 J kg‑1 K‑1 for the magnetic field changes, ΔH = 0–1 T and 0–2 T, respectively, which is significantly larger than that of MCE materials with a second-order magnetic transition (SOMT). Besides the large ΔSM, the low-level both thermal and field hysteresis make TlFe3Te3 compound an attractive candidate for magnetic refrigeration. Our findings should inspire the exploration of high performance new MCE materials.

  19. Theoretical investigation of the magnetocaloric effect on La0.7(Ba, Sr)0.3Mn0.9Ga0.1O3 compound at room temperature

    Science.gov (United States)

    Tlili, R.; Hammouda, R.; Bejar, M.; Dhahri, E.

    2015-07-01

    Based on a phenomenological model, the magnetic and magnetocaloric properties of La0.7(Ba, Sr)0.3Mn0.9Ga0.1O3 oxide have been studied. Indeed, the magnetic measurements have demonstrated that the sample exhibits a ferromagnetic-paramagnetic transition at room temperature. The value of the magnetocaloric effect such as magnetic entropy change, full width at half-maximum, relative cooling power and magnetic specific heat change has been determined from the calculation of magnetization as a function of temperature under different external magnetic fields. The maximum magnetic entropy change (- ΔSMmax) and the relative cooling power (RCP) are, respectively, 0.57 J kg-1 K-1 and 28.68 J kg-1 for a 10 kOe field change at 300 K, which are the characteristics of a good magnetocaloric material. Hence, the La0.7(Ba, Sr)0.3Mn0.9Ga0.1O3 compound can be considered as a promising material in magnetic refrigeration technology. According to the master curve behavior for the temperature dependence of ΔSM predicted for different maximum fields, this work has confirmed that the paramagnetic-ferromagnetic phase transition observed for our sample is of a second order.

  20. Thermopower and electrical resistivity behavior near the martensitic transition in Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} magnetocaloric compounds

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, R.P. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Sousa, J.B. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal)]. E-mail: jbsousa@fc.up.pt; Correia, F.C. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Araujo, J.P. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Braga, M.E. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Pereira, A.M. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Morellon, L. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain); Algarabel, P.A. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain); Magen, C. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain); Ibarra, M.R. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain)

    2005-04-15

    Recently, the Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} system exhibits fascinating physical properties, namely giant magnetocaloric, magnetoresistance and magnetostriction effects near a first-order (martensitic like; T=T{sub S}) magneto-structural transition. We report the thermopower behavior S(T) between 10 and 300K for compounds with x=0, 0.10 and 0.45, belonging to three distinct regions of the magnetic/structural phase diagram. Large thermopower changes are observed near T{sub S} for x=0.10 (T{sub S}=78K; AFM-Orthorhombic II/FM-Ortho.I) and for x=0.45 (T{sub S}=242K; PM-Monoc/FM-Ortho.I) with a Gaussian distribution in dS/dT, characteristic of a first-order phase transition. Near the purely magnetic transitions (PM/AFM) for x=0(T{sub N}=122K) and x=0.10(T{sub N}=127K) we observe dS/dT peaks governed by spin fluctuation effects. A comparative analysis between dS/dT and the resistivity derivative d{rho}/dT near T{sub S} is made. At low temperatures S(T) behaves similarly in the ferromagnetic x=0.10 and 0.45 compounds (S{approx}AT+BT{sup 2}), the anomalous B term being related to the mean internal field (spin wave excitations). For x=0 (AFM phase at low T) one has S=AT (no B term; zero mean internal field)

  1. Effect of Si/Ge ratio on resistivity and thermopower in Gd{sub 5}Si{sub x}Ge{sub 4-x} magnetocaloric compounds

    Energy Technology Data Exchange (ETDEWEB)

    Raj Kumar, D.M. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Manivel Raja, M., E-mail: mraja@dmrl.drdo.i [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Prabahar, K.; Chandrasekaran, V. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Poddar, Asok; Ranganathan, R. [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Suresh, K.G. [Indian Institute of Technology Bombay, Mumbai 400076 (India)

    2011-07-15

    The effect of Si/Ge ratio on resistivity and thermopower behavior has been investigated in the magnetocaloric ferromagnetic Gd{sub 5}Si{sub x}Ge{sub 4-x} compounds with x=1.7-2.3. Microstructural studies reveal the presence of Gd{sub 5}(Si,Ge){sub 4}-matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The x=1.7 and 2.0 samples display the presence of a first order structural transition from orthorhombic to monoclinic phase followed by a magnetic transition of the monoclinic phase. The alloys with x=2.2 and 2.3 display only magnetic transitions of the orthorhombic phase. A low temperature feature apparent in the AC susceptibility and resistivity data below 100 K reflects an antiferromagnetic transition of secondary phase(s) present in these compounds. The resistivity behavior study correlates with microstructural studies. A large change in thermopower of -8 {mu}V/K was obtained at the magneto-structural transition for the x=2 compound. - Research highlights: Effect of Si/Ge ratio on microstructure, magneto-structural transitions, resistivity ({rho}) and thermopower S(T) behaviour has been investigated in Gd{sub 5}Si{sub x}Ge{sub 4-x} compounds with x=1.7, 2.0, 2.2 and 2.3. Microstructural studies reveal the presence of a Gd{sub 5}(Si,Ge){sub 4} -matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The resistivity behaviour has shown good correlation with the microstructural studies. A large change in thermopower of -8{mu}V/K was obtained at the magneto-structural transition for the x=2 compound. The resistivity and change in thermopower values were high for the alloys with Si/Ge ratio {<=}1 compared to that of the alloys with Si/Ge ratio >1.

  2. Corrosion and latent heat in thermal cycles for La(Fe,Mn,Si){sub 13} magnetocaloric compounds

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jie; Guan, Lin; Fu, Song; Sun, Yongyang; Long, Yi, E-mail: longy@mater.ustb.edu.cn

    2014-03-15

    Corrosion and latent heat in thermal cycles for LaFe{sub 11.5−x}Mn{sub x}Si{sub 1.5} (x=0.00, 0.10, 0.20, and 0.25) compounds were investigated for practical application. The corrosion resistance of the compounds was tested by means of potentiodynamic polarization and immersion test in the distilled water. The results show that the corrosion resistance of the compounds was improved by Mn doping. The latent heat of the compounds in the thermal cycles was tested by differential scanning calorimetry (DSC). The latent heat decreased with the increase in the number of thermal cycles. The substitution of Mn in the compounds speeded up the decrease of the latent heat in the thermal cycles. But the latent heat of all compounds tended to be stable after eight thermal cycles. The maximum ΔS{sub M} under a low magnetic field (0–1 T) was 12.7, 9.9, 8.2 and 7.6 J/kg K with increasing of Mn content from x=0.00 to 0.25, respectively. The magnetic entropy changes and adiabatic temperature changes for LaFe{sub 11.5−x}Mn{sub x}Si{sub 1.5} compounds decreased with the increase of Mn content. - Highlights: • Mn doping can improve the corrosion resistance of La(Fe,Mn,Si){sub 13} compounds. • Mn doping speeded up the decrease of the latent heat during the thermal cycles. • The latent heat of all compounds tends to be stable after eight thermal cycles. • −ΔS and ΔT{sub ad} decreased with the increase of Mn content.

  3. Stabilization by Si substitution of the pseudobinary compound Gd(2)(Co(3-x)Si(x)) with magnetocaloric properties around room temperature.

    Science.gov (United States)

    Tencé, Sophie; Caballero Flores, Rafael; Chable, Johann; Gorsse, Stéphane; Chevalier, Bernard; Gaudin, Etienne

    2014-07-07

    We report the discovery of a new solid solution Gd2(Co3-xSix) with 0.29 magnetocaloric effect, which amounts to around 1.7 J K(-1) kg(-1) for ΔH = 2 T, is interestingly tunable around room temperature over a temperature span of 60 K through only 4-5% of composition change.

  4. From single- to double-first-order magnetic phase transition in magnetocaloric Mn1−xCrxCoGe compounds

    NARCIS (Netherlands)

    Trung, N.T.; Biharie, V.; Zhang, L.; Caron, L.; Buschow, K.H.J.; Brück, E.H.

    2010-01-01

    Substitution of some Cr for Mn atoms in MnCoGe was employed to control the magnetic and structural transitions in this alloy to coincide, leading to a single first-order magnetostructural transition from the ferromagnetic to the paramagnetic state with a giant magnetocaloric effect observed near roo

  5. Semiclassical electronic transport in MnAs thin films

    Energy Technology Data Exchange (ETDEWEB)

    Helman, C. [Dpto de Fisica, ' Juan Jose Giambiagi' , Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Unidad de Actividad Fisica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Buenos Aires (Argentina)], E-mail: helman@tandar.cnea.gov.ar; Milano, J.; Steren, L. [Departamento de Fisica, Centro Atomico Bariloche, Comision Nacional de Energia Atomica, S.C. Bariloche (Argentina); Llois, A.M. [Dpto de Fisica, ' Juan Jose Giambiagi' , Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Unidad de Actividad Fisica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Buenos Aires (Argentina)

    2008-07-15

    Magneto-transport experiments have been recently performed on MnAs thin films. Hall effect and transverse magnetoresistance measurements have shown interesting and, until now, unknown results. For instance, the transverse magnetoresistance shows no saturation in the presence of very high magnetic fields. In order to understand the contribution of the electronic band structure to the non-saturating magnetoresistance, we perform ab initio calculations, using the Wien2K code and analyze the magneto-transport properties within the semiclassical approximation. We show that non-saturation may be due to the presence of open orbits on the majority Fermi surface.

  6. LEEM image phase contrast of MnAs stripes

    Energy Technology Data Exchange (ETDEWEB)

    Pang, A.B., E-mail: pangangbo@gmail.com [School of Physics and Electronic Information, Huaibei Normal University, Huaibei, Anhui, 235000 (China); Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Pavlovska, A. [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States); Däweritz, L. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Locatelli, A. [Sincrotrone Trieste, S.C.p.a., Basovizza, Trieste 34012 (Italy); Bauer, E. [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States); Altman, M.S. [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

    2013-07-15

    Low energy electron microscopy (LEEM) imaging of strained MnAs layers epitaxially grown on GaAs(001) reveals striped contrast features that become more pronounced and vary systematically in width with increasing defocus, but that are completely absent in focus. Weaker subsidiary fringe-like features are observed along the stripe lengths, while asymmetric contrast reversal occurs between under-focus and over-focus conditions. A Fourier optics calculation is performed that demonstrates that these unusual observations can be attributed to a phase contrast mechanism between the hexagonal α phase and orthorhombic β phase regions of the MnAs film, which self-organize into a periodic stripe array with ridge-groove morphology. The unequal widths of the α and β phase regions are determined accurately from the through focus series, while the height variation in this system can also be determined in principle from the energy dependence of contrast. - Highlights: • LEEM image of MnAs/GaAs(001) reveals striped contrast features varying with defocus. • Duplex contrast and asymmetric reversal between under- and over-focus are observed. • Fourier optics calculation attributes the contrast to a phase contrast mechanism. • Widths of the α and β phase regions are determined accurately. • Height variation in this system can also be determined in principle.

  7. Influence of heat treatment on the magnetic and magnetocaloric properties in Nd0.6Sr0.4MnO3 compound

    Science.gov (United States)

    Ahmed, A. M.; Mohamed, H. F.; Diab, A. K.; Mohamed, Sara A.; García-Granda, S.; Martínez-Blanco, D.

    2016-07-01

    In the present investigation, the effect of annealing temperature on the structural, electrical transport and the magnetocaloric effect of Nd0.6Sr0.4MnO3 manganites have been studied. Rietveld refinement of XRD data reveals that all samples are single phase with a space group (Pnma). Heat treatment enhances the grain size and decreases the porosity. All samples suffer Curie transition from ferromagnetic to paramagnetic. Magnetocaloric parameters have been determined by the analysis of isothermal M (H) curves around Curie temperature (ΔH = 2 T) for samples. Heat treatment enhances magnetic entropy, which reaches a maximum at Tan = 900 °C. In addition, the rate cooling power records highest value at Tan = 700 °C.

  8. Enhanced magnetocaloric effects and tunable thermal hysteresis in transition metal pnictides

    NARCIS (Netherlands)

    Brück, E.; Trung, N.T.; Ou, Z.Q.; Buschow, K.H.J.

    2012-01-01

    The effect of Co and Ni substitutions for Fe on the magnetocaloric properties of MnFe(P,Ge) compounds crystallizing in the hexagonal Fe2P type of structure was studied. It was found that, by changing composition, a small thermal hysteresis and a giant magnetocaloric effect can be obtained simultaneo

  9. Mastering hysteresis in magnetocaloric materials.

    Science.gov (United States)

    Gutfleisch, O; Gottschall, T; Fries, M; Benke, D; Radulov, I; Skokov, K P; Wende, H; Gruner, M; Acet, M; Entel, P; Farle, M

    2016-08-13

    Hysteresis is more than just an interesting oddity that occurs in materials with a first-order transition. It is a real obstacle on the path from existing laboratory-scale prototypes of magnetic refrigerators towards commercialization of this potentially disruptive cooling technology. Indeed, the reversibility of the magnetocaloric effect, being essential for magnetic heat pumps, strongly depends on the width of the thermal hysteresis and, therefore, it is necessary to understand the mechanisms causing hysteresis and to find solutions to minimize losses associated with thermal hysteresis in order to maximize the efficiency of magnetic cooling devices. In this work, we discuss the fundamental aspects that can contribute to thermal hysteresis and the strategies that we are developing to at least partially overcome the hysteresis problem in some selected classes of magnetocaloric materials with large application potential. In doing so, we refer to the most relevant classes of magnetic refrigerants La-Fe-Si-, Heusler- and Fe2P-type compounds.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  10. The effect of Dy doped on structural, magnetic and magnetocaloric properties of La0.67-xDyxPb0.33MnO3 (x=0.00, 0.15 and 0.20) compounds

    Science.gov (United States)

    Zaidi, N.; Mnefgui, S.; Dhahri, A.; Dhahri, J.; Hlil, E. K.

    2014-10-01

    La0.67-xDyxPb0.33MnO3 (x=0.00, 0.15 and 0.20) compounds were prepared using solid-state reaction. X-ray diffraction and magnetic measurements were used to investigate the effects of Dy doping on the physical properties of La0.67-xDyxPb0.33MnO3. XRD data have been analyzed by Rietveld refinement technique. Results have shown that all obtained perovskite manganites were a single phase. Moreover they crystallized in a rhombohedric structure with R3barc space group. Magnetization as a function of temperature has shown that these compounds exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. A magnetocaloric effect in the obtained samples has been deduced by two methods: Classical Maxwell relation and Landau theory. The maximum of magnetic entropy change |ΔSMmax| in a magnetic field change of 5 T is found to be 4.26 J kg-1 K-1 at 360 K, 3.51 J kg-1 K-1 at 290 K and 2.3 J kg-1 K-1 at 277 K for x=0.00, 0.15 and 0.20, respectively. At this value of magnetic field, the relative cooling power (RCP) is found to be 292, 246 and 215 J kg-1 for x=0.00, 0.15 and 0.20, respectively. Our result on magnetocaloric properties suggests that La0.67-xDyxPb0.33MnO3 (x=0.00, 0.15 and 0.2) compounds are attractive as possible refrigerants for near room temperature magnetic refrigeration.

  11. Large magnetocaloric effect in Ln{sub 0.5}Ca{sub 0.5}MnO{sub 3} (Ln=Gd, DY) compounds: Conseqence of magnetic precursor effect of rare earth ions

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kalipada, E-mail: kalipada.das@saha.ac.in; Paramanik, Tapas; Das, I.

    2015-01-15

    Magnetic, specific heat and magnetocaloric studies have been performed on rare earth calcium manganites; Ln{sub 0.5}Ca{sub 0.5}MnO{sub 3} (Ln=Gd, Dy). The observed isothermal magnetic entropy change is fairly large at low temperature in the manganites family, which is attributed to the magnetic precursor effect of rare-earth ions. For Gd{sub 0.5}Ca{sub 0.5}MnO{sub 3}, the isothermal magnetic entropy change (−ΔS) at 4 K, obtained for 7 T magnetic field, is as high as 22.8 J/kg K. On the other hand, −ΔS is 8.5 J/kg K for Dy{sub 0.5}Ca{sub 0.5}MnO{sub 3}. The large value of magnetic entropy change at the cryogenic temperature range for these compounds is interesting from application point of view. - Highlights: • No long range magnetic ordering of Gd{sub 0.5}Ca{sub 0.5}MnO{sub 3} and Dy{sub 0.5}Ca{sub 0.5}MnO{sub 3} has been observed in magnetization measurement down to T=2 K still these compounds show large magnetocaloric effect. • Specific heat of the compounds in absence of magnetic field increases at low temperature (down to 3 K). • Results are analyzed considering magnetic precursor effect of rare earth ions (Gd and Dy ions)

  12. Effect of R substitution on magnetic properties and magnetocaloric effects of La1-xRxFe11.5Si1.5 compounds with R=Ce, Pr and Nd

    Institute of Scientific and Technical Information of China (English)

    Shen Jun; Li Yang-Xian; Sun Ji-Rong; Shen Bao-Gen

    2009-01-01

    Magnetic properties and magnetocaloric effects of La1-xRxFe11.5Sil.5 (R=Pr, (0 ≤ x ≤ 0.5); R = Ce and Nd, (0 ≤ x ≤ 0.3)) compounds are investigated. Partially replacing La with R = Ce, Pr and Nd in La1-xRxFe11.5Si1.5 leads to a reduction in Curie temperature due to the lattice contraction. The substitution of R for La causes an enhancement in field-induced itinerant electron metamagnetic transition, which leads to a remarkable increase in magnetic entropy change △Sm and also in hysteresis loss. However, a high effective refrigerant capacity Rceff is still maintained in La1-xPxFe11.5Si1.5. In the present samples, a large △Sm and a high Rceff have been achieved simultaneously.

  13. Magnetism and Magnetocaloric Properties of Mn3Zn1-xSnxC and Mn3-xCrxZnC Compounds

    Institute of Scientific and Technical Information of China (English)

    Naikun Sun; Yaobiao Li; Feng Liu; Tongbo Ji

    2012-01-01

    Upon substitution of Sn for Zn, the Curie temperature of Mn3ZnC is lowered from 380 to 375 K for MnzZno.gsSno.osC and to 305 K for Mn3Zno.75Sno.25C. In accordance with the second-order ferromagnetic-paramagnetic transition, a room-temperature magnetocaloric effect without thermal and magnetic hysteresis is observed over a wide temperature range. The maximum value of the magnetic-entropy change ABM for a magnetic-field change from 0 to 5 T is 2.42 J.kg^-1·-K^-1 at 386 K for Mn3Zno.95Sno.osC and 1.70 J·kg^-1.K^-1 at 308 K for Mn3Zn0.75Sno.25C. Meanwhile, substitution of Cr for Mn lowers the temperature of ferromagnetic-ferrimagnetic transition from 233 K for Mn3ZnC to 230 K for Mn2.9Cro.tZnC and to 175 K for Mn2.iCro.oZnC. An inverse magnetocaloric effect with △Bu equal to 0.28 J·kg^-1.K^-1 at 223 K for a field change from 0 to 1.47 T is observed for Mn2.gCro.zZnC.

  14. Effect of Fe substitution on magnetocaloric effect in metamagnetic boron-carbide ErNi{sub 2−x}Fe{sub x}B{sub 2}C compounds

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yikun, E-mail: zhangyk@epm.neu.edu.cn [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China); Yang, Baijun [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2014-10-15

    Highlights: • Magnetism and magnetocaloric effect in ErNi{sub 2−x}Fe{sub x}B{sub 2}C were studied. • Ni site Fe substitution can reduce the magnetic hysteresis of ErNi{sub 2}B{sub 2}C. • The origin of MCE and its potential application in ErNi{sub 2−x}Fe{sub x}B{sub 2}C were discussed. - Abstract: The magnetic properties and magnetocaloric effect (MCE) in ErNi{sub 2−x}Fe{sub x}B{sub 2}C have been studied. Substitution of Fe for Ni lowered the magnetic transition temperature T{sub M}, and reduced the magnetic hysteresis of ErNi{sub 2}B{sub 2}C. An inverse MCE was observed under low magnetic field and at low temperatures, which is attributed to the nature of antiferromagnetic state for the present ErNi{sub 2−x}Fe{sub x}B{sub 2}C compounds. A normal MCE was observed under higher magnetic field changes, which is related to a field-induced first order metamagnetic transition from antiferromagnetic to ferromagnetic state. The maximum values of magnetic entropy change −ΔS{sub M}{sup max} are 14.5, 12.7, and 10.6 J/kg K with a magnetic field change of 0–70 kOe for x = 0, 0.1, and 0.2 in ErNi{sub 2−x}Fe{sub x}B{sub 2}C, respectively.

  15. Magnetic, magnetocaloric and magnetotransport properties of RSn{sub 1+x}Ge{sub 1−x} compounds (R=Gd, Tb, and Er; x=0.1)

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sachin [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Suresh, K.G., E-mail: suresh@phy.iitb.ac.in [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Nigam, A.K. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

    2013-09-15

    We have studied the magnetic, magnetocaloric and magnetotransport properties of RSn{sub 1+x}Ge{sub 1−x}(R=Gd, Tb, and Er; x=0.1) series by means of magnetization, heat capacity and resistivity measurements. It has been found that all the compounds crystallize in the orthorhombic crystal structure described by the centrosymmetric space group Cmcm (No. 63). The magnetic susceptibility and heat capacity data suggest that all the compounds are antiferromagnetic. Large negative values of θ{sub p} in case of GdSn{sub 1.1}Ge{sub 0.9} and TbSn{sub 1.1}Ge{sub 0.9} indicate that strong antiferromagnetic interactions are involved, which is also reflected in the magnetization isotherms. On the other hand ErSn{sub 1.1}Ge{sub 0.9} shows weak antiferromagnetic interaction. The heat capacity data have been analyzed by fitting the temperature dependence and the values of θ{sub D} and γ have been estimated. Among these three compounds, ErSn{sub 1.1}Ge{sub 0.9} shows considerable magnetic entropy change of 9.5 J/kg K and an adiabatic temperature change of 3.2 K for a field of 50 kOe. The resistivity data in different temperature regimes have been analyzed and the dominant contributions have been identified. All the compounds show small but positive magnetoresistance. - Highlights: • The large negative value of paramagnetic Curie temperature suggested that GdSnGe and TbSnGe are strongly antiferromagnetic. • From magnetization, heat capacity and MCE data, it is found that below 12 K, magnetic moments in TbSnGe are weakly ferromagnetically coupled. • ErSnGe compound shows considerable magnetocaloric effect (MCE), with an isothermal magnetic entropy change of 9.5 J/kg K for a field of 50 kOe. • Resistivity data in TbSnGe shows an increase in resistivity below T{sub N}, which are due to formation of superzone gaps in the conduction electron energy bands.

  16. Magnetocaloric effect study of ferromagnetic-charge ordered core-shell type manganite nanostructures

    Science.gov (United States)

    Das, Kalipada; Das, I.

    2017-08-01

    In the present study we have presented the magnetic and magnetocaloric properties of ferromagnetic (La0.67Sr0.33MnO3)-charge ordered (Pr0.67Ca0.33MnO3) core-shell nanostructures. We have also compared the magnetocaloric properties of Pr0.67Ca0.33MnO3 (PCMO) nanoparticles. Our study indicates that in case of the core-shell nanostructures, the magnetocaloric properties markedly modifies compared to its parent compound PCMO, additionally the low field magnetocaloric effect enhanced. More specifically, the large value of magnetocaloric entropy change (- Δ S(T)) was observed in wider temperature range in core-shell nanostructure which may be important from application point of view.

  17. Giant magnetoresistance in the Ge-rich magnetocaloric compound, Gd{sub 5}(Si{sub 0.1}Ge{sub 0.9}){sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Morellon, L. E-mail: morellon@posta.unizar.es; Algarabel, P.A.; Magen, C.; Ibarra, M.R

    2001-12-01

    We have measured the zero-field electrical resistivity in the temperature range 5-295 K and magnetoresistance in magnetic fields of up to 12 T of Gd{sub 5}(Si{sub 0.1}Ge{sub 0.9}){sub 4}. The resistivity changes drastically at the magnetostructural first-order transition (T{sub C} congruent with 80 K on heating). This transition can be induced reversibly by the application of an external magnetic field above T{sub C}, producing a concomitant giant magnetoresistance (GMR) effect, {delta}{rho}/{rho} congruent with -50%. This study demonstrates that (in addition to giant magnetocaloric and magnetoelastic effects) GMR can be tuned between {approx}20 and {approx}290 K in Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} with x{<=}0.5 by simply adjusting the Si : Ge ratio.

  18. Structural, magnetic and magnetocaloric properties of AMn{sub 1-x}Ga{sub x}O{sub 3} compounds with 0{<=}x{<=}0.2

    Energy Technology Data Exchange (ETDEWEB)

    Omri, A., E-mail: omriaref@yahoo.fr [Laboratoire de Physique Appliquee, Faculte des Sciences de Sfax, Universite de Sfax, BP 1171, Sfax 3000 (Tunisia); Bejar, M. [Laboratoire de Physique Appliquee, Faculte des Sciences de Sfax, Universite de Sfax, BP 1171, Sfax 3000 (Tunisia); Sajieddine, M. [Laboratoire de Physique et Mecanique des Materiaux, Faculte des Sciences et Techniques, BP 523, 23000, Beni-Mellal-Universite Sultan Moulay Sliman, Maroc (Morocco); Dhahri, E. [Laboratoire de Physique Appliquee, Faculte des Sciences de Sfax, Universite de Sfax, BP 1171, Sfax 3000 (Tunisia); Hlil, E.K. [Institut Neel, CNRS-Universite J. Fourier, BP 166, 38042 Grenoble (France); Es-Souni, M. [University of Applied Sciences, Institute for Materials and Surface Technology, Grenzstrasse 3, Kiel (Germany)

    2012-07-01

    Structural, magnetic and magnetocaloric properties of manganites series with the AMn{sub 1-x}Ga{sub x}O{sub 3} (A=La{sub 0.75}Ca{sub 0.08}Sr{sub 0.17} and x=0, 0.05, 0.1 and 0.2) composition have been investigated to shed light on Ga-doping influence. Solid-state reaction method was used for preparation. From XRD study, all samples are found single phase and crystallize in the orthorhombic structure with the Pnma space group. The variation of the magnetization M vs. temperature T, under an applied magnetic field of 0.05 T, reveals a ferromagnetic-paramagnetic transition for all samples. The experimental results indicate that T{sub C} decreases from 336 to 135 K with increasing Ga substitution. Magnetocaloric effect (MCE) was estimated, in terms of isothermal magnetic entropy change (-{Delta}S{sub M}), using the M(T, {mu}{sub 0}H) data and employing the thermodynamic Maxwell equation. The maximum entropy change and Relative Cooling Power (RCP) show non-monotonic behaviors with increasing the concentration of Gallium. In fact, the maximum value of {Delta}S{sub Mmax}of AMn{sub 1-x}Ga{sub x}O{sub 3} for x=0.00 and 0.2 samples is found to be, respectively, 2.87 and 1.17 J/kg/K under an applied magnetic field change of 2 T. For the same applied magnetic field ({mu}{sub 0}H=2 T), the RCP values are found to vary between 97.58 and 89 J/kg.

  19. Cluster method calculation of the Curie temperature and exchange parameters for the magnetocaloric compounds MnFeAs {sub x} P{sub 1-x} (0.25≤ x ≤0.65) and hexagonal MnFeAs

    Energy Technology Data Exchange (ETDEWEB)

    Schilling, Osvaldo F., E-mail: osvaldo.neto@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis (Brazil). Departamento de Fisica

    2013-08-15

    A wealth of experimental and theoretical data on the crystallographic and magnetic properties of the magnetocaloric compounds MnFeAs {sub x} P{sub 1-x} (0.25 ≤ x ≤0.65) and MnFeAs has become available in the last decade. By analyzing the data and treating the spin interactions with Callen's cluster expansion method, we extrapolate first-principle results for the exchange-coupling constants of MnFeAs to the P-substituted compounds and find Curie temperatures that agree, within 5 % deviation, with experiment. Simulations with different coupling parameters show that T{sub c} is weakly dependent on the Fe-Fe interactions. Analysis of lattice expansion as a function of composition shows that changes in the lattice parameters a and c have opposite effects upon the strength of the magnetic interactions between ions. The results indicate that the cluster expansion method provides reliable estimates of magnetic properties, even for metallic compounds characterized by multiple interactions among ions with distinct magnetic moments. (author)

  20. Heat capacity and magnetocaloric effect in polycrystalline Gd1-xSmxMn2Si2

    OpenAIRE

    2006-01-01

    We report the magnetocaloric effect in terms of isothermal magnetic entropy change as well as adiabatic temperature change, calculated using the heat capacity data. Using the zero field heat capacity data, the magnetic contribution to the heat capacity has been estimated. The variations in the magnetocaloric behavior have been explained on the basis of the magnetic structure of these compounds. The refrigerant capacities have also been calculated for these compounds.

  1. Magnetic properties and low-temperature large magnetocaloric effect in the antiferromagnetic HoCu{sub 0.33}Ge{sub 2} and ErCu{sub 0.25}Ge{sub 2} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gao, R.L. [School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331 (China); Xu, Z.Y., E-mail: zhyxu@nim.ac.cn [National Institute of Metrology, Beijing 100029 (China); Wang, L.C. [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Dong, Q.Y.; Zhang, Y. [Department of Physics, Capital Normal University, Beijing 100048 (China); Liu, F.H. [National Space Science Center, Beijing 100190 (China); Mo, Z.J. [School of material Science and Engineering, Hebei University of Technology, Tianjin 300401 (China); Niu, E. [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Fu, C.L.; Cai, W.; Chen, G.; Deng, X.L. [School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331 (China)

    2015-05-15

    Highlights: • Antiferromagnetic material RCu{sub x}Ge{sub 2} of high purity was prepared. • Large MCE as −10.2 J/kg K and −10.5 J/kg K for RCu{sub x}Ge{sub 2} (Ho, Er) was obtained for field change of 0–50 kOe. • The RCu{sub x}Ge{sub 2} compounds with variable x had different transition temperature which made them suitable for ‘table-like’ magnetocaloric refrigerant. - Abstract: Magnetic properties and magnetocaloric effect (MCE) of HoCu{sub 0.33}Ge{sub 2} and ErCu{sub 0.25}Ge{sub 2} compounds have been investigated. The compounds were determined to be antiferromagnetic with the Néel temperatures T{sub N} = 9 K and 3.9 K, respectively. The critical transition magnetic fields for the metamagnetic transition from antiferromagnetic to ferromagnetic state below T{sub N} were determined to be 10 kOe for HoCu{sub 0.33}Ge{sub 2} at 5 K and 6 kOe for ErCu{sub 0.25}Ge{sub 2} at 2 K. Large MCE with the maximal values of magnetic entropy changes (ΔS{sub M}) as −10.2 J/kg K at 10.5 K were found in HoCu{sub 0.33}Ge{sub 2} for field changes of 0–70 kOe and −10.5 J/kg K at 5.5 K in ErCu{sub 0.25}Ge{sub 2} for field changes of 0–50 kOe, respectively. The large ΔS{sub M} around T{sub N} as well as no hysteresis loss made RCu{sub x}Ge{sub 2} competitive candidates as low temperature magnetic refrigerant.

  2. Unforeseen properties of MnAs epilayers grown on GaAs semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Rache Salles, B., E-mail: salles@insp.jussieu.f [Institut des NanoSciences de Paris, INSP, UPMC-Paris 6, CNRS UMR 7588, 140 rue de Lourmel, 75015 Paris (France); Vidal, F.; Etgens, V.H. [Institut des NanoSciences de Paris, INSP, UPMC-Paris 6, CNRS UMR 7588, 140 rue de Lourmel, 75015 Paris (France); Breitwieser, R. [Institut des NanoSciences de Paris, INSP, UPMC-Paris 6, CNRS UMR 7588, 140 rue de Lourmel, 75015 Paris (France); LCPMR, UPMC-Paris 6, CNRS UMR 7614, 11 rue Pierre et Marie Curie, 75005 Paris (France); Marangolo, M.; Eddrief, M. [Institut des NanoSciences de Paris, INSP, UPMC-Paris 6, CNRS UMR 7588, 140 rue de Lourmel, 75015 Paris (France)

    2009-10-01

    This paper reviews some recent works performed on MnAs/GaAs thin films and other related structures grown by molecular beam epitaxy. The impact of epitaxy on the magneto-structural properties of MnAs and possible applications of MnAs epilayers are discussed. A brief account of recent results obtained on the magneto-transport in MnAs/GaAs/MnAs magnetic tunnel junctions is also given, highlighting several appealing and promising properties of this system for spintronics applications.

  3. A europium-151 Mössbauer spectral study of Eu(14)MnP(11), Eu(14)MnAs(11), and Eu(14)MnSb(11).

    Science.gov (United States)

    Hermann, Raphaël P; Grandjean, Fernande; Kauzlarich, Susan M; Jiang, Jiong; Brown, Shawna; Long, Gary J

    2004-11-01

    The europium-151 Mossbauer spectra of the Eu(14)MnP(11), Eu(14)MnAs(11), and Eu(14)MnSb(11) Zintl compounds, measured between 4.2 and 100 K, reveal europium(II) for all four crystallographically inequivalent europium sites in Eu(14)MnAs(11) and Eu(14)MnSb(11) and europium(II) and europium(III) for the three 32g and the 16f europium sites in Eu(14)MnP(11), respectively. Below the ordering temperatures of 52, 74, and 92 K, only very small hyperfine fields of 2-4 T are observed at the europium sites as a result of the polarization by the manganese magnetic moments. At 4.2 K, the europium(II) magnetic moments are ordered, and hyperfine fields of 24.4, 24.8, and 19.3 T are observed in Eu(14)MnP(11), Eu(14)MnAs(11), and Eu(14)MnSb(11), respectively, fields that are typical for magnetically ordered europium(II) ions. At 4.2 K the 16f europium(III) sites in Eu(14)MnP(11) experience a transferred hyperfine field of 33 T from the neighboring ordered europium(II) moments. Between its Curie temperature and 4.2 K, the europium-151 Mossbauer spectra of Eu(14)MnSb(11) reveal that the europium(II) moments order below ca. 13 K, i.e., below the second magnetic transition observed in magnetic measurements. Between their Curie temperatures and 4.2 K, the europium-151 Mossbauer spectra of Eu(14)MnP(11) and Eu(14)MnAs(11) are complex and have been analyzed with two models, models that give equivalently good fits. However, the second model in which the spectra are fit with a three-dimensional relaxation of the europium(II) and europium(III) hyperfine fields is preferred for its physical meaning and its reduced number of fitted parameters.

  4. Magnetic properties and magnetocaloric effect in NdxLa1-xFe11.5Al1.5 compounds

    Institute of Scientific and Technical Information of China (English)

    Wang Fang; Wang Guang-Jun; Sun Ji-Rong; Shen Bao-Gen

    2008-01-01

    Effects of Nd-doping on the magnetic properties and magnetocaloric effects (MCEs) of NdxLa1-xFe11.5Al1.5 have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic (AFM) coupling and an enhancement of the ferromagnetic (FM) coupling. This in turn results in a complex magnetic behaviour for Nd0.2La0.8Fe11.52Al1.5 characterized by the occurrence of two phase transitions at ~188 K (PM-AFM) and ~159 K (AFM-FM). As a result, a table-like MCE (9 J/kg·K) is found in a wide temperature range (160-185 K) for a field change of 0-5 T around the transition temperature, as evidenced by both the magnetic and calorimetric measurements. Based on the analysis of low-temperature heat capacity, it is found that the AFM-FM phase transition modifies the electron density significantly, and the major contribution to the entropy change comes from the electronic entropy change.

  5. Magnetocaloric heat pump device, a heating or cooling system and a magnetocaloric heat pump assembly

    DEFF Research Database (Denmark)

    2014-01-01

    The invention provides a magnetocaloric heat pump device, comprising a magnetocaloric bed; a magnetic field source, the magnetocaloric bed and the magnetic field source being arranged to move relative to each other so as to generate a magnetocaloric refrigeration cycle within the heat pump, wherein...

  6. Magnetocaloric effect and negative thermal expansion in hexagonal Fe doped MnNiGe compounds with a magnetoelastic AFM-FM-like transition.

    Science.gov (United States)

    Xu, Kun; Li, Zhe; Liu, Enke; Zhou, Haichun; Zhang, Yuanlei; Jing, Chao

    2017-01-30

    We report a detailed study of two successive first-order transitions, including a martensitic transition (MT) and an antiferromagnetic (AFM)-ferromagnetic (FM)-like transition, in Mn1-xFexNiGe (x = 0, 0.06, 0.11) alloys by X-ray diffraction, differential scanning calorimetry, magnetization and linear thermal expansion measurements. Such an AFM-FM-like transition occurring in the martensitic state has seldom been observed in the M(T) curves. The results of Arrott plot and linear relationship of the critical temperature with M(2) provide explicit evidence of its first-order magnetoelastic nature. On the other hand, their performances as magnetocaloric and negative thermal expansion materials were characterized. The isothermal entropy change for a field change of 30 kOe reaches an impressive value of -25.8 J/kg K at 203 K for x = 0.11 compared to the other two samples. It demonstrates that the magneto-responsive ability has been significantly promoted since an appropriate amount of Fe doping can break the local Ni-6Mn AFM configuration. Moreover, the Fe-doped samples reveal both the giant negative thermal expansion and near-zero thermal expansion for different temperature ranges. For instance, the average thermal expansion coefficient ā of x = 0.06 reaches -60.7 × 10(-6)/K over T = 231-338 K and 0.6 × 10(-6)/K over T = 175-231 K during cooling.

  7. Influence of Domain Wall on Magnetocaloric Effect in GdPt$_{2}$

    OpenAIRE

    2006-01-01

    The resistivity, magnetoresistance and in-field heat capacity measurements were performed on GdPt$_{2}$ intermetallic compound. The magnetocaloric parameters $\\Delta T_{ad}$ and $-\\Delta S$ were derived from the in-field heat capacity data. Comparison has been made between the magnetocaloric effect $-\\Delta S$ and difference in resistivity $-\\Delta \\rho$ $(=\\rho(H)-\\rho(0))$ as a function of temperature. There is distinct difference in the temperature dependence of $-\\Delta S$ and $-\\Delta \\r...

  8. Electronic states in arsenic-decapped MnAs (11xAF00) films grown on GaAs(001): A photoemission spectroscopy study

    Science.gov (United States)

    Moreno, M.; Kumar, A.; Tallarida, M.; Horn, K.; Ney, A.; Ploog, K. H.

    2008-02-01

    We examine the arsenic bonding in the near-surface region of initially arsenic-capped MnAs(11¯00) films grown on GaAs(001), as it evolves upon arsenic decapping. Line-shape analyses of high-resolution As 3d photoelectron emission spectra recorded at room temperature (RT) allow us to identify electronically distinct As-bonding states associated to bulk MnAs phases, bulk arsenic, and interfacial environments. Stable MnAs phases appear to be affected by the presence of a thin arsenic coating, an effect that could be advantageously used to enhance the ferromagnetic properties of MnAs films around RT.

  9. Hysteresis in Magnetocaloric Materials

    DEFF Research Database (Denmark)

    von Moos, Lars

    , obtained at the initial low and final high field. However, in first order materials thermal entropy hysteresis loops are obtained through characterization, corresponding to measurements done in an increasing and a decreasing temperature mode. Indirectly determining the MCE through the use of the Maxwell...... characterization of the magnetocaloric effect (MCE) in these materials is done through conventional indirect magnetometric and calorimetric methods, as well as newly developed direct methods. The determination of the MCE due to a magnetic field change is in principle given by the isofield material entropy curves...... relation or calorimetric measurements done only in a heating or cooling mode, estimate the MCE as the reversible difference between the set isofield heating-heating or cooling-cooling entropy curves. Here it is shown that direct measurements suggest that the real MCE is given by the difference between...

  10. Structural, electronic, and magnetic properties of single MnAs nanoclusters in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Smakman, E. P., E-mail: e.p.smakman@tue.nl; Mauger, S.; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); Rench, D. W.; Samarth, N. [Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-12-08

    MnAs nanoclusters in GaAs were investigated with cross-sectional scanning tunneling microscopy. The topographic images reveal that the small clusters have the same zinc-blende crystal structure as the host material, while the larger clusters grow in a hexagonal crystal phase. The initial Mn concentration during molecular beam epitaxy growth has a strong influence on the size of the clusters that form during the annealing step. The local band structure of a single MnAs cluster is probed with scanning tunneling spectroscopy, revealing a Coulomb blockade effect that correlates with the size of the cluster. With a spin-sensitive tip, for the smaller clusters, superparamagnetic switching between two distinct states is observed at T = 77 K. The larger clusters do not change their magnetic state at this temperature, i.e., they are superferromagnetic, confirming that they are responsible for the ferromagnetic behavior of this material at room-temperature.

  11. Spin diffusion in bulk GaN measured with MnAs spin injector

    KAUST Repository

    Jahangir, Shafat

    2012-07-16

    Spin injection and precession in bulk wurtzite n-GaN with different doping densities are demonstrated with a ferromagnetic MnAs contact using the three-terminal Hanle measurement technique. Theoretical analysis using minimum fitting parameters indicates that the spin accumulation is primarily in the n-GaN channel rather than at the ferromagnet (FM)/semiconductor (SC) interface states. Spin relaxation in GaN is interpreted in terms of the D’yakonov-Perel mechanism, yielding a maximum spin lifetime of 44 ps and a spin diffusion length of 175 nm at room temperature. Our results indicate that epitaxial ferromagnetic MnAs is a suitable high-temperature spin injector for GaN.

  12. CALCULATION OF THE MAGNETIZATION AND MAGNETOCALORIC EFFECT IN THE MnFeP0.45AS0.55 COMPOUND

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A magnetic state equation of the MnFeP0.45As0.55 compound has been obtained by minimizing the Gibbs free energy with respect to the volume and the magnetization based on the Bean-Rodbell model. The isothermal magnetization of the compound has been calculated using this equation. The magnetic entropy change of the compound was determined from the surface area between the two adjacent isothermal magnetization curves divided by the average temperature. A comparison and an error analysis of the calculated magnetic entropy change and the one determined from the experimental data were given.

  13. Magnetocaloric properties of metallic nanostructures

    Directory of Open Access Journals (Sweden)

    Khurram S. Khattak

    2015-12-01

    Full Text Available A compilation of magnetocaloric properties of metallic nanostructures with Curie temperature (TC between 260 and 340 K has been tabulated. The tabulated data show that nanostructure plays an important role in enhancing the magnetocaloric properties of a material, namely by reducing the peak of magnetic entropy, but broadening of the magnetocaloric effect curve with an average of 10 K sliding window for Curie temperature. A second table lists all bulk metallic and intermetallic materials, in which there is no nanostructural data, with an entropy change of at least 20 J/kg K and a Curie temperature between 260 and 340 K. We propose that further experiments should be made on the nanostructured form of these materials.

  14. Who discovered the magnetocaloric effect?

    DEFF Research Database (Denmark)

    Smith, Anders

    2013-01-01

    A magnetic body changes its thermal state when subjected to a changing magnetic field. In particular, if done under adiabatic conditions, its temperature changes. For the past 15 years the magnetocaloric effect has been the focus of significant research due to its possible application for efficient...... refrigeration near room temperature. At the same time, it has become common knowledge within the magnetic refrigeration research community that the magnetocaloric effect was discovered by the German physicist E. Warburg in 1881. We re-examine the original literature and show that this is a misleading reading...

  15. Taming the first-order transition in giant magnetocaloric materials.

    Science.gov (United States)

    Guillou, François; Porcari, Giacomo; Yibole, Hargen; van Dijk, Niels; Brück, Ekkes

    2014-05-01

    Large magnetically driven temperature changes are observed in MnFe(P,Si,B) materials simultaneously with large entropy changes, limited (thermal or magnetic) hysteresis, and good mechanical stability. The partial substitution of B for P in MnFe(P,Si) compounds is found to be an ideal parameter to control the latent heat observed at the Curie point without deteriorating the magnetic properties, which results in promising magnetocaloric properties suitable for magnetic refrigeration.

  16. Magnetocaloric effect of RM2 (R = rare earth, M = Ni, Al) intermetallic compounds made by centrifugal atomization process for magnetic refrigerator

    Science.gov (United States)

    Matsumoto, K.; Asamato, K.; Nishimura, Y.; Zhu, Y.; Abe, S.; Numazawa, T.

    2012-12-01

    RM2 (R = rare earth, M = Al, Ni and Co) compounds have large entropy change and magnetic transition temperatures can be controlled by change of R and/or M so that are suitable to a magnetic refrigerator for hydrogen liquefaction under development. In order to improve refrigerator performance, spherical powdered HoAl2, DyAl2, and GdNi2 compounds with submillimeter diameter were synthesized by centrifugal atomization process. By measuring the magnetization and heat capacity, we obtained entropy change by magnetic fields and entropy as functions of temperature and magnetic field, which are essential for analysing the magnetic refrigeration cycle. All samples showed sharp magnetic transitions and had good potentials for use in magnetic refrigeration.

  17. Magnetic phase transitions and magnetocaloric effect in layered intermetallic La0.75Sm0.25Mn2Si2 compound

    Science.gov (United States)

    Mushnikov, N. V.; Gerasimov, E. G.; Terentev, P. B.; Gaviko, V. S.; Yazovskikh, K. A.; Aliev, A. M.

    2017-10-01

    Magnetic and magnetothermal properties have been studied for the La0.75Sm0.25Mn2Si2 compound which has the spontaneous first-order antiferromagnetic to ferromagnetic (AF-F) transition at a temperature of 160 K. The transition is accompanied by the anisotropic lattice distortion. Isothermal entropy change has been estimated for different magnetic states using the heat capacity and magnetization data. Direct measurements of the adiabatic temperature change have been performed in the fields applied both along the easy c-axis and in the basal plane of a quasi-single crystal. Near the transition temperature, the AF-F transition can be realized in low magnetic fields, which makes such compounds attractive for magnetoelastic and magnetothermal applications.

  18. Structural, magnetic and magnetocaloric properties of La{sub 0.7}Ca{sub 0.2}Sr{sub 0.1}Mn{sub 1−x}Cr{sub x}O{sub 3} compounds with x = 0, 0.05 and 0.1

    Energy Technology Data Exchange (ETDEWEB)

    Dhahri, Ah., E-mail: dhahri.ahmad@outlook.fr [Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); Jemmali, M. [Laboratoire des Sciences des Matériaux et de l’Environnement, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); Taibi, K. [Département SDM, FGMGP/USTHB, 16311 (Algeria); Dhahri, E. [Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); Hlil, E.K. [Institut Néel, CNRS et Université J. Fourier, BP 166, 38042 Grenoble (France)

    2015-01-05

    Highlights: • The samples crystallize in the rhombohedral structure with the R3{sup ¯}c space group. • Enhancement of T{sub C} for the rhombohedral samples. • The relative cooling power increases with Cr-doping. • All samples exhibit a large magnetocaloric effect. • High values of the magnetoresistance in all samples. - Abstract: Structural, magnetic and magnetocaloric properties of La{sub 0.7}Sr{sub 0.1}Ca{sub 0.2}Mn{sub 1−x}Cr{sub x}O{sub 3} compounds with x = 0, 0.05 and 0.1 have been investigated to shed light on Cr-doping influence. X-ray diffraction studies show that all samples crystallize in the rhombohedral symmetry with R3{sup ¯}c space group. Rietveld refinement structure shows that the insertion of Cr in Mn network modifies the structural parameters such as the volume, Mn–O–Mn angles and the Mn–O bond length. The substitution of Mn by Cr decreases the 2p-3d hybridization between O and Mn ions, reduces the bandwidth and increases the electron–phonon coupling. The investigation of magnetic and magnetocaloric properties reveals that the samples exhibit a paramagnetic(PM)–ferromagnetic (FM) transition with decreasing Curie temperature (T{sub C}) from 294 K to 255 K when Cr doping level increases. The magnetic entropy change (ΔS{sub M}{sup max}) also decreases from 6.20 J kg{sup −1} K{sup −1} for x = 0 to3.80 J kg{sup −1} K{sup −1} for x = 0.1, while the relative cooling power (RCP) increases from 234.5 to 240 J kg{sup −1}, respectively, under a magnetic field of 5 T. These outcomes suggest that Mn-site Cr doping inhibits the enhancement of the magnetocaloric effect in some perovskite manganites. This is explained by the weakening of the ferromagnetic double-exchange interaction between Mn{sup 3+} and Mn{sup 4+} ions.

  19. Anisotropic magnetocaloric effect in antiferromagnetic systems: Application to EuTiO3

    Science.gov (United States)

    Alho, B. P.; Carvalho, A. Magnus G.; von Ranke, P. J.

    2014-09-01

    In this work, we theoretically predicted an anisotropic magnetocaloric effect of the same order of magnitude of the usual magnetocaloric effect for antiferromagnetic systems. The anisotropic magnetic properties come from the anti-parallel alignment of the magnetic sites and can be optimized depending on the magnetic field change. This result highlights the applicability of antiferromagnetic compounds as refrigerants based on the anisotropic magnetocaloric effect. For this purpose, we considered a Hamiltonian model, including the exchange and Zeeman interactions in a two sublattices framework. It is worth noting that no anisotropy is explicitly included on the Hamiltonian model, although the system presents an anisotropic behavior. The calculations were applied to the G-type antiferromagnetic compound EuTiO3.

  20. Magnetic properties and magnetocaloric effect of NdMn{sub 2−x}Cu{sub x}Si{sub 2} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Md Din, M. F., E-mail: mfmd999@uowmail.edu.au [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Department of Electrical and Electronic Engineering, Faculty of Engineering, National Defence University of Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur (Malaysia); Wang, J. L. [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Bragg Institute, ANSTO, Lucas Heights, NSW 2234 (Australia); Avdeev, M.; Kennedy, S. J. [Bragg Institute, ANSTO, Lucas Heights, NSW 2234 (Australia); Gu, Q. F. [Australian Synchrotron, 800 Blackburn Rd, Clayton 3168 (Australia); Zeng, R.; Dou, S. X. [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Campbell, S. J. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT 2600 (Australia)

    2014-05-07

    Structural and magnetic properties of NdMn{sub 2−x}Cu{sub x}Si{sub 2} compounds (x = 0–1.0) have been investigated by high intensity x-ray and resolution neutron diffraction (3–450 K), specific heat, dc magnetization, and differential scanning calorimetry measurements. Substitution of Cu for Mn leads to an increase in the lattice parameter a but a decrease in c at room temperature. Two magnetic phase transitions have been found for NdMn{sub 2−x}Cu{sub x}Si{sub 2} compounds with T{sub N} for the antiferromagnetic ordering of Mn-sublatttice and T{sub C} for the Nd-sublattice ferromagnetic ordering, respectively. T{sub C} increases significantly with increasing Cu content from 36 K at x = 0 to 100 K at x = 1.0. Moreover, it is found that the order of magnetic phase transition around T{sub C} also changes from first order at x < 0.6 to second order transition for x ≥ 0.6. The spontaneous magnetization found to decrease with the increase in Cu concentration which can be understood in the term of the dilution effect of Cu for Mn. The values of −ΔS{sub M} around T{sub C} decrease with increasing x from 27 J kg{sup −1} K{sup −1} for x = 0 to 0.5 J kg{sup −1} K{sup −1} for x = 1.0 under 0–5 T field. Refinement of neutron diffraction patterns for x = 0.2 confirms the magnetic states detected by magnetic study and also indicates that the lattice constants a and c show a distinct variation around T{sub C}.

  1. Thermal diffusion of Mn through GaAs overlayers on (Ga, Mn)As

    Energy Technology Data Exchange (ETDEWEB)

    Adell, J; Ulfat, I; Ilver, L; Kanski, J [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Sadowski, J [Institute of Physics, Polish Academy of Sciences, PL-02-668 Warsaw (Poland); Karlsson, K [Department of Life Sciences, University of Skoevde, SE-541 28 Skoevde (Sweden)

    2011-03-02

    Thermally stimulated diffusion of Mn through thin layers of GaAs has been studied by x-ray photoemission. (Ga, Mn)As samples with 5 at% Mn were capped with 4, 6 and 8 monolayer (ML) GaAs, and Mn diffusing through the GaAs was trapped on the surface by means of amorphous As. It was found that the out-diffusion is completely suppressed for an 8 ML thick GaAs film. The short diffusion length is attributed to an electrostatic barrier formed at the (Ga, Mn)As/GaAs interface.

  2. Thermal diffusion of Mn through GaAs overlayers on (Ga, Mn)As.

    Science.gov (United States)

    Adell, J; Ulfat, I; Ilver, L; Sadowski, J; Karlsson, K; Kanski, J

    2011-03-02

    Thermally stimulated diffusion of Mn through thin layers of GaAs has been studied by x-ray photoemission. (Ga, Mn)As samples with 5 at% Mn were capped with 4, 6 and 8 monolayer (ML) GaAs, and Mn diffusing through the GaAs was trapped on the surface by means of amorphous As. It was found that the out-diffusion is completely suppressed for an 8 ML thick GaAs film. The short diffusion length is attributed to an electrostatic barrier formed at the (Ga, Mn)As/GaAs interface.

  3. A magnetocaloric pump for microfluidic applications.

    Science.gov (United States)

    Love, Lonnie J; Jansen, John F; McKnight, Timothy E; Roh, Yul; Phelps, Tommy J

    2004-06-01

    A magnetocaloric pump provides a simple means of pumping fluid using only external thermal and magnetic fields. The principle, which can be traced back to the early work of Rosensweig, is straightforward. Magnetic materials tend to lose their magnetization as the temperature approaches the material's Curie point. Exposing a column of magnetic fluid to a uniform magnetic field coincident with a temperature gradient produces a pressure gradient in the magnetic fluid. As the fluid heats up, it loses its attraction to the magnetic field and is displaced by cooler fluid. The impact of such a phenomenon is obvious: fluid propulsion with no moving mechanical parts. Until recently, limitations in the magnetic and thermal properties of conventional materials severely limited practical operating pressure gradients. However, recent advancements in the design of metal substituted magnetite enable fine control over both the magnetic and thermal properties of magnetic nanoparticles, a key element in colloidal-based magnetic fluids (ferrofluids). This paper begins with a basic description of the process and previous limitations due to material properties. This is followed by a review of existing methods of synthesizing magnetic nanoparticles as well as an introduction to a new approach based on thermophilic metal-reducing bacteria. We compare two compounds and show, experimentally, significant variation in specific magnetic and thermal properties. We develop the constitutive thermal, magnetic, and fluid dynamic equations associated with a magnetocaloric pump and validate our finite-element model with a series of experiments. Preliminary results show a good match between the model and experiment as well as approximately an order of magnitude increase in the fluid flow rate over conventional magnetite-based ferrofluids operating below 80 degrees C. Finally, as a practical demonstration, we describe a novel application of this technology: pumping fluids at the "lab

  4. The magnetocaloric effect in dysprosium

    Science.gov (United States)

    Benford, S. M.

    1979-01-01

    The magnetocaloric effect in polycrystalline Dy was measured in the 84-280-K range in measuring fields from 1 to 7 T. These adiabatic temperature changes reflect structural changes in Dy with applied field and temperature, and include the first magnetocaloric data for a helical antiferromagnet. Above the Neel point (179 K) a field increase always caused heating; below the Neel point fields less than about 2 T cause cooling for some values of initial temperature. The largest temperature increase with a 7 T field occurs at the Neel point and at fields below 2 T near the Curie point. For refrigeration purposes the optimal working region for a Dy cooling element is field dependent.

  5. Aberration-corrected electron microscopy of MnAs and As nanocrystals and voids in annealed (Ga,Mn)As

    DEFF Research Database (Denmark)

    Kovács, András; Kasama, Takeshi; Sadowski, J.

    2011-01-01

    Aberration-corrected transmission electron microscopy is used to study voids and nano-crystalline MnAs and As phases formed during the annealing of Mn-doped GaAs. The effects of defocus and inner annular dark-field detector semi-angle on contrast of the nanocrystals are discussed....

  6. Magnetocaloric effect of Gd5Si2Ge2 alloys in low magnetic field

    Indian Academy of Sciences (India)

    Hong Zeng; Chunjiang Kuang; Jiuxing Zhang; Ming Yue

    2011-07-01

    The magnetocaloric effect of Gd5Si2Ge2 alloys under heat treatment conditions are investigated in low magnetic fields. The magnetocaloric effect (MCE) is studied by measuring magnetic entropy change ( M) and adiabatic temperature change ( ad) in a magnetic field of 1.5 T using a vibrating sample magnetometer (VSM) and a home-made magnetocaloric effect measuring apparatus, respectively. The maximum M of the alloys increases by 200% from 4.38 to 13.32 J kg-1 K-1, the maximum ad increases by 105% from 1.9 to 3.9 K when compared to the as-cast due to the homogeneous composition distribution and microstructure, while the magnetic ordering temperature is slightly reduced. These results indicate that the annealed Gd5Si2Ge2 compounds are promising as high-performance magnetic refrigerants working room temperature in relatively low magnetic fields.

  7. Magnetocaloric pump. [for cryogenic fluids

    Science.gov (United States)

    Brown, G. V. (Inventor)

    1974-01-01

    A vessel having inlet and outlet valves is disposed in a container with a fluid to be pumped which may be evolved from a liquid in the container below the vessel. A magnetocaloric substance is disposed in the vessel and causes fluid vapor in the vessel to expand and be expelled through the outlet valve. Vapor is drawn in through the inlet valve as the substance cools. The inlet valves may be one-way check valves or may be solenoid valves energized at appropriate times by timing circutis. A timer controlled heating element may also be disposed in the vessel to operate in conjunction with the magnetic field.

  8. Topological description of the half-metallic transition of MnAs

    Directory of Open Access Journals (Sweden)

    SH Khosravizadeh

    2011-09-01

    Full Text Available Topological analysis of the electronic charge density is introduced as a new tool for studying the electronic properties of the materials. In this method, the eigen values of the Hessian matrix of the electronic charge density as an scalar field are used to estimate the strength of the atomic bonds. We employ this method to study the half-metallic phase transition of MnAs in zinc blende structure. The results show that the topology of the electron density is preserved in this phase transition. So the total magnetization as the order parameter of the system changes continually and the phase transition is regarded as a second order transition. The geometrical changes observed in the electron density are interpreted by investigating the electronic structure.

  9. High performance magnetocaloric perovskites for magnetic refrigeration

    OpenAIRE

    Velázquez, David

    2012-01-01

    We have applied mixed valance manganite perovskites as magnetocaloric materials in a magnetic refrigeration device. Relying on exact control of the composition and a technique to process the materials into single adjoined pieces, we have observed temperature spans above 9 K with two materials. Reasonable correspondence is found between experiments and a 2D numerical model, using the measured magnetocaloric properties of the two materials as input. © 2012 American Institute of Physics.

  10. The effect of demagnetization on the magnetocaloric properties of gadolinium

    DEFF Research Database (Denmark)

    Bahl, Christian Robert Haffenden; Nielsen, Kaspar Kirstein

    2009-01-01

    Gadolinium displays a strong magnetocaloric effect at temperatures close to room temperature making it useful in the field of room temperature magnetic refrigeration. We discuss the importance of including the effects of the demagnetization field when considering the magnetocaloric properties...

  11. Tunable magnetocaloric effect in transition metal alloys.

    Science.gov (United States)

    Belyea, Dustin D; Lucas, M S; Michel, E; Horwath, J; Miller, Casey W

    2015-10-28

    The unpredictability of geopolitical tensions and resulting supply chain and pricing instabilities make it imperative to explore rare earth free magnetic materials. As such, we have investigated fully transition metal based "high entropy alloys" in the context of the magnetocaloric effect. We find the NiFeCoCrPdx family exhibits a second order magnetic phase transition whose critical temperature is tunable from 100 K to well above room temperature. The system notably displays changes in the functionality of the magnetic entropy change depending on x, which leads to nearly 40% enhancement of the refrigerant capacity. A detailed statistical analysis of the universal scaling behavior provides direct evidence that heat treatment and Pd additions reduce the distribution of exchange energies in the system, leading to a more magnetically homogeneous alloy. The general implications of this work are that the parent NiFeCoCr compound can be tuned dramatically with FCC metal additives. Together with their relatively lower cost, their superior mechanical properties that aid manufacturability and their relative chemical inertness that aids product longevity, NiFeCoCr-based materials could ultimately lead to commercially viable magnetic refrigerants.

  12. Tunable magnetocaloric effect in transition metal alloys

    Science.gov (United States)

    Belyea, Dustin D.; Lucas, M. S.; Michel, E.; Horwath, J.; Miller, Casey W.

    2015-10-01

    The unpredictability of geopolitical tensions and resulting supply chain and pricing instabilities make it imperative to explore rare earth free magnetic materials. As such, we have investigated fully transition metal based “high entropy alloys” in the context of the magnetocaloric effect. We find the NiFeCoCrPdx family exhibits a second order magnetic phase transition whose critical temperature is tunable from 100 K to well above room temperature. The system notably displays changes in the functionality of the magnetic entropy change depending on x, which leads to nearly 40% enhancement of the refrigerant capacity. A detailed statistical analysis of the universal scaling behavior provides direct evidence that heat treatment and Pd additions reduce the distribution of exchange energies in the system, leading to a more magnetically homogeneous alloy. The general implications of this work are that the parent NiFeCoCr compound can be tuned dramatically with FCC metal additives. Together with their relatively lower cost, their superior mechanical properties that aid manufacturability and their relative chemical inertness that aids product longevity, NiFeCoCr-based materials could ultimately lead to commercially viable magnetic refrigerants.

  13. Strain-induced high ferromagnetic transition temperature of MnAs epilayer grown on GaAs (110

    Directory of Open Access Journals (Sweden)

    Pan Guoqiang

    2011-01-01

    Full Text Available Abstract MnAs films are grown on GaAs surfaces by molecular beam epitaxy. Specular and grazing incidence X-ray diffractions are used to study the influence of different strain states of MnAs/GaAs (110 and MnAs/GaAs (001 on the first-order magnetostructural phase transition. It comes out that the first-order magnetostructural phase transition temperature T t, at which the remnant magnetization becomes zero, is strongly affected by the strain constraint from different oriented GaAs substrates. Our results show an elevated T t of 350 K for MnAs films grown on GaAs (110 surface, which is attributed to the effect of strain constraint from different directions. PACS: 68.35.Rh, 61.50.Ks, 81.15.Hi, 07.85.Qe

  14. A Green's function model for ferromagnetism and spin excitations of (Ga, Mn)As diluted magnetic semiconductors

    Institute of Scientific and Technical Information of China (English)

    Liu Gui-Bin; Liu Bang-Gui

    2009-01-01

    We study (Ga, Mn)As diluted magnetic semiconductors in terms of the Ruderman-Kittel-Kasuya-Yosida quantum spin model in Green's function approach. Random distributions of the magnetic atoms are treated by using an analytical average of magnetic configurations. Average magnetic moments and spin excitation spectra as functions of temperature can be obtained by solving self-consistent equations, and the Curie temperature T_C is given explicitly. T_C is proportional to magnetic atomic concentration, and there exists a maximum for T_C as a function of carrier concentration. Applied to (Ga, Mn)As, the theoretical results are consistent with experiment and the experimental T_C can be obtained with reasonable parameters. This modelling can also be applied to other diluted magnetic semiconductors.

  15. Magnetocaloric and magnetoresistive properties of La0.67Ca0.33-xSrxMnO3

    DEFF Research Database (Denmark)

    Dinesen, Anders Reves

    This thesis presents results of an experimental investigation of magneto-caloric and magnetoresistive properties of a series of polycrystalline Ca- and Sr-doped lanthanum manganites, La0.67Ca0.33-xSrxMnO3 (0=x=0.33 ), with the perovskite structure. The samples consisted of sintered oxide powders...... a magnetocaloric effect in the vicinity of TC. A model for the mag-netocaloric effect based on Weiss mean field theory and classical theories for heat capacities was developed. The model provided reasonable predictions of the magne-tocaloric properties of the samples. The compounds with low Sr content showed...... a magnetocaloric effect comparable to that of Gadolinium, the prototypical working material for magnetic refrigeration at room temperature. A less comprehensive part of the investigation regarded the magnetoresistive properties of the La0.67Ca0.33-xSrxMnO3 system. It was found that the polycrystalline nature...

  16. Magnetic properties and magnetocaloric effects of Mn5Ge3-xGax

    Institute of Scientific and Technical Information of China (English)

    Liu Xi-Bin; Zhang Shao-Ying; Shen Bao-Gen

    2004-01-01

    We report on the magnetic properties and magnetocaloric effects of Mn5Ge3-xGax compounds with x=0.1, 0.2,0.3, 0.4, 0.6 and 0.9. All samples crystallize in the hexagonal Mn5Si3-type structure with space group P63/mcm and order ferromagnetically. The Curie temperature of these compounds decreases with increasing x, from 306K (x=0.1) to 274K (x=0.9). The average Mn magnetic moments increases with increasing Ga content, reaching a maximum value at x=0.6. The magnetic entropy changes in these compounds are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation. The Ga substitution has two kinds of influence on the magnetocaloric effect (MCE) of Mn5Ge3. One is that the magnitude of the magnetic entropy change decreases, the other is that the MCE peak becomes broadened.

  17. Pressure-induced changes in the magnetic and magnetocaloric properties of RMn2Ge2 (R=Sm,Gd)

    Science.gov (United States)

    Kumar, Pramod; Suresh, K. G.; Nigam, A. K.; Magnus, A.; Coelho, A. A.; Gama, S.

    2008-06-01

    We have studied the variation of magnetic and magnetocaloric properties of polycrystalline compounds SmMn2Ge2 and GdMn2Ge2 as a function of applied hydrostatic pressure. The magnetic transition temperatures are found to change considerably with pressure. The temperature regime of existence of antiferromagnetic (AFM) ordering is found to increase with pressure, in both the compounds. In SmMn2Ge2 , the sign of the magnetocaloric effect at the low-temperature ferromagnetic (FM)-AFM transition changes with pressure. The isothermal magnetic entropy change in this compound is found to increase by about 20 times as the pressure is increased from the ambient value to 6.8 kbar. Effect of pressure in GdMn2Ge2 is less compared to that in SmMn2Ge2 . The variations in the magnetic and magnetocaloric properties are attributed to the changes in the magnetic state of the Mn sublattice under pressure. The difference in R-Mn coupling in Sm and Gd compounds is also found to play a role in determining the magnetic and magnetocaloric properties, both at ambient as well as under applied pressures.

  18. Ferromagnetic Order, Strong Magnetocrystalline Anisotropy, and Magnetocaloric Effect in the Layered Telluride Fe(3-δ)GeTe2.

    Science.gov (United States)

    Verchenko, Valeriy Yu; Tsirlin, Alexander A; Sobolev, Alexei V; Presniakov, Igor A; Shevelkov, Andrei V

    2015-09-08

    The ternary transition-metal compound Fe(3-δ)GeTe2 is formed for 0 magnetocaloric effect with the magnetic entropy change upon the ferromagnetic ordering transition, -ΔS ∼ 1.1 J·kg(-1)·K(-1) at 5 T, is found.

  19. Magnetocaloric materials and first order phase transitions

    DEFF Research Database (Denmark)

    Neves Bez, Henrique

    of the properties of such materials.The experimental characterization of these materials is done through various different methods, such as X-ray diffraction, magnetometry, calorimetry, direct measurements of entropy change, capacitance dilatometry, scanning electron microscopy,energy-dispersive X-ray spectrometry......This thesis studies the first order phase transitions of the magnetocaloric materials La0.67Ca0.33MnO3 and La(Fe,Mn,Si)13Hz trying to overcome challenges that these materials face when applied in active magnetic regenerators. The study is done through experimental characterization and modelling...... and magnetocaloric regenerative tests. The magnetic, thermal and structural properties obtained from such measurements are then evaluated through different models, i.e. the Curie-Weiss law, the Bean-Rodbell model, the free electron model and the Debye model.The measured magnetocaloric properties of La0.67Ca0.33MnO3...

  20. Scaling and universality in magnetocaloric materials

    DEFF Research Database (Denmark)

    Smith, Anders; Nielsen, Kaspar Kirstein; Bahl, Christian R. H.

    2014-01-01

    The magnetocaloric effect of a magnetic material is characterized by two quantities, the isothermal entropy change and the adiabatic temperature change, both of which are functions of temperature and applied magnetic field. We discuss the scaling properties of these quantities close to a second...... change at the critical temperature depends on the nonsingular part of the specific heat. The field dependence can still be fitted to a power-law expression but with nonuniversal exponents, as we show explicitly both within mean-field theory and using the so-called Arrott-Noakes equation of state. Within...... the framework of the Bean-Rodbell model, we briefly consider the scaling properties of the magnetocaloric effect in first-order materials. Finally, we discuss the implications of our findings for a widely used phenomenological scaling procedure for magnetocaloric quantities....

  1. Monte Carlo simulation study of magnetocaloric effect in NdMnO3 perovskite

    Science.gov (United States)

    Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.; Hlil, E. K.

    2016-03-01

    The magnetocaloric effect in NdMnO3 perovskite is investigated by using the Monte Carlo simulations. The Curie temperature TC of NdMnO3 compound is deduced from the variation of the magnetization vs. the temperature with different values of external magnetic field. The variation of magnetization with the external magnetic field H is given. The specific heat with the temperature is established for different external magnetic field. The thermal magnetic entropy for different external magnetic field and different exchange interactions in NdMnO3 compound is obtained. The adiabatic temperature change is obtained. The relative cooling power with different external magnetic field is established. The magnetocaloric effect has been investigated from magnetization.

  2. Magnetocaloric materials for energy efficient cooling

    Science.gov (United States)

    Lyubina, Julia

    2017-02-01

    Solid-state magnetic cooling near room temperature has recently gained a prominent position among alternative cooling technologies that are deemed to have higher energy efficiency compared to vapour compression. This prospect has surged a rapid growth of the area of magnetocaloric materials. Although several breakthroughs were achieved, the extensive study revealed a number of challenges in the effective deployment of the magnetic refrigerants. This review focuses on fundamentally and technologically relevant aspects of the cooling with magnetocaloric materials. A critical evaluation of magnetic refrigerants and progress made in improvement of their performance is provided. Future development trends in the field of materials for the solid state cooling are highlighted.

  3. Magnetic Refrigeration and the Magnetocaloric Effect

    DEFF Research Database (Denmark)

    Petersen, Thomas Frank; Pryds, Nini; Smith, Anders

    2006-01-01

    Magnetic refrigeration at room temperature is an emerging technology for refrigeration, which promises low energy consumption and is environmentalle friendly. Magnetic refrigeration is based on the magnetocaloric effect, which manifests itself as a reversibel increase in temperature when magnetic...... material are plased in a magnetic field. This paper introduces and describes magnetic refrigeration cycles and the magnetocaloric effect, and shows how magnetic refrigeration can be an alternative to vapour-compression refrigeration,. A review of the Danish research on magnetic refrigeration at Risø...

  4. Magnetic properties of epitaxial MnAs thin films on GaAs (001)

    CERN Document Server

    Park, Y S

    2000-01-01

    The magnetic properties of two types of epitaxial MnAs films on GaAs (001) substrates in the thickness range of 20 approx 200 nm were studied. Using longitudinal a magneto-optical Kerr-effect(MOKE) apparatus at lambda=632.8 nm, we determined the Curie temperatures of the 100-nm thick films to be 54.0+-0.5 .deg. C and 63.7+-0.5 .deg. C for type A films and type B films, respectively. The observed Curie temperatures corresponded to increases of 36.8 .deg. C and 33.9 .deg. C per one percent increase in the unit cell volume for type A and B, respectively. The normalized maximum MOKE signal from the type A film exhibited a first-order-like magnetic transition while that of type B underwent a second-order-like transition. These different behaviors between types A and B stem from different residual stresses being exerted on the hexagonal phase. Utilizing a Foner-type vibrating sample magnetometer at room temperature, we examined the thickness dependence of the coercive force and the saturation magnetization of the f...

  5. The magnetocaloric effect in Er2Fe17 near the magnetic phase transition.

    Science.gov (United States)

    Alvarez-Alonso, Pablo; Gorria, Pedro; Sánchez Marcos, Jorge; Sánchez Llamazares, José L; Blanco, Jesús A

    2013-12-11

    Recent investigations in R2Fe17 intermetallic compounds have evidenced that these materials present a moderate magnetocaloric effect (MCE) near room temperature. A series of accurate magnetization measurements was carried out to show that the value of the demagnetizing factor has a significant influence on the absolute MCE value of Er2Fe17. In addition, the critical exponents determined from heat capacity and magnetization measurements allow us to describe the field dependence of the observed MCE around the Curie temperature.

  6. Magnetocaloric Pumping of Liquid Oxygen

    Science.gov (United States)

    Immer, Christopher; Kandula, Max; Lane, John; Youngquist, Robert

    2004-01-01

    The field-induced force density on a magnetic fluid is proportional to the magnetic susceptibility times the gradient of the magnetic field squared. The direction of the force is towards increasing magnetic field (positive gradient). Applying a magnetic field to a magnetic fluid will result in a force from all directions towards the location of peak field. Since the magnetic field is conservative and there are no magnetic monopoles, the net field-induced force on any fluid of constant susceptibly will be zero. The only manner to obtain a nonzero net field-induced force is to vary the susceptibility of the fluid. At the gas/liquid interface of liquid oxygen, the susceptibility varies drastically, and the exploitation of the resultant large net forces. An alternative method of varying the magnetic susceptibility is to vary the temperature of the fluid. The magnetic susceptibility of paramagnetic liquid oxygen obeys the Curie-Weiss law: it is inversely proportional to temperature. By applying a temperature gradient in the presence of a symmetric magnetic field, a nonzero net force results. Much of the theory of the so-called Magnetocaloric Effect has previously been developed for and applied to ferromagnetic fluids, or ferrofluids, but is readily applied to paramagnetic liquid oxygen.

  7. Thermofluid Analysis of Magnetocaloric Refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Abdelaziz, Omar [ORNL; Gluesenkamp, Kyle R [ORNL; Vineyard, Edward Allan [ORNL; Benedict, Michael [GE Appliances

    2014-01-01

    While there have been extensive studies on thermofluid characteristics of different magnetocaloric refrigeration systems, a conclusive optimization study using non-dimensional parameters which can be applied to a generic system has not been reported yet. In this study, a numerical model has been developed for optimization of active magnetic refrigerator (AMR). This model is computationally efficient and robust, making it appropriate for running the thousands of simulations required for parametric study and optimization. The governing equations have been non-dimensionalized and numerically solved using finite difference method. A parametric study on a wide range of non-dimensional numbers has been performed. While the goal of AMR systems is to improve the performance of competitive parameters including COP, cooling capacity and temperature span, new parameters called AMR performance index-1 have been introduced in order to perform multi objective optimization and simultaneously exploit all these parameters. The multi-objective optimization is carried out for a wide range of the non-dimensional parameters. The results of this study will provide general guidelines for designing high performance AMR systems.

  8. Magnetic properties,magnetoresistivity and magnetocaloric effect in GdxLa1-x-MnSi alloys

    Institute of Scientific and Technical Information of China (English)

    T.I.Ivanova; S.A.Nikitin; W.Suski; GA.Tskhadadze; I.A.Ovtchenkova; D.Badurski

    2009-01-01

    The results of magnetization,magnetoresistivity and magnetocaloric effect (MCE) studies performed on polycrystalline samples of the GdxLa1-xMnSi (x=0.5,0.6,0.7,0.8,0.9,1.0) compounds were presented.Complex measurements were carried out on the GdxLa1-xMnSi compounds to determine the influence of substitution in the rare earth (R) sublattice on the magnetic and related properties of these compounds.The compounds with x≤0.6 demonstrated two magnetic phase transitions (ferromagnetic to paramagnetic and antiferromagnetic to ferromagnetic) both of which were first order.Anomalies in the magnetocaloric effect,electroresistivity and magnetoresistivity were observed in the temperature ranges of the magnetic phase transitions.The temperature dependences of MCE and magnetoresistivity for these compounds correlated with the temperature dependence of magnetization.

  9. Developing a Magnetocaloric Domestic Heat Pump

    DEFF Research Database (Denmark)

    Bahl, Christian R.H.

    2014-01-01

    beverage coolers, A/Cs for cars and electronics cooling. Devices for heating have not been extensively demonstrated. Here we consider a promising application of magnetocaloric heat pumps for domestic heating. The task of designing and building such a device is a multidisciplinary one encompassing materials...

  10. High performance magnetocaloric perovskites for magnetic refrigeration

    DEFF Research Database (Denmark)

    Bahl, Christian R. H.; Velazquez, David; Nielsen, Kaspar K.

    2012-01-01

    We have applied mixed valance manganite perovskites as magnetocaloric materials in a magnetic refrigeration device. Relying on exact control of the composition and a technique to process the materials into single adjoined pieces, we have observed temperature spans above 9 K with two materials. Re...

  11. Arsenic-bridged magnetic interactions in an emerging two-dimensional FeAs nanostructure on MnAs

    Science.gov (United States)

    Helman, Christian; Ferrari, Valeria; Llois, Ana Maria

    2015-08-01

    The extreme case of an Fe monolayer deposited onto a manganese arsenide (MnAs) substrate is analyzed using density functional theory. We find that an FeAs quasi-two-dimensional antiferromagnetic surface nanostructure emerges. This nanostructure, which is magnetically nearly decoupled from the substrate, is due to bonding effects arising from the arsenic atoms bridging the Fe magnetic interactions. These interactions are studied and modeled using a Heisenberg-type Hamiltonian. They display an angular dependence which is characteristic of superexchange-like interactions, which are of the same order of magnitude as those appearing in Fe-based pnictides.

  12. Magnetocaloric Materials and the Optimization of Cooling Power Density

    Science.gov (United States)

    Wikus, Patrick; Canavan, Edgar; Heine, Sarah Trowbridge; Matsumoto, Koichi; Numazawa, Takenori

    2014-01-01

    The magnetocaloric effect is the thermal response of a material to an external magnetic field. This manuscript focuses on the physics and the properties of materials which are commonly used for magnetic refrigeration at cryogenic temperatures. After a brief overview of the magnetocaloric effect and associated thermodynamics, typical requirements on refrigerants are discussed from a standpoint of cooling power density optimization. Finally, a compilation of the most important properties of several common magnetocaloric materials is presented.

  13. AC measurement of heat capacity and magnetocaloric effect for pulsed magnetic fields.

    Science.gov (United States)

    Kohama, Yoshimitsu; Marcenat, Christophe; Klein, Thierry; Jaime, Marcelo

    2010-10-01

    A new calorimeter for measurements of the heat capacity and magnetocaloric effect of small samples in pulsed magnetic fields is discussed for the exploration of thermal and thermodynamic properties at temperatures down to 2 K. We tested the method up to μ(0)H=50 T, but it could be extended to higher fields. For these measurements we used carefully calibrated bare-chip Cernox(®) and RuO(2) thermometers, and we present a comparison of their performances. The monotonic temperature and magnetic field dependences of the magnetoresistance of RuO(2) allow thermometry with a precision as good as ±4 mK at T=2 K. To test the performance of our calorimeter, heat capacity and magnetocaloric effect for the spin-dimer compound Sr(3)Cr(2)O(8) and the triangular lattice antiferromagnet RbFe(MoO(4))(2) are presented.

  14. Sample dependence of giant magnetocaloric effect in a cluster-glass system Ho5Pd2

    Science.gov (United States)

    Toyoizumi, Saori; Kitazawa, Hideaki; Kawamura, Yukihiko; Mamiya, Hiroaki; Terada, Noriki; Tamura, Ryo; Dönni, Andreas; Morita, Kengo; Tamaki, Akira

    2015-05-01

    In order to investigate the effect of vacancy on the magnetocaloric effect in Ho5Pd2, we have carried out X-ray diffraction, magnetization, and specific heat measurements in the rare-earth intermetallic compound Ho5+xPd2(-0.4 ≤ x ≤ 0.4). The maximum magnetic entropy change -ΔSmmax , the maximum adiabatic temperature change ΔTadmax , and the relative cooling power of Ho5+xPd2 take large values at x = 0-0.4 for the field change of 5 T. The paramagnetic Curie temperature θp increases with an increase of x. This fact suggests that the enhancement of ferromagnetic coupling among the correlated spins leads to the increase of magnetocaloric effect.

  15. Microstructural Anisotropy of Magnetocaloric Gadolinium Cylinders: Effect on the Mechanical Properties of the Material

    Directory of Open Access Journals (Sweden)

    Darja Steiner Petrovič

    2016-05-01

    Full Text Available The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy, EDS (Energy-dispersive X-ray Spectroscopy, and BSE (Back-scattered Electrons in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces.

  16. Microstructural Anisotropy of Magnetocaloric Gadolinium Cylinders: Effect on the Mechanical Properties of the Material.

    Science.gov (United States)

    Petrovič, Darja Steiner; Šturm, Roman; Naglič, Iztok; Markoli, Boštjan; Pepelnjak, Tomaž

    2016-05-17

    The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy), EDS (Energy-dispersive X-ray Spectroscopy), and BSE (Back-scattered Electrons) in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction) analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces.

  17. Magnetocaloric properties of Co/Cr superlattices

    Science.gov (United States)

    Mukherjee, Tathagata; Skomski, Ralph; Sellmyer, David; Binek, Christian

    2010-03-01

    Nanostructured materials aiming on refrigeration applications are experimentally realized by molecular beam epitaxial (MBE) growth of Co/Cr superlattices using mean-field theoretical concepts as guiding principles.footnotetextT. Mukherjee, S. Sahoo, R. Skomski, D. J. Sellmyer, and Ch. Binek, Phys. Rev. B 79, 144406-1-9 (2009). Magnetocaloric properties are deduced from measurements of the temperature and field dependence of the magnetization of our samples. More generally, the potential of artificial antiferromagnets for near room-temperature refrigeration is explored. The effects of intra-plane and inter-plane exchange interactions on the magnetic phase diagram in Ising-type model systems are revisited in mean-field considerations with special emphasis on tailoring magnetocaloric properties. The experimental results are discussed in light of our theoretical findings, and extrapolations for future improved nanostructures are provided. Financial support by NRI, and NSF through EPSCoR, Career DMR-0547887, and MRSEC.

  18. Direct magnetocaloric characterization and simulation of thermomagnetic cycles

    NARCIS (Netherlands)

    Porcari, G.; Buzzi, M.; Cugini, F.; Pellicelli, R.; Pernechele, C.; Caron, L.; Brück, E.; Solzi, M.

    2013-01-01

    n experimental setup for the direct measurement of the magnetocaloric effect capable of simulating high frequency magnetothermal cycles on laboratory-scale samples is described. The study of the magnetocaloric properties of working materials under operative conditions is fundamental for the developm

  19. Magnetocrystalline anisotropy and the magnetocaloric effect in Fe2P

    NARCIS (Netherlands)

    Caron, L.; Hudl, M.; Höglin, V.; Dung, N.H.; Gomez, C.P.; Sahlberg, M.; Brück, E.; Andersson, Y.; Nordblad, P.

    2013-01-01

    Magnetic and magnetocaloric properties of high-purity, giant magnetocaloric polycrystalline and single-crystalline Fe2P are investigated. Fe2P displays a moderate magnetic entropy change, which spans over 70 K and the presence of strong magnetization anisotropy proves this system is not fully itiner

  20. Constraints on the Adiabatic Temperature Change in Magnetocaloric Materials

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Bahl, Christian Robert Haffenden; Smith, Anders

    2010-01-01

    The thermodynamics of the magnetocaloric effect implies constraints on the allowed variation in the adiabatic temperature change for a magnetocaloric material. An inequality for the derivative of the adiabatic temperature change with respect to temperature is derived for both first- and second...

  1. Electric field control of the magnetocaloric effect.

    Science.gov (United States)

    Gong, Yuan-Yuan; Wang, Dun-Hui; Cao, Qing-Qi; Liu, En-Ke; Liu, Jian; Du, You-Wei

    2015-02-04

    Through strain-mediated magnetoelectric coupling, it is demonstrated that the magnetocaloric effect of a ferromagnetic shape-memory alloy can be controlled by an electric field. Large hysteresis and the limited operating temperature region are effectively overcome by applying an electric field on a laminate comprising a piezoelectric and the alloy. Accordingly, a model for an active magnetic refrigerator with high efficiency is proposed in principle.

  2. Magnetocaloric Properties Response in High-Speed Melt-Spun La-Ce-Fe-Si Ribbons

    Science.gov (United States)

    Hou, Xueling; Han, Ning; Xue, Yun; Lu, Qianqian; Wang, Xiaochen; Phan, Manh-Huong

    2016-10-01

    The structure and magnetocaloric properties of La-Ce-Fe-Si alloys have been studied. The samples were prepared by melt spinning, the surface speed of the Cu wheel being 55 m/s. The as-spun ribbons were subsequently annealed at 1273 K for different times (10 min-1 h) and then quenched to room temperature. When the annealing time was 20 min, on a 1.5-T applied magnetic field, the maximum magnetic entropy change (Δ S M) of the ribbons reached values of 33.8 J/kg K at the Curie temperature of T C ˜ 182 K. When the annealing time was longer than 20 min, the maximum magnetic entropy change (|Δ S M,Max|) tended to decrease while the T C remained almost unchanged. In the annealing process, La/Ce located at grain boundaries was easily oxidized on the ribbon surface. The presence of large grain sizes and La2O3 or LaO were shown to degrade the magnetocaloric properties. On the other hand, the substitution of Ce for La improved the magnetocaloric effect of La-Fe-Si compounds, which is of practical importance for magnetic refrigeration.

  3. Tuneable Giant Magnetocaloric Effect in (Mn,Fe)2(P,Si) Materials by Co-B and Ni-B Co-Doping

    OpenAIRE

    Nguyen Thang; Niels Harmen van Dijk; Ekkes Brück

    2016-01-01

    The influence of Co (Ni) and B co-doping on the structural, magnetic and magnetocaloric properties of (Mn,Fe) 2 (P,Si) compounds is investigated by X-ray diffraction (XRD), differential scanning calorimetry, magnetic and direct temperature change measurements. It is found that Co (Ni) and B co-doping is an effective approach to tune both the Curie temperature and the thermal hysteresis of (Mn,Fe) 2 (P,Si) materials without losing either the giant magnetocaloric effect or the pos...

  4. Mn1.2Fe0.8-xCoxP0.48Si0.52化合物磁热效应研究%Experimental study on the magnetocaloric effect in Mn1.2Fe0.8-xCoxP0.48Si0.52 compounds

    Institute of Scientific and Technical Information of China (English)

    耿遥祥; 特古斯

    2011-01-01

    用机械合金化方法制备了Mn12Fe0.8-xCoxP0.48Si0.52 (x=0,0.01,0.03和0.05)化合物.对比研究了用少量Co替代Fe对Mn1.2Fe0.8P0.48Si0.52化合物磁热效应的影响.X射线衍射和扫描电镜观测表明,不同Co替代量化合物的主相呈Fe2P型六角结构,此外含有少量的(Fe,Mn)3Si杂相.磁性测量表明,当用Co替代Fe时,化合物的居里温度在293K (x=0.01)到230K(x=0.05)内变化,热滞由7K(x=0)降低到4K (x=0.05).Co的加入使得Mn1.2Fe0.75Co0.05P0.4sSi0.52化合物在低磁场下产生场致变磁转变.根据麦克斯韦关系,用等温磁化强度数据确定了化合物的磁熵变.其中Mn1.2Fe0.75Co0.01P0.48Si0.52化合物在1.5T磁场变化下具有磁熵变最大值,为16.4 J/kg.K.%The Mn1.2Fe0.8-xCoxP0.48Si0.52 compounds (x=0, 0.01, 0.03 and 0.05) were prepared by mechanical alloying technology. The influence of Co substitution on the magnetocaloric effect in Mn12Fe0.8-xCOxP0.48Si0.52 compounds was investigated. X-ray diffraction and scanning electron microscopy results showed that these compounds consist of main phase of Fe2P-type hexagonal structure and small content of second phase of (Fe,Mn)3Si. Magnetization measurements showed that the Curie temperature of the compounds range from 293 (x = 0.01) to 230 K (x = 0.05), and the thermal hysteresis decreases from 7 to 4K. A field-induced metamagnetic transition was observed in the Co-substituted compound. The magnetic-entropy change of the compounds was derived from the isothermal magnetization data according to the Maxwell relation. The maximal magnetic entropy change of the compounds for a magnetic field change from 0 to 1.5T is -16.4 J/kg·K for Mn1.2Fe0.75Co0.01P0.48Si0.52 compound.

  5. Green Function Calculations of Properties for the Magnetocaloric Layered Structures Based Upon FeMnAsP

    Science.gov (United States)

    Schilling, Osvaldo F.

    2016-11-01

    The alternating Fe-Mn layered structures of the compounds FeMnAsxP1-x display properties which have been demonstrated experimentally as very promising as far as commercial applications of the magnetocaloric effect are concerned. However, the theoretical literature on this and other families of magnetocaloric compounds still adopts simple molecular-field models in the description of important statistical mechanical properties like the entropy variation that accompanies applied isothermal magnetic field cycling, as well as the temperature variation following adiabatic magnetic field cycles. In the present paper, a random phase approximation Green function theoretical treatment is applied to such structures. The advantages of such approach are well known since the details of the crystal structure are easily incorporated in the model, as well as a precise description of correlations between neighbor spins can be obtained. We focus on a simple one-exchange parameter Heisenberg model, and the observed first-order phase transitions are reproduced by the introduction of a biquadratic term in the Hamiltonian whose origin is related both to the magnetoelastic coupling with the phonon spectrum in these compounds as well as with the values of spins in the Fe and Mn ions. The calculations are compared with experimental magnetocaloric data for the FeMnAsxP1-x compounds. In particular, the magnetic field dependence for the entropy variation at the transition temperature predicted from the Landau theory of continuous phase transitions is reproduced even in the case of discontinuous transitions.

  6. Dodecanuclear 3d/4f-metal clusters with a 'Star of David' topology: single-molecule magnetism and magnetocaloric properties.

    Science.gov (United States)

    Alexandropoulos, Dimitris I; Cunha-Silva, Luís; Lorusso, Giulia; Evangelisti, Marco; Tang, Jinkui; Stamatatos, Theocharis C

    2016-01-28

    A family of interwoven molecular inorganic knots, shaped like the 'Star of David', was prepared by the employment of naphthalene-2,3-diol in 3d/4f-metal cluster chemistry; the isoskeletal dodecanuclear compounds exhibit slow relaxation of the magnetization and magnetocaloric properties, depending on the metal ion.

  7. Giant enhancement of magnetocaloric effect in metallic glass matrix composite

    Institute of Scientific and Technical Information of China (English)

    WANG YongTian; BAI HaiYang; PAN MingXiang; ZHAO DeQian; WANG WeiHua

    2008-01-01

    The magnetocaloric effect (MCE) has made great success in very low temperature refrigeration, which is highly desirable for application to the extended higher tem-perature range. Here we report the giant enhancement of MCE in the metallic glass composite. The large magnetic refrigerant capacity (RC) up to 103 J·kg-1 is more than double the RC of the well-known crystalline magnetic refrigerant compound Gd5Si2Ge1.9Fe0.1 (357 J·kg-1) and MnFeP0.45As0.55 (390 J·kg-1)(containing either ex-orbitant-cost Ge or poisonous As). The full width at half maximum of the magnetic entropy change (△Sm) peak almost spreads over the whole low-temperature range (from 303 to 30 K), which is five times wider than that of the Gd5Si2Ge1.9Fe0.1 and pure Gd. The maximum △Sm approaches a nearly constant value in a wide tem-perature span over 100 K, and however, such a broad table-like region near room temperature has seldom been found in alloys and compounds. In combination with the intrinsic amorphous nature, the metallic glass composite may be potential for the ideal Ericsson-cycle magnetic refrigeration over a broad temperature range near room temperature.

  8. Giant enhancement of magnetocaloric effect in metallic glass matrix composite

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The magnetocaloric effect (MCE) has made great success in very low temperature refrigeration, which is highly desirable for application to the extended higher tem-perature range. Here we report the giant enhancement of MCE in the metallic glass composite. The large magnetic refrigerant capacity (RC) up to 103 J·kg-1 is more than double the RC of the well-known crystalline magnetic refrigerant compound Gd5Si2Ge1.9Fe0.1 (357 J·kg-1) and MnFeP0.45As0.55 (390 J·kg-1)(containing either ex-orbitant-cost Ge or poisonous As). The full width at half maximum of the magnetic entropy change (ΔSm) peak almost spreads over the whole low-temperature range (from 303 to 30 K), which is five times wider than that of the Gd5Si2Ge1.9Fe0.1 and pure Gd. The maximum ΔSm approaches a nearly constant value in a wide tem-perature span over 100 K, and however, such a broad table-like region near room temperature has seldom been found in alloys and compounds. In combination with the intrinsic amorphous nature, the metallic glass composite may be potential for the ideal Ericsson-cycle magnetic refrigeration over a broad temperature range near room temperature.

  9. Magnetocaloric refrigeration concepts: current state of the art

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein

    2014-01-01

    Refrigeration devices based on the magnetocaloric effect have been prototyped in great numbers during the past decade. The search for the optimal combination of magnetic field source, regenerator geometry, magnetocaloric material composition and flow system design has resulted in a variety...... of designs and concepts. In this paper key parts constituting a magnetocaloric refrigeration device are reviewed in terms of how they have been implemented in actual machines. Some of the major design choices are then evaluated and, based on numerical modeling tools, recommendations on how to optimize...

  10. Magnetocaloric effect in Gd-based ferromagnet GdZn2

    Science.gov (United States)

    Matsumoto, Keisuke T.; Hiraoka, Koichi

    2017-02-01

    Magnetic properties and magnetocaloric effect of the Gd-based compound GdZn2 have been investigated. GdZn2 shows a ferromagnetic transition at TC = 85 K and spin-reorientation transition at TSR = 58 K. The maximum entropy change and relative cooling power (RCP) are estimated to be 11.5 J/K kg and 690 J/kg, respectively, for a magnetic field change of 7 T. The large value of RCP is suggested that GdZn2 is an attractive candidate for a low-temperature magnetic refrigerant.

  11. Magnetocaloric effect and refrigeration cooling power in amorphous Gd7Ru3 alloys

    Science.gov (United States)

    Kumar, Pramod; Kumar, Rachana

    2015-07-01

    In this paper, we report the magnetic, heat capacity and magneto-caloric effect (MCE) of amorphous Gd7Ru3 compound. Both, temperature dependent magnetization and heat capacity data reveals that two transitions at 58 K and 34 K. MCE has been calculated in terms of isothermal entropy change (ΔSM) and adiabatic temperature change (ΔTad) using the heat capacity data in different fields. The maximum values of ΔSM and ΔTad are 21 Jmol-1K-1 and 5 K respectively, for field change of 50 kOe whereas relative cooling power (RCP) is ˜735 J/kg for the same field change.

  12. Strong pressure dependences of the magnetization and Curie temperature for CrTe and MnAs with NiAs-type structure

    CERN Document Server

    Yamada, H; Kondo, K; Goto, T

    2002-01-01

    To study the strong magneto-volume effects observed in CrTe and MnAs with NiAs-type crystal structure, first-principle band calculations are carried out by a self-consistent linear muffin-tin orbital method within the atomic sphere approximation. The equilibrium volume of the unit cell is obtained as a function of the magnetization M, which gives the volume magnetostriction. The dependence on M of the bulk modulus is also estimated. The coefficients a sub 0 and b sub 0 in the Landau expansion, DELTA E(M) = a sub 0 M sup 2 /2 + b sub 0 M sup 4 /4, are estimated by the fixed-spin-moment method. The calculated results for CrTe and MnAs are compared with those for bcc Fe. It is shown that the values of vertical bar a sub 0 vertical bar and b sub 0 for CrTe and MnAs are so small that the correction term from the magneto-volume coupling constants becomes significant. This fact gives a strong pressure dependence of the spontaneous magnetization. The pressure dependence of the Curie temperature is also discussed by m...

  13. Transport and magnetic study of the spin reorientation transition in the Tb{sub 5}(Si{sub 0.5}Ge{sub 0.5}){sub 4} magnetocaloric compound

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, J P [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Pereira, A M [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Braga, M E [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Pinto, R P [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Teixeira, J M [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Correia, F C [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Sousa, J B [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Morellon, L [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas and Instituto de Nanociencia de Aragon, 50009 Zaragoza (Spain); Algarabel, P A [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas, 50009 Zaragoza (Spain); Magen, C [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas, 50009 Zaragoza (Spain); Ibarra, M R [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas and Instituto de Nanociencia de Aragon, 50009 Zaragoza (Spain)

    2005-08-17

    Detailed measurements of the electrical resistivity {rho}(T), thermopower S(T) and magnetization of Tb{sub 5}(Si{sub 0.5}Ge{sub 0.5}){sub 4} in the vicinity of the spin reorientation transitions observed in this compound are reported. Our results indicate a complex spin reorientation process associated with three different lattice sites occupied by the Tb ions. We identify two critical transition temperatures: one at T{sub SR{sub 1}} = 57 K, as previously reported, and a new one at T{sub SR{sub 2}} = 40 K. A simple model based on an approximate magnetic anisotropy energy is presented; it gives a satisfactory qualitative description of the main features of the reorientation processes.

  14. Normal and inverse magnetocaloric effects in LaCaMnNiO

    Science.gov (United States)

    Krishnamoorthi, C.; Barik, S. K.; Siu, Z.; Mahendiran, R.

    2010-09-01

    We have investigated magnetic and magnetocaloric properties of La 0.5Ca 0.5Mn 1- xNi xO 3 ( x=0, 0.02, 0.04, 0.06, & 0.08). It is shown that charge-ordered antiferromagnetic ground state of x=0 is destabilized and ferromagnetism is induced by just 2% Ni substitution. The ferromagnetic Curie temperature (TC) decreases from TC=220 K for x=0 to 85 K (x=0.08). Unusual field-induced metamagnetic transition is found above TC for x=0.02-0.06 and even below TC in the parent compound (x=0). Magnetic entropy change (ΔSm) was estimated from isothermal magnetization data and it is found that the parent compound (x=0) exhibits both normal (negative ΔSm) and inverse (positive ΔSm) magnetocaloric effects at TC and TN (Neel temperature), respectively. The ΔSm=+6.5 J kg K at TN is twice larger than that at TC(ΔSm=-3 JkgK) for a field change (ΔH) of 5 T. However, all the Ni doped samples in La 0.5Ca 0.5Mn 1- xNi xO 3 system show only normal magnetocaloric effect at TC. The largest MCE in the Ni doped series occurs for x=0.04 (ΔSm=-3.9 JkgK,ΔH=5 T) which also has the largest relative cooling power (RCP=235 J/kg,ΔH=5 T) in the series. We discuss our results in the scenario of phase separation induced by Ni substitution.

  15. Magnetocaloric phenomena in Mg-ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Burianova, S; Holec, P; Plocek, J [Charles University, Faculty of Science, Department of Inorganic chemistry, Prague (Czech Republic); Poltierova-Vejpravova, J, E-mail: burianovasimona@email.c, E-mail: jana@mag.mff.cuni.c

    2010-01-01

    A comparative study of magnetocaloric effect (MCE) in superparamagnetic (SPM) regime is reported in two different types of magnesium ferrite nanostructures. The samples were prepared either by microemulsion method as MgFe{sub 2}O{sub 4} nanoparticles encapsulated in amorphous SiO{sub 2}, or as matrix-less nanoparticles using hydrothermal synthesis in supercritical water conditions. The particle diameter in all prepared samples was obtained from XRD measurements and TEM analysis. All samples show a SPM behavior above the blocking temperature, T{sub B}. The entropy change, {Delta}S was finally derived from the measurements of magnetization, M(H,T) curves at defined temperature intervals. We observed, that all samples show a broad peak of {Delta}S in the temperature range that is fairly above the T{sub B}. The values of the {Delta}S also depend on the particle size, and they are of about two orders lower than those reported in the famous giant magnetocaloric materials.

  16. Magnetocaloric and Hopkinson effects in slowly and rapidly cooled Gd{sub 7}Pd{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Talik, Ewa; Guzik, Adam; Oboz, Monika; Zajdel, Pawel; Ziolkowski, Grzegorz [Silesia Univ., Katowice (Poland). Inst. of Physics

    2016-01-15

    Gd{sub 7}Pd{sub 3} intermetallic compound was prepared as slowly cooled polycrystal and rapidly cooled (rc) casts. The slowly cooled polycrystalline samples were obtained by melting in an induction coil. The rc-cast Gd{sub 7}Pd{sub 3} sample was obtained by means of a mould casting technique. The samples were characterized by means of X-ray diffraction, SQUID magnetometry and scanning electron microscopy in order to elucidate the Hopkinson effect and magnetocaloric properties in relation to the technological aspects. The investigated ferromagnetic system is sensitive to grain size. The magnetocaloric and Hopkinson effect decreases with the decrease of the grain size. The results were compared to the data of single crystal obtained by the Czochralski method from a levitating melt.

  17. Sample dependence of giant magnetocaloric effect in a cluster-glass system Ho{sub 5}Pd{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Toyoizumi, Saori, E-mail: 14udb03@ms.dendai.ac.jp; Tamaki, Akira [Graduate School of Advanced Science and Technology, Tokyo Denki University, 5 Senju Asahi-cho, Adachi, Tokyo 120–8551 (Japan); Kitazawa, Hideaki; Mamiya, Hiroaki; Terada, Noriki; Tamura, Ryo; Dönni, Andreas [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305–0047 (Japan); Kawamura, Yukihiko [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305–0047 (Japan); Research Center for Neutron Science and Technology, Comprehensive Research Organization for Science and Society, 162-1 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319–1106 (Japan); Morita, Kengo [School of Engineering, Tokyo Denki University, 5 Senju Asahi-cho, Adachi, Tokyo 120-8551 (Japan)

    2015-05-07

    In order to investigate the effect of vacancy on the magnetocaloric effect in Ho{sub 5}Pd{sub 2}, we have carried out X-ray diffraction, magnetization, and specific heat measurements in the rare-earth intermetallic compound Ho{sub 5+x}Pd{sub 2}(−0.4 ≤ x ≤ 0.4). The maximum magnetic entropy change −ΔS{sub m}{sup max}, the maximum adiabatic temperature change ΔT{sub ad}{sup max}, and the relative cooling power of Ho{sub 5+x}Pd{sub 2} take large values at x = 0−0.4 for the field change of 5 T. The paramagnetic Curie temperature θ{sub p} increases with an increase of x. This fact suggests that the enhancement of ferromagnetic coupling among the correlated spins leads to the increase of magnetocaloric effect.

  18. Magnetism and magnetocaloric effect study of CaFe0.7Co0.3O3

    Science.gov (United States)

    Xia, H. L.; Y Yin, Y.; Dai, J. H.; Y Yang, J.; Qin, X. M.; Jin, C. Q.; Long, Y. W.

    2015-04-01

    The CaFe0.7Co0.3O3 single crystal was grown for the first time by a two-step method and its magnetism and magnetocaloric effect were investigated. This compound experiences a second-order paramagnetism-to-ferromagnetism transition in a wide temperature window between 200 and 150 K due to the presence of multiple ferromagnetic interactions. Since the spin entropy is gradually released above the ferromagnetic Curie temperature (˜177 K), no sharp λ-type anomaly is observed in specific heat. On the basis of magnetization measurements, however, a considerable entropy change is found in this perovskite oxide. More interesting, this compound exhibits a broadening working temperature, and a significant refrigerant capacity (˜355 J kg-1 at 6 T) which is comparable with those found in some giant magnetocaloric alloys with first-order magnetic transitions. The present study therefore provides an example on how to enhance the refrigerant capacity by extending the working temperature of magnetocaloric material.

  19. Performance-oriented Analysis of a Hybrid magnetic Assembly for a Heat-pump Magnetocaloric Device

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Smith, Anders; Bahl, Christian R.H.

    2014-01-01

    Conventional active-regenerator magnetocaloric devices include moving parts, with the purpose of generating an oscillating magnetic field in the magneto-caloric material, placed inside the regenerator. In this work a different design is analyzed, for application in a magnetocaloric heat pump...

  20. Near room temperature magnetocaloric properties and the universal curve of MnCoGe1-xCux

    Science.gov (United States)

    Si, Xiaodong; Liu, Yongsheng; Lu, Xiaofei; Shen, Yulong; Wang, Wenli; Yu, Wenying; Zhou, Tao; Gao, Tian

    2017-05-01

    Intermetallic compounds based on MnCoGe have drawn attention due to the coupled magnetic and structural transformations and the large magnetocaloric entropy. Here, we provide a systematic comparison of experimental data under different magnetic fields with magnetic and the magnetocaloric properties. The ferromagnetic transition temperature (TC) increases from 353.4(6) K for x = 0.01 to 363.4(4) K for x = 0.04 with increasing nominal copper content. The maximum magnetic entropy change |ΔSM| in a magnetic field change of 5 T is found to be 18.3(2) J/(kg K) with a large relative cooling power (RCP) value of 292.5(4) J/kg for x = 0.01, revealing that the present system can provide an acceptable magnetocaloric effect at a cheaper price for magnetic refrigeration materials. Making attempt to contrast a master curve for the present system, we find the experimental values of magnetic field dependence of the magnetic entropy change are consistent with a phenomenological universal curve.

  1. Magnetostructural phase transitions and magnetocaloric effect in Tb-Dy-Ho-Co-Al alloys with a Laves phase structure

    Science.gov (United States)

    Tereshina, I. S.; Chzhan, V. B.; Tereshina, E. A.; Khmelevskyi, S.; Burkhanov, G. S.; Ilyushin, A. S.; Paukov, M. A.; Havela, L.; Karpenkov, A. Yu.; Cwik, J.; Koshkid'ko, Yu. S.; Miller, M.; Nenkov, K.; Schultz, L.

    2016-07-01

    The influence of simultaneous substitution within the rare earth (R) and Co sublattices on the structural, magnetic, and magnetocaloric properties of the Laves phase RCo2-type compounds is studied. Main attention is devoted to the studies of the magnetostructural phase transitions and the transition types with respect to the alloy composition. Multicomponent alloys Tbx(Dy0.5Ho0.5)1-xCo2 and Tbx(Dy0.5Ho0.5)1-xCo1.75Al0.25 were prepared with the use of high purity metals. Majority of the Tbx(Dy0.5Ho0.5)1-xCo2 alloys exhibit magnetic transitions of the first-order type and a large magnetocaloric effect. The substitution of Al for Co in Tbx(Dy0.5Ho0.5)1-xCo2 increases the Curie temperature (TC) but changes the transition type from first-to the second-order. The discussion of the physical mechanisms behind the observed phenomena is given on the basis of the first principles electronic-structure calculations taking into account both the atomic disorder and the magnetic disorder effects at finite temperatures. The advantage of Al-containing materials is that sufficiently high magnetocaloric effect values are preserved at T > TC.

  2. Applicability of scaling behavior and power laws in the analysis of the magnetocaloric effect in second-order phase transition materials

    Science.gov (United States)

    Romero-Muñiz, Carlos; Tamura, Ryo; Tanaka, Shu; Franco, Victorino

    2016-10-01

    In recent years, universal scaling has gained renewed attention in the study of magnetocaloric materials. It has been applied to a wide variety of pure elements and compounds, ranging from rare-earth-based materials to transition metal alloys, from bulk crystalline samples to nanoparticles. It is therefore necessary to quantify the limits within which the scaling laws would remain applicable for magnetocaloric research. For this purpose, a threefold approach has been followed: (a) the magnetocaloric responses of a set of materials with Curie temperatures ranging from 46 to 336 K have been modeled with a mean-field Brillouin model, (b) experimental data for Gd has been analyzed, and (c) a 3D-Ising model—which is beyond the mean-field approximation—has been studied. In this way, we can demonstrate that the conclusions extracted in this work are model-independent. It is found that universal scaling remains applicable up to applied fields, which provide a magnetic energy to the system up to 8% of the thermal energy at the Curie temperature. In this range, the predicted deviations from scaling laws remain below the experimental error margin of carefully performed experiments. Therefore, for materials whose Curie temperature is close to room temperature, scaling laws at the Curie temperature would be applicable for the magnetic field range available at conventional magnetism laboratories (˜10 T), well above the fields which are usually available for magnetocaloric devices.

  3. Understanding the inverse magnetocaloric effect in antiferro- and ferrimagnetic arrangements.

    Science.gov (United States)

    von Ranke, P J; de Oliveira, N A; Alho, B P; Plaza, E J R; de Sousa, V S R; Caron, L; Reis, M S

    2009-02-04

    The inverse magnetocaloric effect occurs when a magnetic material cools down under applied magnetic field in an adiabatic process. Although the existence of the inverse magnetocaloric effect was recently reported experimentally, a theoretical microscopic description is almost nonexistent. In this paper we theoretically describe the inverse magnetocaloric effect in antiferro- and ferrimagnetic systems. The inverse magnetocaloric effects were systematically investigated as a function of the model parameters. The influence of the Néel and the compensation temperature on the magnetocaloric effect is also analyzed using a microscopic model.

  4. The Influence of Substitutions in 3 d-Sublattice on the Exchange Interactions in Compounds Based on NdMnGe

    Science.gov (United States)

    Ovchenkova, I. A.; Bogdanov, A. E.; Smirnov, A. V.; Ovchenkov, E. A.; Morozkin, A. V.; Yapaskurt, V. O.; Nikitin, S. A.

    2016-12-01

    Magnetic properties of CeFeSi-type NdMn_{1-x}TixGe compounds studied by magnetization and magnetocaloric measurements are reported. The increase in Ti content leads to the essential increase in magnetic ordering temperature of the Nd sublattice and the magnetocaloric effect. The results are compared with those obtained on isotypic RTX compounds and discussed assuming the itinerant character of magnetism of these compounds.

  5. Observation of weak ferromagnetism and the sizable magnetocaloric effect in Co2V2O7

    Science.gov (United States)

    Sannigrahi, J.; Giri, S.; Majumdar, S.

    2017-02-01

    The magnetic behavior of cobalt pyrovanadate compound Co2V2O7 with dichromate structure is reported. The compound undergoes long range magnetic ordering below TC=8 K and our study identifies the ground state to be a canted antiferromagnetic type with a weak ferromagnetic component. The transition at TC is found to be first-order in nature as evident from the presence of distinct thermal hysteresis in the temperature dependent magnetization data. Below TC, a significantly large value of magnetic relaxation is observed which is possibly due to the metastability associated with the first order phase transition. Interestingly, the sample exhibits a sizable magneto-caloric effect around TC (∼4.1 J kg-1. K-1 for 50 kOe of field change) which is reasonably high among antiferromagnetic transition metal oxides with weak ferromagnetism.

  6. Universal field dependence of conventional and inverse magnetocaloric effects in DyCo2Si2

    Science.gov (United States)

    Karmakar, S. K.; Giri, S.; Majumdar, S.

    2017-01-01

    The rare-earth intermetallic compound DyCo2Si2 orders antiferromagnetically below TN = 23 K followed by a second magnetic anomaly at Tt = 9 K. The sample is known to show multiple metamagnetic transitions, which are reproduced in our present study. Our investigations on this sample indicate that the magnetocaloric effect (MCE) calculated from the magnetization data (in terms of change in entropy, ΔSM ) is quite fascinating, and it is characterized by multiple sign reversals around TN and Tt. The MCE is found to be conventional (i.e., ΔSM is negative) above TN and below Tt, while it is inverse (i.e., ΔSM is positive) between TN and Tt. We performed a comprehensive analysis of the field dependence of the observed MCE, and a universal quadratic variation is observed at temperatures above and below TN (including the region below Tt) as long as the applied field is lower than the critical field for metamagnetic transition. The present work is able to show that the field dependence of the MCE in this antiferromagnetic material is quadratic despite the fact that the magnetocaloric effect is conventional or inverse in different temperature regions.

  7. Influence of the small substitution of Z=Ni, Cu, Cr, V for Fe on the magnetic, magnetocaloric, and magnetoelastic properties of LaFe{sub 11.4}Si{sub 1.6}

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, Arjun K., E-mail: pathak@siu.ed [Department of Physics, Southern Illinois University Carbondale, 1245 Lincoln Dr., Carbondale, IL 62901 (United States); Basnyat, Prakash; Dubenko, Igor [Department of Physics, Southern Illinois University Carbondale, 1245 Lincoln Dr., Carbondale, IL 62901 (United States); Stadler, Shane [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Ali, Naushad [Department of Physics, Southern Illinois University Carbondale, 1245 Lincoln Dr., Carbondale, IL 62901 (United States)

    2010-03-15

    We have studied the magnetic, magnetocaloric, and magnetostriction properties of LaFe{sub 11.4}Si{sub 1.6} and La(Fe{sub 0.99}Z{sub 0.01}){sub 11.4}Si{sub 1.6} (Z=Ni, Cu, Cr, V) compounds using magnetization and strain gauge techniques. It was found that substitution of 1% of the Fe by Z-elements results in an increase in the Curie temperature (T{sub C}), and affects the magnetostriction and magnetocaloric properties of the parent compound, LaFe{sub 11.4}Si{sub 1.6}. A maximum shift in T{sub C} of about 11 K, and significantly smaller hysteresis losses in the vicinity of T{sub C} compared with those of the base compound, were found for Z=V. The maximum magnetovolume coupling constant was estimated to be n{sub dd}approx2.7x10{sup -3} (mu{sub B}/Fe atom){sup -2} for the parent compound. The changes in the volume magnetostriction, the magnetovolume coupling constant, and the magnetocaloric properties are strongly correlated with composition. The relative effects of the variation in cell parameters and electron concentration on the magnetostriction, T{sub C}, and the magnetocaloric properties are discussed.

  8. Consequenses of the magnetocaloric effect on magnetometry measurements

    DEFF Research Database (Denmark)

    Hansen, Britt Rosendahl; Bahl, Christian Robert Haffenden; Kuhn, Luise Theil

    2010-01-01

    is a measure of the magnetocaloric effect, the discrepancies demonstrated here are more severe close to a peak in ΔSM, which is precisely the quantity that is of interest and reported on in the literature from possibly erroneous magnetization data. We also demonstrate how, through simple measurements......Magnetization curves recorded at high sweep-rates on magnetic materials near a phase transition temperature can be affected by temperature changes in the material due to the magnetocaloric effect. This change in the sample temperature is a result of the quasiadiabatic conditions that can occur...... under such conditions and we demonstrate its effects on magnetization curves of two magnetocaloric materials, La(Fe0.945Co0.055)11.9Si1.1 and Gd5Si2Ge2. We show how a quantity calculated from isothermal magnetization curves, the magnetic entropy change, ΔSM, is affected by the erroneous data. As ΔSM...

  9. Evaluating the effect of magnetocaloric properties on magnetic refrigeration performance

    DEFF Research Database (Denmark)

    Engelbrecht, Kurt; Bahl, Christian Robert Haffenden

    2010-01-01

    Active magnetic regenerator (AMR) refrigerators represent an alternative to vapor compression technology that relies on the magnetocaloric effect in a solid refrigerant. Magnetocaloric materials are in development and properties are reported regularly. Recently, there has been an emphasis...... on developing materials with a high entropy change with magnetization while placing lower emphasis on the adiabatic temperature change. This work uses model magnetocaloric materials and a numerical AMR model to predict how the temperature change and entropy change with magnetization interact and how they affect...... that exhibits a sharp peak in isothermal entropy change was shown to produce a significantly lower cooling power than a material with a wide peak in a practical AMR system. © 2010 American Institute of Physics...

  10. Direct magnetocaloric characterization and simulation of thermomagnetic cycles.

    Science.gov (United States)

    Porcari, G; Buzzi, M; Cugini, F; Pellicelli, R; Pernechele, C; Caron, L; Brück, E; Solzi, M

    2013-07-01

    An experimental setup for the direct measurement of the magnetocaloric effect capable of simulating high frequency magnetothermal cycles on laboratory-scale samples is described. The study of the magnetocaloric properties of working materials under operative conditions is fundamental for the development of innovative devices. Frequency and time dependent characterization can provide essential information on intrinsic features such as magnetic field induced fatigue in materials undergoing first order magnetic phase transitions. A full characterization of the adiabatic temperature change performed for a sample of Gadolinium across its Curie transition shows the good agreement between our results and literature data and in-field differential scanning calorimetry.

  11. A novel magnetic valve using room temperature magnetocaloric materials

    DEFF Research Database (Denmark)

    Eriksen, Dan; Bahl, Christian; Pryds, Nini;

    2012-01-01

    Magnetocaloric materials with near-room-temperature tuneable Curie temperatures have been utilized to develop a novel magnetic valve technology. The temperature dependent attractive force between the materials and a permanent magnet assembly is used to actuate valves as a response to temperature...... changes. This is made possible by the strong temperature dependence of the magnetization close to the Curie temperature of the magnetocaloric materials. Different compositions of both La0.67(Ca,Sr)0.33MnO3 and La(Fe,Co,Si)13 have been considered for use in prototype valves. Based on measured magnetization...

  12. GaAs:Mn nanowires grown by molecular beam epitaxy of (Ga,Mn)as at MnAs segregation conditions.

    Science.gov (United States)

    Sadowski, Janusz; Dłuzewski, Piotr; Kret, Sławomir; Janik, Elzbieta; Lusakowska, Elzbieta; Kanski, Janusz; Presz, Adam; Terki, Ferial; Charar, Salam; Tang, Dong

    2007-09-01

    GaAs:Mn nanowires were obtained on GaAs(001) and GaAs(111)B substrates by molecular beam epitaxial growth of (Ga,Mn)As at conditions leading to MnAs phase separation. Their density is proportional to the density of catalyzing MnAs nanoislands, which can be controlled by the Mn flux and/or the substrate temperature. After deposition corresponding to a 200 nm thick (Ga,Mn)As layer the nanowires are around 700 nm long. Their shapes are tapered, with typical diameters around 30 nm at the base and 7 nm at the tip. The wires grow along the 111 direction, i.e., along the surface normal on GaAs(111)B and inclined on GaAs(001). In the latter case they tend to form branches. Being rooted in the ferromagnetic semiconductor (Ga,Mn)As, the nanowires combine one-dimensional properties with the magnetic properties of (Ga,Mn)As and provide natural, self-assembled structures for nanospintronics.

  13. Magnetocaloric effect of a series of remarkably isostructural intermetallic [Ni(II)3Ln(III)] cubane aggregates.

    Science.gov (United States)

    Wang, Pei; Shannigrahi, Santiranjan; Yakovlev, Nikolai L; Hor, T S Andy

    2014-01-07

    A new series of remarkably isostructural 3d-4f compounds, [Ni3Ln(hmp)4(OAc)5]·H2O·CH2Cl2 (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Y (5)) were synthesized based on a simple one-pot self-assembly method. Magnetic measurements demonstrated the ferromagnetic property of the [Ni3Ln] cores and the heterometallic influence on the magnetocaloric properties. This study suggested that robust and discrete intermetallic cubanes can be an alternative to other magnetically active materials such as high-nuclearity aggregates or clusters whose structures are not generally controlled by common synthetic methodological designs.

  14. Microscopic theory of magnetism in the magnetocaloric material Fe2P1-xTx (T=B and Si)

    Science.gov (United States)

    Delczeg-Czirjak, E. K.; Bergqvist, L.; Eriksson, O.; Gercsi, Z.; Nordblad, P.; Szunyogh, L.; Johansson, B.; Vitos, L.

    2012-07-01

    Landau phenomenological theory in combination with first-principles calculations was used to reveal the origin of the metamagnetic nature and the unusually strong dependence of the ordering temperature with doping of the Fe2P compound. We show that the magnetism of the two sublattices occupied by Fe atoms has an entwined codependency, which is strongly influenced by alloying. We furthermore demonstrate that a constrained disordered local moment approach combined with Monte Carlo simulations can only reproduce the experimental ordering temperatures in these technologically important prototype alloys for magnetocaloric refrigeration.

  15. Magnetic Properties and Magnetocaloric Effect in Layered NdMn1.9V0.1Si2

    OpenAIRE

    Din M.F. Md; Wang J.L.; Zeng R; Kennedy S.J.; Campbell S.J; Dou S.X.

    2014-01-01

    The structural and magnetic properties of the compounds NdMn2-xVxSi2 have been studied by x-ray and high resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range 3-450 K. The Curie temperature and Néel temperature of layered NdMn1.9V0.1Si2 are been indicate at TC ~ 24 K and TN ~ 376 K respectively. The giant magnetocaloric effect (GMCE) around TC is found in layered NdMn1.9V0.1Si2 associated with firs...

  16. Magnetocaloric effect in temperature-sensitive magnetic fluids

    Indian Academy of Sciences (India)

    Kinnari Parekh; R V Upadhyay; R V Mehta

    2000-04-01

    The magnetocaloric properties of three different temperature-sensitive magnetic fluids were studied. The pyromagnetic coefficient for all the materials were obtained and it was found that this property depends on physical and magnetic properties like size, magnetization and Curie temperature. A theoretical model was developed to explain the behaviour of change in entropy with temperature.

  17. Anisotropic thermal conductivity in epoxy-bonded magnetocaloric composites

    Science.gov (United States)

    Weise, Bruno; Sellschopp, Kai; Bierdel, Marius; Funk, Alexander; Bobeth, Manfred; Krautz, Maria; Waske, Anja

    2016-09-01

    Thermal management is one of the crucial issues in the development of magnetocaloric refrigeration technology for application. In order to ensure optimal exploitation of the materials "primary" properties, such as entropy change and temperature lift, thermal properties (and other "secondary" properties) play an important role. In magnetocaloric composites, which show an increased cycling stability in comparison to their bulk counterparts, thermal properties are strongly determined by the geometric arrangement of the corresponding components. In the first part of this paper, the inner structure of a polymer-bonded La(Fe, Co, Si)13-composite was studied by X-ray computed tomography. Based on this 3D data, a numerical study along all three spatial directions revealed anisotropic thermal conductivity of the composite: Due to the preparation process, the long-axis of the magnetocaloric particles is aligned along the xy plane which is why the in-plane thermal conductivity is larger than the thermal conductivity along the z-axis. Further, the study is expanded to a second aspect devoted to the influence of particle distribution and alignment within the polymer matrix. Based on an equivalent ellipsoids model to describe the inner structure of the composite, numerical simulation of the thermal conductivity in different particle arrangements and orientation distributions were performed. This paper evaluates the possibilities of microstructural design for inducing and adjusting anisotropic thermal conductivity in magnetocaloric composites.

  18. Materials Challenges for High Performance Magnetocaloric Refrigeration Devices

    DEFF Research Database (Denmark)

    Smith, Anders; Bahl, Christian; Bjørk, Rasmus

    2012-01-01

    Magnetocaloric materials with a Curie temperature near room temperature have attracted signifi cant interest for some time due to their possible application for high-effi ciency refrigeration devices. This review focuses on a number of key issues of relevance for the characterization, performance...

  19. Gadolinium(III)-hydroxy ladders trapped in succinate frameworks with optimized magnetocaloric effect.

    Science.gov (United States)

    Chen, Yan-Cong; Guo, Fu-Sheng; Zheng, Yan-Zhen; Liu, Jun-Liang; Leng, Ji-Dong; Tarasenko, Róbert; Orendáč, Martin; Prokleška, Jan; Sechovský, Vladimír; Tong, Ming-Liang

    2013-09-27

    Two kinds of inorganic gadolinium(III)-hydroxy "ladders", [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd2(OH)2(suc)2(H2O)]n·2nH2O (1) and [Gd6(OH)8(suc)5(H2O)2 ]n·4n H2O (2), respectively. Such coordination polymers could be regarded as alternating inorganic-organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg(-1) K(-1) for complex 1 and 48.0 J kg(-1) K(-1) for complex 2. The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm(-3) K(-1) for complexes 1 and 2, respectively.

  20. Magnetocaloric effect and refrigeration cooling power in amorphous Gd7Ru3 alloys

    Directory of Open Access Journals (Sweden)

    Pramod Kumar

    2015-07-01

    Full Text Available In this paper, we report the magnetic, heat capacity and magneto-caloric effect (MCE of amorphous Gd7Ru3 compound. Both, temperature dependent magnetization and heat capacity data reveals that two transitions at 58 K and 34 K. MCE has been calculated in terms of isothermal entropy change (ΔSM and adiabatic temperature change (ΔTad using the heat capacity data in different fields. The maximum values of ΔSM and ΔTad are 21 Jmol−1K−1 and 5 K respectively, for field change of 50 kOe whereas relative cooling power (RCP is ∼735 J/kg for the same field change.

  1. Magnetocaloric effect in a cluster-glass system Ho5Pd2-xNix

    Science.gov (United States)

    Toyoizumi, Saori; Kitazawa, Hideaki; Morita, Kengo; Tamaki, Akira

    2016-02-01

    In order to investigate the effect of chemical pressure on the large magnetocaloric effect in Ho5 Pd2, we conducted X-ray diffraction, magnetization, and specific heat measurements on Ho5Pd2-xNix(0≤ x ≤ 1.0) rare-earth intermetallic compounds. The linear x dependence of the lattice constant a suggests that Ni is replaced with Pd in the case of Ho5Pd2-xNix (0 ≤ x ≤ 0.5). The spin-glass transition temperature Tg and paramagnetic Curie temperature θP indicate a weak oscillatory x dependence. However, the magnetic entropy change —ΔSm and the relative cooling power (RCP) are rapidly suppressed with increasing x. These large reductions in —ΔSm and RCP cannot be explained only in terms of normal Ruderman-Kittel- Kasuya-Yoshida (RKKY)-type indirect exchange interactions.

  2. Nitronyl nitroxide based 2p-3d-4f chains with the magnetocaloric effect and slow magnetic relaxation.

    Science.gov (United States)

    Wang, Xiufeng; Li, Cun; Sun, Juan; Li, Licun

    2015-11-14

    Four new nitronyl nitroxide radical based hetero-tri-spin one-dimensional compounds, namely [{Ln(hfac)3}3{Cu(hfac)2}{NIT-Ph(OMe)2}4]n (Ln = Gd (1), Tb (2), Dy (3), Er (4); hfac = hexafluoroacetylacetonate; NIT-Ph(OMe)2 = 2-(2',4'-dimethoxyphenyl)-4,4,5,5-tetramethyl-imidazolyl-1-oxyl-3-oxide) have been successfully prepared. Single crystal X-ray crystallographic analysis reveals that complexes 1-4 possess a 1D chain structure with a repeating [Cu-Rad-Ln-Rad-Ln-Rad-Ln-Rad] moiety in which Ln(hfac)3 and Cu(hfac)2 units are bridged by nitronyl nitroxide radicals through the NO groups. DC magnetic studies found that ferromagnetic interactions between metals and the coordinated NO groups are active in all four compounds. The Tb derivative displays frequency dependent ac magnetic susceptibilities, indicating slow magnetic relaxation behavior. The Gd complex shows an important cryogenic magnetocaloric effect with the entropy change (-ΔSm) of 13.5 J kg(-1) K(-1) at 2 K and a magnetic field of 7 T, representing the first example of Gd-radical molecular species exhibiting the magnetocaloric effect.

  3. Magnetostructural phase transitions and magnetocaloric effect in Tb-Dy-Ho-Co-Al alloys with a Laves phase structure

    Energy Technology Data Exchange (ETDEWEB)

    Tereshina, I. S., E-mail: irina-tereshina@mail.ru [Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119991 (Russian Federation); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw 53-421 (Poland); Chzhan, V. B. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119991 (Russian Federation); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw 53-421 (Poland); National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Tereshina, E. A. [Institute of Physics CAS, Prague 18221 (Czech Republic); Khmelevskyi, S. [Center for Computational Materials Science, IAP, Vienna University of Technology, Vienna A-1040 (Austria); Burkhanov, G. S. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119991 (Russian Federation); Ilyushin, A. S. [Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Complex Research Institute named after Kh. I. Ibragimov, Russian Academy of Sciences, Groznyi 364906 (Russian Federation); Paukov, M. A.; Havela, L. [Faculty of Mathematics and Physics, Charles University, Prague 12116 (Czech Republic); Karpenkov, A. Yu. [Physics Faculty, Tver State University, Tver 170100 (Russian Federation); Department of Physics, Chelyabinsk State University, Chelyabinsk 454001 (Russian Federation); Cwik, J.; Koshkid' ko, Yu. S.; Miller, M. [International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw 53-421 (Poland); Nenkov, K.; Schultz, L. [Leibniz-Institut fur Festkorper- und Werkstoffforschung, Dresden D-01171 (Germany)

    2016-07-07

    The influence of simultaneous substitution within the rare earth (R) and Co sublattices on the structural, magnetic, and magnetocaloric properties of the Laves phase RCo{sub 2}-type compounds is studied. Main attention is devoted to the studies of the magnetostructural phase transitions and the transition types with respect to the alloy composition. Multicomponent alloys Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 2} and Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 1.75}Al{sub 0.25} were prepared with the use of high purity metals. Majority of the Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 2} alloys exhibit magnetic transitions of the first-order type and a large magnetocaloric effect. The substitution of Al for Co in Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 2} increases the Curie temperature (T{sub C}) but changes the transition type from first-to the second-order. The discussion of the physical mechanisms behind the observed phenomena is given on the basis of the first principles electronic-structure calculations taking into account both the atomic disorder and the magnetic disorder effects at finite temperatures. The advantage of Al-containing materials is that sufficiently high magnetocaloric effect values are preserved at T > T{sub C}.

  4. A Magnetocaloric Pump for Lab-On-Chip Technology: Phase I Report

    Energy Technology Data Exchange (ETDEWEB)

    Love, L.J.

    2004-04-05

    A magnetocaloric pump provides a simple means of pumping fluid using only external thermal and magnetic fields. The principle, which can be traced back to the early work of Rosensweig, is straightforward. Magnetic materials tend to lose their magnetization as the temperature approaches the material's Curie point. Exposing a column of magnetic fluid to a uniform magnetic field coincident with a temperature gradient produces a pressure gradient in the magnetic fluid. As the fluid heats up, it loses its attraction to the magnetic field and is displaced by cooler fluid. The impact of such a phenomenon is obvious: fluid propulsion with no moving mechanical parts. Until recently, limitations in the magnetic and thermal properties of conventional materials severely limited practical operating pressure gradients. However, recent advancements in the design of metal substituted magnetite enable fine control over both the magnetic and thermal properties of magnetic nanoparticles, a key element in colloidal based magnetic fluids (ferrofluids). This manuscript begins with a basic description of the process and previous limitations due to material properties. This is followed by a review of existing methods of synthesizing magnetic nanoparticles as well as an introduction to a new approach based on thermophilic metal-reducing bacteria. We compare two compounds and show, experimentally, significant variation in specific magnetic and thermal properties. We develop the constitutive thermal, magnetic, and fluid dynamic equations associated with magnetocaloric pump and validate our finite element model with a series of experiments. Preliminary results show a good match between the model and experiment as well as approximately an order of magnitude increase in the fluid flow rate over conventional magnetite based ferrofluids operating below 80 C. Finally, as a practical demonstration, we describe a novel application of this technology: pumping fluids at the &apos

  5. A Magnetocaloric Pump for Lab-On-A-Chip Technology: Phase I Report

    Energy Technology Data Exchange (ETDEWEB)

    Love, LJL

    2004-05-08

    A magnetocaloric pump provides a simple means of pumping fluid using only external thermal and magnetic fields. The principle, which can be traced back to the early work of Rosensweig, is straightforward. Magnetic materials tend to lose their magnetization as the temperature approaches the material's Curie point. Exposing a column of magnetic fluid to a uniform magnetic field coincident with a temperature gradient produces a pressure gradient in the magnetic fluid. As the fluid heats up, it loses its attraction to the magnetic field and is displaced by cooler fluid. The impact of such a phenomenon is obvious: fluid propulsion with no moving mechanical parts. Until recently, limitations in the magnetic and thermal properties of conventional materials severely limited practical operating pressure gradients. However, recent advancements in the design of metal substituted magnetite enable fine control over both the magnetic and thermal properties of magnetic nanoparticles, a key element in colloidal based magnetic fluids (ferrofluids). This manuscript begins with a basic description of the process and previous limitations due to material properties. This is followed by a review of existing methods of synthesizing magnetic nanoparticles as well as an introduction to a new approach based on thermophilic metal-reducing bacteria. We compare two compounds and show, experimentally, significant variation in specific magnetic and thermal properties. We develop the constitutive thermal, magnetic, and fluid dynamic equations associated with magnetocaloric pump and validate our finite element model with a series of experiments. Preliminary results show a good match between the model and experiment as well as approximately an order of magnitude increase in the fluid flow rate over conventional magnetite based ferrofluids operating below 80 C. Finally, as a practical demonstration, we describe a novel application of this technology: pumping fluids at the &apos

  6. Numerical simulation of magnetocaloric system behaviour for an industrial application

    Energy Technology Data Exchange (ETDEWEB)

    Risser, M.; Vasile, C.; Keith, B. [National Institute of Applied Sciences (INSA) Strasbourg, 24 Bd de la Victoire, 67084 Strasbourg Cedex (France); Laboratoire de Genie de la Conception (LGeCo) (France); Engel, T. [National Institute of Applied Sciences (INSA) Strasbourg, 24 Bd de la Victoire, 67084 Strasbourg Cedex (France); Laboratoire des Systemes Photoniques (LSP) (France); Muller, C. [Cooltech Applications, Impasse Antoine IMBS, 67810 Holtzheim (France)

    2010-08-15

    This paper presents a numerical model conceived for a multi-physics evaluation of a magnetic refrigeration system. The model takes into account the variable magnetic field, the characteristics of the magnetocaloric materials (MCM) as well as the efficiency of the fluid flow heat transfer between the hot and the cold sources via the MCM. This model allows us to optimize these elements and to determine their impact on the overall performance of a magnetocaloric device. We present here a finite-difference model of AMRR cycles for a sub-unit of MCM crossed by micro-channels of fluid connected to cold and hot regenerative receivers. Thus, the calculation of the output parameters such as the temperature span, and thermal power passing from the cold receiver to the hot receiver has been performed. The influence of the geometry of the MCM and the fluid flow were investigated over the working domain highlighting the current technological achievements and indicating possible improvements. (author)

  7. Quantum signatures of a molecular nanomagnet in direct magnetocaloric measurements.

    Science.gov (United States)

    Sharples, Joseph W; Collison, David; McInnes, Eric J L; Schnack, Jürgen; Palacios, Elias; Evangelisti, Marco

    2014-10-22

    Geometric spin frustration in low-dimensional materials, such as the two-dimensional kagome or triangular antiferromagnetic nets, can significantly enhance the change of the magnetic entropy and adiabatic temperature following a change in the applied magnetic field, that is, the magnetocaloric effect. In principle, an equivalent outcome should also be observable in certain high-symmetry zero-dimensional, that is, molecular, structures with frustrated topologies. Here we report experimental realization of this in a heptametallic gadolinium molecule. Adiabatic demagnetization experiments reach ~200 mK, the first sub-Kelvin cooling with any molecular nanomagnet, and reveal isentropes (the constant entropy paths followed in the temperature-field plane) with a rich structure. The latter is shown to be a direct manifestation of the trigonal antiferromagnetic net structure, allowing study of frustration-enhanced magnetocaloric effects in a finite system.

  8. Properties of magnetocaloric La(Fe,Co,Si)13 produced by powder metallurgy

    DEFF Research Database (Denmark)

    Hansen, Britt Rosendahl; Kuhn, Luise Theil; Bahl, Christian Robert Haffenden;

    2010-01-01

    We present a comprehensive study of the magnetocaloric materials series La(Fe1−xCox)11.9Si1.1 with 0.055......We present a comprehensive study of the magnetocaloric materials series La(Fe1−xCox)11.9Si1.1 with 0.055...

  9. Europium substitution effects on structural, magnetic and magnetocaloric properties in La0.5Ca0.5MnO3

    Directory of Open Access Journals (Sweden)

    Boujelben W.

    2012-06-01

    Full Text Available We have investigated structural, magnetic and magnetocaloric properties of polycrystalline samples La0.5-xEuxCa0.5MnO3 (x=0 and 0.1. Rietveld refinement of the X-ray diffraction patterns show that our samples are single phase and crystallize in the orthorhombic structure with Pnma space group. Magnetization measurements versus temperature at a magnetic applied field of 500 Oe indicate that La0.4Eu0.1Ca0.5MnO3 sample exhibits a paramagnetic to ferromagnetic transition with decreasing temperature. Magnetic measurements reveal strong magnetocaloric effect in the vicinity of the Curie temperature TC. The parent compound shows a negative magnetic entropy change of ∆SM=−1.13Jkg−1K−1 at 220K and a positive magnetocaloric effects ∆SM=1Jkg−1K−1 at 150K under a magnetic applied field of 2T. La0.4Eu0.1Ca0.5MnO3 exhibits a maximum value of magnetic entropy change ∆SM=−1.15Jkg−1K−1 at 130K under an applied field of 2T and a large relative cooling power RCP with a maximum value of 72 J/kg.

  10. Giant low-field magnetocaloric effect in single-crystalline EuTi0.85Nb0.15O3

    Science.gov (United States)

    Roy, S.; Khan, N.; Mandal, P.

    2016-02-01

    The magnetocaloric effect in ferromagnetic single crystal EuTi0.85Nb0.15O3 has been investigated using magnetization and heat capacity measurements. EuTi0.85Nb0.15O3 undergoes a continuous ferromagnetic phase transition at TC = 9.5 K due to the long range ordering of magnetic moments of Eu2+ (4f7). With the application of magnetic field, the spin entropy is strongly suppressed and a giant magnetic entropy change is observed near TC. The values of entropy change ΔSm and adiabatic temperature change ΔTad are as high as 51.3 J kg-1 K-1 and 22 K, respectively, for a field change of 0-9 T. The corresponding magnetic heating/cooling capacity is 700 J kg-1. This compound also shows large magnetocaloric effect even at low magnetic fields. In particular, the values of ΔSm reach 14.7 and 23.8 J kg-1 K-1 for field changes of 0-1 T and 0-2 T, respectively. The low-field giant magnetocaloric effect, together with the absence of thermal and field hysteresis makes EuTi0.85Nb0.15O3 a very promising candidate for low temperature magnetic refrigeration.

  11. Giant low-field magnetocaloric effect in single-crystalline EuTi0.85Nb0.15O3

    Directory of Open Access Journals (Sweden)

    S. Roy

    2016-02-01

    Full Text Available The magnetocaloric effect in ferromagnetic single crystal EuTi0.85Nb0.15O3 has been investigated using magnetization and heat capacity measurements. EuTi0.85Nb0.15O3 undergoes a continuous ferromagnetic phase transition at TC = 9.5 K due to the long range ordering of magnetic moments of Eu2+ (4f7. With the application of magnetic field, the spin entropy is strongly suppressed and a giant magnetic entropy change is observed near TC. The values of entropy change ΔSm and adiabatic temperature change ΔTad are as high as 51.3 J kg−1 K−1 and 22 K, respectively, for a field change of 0–9 T. The corresponding magnetic heating/cooling capacity is 700 J kg−1. This compound also shows large magnetocaloric effect even at low magnetic fields. In particular, the values of ΔSm reach 14.7 and 23.8 J kg−1 K−1 for field changes of 0–1 T and 0–2 T, respectively. The low-field giant magnetocaloric effect, together with the absence of thermal and field hysteresis makes EuTi0.85Nb0.15O3 a very promising candidate for low temperature magnetic refrigeration.

  12. Magnetocaloric effect, thermal conductivity, and magnetostriction of epoxy-bonded La(Fe0.88Si0.12)13 hydrides

    Science.gov (United States)

    Matsumoto, K.; Murayama, D.; Takeshita, M.; Ura, Y.; Abe, S.; Numazawa, T.; Takata, H.; Matsumoto, Y.; Kuriiwa, T.

    2017-09-01

    Magnetic materials with large magnetocaloric effect are significantly important for magnetic refrigeration. La(Fe0.88Si0.12)13 compounds are one of the promising magnetocaloric materials that have a first order magnetic phase transition. Transition temperature of hydrogenated La(Fe0.88Si0.12)13 increased up to room temperature region while keeping metamagnetic transition properties. From view point of practical usage, bonded composite are very attractive and their properties are important. We made epoxy bonded La(Fe0.88Si0.12)13 hydrides. Magnetocaloric effect was studied by measuring specific heat, magnetization, and temperature change in adiabatic demagnetization. The composite had about 20% smaller entropy change from the hydrogenated La(Fe0.88Si0.12)13 powder in 2 T. Thermal conductivity of the composite was several times smaller than La(Fe,Si)13. The small thermal conductivity was explained due to the small thermal conductivity of epoxy. Thermal conductivity was observed to be insensitive to magnetic field in 2 T. Thermal expansion and magnetostriction of the composite material were measured. The composite expanded about 0.25% when it entered into ferromagnetic phase. Magnetostriction of the composite in ferromagnetic phase was about 0.2% in 5 T and much larger than that in paramagnetic phase. The composite didn’t break after about 100 times magnetic field changes in adiabatic demagnetization experiment even though it has magnetostriction.

  13. Thermodynamic and magnetocaloric properties of geometrically frustrated Ising nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Žukovič, M., E-mail: milan.zukovic@upjs.sk

    2015-01-15

    Thermodynamic and magnetocaloric properties of geometrically frustrated Ising spin clusters of selected shapes and sizes are studied by exact enumeration. In the ground state the magnetization and the entropy show step-wise variations with an applied magnetic field. The number of steps, their widths and heights depend on the cluster shape and size. While the character of the magnetization plateau heights is always increasing, the entropy is not necessarily decreasing function of the field, as one would expect. For selected clusters showing some interesting ground-state properties, the calculations are extended to finite temperatures by exact enumeration of densities of states in the energy-magnetization space. In zero field the focus is laid on a peculiar behavior of some thermodynamic quantities, such as the entropy, the specific heat and the magnetic susceptibility. In finite fields various thermodynamic functions are studied in the temperature-field parameter plane and particular attention is paid to the cases showing an enhanced magnetocaloric effect. The exact results on the finite clusters are compared with the thermodynamic limit behavior obtained from Monte Carlo simulations. - Highlights: • We study frustrated spin clusters of various shapes and sizes on a triangular lattice. • Ground-state magnetizations and entropies in a field are exactly determined. • Peculiar behavior of some quantities is studied in zero field and finite temperatures. • Enhanced magnetocaloric effect is observed at relatively low temperatures and fields. • Thermodynamic limit behavior is estimated by Monte Carlo simulations.

  14. Direct measurement of the magnetocaloric effect in cementite

    Energy Technology Data Exchange (ETDEWEB)

    Kaeswurm, B., E-mail: Barbara.Kaeswurm@fau.de [Geo- und Materialwissenschaften, Technische Universität Darmstadt, Darmstadt (Germany); Friemert, K. [Geo- und Materialwissenschaften, Technische Universität Darmstadt, Darmstadt (Germany); Gürsoy, M. [Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Darmstadt (Germany); Skokov, K.P. [Geo- und Materialwissenschaften, Technische Universität Darmstadt, Darmstadt (Germany); Gutfleisch, O., E-mail: gutfleisch@fm.tu-darmstadt.de [Geo- und Materialwissenschaften, Technische Universität Darmstadt, Darmstadt (Germany)

    2016-07-15

    Measurements of the magnetocaloric effect of cementite at its Curie temperature of 475 K are presented. An adiabatic temperature change of 1.76±0.01 K was measured using a direct measurement technique. The isothermal entropy change was determined from measurements of magnetisation isotherms and was shown to be 3.07 J K{sup −1} kg{sup −1} in a field change of 2 T. The field dependencies of both magnetocaloric properties follow the H{sup 2/3} dependence typical for ferromagnetic materials with a second order phase transition. The material may be of interest in magnetocaloric applications such as magnetic refrigeration or thermomagnetic power generation. - Highlights: • The magnetocaloriceffect of Fe{sub 3}C was investigated at its Curie temperature of 475 K. • First direct measurement of adiabatic temperature change in cementite. • ΔT{sub ad}=1.77 K and ΔS=3.07 J K{sup −1} kg{sup −1} in 2 T. • MCE follows H{sup 2/3} dependence typical for second order phase transition. • Possible applications include magnetic refrigeration and heat power conversion.

  15. Tunable thermal hysteresis in MnFe(P,Ge) compounds

    NARCIS (Netherlands)

    Trung, N.T.; Ou, Z.Q.; Gortenmulder, T.J.; Tegus, O.; Buschow, K.H.J.; Brück, E.

    2009-01-01

    Structural, magnetic, and magnetocaloric properties of the MnFe(P,Ge) compounds were systematically studied on both bulk alloys and melt-spun ribbons. The experimental results show that the critical behavior of the phase transition can be controlled by changing either the compositions or the anneali

  16. Tunable thermal hysteresis in MnFe(P,Ge) compounds

    NARCIS (Netherlands)

    Trung, N.T.; Ou, Z.Q.; Gortenmulder, T.J.; Tegus, O.; Buschow, K.H.J.; Brück, E.

    2009-01-01

    Structural, magnetic, and magnetocaloric properties of the MnFe(P,Ge) compounds were systematically studied on both bulk alloys and melt-spun ribbons. The experimental results show that the critical behavior of the phase transition can be controlled by changing either the compositions or the anneali

  17. Heat flux measurements of Tb3M series (M=Co, Rh and Ru): Specific heat and magnetocaloric properties

    Science.gov (United States)

    Monteiro, J. C. B.; Lombardi, G. A.; dos Reis, R. D.; Freitas, H. E.; Cardoso, L. P.; Mansanares, A. M.; Gandra, F. G.

    2016-12-01

    We report on the magnetic properties and magnetocaloric effect (MCE) for the Tb3M series, with M=Co, Rh and Ru, obtained using a heat flux technique. The specific heat of Tb3Co and Tb3Rh are very similar, with a first order type transition occurring around 6 K below the magnetic ordering temperature without any corresponding feature on the magnetization. The slightly enhanced electronic specific heat, the Debye temperature around 150 K and the presence of the magnetic specific heat well above the ordering temperature are also characteristic of many other compounds of the R3M family (R=Rare Earth). The specific heat for Tb3Ru, however, presents two peaks at 37 K and 74 K. The magnetization shows that below the first peak the system presents an antiferromagnetic behavior and is paramagnetic above 74 K. We obtained a magnetocaloric effect for M=Co and Rh, -∆S=12 J/kg K, but for Tb3Ru it is less than 3 J/kg K (μ0∆H=5 T). We believe that the experimental results show that the MCE is directly related with the process of hybridization of the (R)5d-(M)d electrons that occurs in the R3M materials.

  18. 1,2,3-triazolate-bridged tetradecametallic transition metal clusters [M14(L)6O6(OMe)18X6] (M=FeIII, CrIII and VIII/IV) and related compounds: ground-state spins ranging from S=0 to S=25 and spin-enhanced magnetocaloric effect.

    Science.gov (United States)

    Shaw, Rachel; Laye, Rebecca H; Jones, Leigh F; Low, David M; Talbot-Eeckelaers, Caytie; Wei, Qiang; Milios, Constantinos J; Teat, Simon; Helliwell, Madeleine; Raftery, James; Evangelisti, Marco; Affronte, Marco; Collison, David; Brechin, Euan K; McInnes, Eric J L

    2007-06-11

    We report the synthesis, by solvothermal methods, of the tetradecametallic cluster complexes [M14(L)6O6(OMe)18Cl6] (M=FeIII, CrIII) and [V14(L)6O6(OMe)18Cl6-xOx] (L=anion of 1,2,3-triazole or derivative). Crystal structure data are reported for the {M14} complexes [Fe14(C2H2N3)6O6(OMe)18Cl6], [Cr14(bta)6O6(OMe)18Cl6] (btaH=benzotriazole), [V14O6(Me2bta)6(OMe)18Cl6-xOx] [Me2btaH=5,6-Me2-benzotriazole; eight metal sites are VIII, the remainder are disordered between {VIII-Cl}2+ and {VIV=O}2+] and for the distorted [FeIII14O9(OH)(OMe)8(bta)7(MeOH)5(H2O)Cl8] structure that results from non-solvothermal synthetic methods, highlighting the importance of temperature regime in cluster synthesis. Magnetic studies reveal the {Fe14} complexes to have ground state electronic spins of Sbta- and H2C2N3-, respectively). The huge spins of the {Fe14} complexes lead to very large magnetocaloric effects (MCE)-the largest known for any material below 10 K-which is further enhanced by spin frustration within the molecules due to the competing antiferromagnetic interactions. The largest MCE is found for [Fe14(C2H2N3)6O6(OMe)18Cl6] with an isothermal magnetic entropy change -DeltaSm of 20.3 J kg-1 K-1 at 6 K for an applied magnetic field change of 0-7 T.

  19. Tuning the magnetic interactions in GaAs:Mn/MnAs hybrid structures by controlling shape and position of MnAs nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Elm, Matthias Thomas

    2010-07-01

    In this work the magnetic properties of hexagonal MnAs nanoclusters and their influence on the transport properties of GaAs:Mn /MnAs hybrid structures were studied. Various arrangements of isolated nanoclusters and cluster chains were grown on (111)B-GaAs substrates by SA-MOVPE. The first part of this work deals with the manufacturing process of the different cluster arrangements investigated. By a suitable pre-structuring of the substrate it was possible to influence the cluster size, cluster shape and cluster position systematically. Preparing various arrangements it could be shown that the hexagonal nanoclusters prefer to grow along their a-axes. In the second part, the magnetic properties of the nanoclusters were studied. Ferromagnetic resonance (FMR) measurements show a hard magnetic axis perpendicular to the sample plane, i.e. parallel to the c-axis. By measurements, where the magnetic field was rotated in the sample plane, it could be demonstrated that the orientation of the magnetization can be forced into a certain direction by controlling the cluster shape. These results are confirmed by measurements using magnetic force microscopy. The third part deals with the influence of the nanoclusters and their arrangement on the transport properties of the GaAs:Mn matrix. For temperatures above 30 K the structures investigated show positive as well as negative magnetoresistance effects, which are typical for granular GaAs:Mn/MnAs hybrid structures. This behaviour can be explained in the context of transport in extended band states. The size of the magnetoresistance effects correlates strongly with the respective cluster arrangement of the sample. This behaviour has been predicted theoretically and could be confirmed experimentally in the context of this work. Below 30 K large positive magnetoresistance effects show up for the regular cluster arrangements, which cannot be observed for hybrid structures with random cluster distributions. These large positive

  20. Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

    DEFF Research Database (Denmark)

    Smith, Anders; Nielsen, Kaspar Kirstein; Neves Bez, Henrique;

    2016-01-01

    We measure the magnetocaloric effect of the manganite series La0.67Ca0.33-xSrxMnO3 by determining the isothermal entropy change upon magnetization, using variable-field calorimetry. The results demonstrate that the field dependence of the magnetocaloric effect close to the critical temperature....... In this way the determination of the nonuniversal field dependence of the magnetocaloric effect close to a phase transition can be used as a method to gain insight into the strength of the spin-lattice interactions of magnetic materials. The approach is shown also to be applicable to first-order transitions....

  1. Simulated magnetocaloric properties of MnCr2O4 spinel

    OpenAIRE

    2016-01-01

    The magnetocaloric properties of MnCr2O4 spinel have been simulated based on a phenomenological model. The simulation of magnetization as function of temperature is used to explore magnetocaloric properties such as magnetic entropy change, heat capacity change, and relative cooling power. The results imply the prospective application of MnCr2O4 spinel to achieve magnetocaloric effect at cryogenic temperatures (20–60 K) near Curie temperatures (38–44 K). According to the obtained results it is...

  2. Theoretical description of magnetocaloric effect in the shape memory alloy exhibiting metamagnetic behavior

    Energy Technology Data Exchange (ETDEWEB)

    L' vov, Victor A. [Institute of Magnetism, Kyiv 03142 (Ukraine); Taras Shevchenko National University, Kyiv 01601 (Ukraine); Kosogor, Anna, E-mail: annakosogor@gmail.com [Institute of Magnetism, Kyiv 03142 (Ukraine); National University of Science and Technology ‘MISiS’, Moscow 119049 (Russian Federation); Barandiaran, Jose M. [BCMaterials and University of Basque Country, UPV/EHU, Bilbao 48080 (Spain); Chernenko, Volodymyr A. [BCMaterials and University of Basque Country, UPV/EHU, Bilbao 48080 (Spain); Ikerbasque, Basque Foundation for Science, Bilbao 48013 (Spain)

    2016-01-07

    A simple thermodynamic theory is proposed for the quantitative description of giant magnetocaloric effect observed in metamagnetic shape memory alloys. Both the conventional magnetocaloric effect at the Curie temperature and the inverse magnetocaloric effect at the transition from the ferromagnetic austenite to a weakly magnetic martensite are considered. These effects are evaluated from the Landau-type free energy expression involving exchange interactions in a system of a two magnetic sublattices. The findings of the thermodynamic theory agree with first-principles calculations and experimental results from Ni-Mn-In-Co and Ni-Mn-Sn alloys, respectively.

  3. Gadolinium oxalate derivatives with enhanced magnetocaloric effect via ionothermal synthesis.

    Science.gov (United States)

    Meng, Yan; Chen, Yan-Cong; Zhang, Ze-Min; Lin, Zhuo-Jia; Tong, Ming-Liang

    2014-09-02

    Two new oxalate-bridged Gd(III) coordination polymers, namely, (choline)[Gd(C2O4)(H2O)3Cl]Cl·H2O (1) and [Gd(C2O4)(H2O)3Cl] (2), were first obtained ionothermally by using a deep eutectic solvent (DES). The magnetic studies and heat capacity measurements reveal that the two-dimensional Gd(III)-based coordination polymer of 2 has the higher magnetic density and exhibits a larger cryogenic magnetocaloric effect (MCE) (ΔS(m) = 48 J kg(-1) K(-1) for ΔH = 7 T at 2.2 K).

  4. Magnetocaloric effect in quantum spin-s chains

    Directory of Open Access Journals (Sweden)

    A. Honecker

    2009-01-01

    Full Text Available We compute the entropy of antiferromagnetic quantum spin-s chains in an external magnetic field using exact diagonalization and Quantum Monte Carlo simulations. The magnetocaloric effect, i. e., temperature variations during adiabatic field changes, can be derived from the isentropes. First, we focus on the example of the spin-s=1 chain and show that one can cool by closing the Haldane gap with a magnetic field. We then move to quantum spin-s chains and demonstrate linear scaling with s close to the saturation field. In passing, we propose a new method to compute many low-lying excited states using the Lanczos recursion.

  5. Magnetocaloric effect at the exchange–inversion with magnetoelastic coupling

    Energy Technology Data Exchange (ETDEWEB)

    Piazzi, Marco, E-mail: m.piazzi@inrim.it; Basso, Vittorio

    2015-09-15

    We develop a thermodynamic model to describe antiferro- (AFM) to ferromagnetic (FM) phase transitions through magnetoelastic coupling in the framework of Kittel's exchange–inversion mechanism. By including both magnetic and structural contributions to the free energy, we derive the conditions to have a direct AFM–FM transition. These are represented either by the presence of a non-zero intra-sublattice coupling constant or by a sufficiently high value of the magnetoelastic coupling parameter. In the paper we establish these conditions by analytical means and we discuss the physical meaning of the model in relation to possible applications to magnetocaloric materials with AFM–FM transitions.

  6. Magnetocaloric effect at the exchange-inversion with magnetoelastic coupling

    Science.gov (United States)

    Piazzi, Marco; Basso, Vittorio

    2015-09-01

    We develop a thermodynamic model to describe antiferro- (AFM) to ferromagnetic (FM) phase transitions through magnetoelastic coupling in the framework of Kittel's exchange-inversion mechanism. By including both magnetic and structural contributions to the free energy, we derive the conditions to have a direct AFM-FM transition. These are represented either by the presence of a non-zero intra-sublattice coupling constant or by a sufficiently high value of the magnetoelastic coupling parameter. In the paper we establish these conditions by analytical means and we discuss the physical meaning of the model in relation to possible applications to magnetocaloric materials with AFM-FM transitions.

  7. Gd2Cu(SO4)2(OH)4: a 3d-4f hydroxysulfate with an enhanced cryogenic magnetocaloric effect.

    Science.gov (United States)

    Tang, Yingying; Guo, Wenbin; Zhang, Suyun; Yang, Ming; Xiang, Hongping; He, Zhangzhen

    2015-10-21

    A 3d-4f hydroxysulfate, Gd2Cu(SO4)2(OH)4, is synthesized by means of a conventional hydrothermal method. Magnetic measurements confirm that the title compound exhibits a paramagnetic behavior down to 2 K, in which an enhanced magnetocaloric effect with a maximum -ΔSm (45.52(1) J kg(-1) K(-1), 212.8(6) mJ cm(-3) K(-1)) is observed at ∼4 K for ΔH = 8 T. The thermal stability using TG analysis and a FT-IR spectrum are also investigated.

  8. Giant magnetocaloric effect in GdAlO3 and a comparative study with GdMnO3

    Science.gov (United States)

    Mahana, Sudipta; Manju, U.; Topwal, D.

    2017-01-01

    The magnetic properties and magnetocaloric effect of polycrystalline GdAlO3 and GdMnO3 have been investigated to assess their potential usage as magnetic refrigerants at cryogenic temperatures. These compounds undergo antiferromagnetic transitions at low temperatures which are associated with the giant magnetic entropy change effect (-\\bigtriangleup {{S}M} )  ˜40.9 J Kg · K-1 under a field change of 0-9 T for GdAlO3 while the moderate effect of 18 J Kg · K-1 is observed for polycrystalline GdMnO3. Though the relative cooling power of both the stated materials is similar however, the absence of magnetic and thermal hysteresis makes GdAlO3 a more efficient magnetic refrigerant than GdMnO3.

  9. New magnetocaloric material based on GdNiH{sub 3.2} hydride for application in cryogenic devices

    Energy Technology Data Exchange (ETDEWEB)

    Smarzhevskaya, Alexandra I.; Verbetsky, Viktor N. [Lomonosov Moscow State University, Moscow (Russian Federation); Iwasieczko, Waclaw [Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Nikitin, Sergey A. [Lomonosov Moscow State University, Moscow (Russian Federation); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw (Poland)

    2014-05-15

    The paper presents the investigation of GdNiH{sub 3.2} hydride magnetocaloric properties. The isothermal magnetization in the fields up to 5 T and heat capacity data are obtained for GdNiH{sub 3.2} and GdNi compounds. The maximum value of magnetic entropy change ΔS{sub M} in GdNiH{sub 3.2} is extremely large and obtained in much lower temperature range compared to GdNi. It is shown that the hydrogenation does not noticeably affect the value of ΔS{sub M} but shifts ΔS{sub M}(T) maximum to lower temperatures (∝ 11K). The possibility of GdNiH{sub 3.2} application in cryogenic devices is discussed. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Observation of a large magnetocaloric effect in a 2D Gd(III)-based coordination polymer.

    Science.gov (United States)

    Biswas, Soumava; Adhikary, Amit; Goswami, Soumyabrata; Konar, Sanjit

    2013-10-07

    A new 2D Gd(III)-based coordination polymer has close to the highest cryogenic magnetocaloric effect of any MOF reported so far. The experimental results reveal its structural features and magnetic properties.

  11. Reducing the nucleation barrier in magnetocaloric Heusler alloys by nanoindentation

    Directory of Open Access Journals (Sweden)

    R. Niemann

    2016-06-01

    Full Text Available Magnetocaloric materials are promising as solid state refrigerants for more efficient and environmentally friendly cooling devices. The highest effects have been observed in materials that exhibit a first-order phase transition. These transformations proceed by nucleation and growth which lead to a hysteresis. Such irreversible processes are undesired since they heat up the material and reduce the efficiency of any cooling application. In this article, we demonstrate an approach to decrease the hysteresis by locally changing the nucleation barrier. We created artificial nucleation sites and analyzed the nucleation and growth processes in their proximity. We use Ni-Mn-Ga, a shape memory alloy that exhibits a martensitic transformation. Epitaxial films serve as a model system, but their high surface-to-volume ratio also allows for a fast heat transfer which is beneficial for a magnetocaloric regenerator geometry. Nanoindentation is used to create a well-defined defect. We quantify the austenite phase fraction in its proximity as a function of temperature which allows us to determine the influence of the defect on the transformation.

  12. Reducing the nucleation barrier in magnetocaloric Heusler alloys by nanoindentation

    Science.gov (United States)

    Niemann, R.; Hahn, S.; Diestel, A.; Backen, A.; Schultz, L.; Nielsch, K.; Wagner, M. F.-X.; Fähler, S.

    2016-06-01

    Magnetocaloric materials are promising as solid state refrigerants for more efficient and environmentally friendly cooling devices. The highest effects have been observed in materials that exhibit a first-order phase transition. These transformations proceed by nucleation and growth which lead to a hysteresis. Such irreversible processes are undesired since they heat up the material and reduce the efficiency of any cooling application. In this article, we demonstrate an approach to decrease the hysteresis by locally changing the nucleation barrier. We created artificial nucleation sites and analyzed the nucleation and growth processes in their proximity. We use Ni-Mn-Ga, a shape memory alloy that exhibits a martensitic transformation. Epitaxial films serve as a model system, but their high surface-to-volume ratio also allows for a fast heat transfer which is beneficial for a magnetocaloric regenerator geometry. Nanoindentation is used to create a well-defined defect. We quantify the austenite phase fraction in its proximity as a function of temperature which allows us to determine the influence of the defect on the transformation.

  13. Magnetocaloric effect at cryogenic temperature in gadolinium oxide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Rima, E-mail: rima.paul@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Paramanik, Tapas; Das, Kalipada [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Sen, Pintu [Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata 700064 (India); Satpati, B.; Das, I. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

    2016-11-01

    We have synthesized fascinating nano-structure of Gadolinium oxide (Gd{sub 2}O{sub 3}) using controlled template-assisted electrochemical deposition technique which showed interesting anisotropic magnetic behavior. The nanotubes of Gd{sub 2}O{sub 3} with average diameter 200 nm, length 10 µm and wall thickness 20 nm are constituted of nanoclusters with average diameter 7.5 nm. The tubes are aligned and are almost uniform throughout their length. Detailed magnetic measurements of aligned Gd{sub 2}O{sub 3} nanotubes have been performed for both parallel and perpendicular magnetic field orientations with respect to the axis of the Gd{sub 2}O{sub 3} nanotube array. Significant differences in magnetization values have been observed between the parallel and perpendicular orientations. Experimental results indicate the superparamagnetic nature of the nanomaterial. Large magnetocaloric effect, associated with the sharp change in magnetization of the Gd{sub 2}O{sub 3} nanotubes, has been observed in the cryogenic temperature regime that shows anisotropic behavior. - Highlights: • Gd{sub 2}O{sub 3} nanotubes of diameter ~200 nm synthesized through electrochemical technique. • The nanotubes are superparamagnetic in nature. • At cryogenic temperature, the nanotubes exhibit large magnetocaloric anisotropic effect.

  14. Inconvenient magnetocaloric effect in ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Khovaylo, Vladimir, E-mail: khovaylo@misis.ru [National University of Science and Technology “MISiS”, Moscow 119049 (Russian Federation)

    2013-11-15

    Highlights: ► Critical analysis of the available experimental results on isothermal magnetic entropy change in ferromagnetic shape memory alloys Ni–Mn–X (X = Ga, In, Sn, Sb) is given. ► Based on available in literature experimental data on total entropy change at martensitic transformation it is shown that the isothermal magnetic entropy change in Ni–Mn–X (X = Ga, In, Sn, Sb) should not greatly exceed 30 J/kg K. -- Abstract: Critical analysis available in the literature experimental results on magnetocaloric effect in ferromagnetic shape memory alloys Ni–Mn–X (X = Ga, In, Sn, Sb) is given. Based on a model developed by Pecharsky et al. [22], it is shown that the isothermal magnetic field-induced entropy change in the Ni–Mn–X alloys should not greatly exceed 30 J/kg K. Considering thermodynamics of temperature- and magnetic field-induced martensitic transformations, it is demonstrated that a contribution of the structural subsystem to the magnetocaloric effect in the Ni–Mn–X alloys studied so far is irreversible in magnetic fields below 5 T. This makes ferromagnetic shape memory alloys an inconvenient system for the practical application in modern magnetic refrigeration technology.

  15. Modelling and comparison studies of packed screen regenerators for active magnetocaloric refrigeration

    DEFF Research Database (Denmark)

    Lei, Tian; Engelbrecht, Kurt; Nielsen, K. K.;

    2011-01-01

    In active magnetic regeneration (AMR) systems, not only the magnetocaloric properties of materials, but also the regenerator geometry plays an important role in the system performance. Packed sphere regenerators are often employed in existing prototypes, however, the characteristics such as relat......In active magnetic regeneration (AMR) systems, not only the magnetocaloric properties of materials, but also the regenerator geometry plays an important role in the system performance. Packed sphere regenerators are often employed in existing prototypes, however, the characteristics...

  16. Magnetic multilayers as a way to increase the magnetic field responsiveness of magnetocaloric materials.

    Science.gov (United States)

    Caballero-Flores, R; Franco, V; Conde, A; Kiss, L F; Péter, L; Bakonyi, I

    2012-09-01

    The magnetocaloric response of Ni-Cu based multilayers has been studied with the aim of optimizing their magnetic field dependence. In contrast to the behavior of single phase materials, whose peak magnetic entropy change follows a power law with exponents close to 0.75, multilayering leads to exponents of -1 for an extended temperature span close to the transition temperature. This demonstrates that nanostructuring can be a good strategy to enhance the magnetic field responsiveness of magnetocaloric materials.

  17. Large Magnetization and Reversible Magnetocaloric Effect at the Second-Order Magnetic Transition in Heusler Materials.

    Science.gov (United States)

    Singh, Sanjay; Caron, Luana; D'Souza, Sunil Wilfred; Fichtner, Tina; Porcari, Giacomo; Fabbrici, Simone; Shekhar, Chandra; Chadov, Stanislav; Solzi, Massimo; Felser, Claudia

    2016-05-01

    In contrast to rare-earth-based materials, cheaper and more environmentally friendly candidates for cooling applications are found within the family of Ni-Mn Heusler alloys. Initial interest in these materials is focused on the first-order magnetostructural transitions. However, large hysteresis makes a magnetocaloric cycle irreversible. Alternatively, here it is shown how the Heusler family can be used to optimize reversible second-order magnetic phase transitions for magnetocaloric applications.

  18. Modelling and comparison studies of packed screen regenerators for active magnetocaloric refrigeration

    DEFF Research Database (Denmark)

    Lei, Tian; Engelbrecht, Kurt; Nielsen, Kaspar Kirstein;

    2014-01-01

    In active magnetic regeneration (AMR) systems, not only the magnetocaloric properties of materials, but also the regenerator geometry plays an important role in the system performance. Packed sphere regenerators are often employed in existing prototypes, however, the characteristics such as relat......In active magnetic regeneration (AMR) systems, not only the magnetocaloric properties of materials, but also the regenerator geometry plays an important role in the system performance. Packed sphere regenerators are often employed in existing prototypes, however, the characteristics...

  19. Specific heat and magnetocaloric effect in Pr1-xAgxMnO3 manganites

    OpenAIRE

    2010-01-01

    The magnetocaloric effect in alternating magnetic fields has been investigated in Pr1-xAgxMnO3 manganites with x=0.05-0.25. The stepwise reversal of the sign of the magnetocaloric effect has been revealed in a weakly doped sample (x=0.05) at low temperatures (~80 K). This reversal is attributed to the coexistence of the ferromagnetic and canted antiferromagnetic phases with different critical temperatures.

  20. Improvement of magnetocaloric properties of Gd-Ge-Si alloys by alloying with iron

    Directory of Open Access Journals (Sweden)

    Erenc-Sędziak T.

    2013-01-01

    Full Text Available The influence of annealing of Gd5Ge2Si2Fex alloys at 1200°C and of alloying with various amount of iron on structure as well as thermal and magnetocaloric properties is investigated. It was found that annealing for 1 to 10 hours improves the entropy change, but reduces the temperature of maximum magnetocaloric effect by up to 50 K. Prolonged annealing of the Gd5Ge2Si2 alloy results in the decrease of entropy change due to the reduction of Gd5Ge2Si2 phase content. Addition of iron to the ternary alloy enhances the magnetocaloric effect, if x = 0.4 – 0.6, especially if alloying is combined with annealing at 1200°C: the peak value of the isothermal entropy change from 0 to 2 T increases from 3.5 to 11 J/kgK. Simultaneously, the temperature of maximum magnetocaloric effect drops to 250 K. The changes in magnetocaloric properties are related to the change in phase transformation from the second order for arc molten ternary alloy to first order in the case of annealed and/or alloyed with iron. The results of this study indicate that the minor addition of iron and heat treatment to Gd-Ge-Si alloys may be useful in improving the materials’ magnetocaloric properties..

  1. Magnetocaloric properties of rare-earth substituted DyCrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    McDannald, A. [Material Science and Engineering Department, University of Connecticut, Storrs, Connecticut 06269 (United States); Jain, M., E-mail: menka.jain@uconn.edu [Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

    2015-07-28

    Recently, there has been a focus on the need for efficient refrigeration technology without the use of expensive or harmful working fluids, especially at temperatures below 30 K. Solid state refrigeration, based on the magnetocaloric effect, provides a possible solution to this problem. The rare-earth chromites (RCrO{sub 3}), especially DyCrO{sub 3}, with its large magnetic moment dysprosium ion, are potential candidates for such an application. The Dy{sup 3+} ordering transition at low temperatures (<10 K) likely causes a large magnetocaloric response in this material. This study investigates the possibility of tuning the magnetocaloric properties through the use of rare-earth substitution. Both Y{sup 3+} and Ho{sup 3+} substitutions were found to decrease the magnetocaloric response by disrupting the R{sup 3+} ordering. Whereas Er{sup 3+} substitution was found to increase the magnetocaloric response, likely due to an increase in the R{sup 3+} ordering temperature. The large magnetocaloric entropy change of Er{sup 3+} substituted DyCrO{sub 3} (10.92 J/kg K with a relative cooling power of 237 J/kg at 40 kOe and 5 K) indicates that this material system is well suited for low temperature (<30 K) solid state refrigeration applications.

  2. Development of Power Electronics Based Test Platform for Characterization and Testing of Magnetocaloric Materials

    Directory of Open Access Journals (Sweden)

    Deepak Elamalayil Soman

    2015-01-01

    Full Text Available Magnetocaloric effects of various materials are getting more and more interesting for the future, as they can significantly contribute towards improving the efficiency of many energy intensive applications such as refrigeration, heating, and air conditioning. Accurate characterization of magnetocaloric effects, exhibited by various materials, is an important process for further studies and development of the suitable magnetocaloric heating and cooling solutions. The conventional test facilities have plenty of limitations, as they focus only on the thermodynamic side and use magnetic machines with moving bed of magnetocaloric material or magnet. In this work an entirely new approach for characterization of the magnetocaloric materials is presented, with the main focus on a flexible and efficient power electronic based excitation and a completely static test platform. It can generate a periodically varying magnetic field using superposition of an ac and a dc magnetic field. The scale down prototype uses a customized single phase H-bridge inverter with essential protections and an electromagnet load as actuator. The preliminary simulation and experimental results show good agreement and support the usage of the power electronic test platform for characterizing magnetocaloric materials.

  3. Magnetic and magnetocaloric properties of Y bMn 6Sn 6- xIn x

    Science.gov (United States)

    Mazet, T.; Ihou-Mouko, H.; Marêché, J. F.; Malaman, B.

    2007-06-01

    We have synthesized three Y bMn 6Sn 6- xIn x representatives ( x=0.45, 0.80, 1.20), the first pseudo-ternary RMn 6Sn 6- xX' x compounds involving a divalent R metal. The crystal structure is found to evolve with the In concentration without modification of the Yb valency: Y bMn 6Sn 5.55In 0.45 is isotypic with HoFe 6Sn 6 ( Immm) while Y bMn 6Sn 5.20In 0.80 and Y bMn 6Sn 4.80In 1.20 crystallize in the TbFe 6Sn 6-type ( Cmcm). The In content is also determining as regards the magnetic and magnetocaloric properties: Y bMn 6Sn 5.55In 0.45 ( TC=216 K) almost behaves like a simple ferromagnet while Y bMn 6Sn 5.20In 0.80 and Y bMn 6Sn 4.80In 1.20 also order ferromagnetically but at significantly lower temperatures ( TC=154 K and 129 K, respectively) and are further characterized by the interference of low temperature antiferromagnetic interactions. The results are discussed and compared to previously published data.

  4. Large magnetocaloric effect and adiabatic demagnetization refrigeration with YbPt2Sn.

    Science.gov (United States)

    Jang, Dongjin; Gruner, Thomas; Steppke, Alexander; Mitsumoto, Keisuke; Geibel, Christoph; Brando, Manuel

    2015-10-23

    Adiabatic demagnetization is currently gaining strong interest in searching for alternatives to (3)He-based refrigeration techniques for achieving temperatures below 2 K. The main reasons for that are the recent shortage and high price of the rare helium isotope (3)He. Here we report the discovery of a large magnetocaloric effect in the intermetallic compound YbPt2Sn, which allows adiabatic demagnetization cooling from 2 K down to 0.2 K. We demonstrate this with a home-made refrigerator. Other materials, for example, paramagnetic salts, are commonly used for the same purpose but none of them is metallic, a severe limitation for low-temperature applications. YbPt2Sn is a good metal with an extremely rare weak magnetic coupling between the Yb atoms, which prevents them from ordering above 0.25 K, leaving enough entropy free for use in adiabatic demagnetization cooling. The large volumetric entropy capacity of YbPt2Sn guarantees also a good cooling power.

  5. Magnetic and magnetocaloric properties of the high-temperature modification of TbTiGe.

    Science.gov (United States)

    Tencé, S; Gaudin, E; Isnard, O; Chevalier, B

    2012-07-25

    The high-temperature form (HT) of the ternary germanide TbTiGe was prepared by melting. The investigation of HT-TbTiGe by x-ray and neutron powder diffractions shows that the compound crystallizes in the tetragonal CeScSi-type structure (space group I4/mmm; a = 404.84(5) and c = 1530.10(9) pm as unit cell parameters). Magnetization and specific heat measurements as well as neutron powder diffraction performed on HT-TbTiGe reveal a ferromagnet having T(C) = 300(1) K as the Curie temperature; the Tb-moments are aligned along the c-axis. This magnetic ordering is associated with a modest magnetocaloric effect around room temperature. The isothermal magnetic entropy change ΔS(m) was determined from the magnetization data; ΔS(m) reaches, respectively, a maximum value of  - 4.3 and  - 2.0 J K(-1) kg(-1) for a magnetic field change of 5 and 2 T.

  6. Giant low field magnetocaloric effect and field-induced metamagnetic transition in TmZn

    Science.gov (United States)

    Li, Lingwei; Yuan, Ye; Zhang, Yikun; Namiki, Takahiro; Nishimura, Katsuhiko; Pöttgen, Rainer; Zhou, Shengqiang

    2015-09-01

    The magnetic properties and the magnetocaloric effect (MCE) in TmZn have been studied by magnetization and heat capacity measurements. The TmZn compound exhibits a ferromagnetic state below a Curie temperature of TC = 8.4 K and processes a field-induced metamagnetic phase transition around and above TC. A giant reversible MCE was observed in TmZn. For a field change of 0-5 T, the maximum values of magnetic entropy change (-ΔSMmax) and adiabatic temperature change (ΔTadmax) are 26.9 J/kg K and 8.6 K, the corresponding values of relative cooling power and refrigerant capacity are 269 and 214 J/kg, respectively. Particularly, the values of -ΔSMmax reach 11.8 and 19.6 J/kg K for a low field change of 0-1 and 0-2 T, respectively. The present results indicate that TmZn could be a promising candidate for low temperature and low field magnetic refrigeration.

  7. Nucleation and dynamics of the metamagnetic transition in magnetocaloric La(Fe,Mn,Si)13

    Science.gov (United States)

    Lovell, E.; Bratko, M.; Caplin, A. D.; Cohen, L. F.

    2017-10-01

    Refrigeration cycle rates of the order of 15 Hz are desirable for efficient solid state based magnetocaloric cooling, placing an upper bound on the combined magnetic transition and the heat transfer times of the order of tens of msecs. We use microcalorimetry and magnetometry to probe the transition dynamics as a function of magnetic field sweep-rate, sample size, thermal environment, temperature and hydrostatic pressure in LaFe11.74Mn0.06Si1.20. Although second order caloric materials follow the magnetisation or demagnetisation driving field without lag, here we show that the field driven evolution of the first-order phase transition in La(Fe,Si)13-based compounds show temporal dynamics on timescales that are significantly longer than tens of msecs, associated with the thermal linkage within the sample and the linkage to the external bath. We observe that features associated with the first nucleation of the transition are field sweep rate independent, and from measurements of the latent heat we infer that the barriers to magnetisation and demagnetisation are of different magnitude. Increasing the temperature or applying hydrostatic pressure reduces the dynamic effects, suggestive of diminishing first-order character of the transition under these conditions.

  8. Direct measurements of conventional and anisotropic magnetocaloric effect in binary RAl2 single crystals

    Science.gov (United States)

    Monteiro, J. C. B.; Gandra, F. G.

    2017-06-01

    We report on specific heat and magnetocaloric effect (MCE) measurements in single crystals of HoAl2, DyAl2, and TbAl2 measured by a heat flux technique using Peltier devices. Those compounds order ferromagnetically at 31 K, 61 K, and 106 K respectively, and present a spin reorientation transition (SRT) below TC. We study the dependence of the SRT with magnetic field and temperature by means of specific heat measurements performed in single crystals oriented at the [" separators="| 100 ], [" separators="| 110 ], and [" separators="| 111 ] directions with the aid of calculations using a simple model. We obtained the conventional MCE for HoAl2 and TbAl2 and also the anisotropic version of the effect obtained indirectly from the specific heat for TbAl2 and DyAl2. We also present the results for a direct determination of the anisotropic MCE for DyAl2 by measuring the heat flux generated by a rotation of the single crystal under constant field.

  9. Magnetocaloric effect in Mn2-pyrazole-[Nb(CN)8] molecular magnet by relaxation calorimetry

    Science.gov (United States)

    Pełka, R.; Gajewski, M.; Miyazaki, Y.; Yamashita, S.; Nakazawa, Y.; Fitta, M.; Pinkowicz, D.; Sieklucka, B.

    2016-12-01

    Magnetocaloric effect in {[Mn(pyrazole)4]2[Nb(CN)8]·4 H2O}n molecular magnet is reported. It crystallizes in tetragonal I41/a space group. The compound exhibits a phase transition to a long range magnetically ordered state at TN ≈ 22.8 K. Temperature dependences of the magnetic entropy change ΔSM as well as the adiabatic temperature change ΔTad due to applied field change μ0 ΔH in the range of 0.1-9 T have been inferred from the relaxation calorimetry measurements. A systematic approximate approach has been used to determine the lattice contribution to the heat capacity. The maximum value of ΔSM for μ0 ΔH = 5 T is 6.83 J mol-1 K-1 (6.65 J kg-1 K-1) at 24.3 K. The corresponding maximum value of ΔTad is 1.4 K at 23.8 K. The temperature dependence of the exponent n characterizing the field dependence of ΔSM has been estimated. It attains the value of 0.64 at the transition temperature, which is consistent with the 3D Heisenberg universality class. A hitherto unobserved two-peak structure has been revealed in the temperature dependence of ΔTad.

  10. EuAu3Al2: Crystal and Electronic Structures and Spectroscopic, Magnetic, and Magnetocaloric Properties.

    Science.gov (United States)

    Schmiegel, Jan-Patrick; Block, Theresa; Gerke, Birgit; Fickenscher, Thomas; Touzani, Rachid St; Fokwa, Boniface P T; Janka, Oliver

    2016-09-06

    The intermetallic compound EuAu3Al2 has been prepared by reaction of the elements in tantalum ampules. The structure was refined from single-crystal data, indicating that the title compound crystallizes in the orthorhombic crystal system (a = 1310.36(4), b = 547.87(1), c = 681.26(2) pm) with space group Pnma (wR2 = 0.0266, 1038 F(2) values, 35 parameters) and is isostructural to SrAu3Al2 (LT-SrZn5 type). Full ordering of the gold and aluminum atoms was observed. Theoretical calculations confirm that the title compound can be described as a polar intermetallic phase containing a polyanionic [Au3Al2](δ-) network featuring interconnected strands of edge-sharing [AlAu4] tetrahedra. Magnetic measurements and (151)Eu Mössbauer spectroscopic investigations confirmed the divalent character of the europium atoms. Ferromagnetic ordering below TC = 16.5(1) K was observed. Heat capacity measurements showed a λ-type anomaly at T = 15.7(1) K, in line with the ordering temperature from the susceptibility measurements. The magnetocaloric properties of EuAu3Al2 were determined, and a magnetic entropy of ΔSM = -4.8 J kg(-1) K(-1) for a field change of 0 to 50 kOe was determined. Band structure calculations found that the f-bands of Eu present at the Fermi level of non-spin-polarized calculations are responsible for the ferromagnetic ordering in this phase, whereas COHP chemical bonding coupled with Bader charge analysis confirmed the description of the structure as covalently bonded polyanionic [Au3Al2](δ-) network interacting ionically with Eu(δ+).

  11. Contribution of energy-gap in the ferromagnetic spin-wave spectrum on magnetocaloric parameters of CeRu(2)Ge(2).

    Science.gov (United States)

    Samanta, Tapas; Das, I; Banerjee, S

    2009-01-14

    A study of the magnetocaloric effect has been performed on a polycrystalline CeRu(2)Ge(2) compound, which exhibits an antiferromagnetic ordering below T(N) = 8.3 K and enters into a ferromagnetic ground state at T(C) = 7.4 K. The origins of the magnetocaloric parameters (the isothermal entropy change: -ΔS and the adiabatic temperature change: ΔT(ad)) of the CeRu(2)Ge(2) compound below T(C) have been analyzed. A sharp decrease in -ΔS has been observed below T(C). However, the ΔT(ad) does not fall as sharply as -ΔS with decreasing temperature in the corresponding temperature region. This behavior results in an additional value of ΔT(ad) at low temperature, which originates from the exponential decrease of the magnetic contribution of specific heat associated with an increase of energy-gap in the ferromagnetic spin-wave spectrum with the application of magnetic field.

  12. Tuneable Giant Magnetocaloric Effect in (Mn,Fe2(P,Si Materials by Co-B and Ni-B Co-Doping

    Directory of Open Access Journals (Sweden)

    Nguyen Van Thang

    2016-12-01

    Full Text Available The influence of Co (Ni and B co-doping on the structural, magnetic and magnetocaloric properties of (Mn,Fe 2 (P,Si compounds is investigated by X-ray diffraction (XRD, differential scanning calorimetry, magnetic and direct temperature change measurements. It is found that Co (Ni and B co-doping is an effective approach to tune both the Curie temperature and the thermal hysteresis of (Mn,Fe 2 (P,Si materials without losing either the giant magnetocaloric effect or the positive effect of the B substitution on the mechanical stability. An increase in B concentration leads to a rapid decrease in thermal hysteresis, while an increase in the Co or Ni concentration hardly changes the thermal hysteresis of the (Mn,Fe 2 (P,Si compounds. However, the Curie temperature decreases slowly as a function of the Co or Ni content, while it increases dramatically for increasing B concentration. Hence, the co-substitution of Fe and P by Co (Ni and B, respectively, offers a new control parameter to adjust the Curie temperature and reduce the thermal hysteresis of the (Mn,Fe 2 (P,Si materials.

  13. Effect of vanadium doping on structural, magnetic and magnetocaloric properties of La{sub 0.5}Ca{sub 0.5}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mansouri, M., E-mail: mansourimoufida23@yahoo.fr [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Omrani, H. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Cheikhrouhou-Koubaa, W. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Centre de Recherche en Informatique, Multimédia et Traitement Numérique des Données, BP 275, Sakiet Ezzit, 3021 Sfax (Tunisia); Koubaa, M. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Madouri, A. [Laboratoire de Photonique et Nanostructure, LPN-CNRS, Route de Nozay, 91460 Marcoussis (France); Cheikhrouhou, A. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia)

    2016-03-01

    We report the effect of vanadium doping on structural, magnetic and magnetocaloric properties of La{sub 0.5}Ca{sub 0.5}Mn{sub 1−x}V{sub x}O{sub 3} (x=0.05; 0.1). Our samples were elaborated using the conventional solid state reaction method at high temperatures. X-Ray powder diffraction at room temperature indicates that our samples crystallize in the orthorhombic structure with Pbnm space group. Magnetic measurements reveal a paramagnetic-ferromagnetic transition with decreasing temperature. Magnetocaloric studies show that the maximum of the magnetic entropy change and the relative cooling power (RCP) are found to be 2.42 J Kg{sup −1} K{sup −1} and 162.75 J Kg{sup −1} for x=0.05 and 3.12 J Kg{sup −1} K{sup −1} and 221.31 J Kg{sup −1} for x=0.1 under a field change of 5 T. - Highlights: • The La{sub 0.5}Ca{sub 0.5}Mn{sub 1−x}V{sub x}O{sub 3}(x=0.05 and x=0.1) compounds were synthesized using conventional solid state reaction method. • T{sub C} increases with V content from 187 K for x=0.05 to 263 K for x=0.1 • Large magnetocaloric effect is reported based on second order phase transition. • Noticeable |∆S{sub M}| at 5 T field makes the system useful for magnetic refrigeration.

  14. Giant low-field magnetocaloric effect in single-crystalline EuTi{sub 0.85}Nb{sub 0.15}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Roy, S.; Khan, N.; Mandal, P., E-mail: prabhat.mandal@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India)

    2016-02-01

    The magnetocaloric effect in ferromagnetic single crystal EuTi{sub 0.85}Nb{sub 0.15}O{sub 3} has been investigated using magnetization and heat capacity measurements. EuTi{sub 0.85}Nb{sub 0.15}O{sub 3} undergoes a continuous ferromagnetic phase transition at T{sub C} = 9.5 K due to the long range ordering of magnetic moments of Eu{sup 2+} (4f{sup 7}). With the application of magnetic field, the spin entropy is strongly suppressed and a giant magnetic entropy change is observed near T{sub C}. The values of entropy change ΔS{sub m} and adiabatic temperature change ΔT{sub ad} are as high as 51.3 J kg{sup −1} K{sup −1} and 22 K, respectively, for a field change of 0–9 T. The corresponding magnetic heating/cooling capacity is 700 J kg{sup −1}. This compound also shows large magnetocaloric effect even at low magnetic fields. In particular, the values of ΔS{sub m} reach 14.7 and 23.8 J kg{sup −1} K{sup −1} for field changes of 0–1 T and 0–2 T, respectively. The low-field giant magnetocaloric effect, together with the absence of thermal and field hysteresis makes EuTi{sub 0.85}Nb{sub 0.15}O{sub 3} a very promising candidate for low temperature magnetic refrigeration.

  15. Magnetocaloric effect in {[Fe(pyrazole)_4]_2[Nb(CN)_8]·4H_2O}{sub n} molecular magnet

    Energy Technology Data Exchange (ETDEWEB)

    Pełka, R., E-mail: robert.pelka@ifj.edu.pl [The H. Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków (Poland); Konieczny, P.; Zieliński, P.M.; Wasiutyński, T. [The H. Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków (Poland); Miyazaki, Y.; Inaba, A. [Research Center for Structural Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Pinkowicz, D.; Sieklucka, B. [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków (Poland)

    2014-03-15

    Magnetocaloric effect in {[Fe(pyrazole)_4]_2[Nb(Cn)_8]·4H_2O}{sub n} molecular magnet is reported. It crystallizes in tetragonal I4{sub 1}/a space group. The compound exhibits a phase transition to a long range magnetically ordered state at T{sub c}≈8.3K. The magnetic entropy change ΔS{sub M} as well as the adiabatic temperature change ΔT{sub ad} due to applied field change μ{sub 0}ΔH=0.1, 0.2, 0.5, 1, 2, 5, 9 T as a function of temperature have been determined by the relaxation calorimetry measurements. The maximum value of ΔS{sub M} for μ{sub 0}ΔH=5T is 4.9 J mol{sup −1} K{sup −1} (4.8 J kg{sup −1} K{sup −1}) at 10.3 K. The corresponding maximum value of ΔT{sub ad} is 2.0 K at 8.9 K. The temperature dependence of the exponent n characterizing the field dependence of ΔS{sub M} has been estimated. It attains the value of 0.64 at the transition temperature, which is consistent with the 3D Heisenberg universality class. - Highlights: • Using the technique of relaxation calorimetry the magnetocaloric effect of a novel molecular magnet is analyzed. • Temperature dependencies of isothermal magnetic entropy change and adiabatic temperature change are estimated. • Scaling behavior of the magnetocaloric effect is discussed.

  16. Magnetocaloric effect in rare-earth intermetallics: Recent trends

    Indian Academy of Sciences (India)

    R Nirmala; A V Morozkin; S K Malik

    2015-06-01

    Magnetocaloric effect (MCE) is the change in isothermal magnetic entropy (m)and adiabatic temperature (ad) that accompany magnetic transitions in materials during the application or the removal of magnetic field under adiabatic conditions. The physics of MCE gets enriched by correlated spin-lattice degrees of freedom. This phenomenon has been actively investigated over the past few decades as it holds a promise for an alternate method of refrigeration/heat pumping. This has already resulted in several reviews on this topic. This paper focusses on some recent trends in this field and prospects of using rare-earth-based materials as active magnetic refrigerants over a broad temperature range that includes gas liquefaction and near-room temperature refrigeration/heating.

  17. Magnetocaloric properties of a frustrated Blume-Capel antiferromagnet

    Directory of Open Access Journals (Sweden)

    Žukovič Milan

    2014-07-01

    Full Text Available Low-temperature magnetization processes and magnetocaloric properties of a geometrically frustrated spin-1 Blume-Capel model on a triangular lattice are studied by Monte Carlo simulations. The model is found to display qualitatively different behavior depending on the sign of the single-ion anisotropy D. For positive values of D we observe two magnetization plateaus, similar to the spin-1/2 Ising antiferromagnet, and negative isothermal entropy changes for any field intensity. For a range of small negative values of D there are four magnetization plateaus and the entropy changes can be either negative or positive, depending on the field. If D is negative but large in absolute value then the entropy changes are solely positive.

  18. Magnetocaloric effect at cryogenic temperature in gadolinium oxide nanotubes

    Science.gov (United States)

    Paul, Rima; Paramanik, Tapas; Das, Kalipada; Sen, Pintu; Satpati, B.; Das, I.

    2016-11-01

    We have synthesized fascinating nano-structure of Gadolinium oxide (Gd2O3) using controlled template-assisted electrochemical deposition technique which showed interesting anisotropic magnetic behavior. The nanotubes of Gd2O3 with average diameter 200 nm, length 10 μm and wall thickness 20 nm are constituted of nanoclusters with average diameter 7.5 nm. The tubes are aligned and are almost uniform throughout their length. Detailed magnetic measurements of aligned Gd2O3 nanotubes have been performed for both parallel and perpendicular magnetic field orientations with respect to the axis of the Gd2O3 nanotube array. Significant differences in magnetization values have been observed between the parallel and perpendicular orientations. Experimental results indicate the superparamagnetic nature of the nanomaterial. Large magnetocaloric effect, associated with the sharp change in magnetization of the Gd2O3 nanotubes, has been observed in the cryogenic temperature regime that shows anisotropic behavior.

  19. Tungsten-encapsulated gadolinium nanoislands with enhanced magnetocaloric response

    Science.gov (United States)

    Logan, J. M.; Rosenmann, D.; Sangpo, T.; Holt, M. V.; Fuesz, P.; McNulty, I.

    2017-07-01

    We report a method for growing chemically pure, oxide-free, air-stable Gd nanoislands with enhanced magnetic properties. These nanoislands are grown by solid-state dewetting and are fully encapsulated in tungsten such that they remain stable in ambient environments. They display good crystalline properties with hexagonally close-packed crystal structure and strong preferential orientation. We show that the choice of substrate strongly affects their shape, crystal orientation, and magnetic properties. The temperature-dependent magnetic coercivity and remanence of the Gd islands can vary by as much as a factor of three depending on the substrate used. The magnetocaloric properties of Gd islands grown on a sapphire substrate exceed those of high-quality Gd thin films.

  20. Large magnetocaloric effect in sintered ferromagnetic EuS

    Science.gov (United States)

    Matsumoto, Koichi; Li, Liang; Hirai, Shinji; Nakamura, Eiji; Murayama, Daiki; Ura, Yutaro; Abe, Satoshi

    2016-10-01

    We present magnetocaloric effect measurements of the ferromagnetic semiconductor EuS in the vicinity of its ordering temperature. Single phase EuS powder was synthesized by CS2 gas sulfurization of Eu2O3. A sintered compact with relative density over 95% was prepared by pulsed electric current sintering of the powder. Temperature and magnetic field dependence of the magnetization and specific heat were characteristic of a paramagnetic to ferromagnetic second order phase transition. The entropy change induced by an external magnetic field and the specific heat were both close to those of a single crystal. We obtained an entropy-temperature (S-T) diagram of the EuS sintered compact. Carnot cycle liquefaction of hydrogen using EuS was compared with several other materials, with results indicating that sintered EuS is an excellent magnetic refrigerant for hydrogen liquefaction.

  1. Some Aspects of Scaling and Universality in Magnetocaloric Materials

    DEFF Research Database (Denmark)

    Smith, Anders; Nielsen, Kaspar Kirstein; Bahl, Christian R.H.

    2014-01-01

    dependent, even at Tc. Furthermore, the scaling exponents at finite fields are not universal: Two models with the same critical exponents can exhibit markedly different scaling behaviour even at relatively low fields. Turning to the adiabatic temperature change, we argue that it is not determined......The magnetocaloric effect of a magnetic material is characterized by two quantities, the isothermal entropy change and the adiabatic temperature change, both of which are functions of temperature and applied magnetic field. We discuss the scaling properties of these quantities close to a second...... order phase transition within the context of critical scaling theory. In the critical region the isothermal entropy change will exhibit universal scaling exponents. However, this is only true close to Tc and for small fields; we show that for finite fields the scaling exponents in general become field...

  2. The magnetocaloric effect and critical behaviour of the Mn(0.94)Ti(0.06)CoGe alloy.

    Science.gov (United States)

    Shamba, P; Wang, J L; Debnath, J C; Kennedy, S J; Zeng, R; Din, M F Md; Hong, F; Cheng, Z X; Studer, A J; Dou, S X

    2013-02-06

    Structural, magnetic and magnetocaloric properties of the Mn(0.94)Ti(0.06)CoGe alloy have been investigated using x-ray diffraction, DC magnetization and neutron diffraction measurements. Two phase transitions have been detected, at T(str) = 235 K and T(C) = 270 K. A giant magnetocaloric effect has been obtained at around T(str) associated with a structural phase transition from the low temperature orthorhombic TiNiSi-type structure to the high temperature hexagonal Ni(2)In-type structure, which is confirmed by neutron study. In the vicinity of the structural transition, at T(str), the magnetic entropy change, -ΔS(M) reached a maximum value of 14.8 J kg(-1) K(-1) under a magnetic field of 5 T, which is much higher than that previously reported for the parent compound MnCoGe. To investigate the nature of the magnetic phase transition around T(C) = 270 K from the ferromagnetic to the paramagnetic state, we performed a detailed critical exponent study. The critical components γ, β and δ determined using the Kouvel-Fisher method, the modified Arrott plot and the critical isotherm analysis agree well. The values deduced for the critical exponents are close to the theoretical prediction from the mean-field model, indicating that the magnetic interactions are long range. On the basis of these critical exponents, the magnetization, field and temperature data around T(C) collapse onto two curves obeying the single scaling equation M(H,ε) = ε(β)f ± (H/ε(β+γ)).

  3. Preliminary Analysis of a Fully Solid State Magnetocaloric Refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Abdelaziz, Omar [ORNL

    2016-01-01

    Magnetocaloric refrigeration is an alternative refrigeration technology with significant potential energy savings compared to conventional vapor compression refrigeration technology. Most of the reported active magnetic regenerator (AMR) systems that operate based on the magnetocaloric effect use heat transfer fluid to exchange heat, which results in complicated mechanical subsystems and components such as rotating valves and hydraulic pumps. In this paper, we propose an alternative mechanism for heat transfer between the AMR and the heat source/sink. High-conductivity moving rods/sheets (e.g. copper, brass, iron, graphite, aluminum or composite structures from these) are utilized instead of heat transfer fluid significantly enhancing the heat transfer rate hence cooling/heating capacity. A one-dimensional model is developed to study the solid state AMR. In this model, the heat exchange between the solid-solid interfaces is modeled via a contact conductance, which depends on the interface apparent pressure, material hardness, thermal conductivity, surface roughness, surface slope between the interfaces, and material filled in the gap between the interfaces. Due to the tremendous impact of the heat exchange on the AMR cycle performance, a sensitivity analysis is conducted employing a response surface method, in which the apparent pressure, effective surface roughness and grease thermal conductivity are the uncertainty factors. COP and refrigeration capacity are presented as the response in the sensitivity analysis to reveal the important factors influencing the fully solid state AMR and optimize the solid state AMR efficiency. The performances of fully solid state AMR and traditional AMR are also compared and discussed in present work. The results of this study will provide general guidelines for designing high performance solid state AMR systems.

  4. 粉末冶金法制备La(Fe11.05Co0.85Si1.1)B0.25化合物的磁热效应%Magnetocaloric Effect of La (Fe11.05Co0.85Si1.1)B,0.25 Compounds Prepared by Powder Metallurgy Method

    Institute of Scientific and Technical Information of China (English)

    武清; 黄焦宏; 刘翠兰; 闫宏伟; 邓沅; 程娟

    2011-01-01

    La( Fe11.05 Co0.85Si1.1 ) B0.25 as-cast was prepared by arc melting fumace in argon atmosphere.The aLloy powder was prepared from the as-cast using mechanical method in argon atmosphere.The alloy bulk prepared from the alloy powder using spark plasma sintering method was heat-treated at 1343 K for 20 h and was cooled in air.The samples of the three different types ( the as-cast alloy,the alloy prepared using SPS and SPS alloy after heat treatment) were investigated by means of XRD and SEM analysis apparatus.And the magnetocaloric effect ( MCE) of the different samples were measured with the MCE direct measurement device and VSM equipment.The results showed that : The grain size of as-cast sample was symmetrical and the erystal boundsry was obvious, the isothermal entropy change and the adiabatic temperature change of as-cast sample under a magnetic field change from 0 to 1.5 T was -5.22J·( kg·K) -1 and 2.3 K respectively. But the crystal boundary of SPS sample was not obvious and lots of impuritiea were found in its microstructure, the adiabatic temperature change and the isothermal entropy change of SPS sample under a magnetic field change from 0 to 1.5 T was -3.90 J·( kg·K) -1 and 1.9 K respectively.The grain size of SPS sample after heat treatment was asymmetrical and few crystal boundary was obvious, the adiabatic temperature change and the isothermal entropy change of SPS sample after heat treatment under a magnetic field change from 0 to 1.5 T was - 3.72 J·( kg· K) -1 and 1.5 K respectively ; Compared to as-cast sample , the adiabatic temperature change and the isothermal entropy change the samples prepared by SPS technology( whatever heat treatment was canied out) was decreased and ita Curie temperature Te and its value of peak breadth is increased.The results indicated that the La ( Fe11.05 Co0.85 Si1.1 ) B0.25 MCE material prepared by SPS technology could be applied under a wide temperature ranSe , but its MCE relatively decreased.%用非自耗电

  5. Synthetic Approach for (Mn,Fe)2(Si,P) Magnetocaloric Materials: Purity, Structural, Magnetic, and Magnetocaloric Properties.

    Science.gov (United States)

    He, Allan; Svitlyk, Volodymyr; Mozharivskyj, Yurij

    2017-03-06

    A conventional solid-state approach has been developed for the synthesis of phase-pure magnetocaloric Mn2-xFexSi0.5P0.5 materials (x = 0.6, 0.7, 0.8, 0.9). Annealing at high temperatures followed by dwelling at lower temperatures is essential to obtain pure samples with x = 0.7, 0.8, and 0.9. Structural features of the samples with x = 0.6 and 0.9 were analyzed as a function of temperature via synchrotron powder diffraction. The Curie temperature, temperature hysteresis, and magnetic entropy change were established from the magnetic measurements. According to the diffraction and magnetization data, all samples undergo a first-order magnetostructural transition, but the first-order nature becomes less pronounced for samples that are more Mn rich.

  6. Magnetocaloric properties and critical behavior of high relative cooling power FeNiB nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhary, V. [Interdisciplinary Graduate School, Nanyang Technological University, Singapore 639798 (Singapore); Energy Research Institute @NTU, Nanyang Technological University, Singapore 637553 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Maheswar Repaka, D. V.; Chaturvedi, A.; Ramanujan, R. V., E-mail: ramanujan@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Sridhar, I. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2014-10-28

    Low cost magnetocaloric nanomaterials have attracted considerable attention for energy efficient applications. We report a very high relative cooling power (RCP) in a study of the magnetocaloric effect in quenched FeNiB nanoparticles. RCP increases from 89.8 to 640 J kg{sup −1} for a field change of 1 and 5 T, respectively, these values are the largest for rare earth free iron based magnetocaloric nanomaterials. To investigate the magnetocaloric behavior around the Curie temperature (T{sub C}), the critical behavior of these quenched nanoparticles was studied. Detailed analysis of the magnetic phase transition using the modified Arrott plot, Kouvel-Fisher method, and critical isotherm plots yields critical exponents of β = 0.364, γ = 1.319, δ = 4.623, and α = −0.055, which are close to the theoretical exponents obtained from the 3D-Heisenberg model. Our results indicate that these FeNiB nanoparticles are potential candidates for magnetocaloric fluid based heat pumps and low grade waste heat recovery.

  7. Magnetocaloric properties and critical behavior of high relative cooling power FeNiB nanoparticles

    Science.gov (United States)

    Chaudhary, V.; Maheswar Repaka, D. V.; Chaturvedi, A.; Sridhar, I.; Ramanujan, R. V.

    2014-10-01

    Low cost magnetocaloric nanomaterials have attracted considerable attention for energy efficient applications. We report a very high relative cooling power (RCP) in a study of the magnetocaloric effect in quenched FeNiB nanoparticles. RCP increases from 89.8 to 640 J kg-1 for a field change of 1 and 5 T, respectively, these values are the largest for rare earth free iron based magnetocaloric nanomaterials. To investigate the magnetocaloric behavior around the Curie temperature (TC), the critical behavior of these quenched nanoparticles was studied. Detailed analysis of the magnetic phase transition using the modified Arrott plot, Kouvel-Fisher method, and critical isotherm plots yields critical exponents of β = 0.364, γ = 1.319, δ = 4.623, and α = -0.055, which are close to the theoretical exponents obtained from the 3D-Heisenberg model. Our results indicate that these FeNiB nanoparticles are potential candidates for magnetocaloric fluid based heat pumps and low grade waste heat recovery.

  8. The expected low field magnetocaloric effect of La0.7Ba0.3MnO3 manganite at room temperature

    Science.gov (United States)

    Mohamed, Abd El-Moez A.; Hernando, B.

    2016-04-01

    La0.7Ba0.3MnO3 manganite oxide was prepared by the sol-gel method. X-ray diffraction has shown the high homogeneity of the compound and Reitveld refinement has proved the R-3C rhombohedral structure. The temperature dependence of magnetization at different applied magnetic fields of 50 Oe, 100 Oe and 200 Oe shows a magnetic phase transition at room temperature around 302 K. The magnetocaloric properties and the related parameters have been calculated theoretically based on a phenomenological model. The results include the magnetic field dependence of magnetic entropy change, relative cooling power and specific heat. The constructed universal curve of the magnetic entropy change has proved the second order nature of magnetic phase transition in the studied compound.

  9. Critical magnetic behavior and large magnetocaloric effect in Pr{sub 0.67}Ba{sub 0.33}MnO{sub 3} perovskite manganite

    Energy Technology Data Exchange (ETDEWEB)

    Varvescu, A.; Deac, I.G., E-mail: iosif.deac@phys.ubbcluj.ro

    2015-08-15

    We report results of critical magnetic behavior and magnetocaloric investigations of the perovskite manganite Pr{sub 0.67}Ba{sub 0.33}MnO{sub 3}. The compound exhibits a paramagnetic (PM) to ferromagnetic (FM) transition at the Curie temperature T{sub C}, and significant negative magnetoresistance in a wide temperature range. To probe the magnetic interactions responsible for the magnetic transitions, we performed a critical exponent analysis in the vicinity of the FM–PM transition region. Magnetic entropy change ΔS{sub M} was estimated from isothermal magnetization data. We have found a remarkable large value of |ΔS{sub M}| around T{sub C}’s, of about 5.50 J/kg K for μ{sub 0}ΔH=4 T and a large relative cooling power (~225 J/kg). The analysis was done by using the modified Arrot plot (MAP) method. The values of the obtained critical exponents associated with this transition, β=0.366, γ=1.375 and δ=4.743 are close to those expected for the short range 3D Heisenberg model. The model was also confirmed by using |ΔS{sub M}|∝(μ{sub 0}H){sup n}, the field dependence of magnetic entropy change method. The large measured magnetocaloric effect is presumed to arise as a consequence of the sample preparation route.

  10. Study of magnetic, structural and magnetocaloric properties of La0.6Pr0.4Mn2Si2 under high pressures and magnetic field

    Science.gov (United States)

    Kaštil, J.; Arnold, Z.; Isnard, O.; Skourski, Y.; Kamarád, J.; Itié, J. P.

    2017-02-01

    The structural, magnetic and magnetocaloric properties of La0.6Pr0.4Mn2Si2 compound were measured in wide range of temperature, magnetic field and hydrostatic pressure. The structural study up to 10 GPa confirmed the existence of critical Mn-Mn distance 0.2883 nm for the ferromagnetic to antiferromagnetic transition at room temperature. The results demonstrated the crucial role of the volume in the suppression of the ferromagnetic phase above the transition temperature T1=168 K under pressure. The huge pressure shift of the transition temperature T1, dT1/dp=230 K/GPa, was observed. Based on our magnetization measurement the low temperature transition at T2=30 K is connected with reorientation of Mn moment and the rare-earth sublattice is not ordered in this case. The direct magnetocaloric measurement showed moderate values of the adiabatic temperature change connected with the magnetic transition at Tc and T1 and confirmed the first order character of the transition at T1 and second order character of the transition at Tc.

  11. Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

    Science.gov (United States)

    Smith, Anders; Nielsen, Kaspar K.; Bez, Henrique N.; Bahl, Christian R. H.

    2016-08-01

    We measure the magnetocaloric effect of the manganite series La0.67Ca0.33 -xSrxMnO3 by determining the isothermal entropy change upon magnetization, using variable-field calorimetry. The results demonstrate that the field dependence of the magnetocaloric effect close to the critical temperature is not given uniquely by the critical exponents of the ferromagnetic-paramagnetic phase transition, i.e., the scaling is nonuniversal. A theoretical description based on the Bean-Rodbell model and taking into account compositional inhomogeneities is shown to be able to account for the observed field dependence. In this way the determination of the nonuniversal field dependence of the magnetocaloric effect close to a phase transition can be used as a method to gain insight into the strength of the spin-lattice interactions of magnetic materials. The approach is shown also to be applicable to first-order transitions.

  12. Simulated magnetocaloric properties of MnCr2O4 spinel

    Directory of Open Access Journals (Sweden)

    Mahmoud A. Hamad

    2016-03-01

    Full Text Available The magnetocaloric properties of MnCr2O4 spinel have been simulated based on a phenomenological model. The simulation of magnetization as function of temperature is used to explore magnetocaloric properties such as magnetic entropy change, heat capacity change, and relative cooling power. The results imply the prospective application of MnCr2O4 spinel to achieve magnetocaloric effect at cryogenic temperatures (20–60 K near Curie temperatures (38–44 K. According to the obtained results it is recommended that MnCr2O4 spinel can be used as a promising practical material in the active magnetic regenerator cycle that cools hydrogen gas.

  13. Development of a new magnetocaloric material used in a magnetic refrigeration device

    Directory of Open Access Journals (Sweden)

    Hardy V.

    2012-06-01

    Full Text Available Testing directly a magnetocaloric material in a magnetic refrigeration (MR system is the best way to judge of its applicative potentialities. In this spirit, an oxide expected to show promising magnetocaloric properties around room temperature (Pr0.65Sr0.35MnO3 was produced in large scale and shaped in order to build a regenerator. Magnetization, heat capacity, resistivity, thermal conductivity and a direct test in a MR device were carried out on this manganite. The results were compared to those observed in the reference material which is Gadolinium. The two main conclusions of these preliminary results are: (i the Pr0.65Sr0.35MnO3 actually displays not only a significant magnetocaloric effect but also a real refrigeration capability at room temperature; (ii the temperature spans reached in these first experiments are even found to well compare with those obtained with Gd.

  14. A multicaloric material as a link between electrocaloric and magnetocaloric refrigeration.

    Science.gov (United States)

    Ursic, Hana; Bobnar, Vid; Malic, Barbara; Filipic, Cene; Vrabelj, Marko; Drnovsek, Silvo; Jo, Younghun; Wencka, Magdalena; Kutnjak, Zdravko

    2016-05-25

    The existence and feasibility of the multicaloric, polycrystalline material 0.8Pb(Fe1/2Nb1/2)O3-0.2Pb(Mg1/2W1/2)O3, exhibiting magnetocaloric and electrocaloric properties, are demonstrated. Both the electrocaloric and magnetocaloric effects are observed over a broad temperature range below room temperature. The maximum magnetocaloric temperature change of ~0.26 K is obtained with a magnetic-field amplitude of 70 kOe at a temperature of 5 K, while the maximum electrocaloric temperature change of ~0.25 K is obtained with an electric-field amplitude of 60 kV/cm at a temperature of 180 K. The material allows a multicaloric cooling mode or a separate caloric-modes operation depending on the origin of the external field and the temperature at which the field is applied.

  15. Structure and giant inverse magnetocaloric effect of epitaxial Ni-Co-Mn-Al films

    Science.gov (United States)

    Teichert, N.; Kucza, D.; Yildirim, O.; Yuzuak, E.; Dincer, I.; Behler, A.; Weise, B.; Helmich, L.; Boehnke, A.; Klimova, S.; Waske, A.; Elerman, Y.; Hütten, A.

    2015-05-01

    The structural, magnetic, and magnetocaloric properties of epitaxial Ni-Co-Mn-Al thin films with different compositions have been studied. The films were deposited on MgO(001) substrates by co-sputtering on heated substrates. All films show a martensitic transformation, where the transformation temperatures are strongly dependent on the composition. The structure of the martensite phase is shown to be 14 M . The metamagnetic martensitic transformation occurs from strongly ferromagnetic austenite to weakly magnetic martensite. The structural properties of the films were investigated by atomic force microscopy and temperature dependent x-ray diffraction. Magnetic and magnetocaloric properties were analyzed using temperature dependent and isothermal magnetization measurements. We find that Ni41Co10.4Mn34.8Al13.8 films show giant inverse magnetocaloric effects with magnetic entropy change of 17.5 J kg-1K-1 for μ0Δ H =5 T.

  16. Magnetocaloric effect in Ni-Fe-Ga Heusler alloys with Co and Al substitutions

    Directory of Open Access Journals (Sweden)

    Tolea F.

    2015-01-01

    Full Text Available The functionality of the ferromagnetic shape memory alloys is related to the martensitic and magnetic order-disorder transformations, both of which may be tailored by doping with other elements or by suitable thermal treatments, so that alloys with concomitant (or sequential but close structural and magnetic phase transitions may be obtained. Concerning the magnetocaloric applications, it is assumed that the thin melt-spun ribbons assure a more efficient heat transfer. In the present work we investigate the influence of Co and Al substitutions on magnetocaloric effect characteristics of NiFeGa in bulk and also in ribbons prepared by melt spinning method and subjected to different thermal treatments. X-ray diffraction, differential scanning calorimetry, magnetocaloric and magnetoresistive characterizations have been performed. The results highlight the differences between the bulk and the ribbons (both as prepared and annealed and the role of substitutions.

  17. Phase transitions and magnetocaloric and transport properties in off-stoichiometric GdNi{sub 2}Mn{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Aryal, Anil; Quetz, Abdiel; Pandey, Sudip; Dubenko, Igor; Mazumdar, Dipanjan; Ali, Naushad [Department of Physics, Southern Illinois University, Carbondale, Illinois 62901 (United States); Samanta, Tapas; Stadler, Shane [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

    2016-01-28

    The structural, magnetic, magnetocaloric, transport, and magnetoresistance properties of the rare-earth intermetallic compounds GdNi{sub 2}Mn{sub x} (0.5 ≤ x ≤ 1.5) have been studied. The compounds with x = 0.5 and 0.6 crystallize in the cubic MgCu{sub 2} type phase, whereas samples with x ≥ 0.8 form a mixed MgCu{sub 2} and rhombohedral PuNi{sub 3} phase. A second order magnetic phase transition from a ferromagnetic to paramagnetic state was observed near the Curie temperature (T{sub C}). The GdNi{sub 2}Mn{sub x} (0.5 ≤ x ≤ 1.5) compounds order in a ferrimagnetic structure in the ground state. The largest observed values of magnetic entropy changes (at T{sub C} for ΔH = 5T) were 3.9, 3.5, and 3.1 J/kg K for x = 0.5, 0.6, and 0.8, respectively. The respective relative values of the cooling power were 395, 483, and 220 J/kg. These values are greater than some well-known prototype magnetocaloric materials such as Gd (400 J/kg) and Gd{sub 5}Si{sub 2}Ge{sub 2} (240 J/kg). Analysis of the resistivity data showed a T{sup 2} dependence at low temperatures, suggesting strong electron-phonon interactions, whereas at higher temperatures s-d scattering was dominated by the electron-phonon contribution, resulting in a slow increase in resistivity. Magnetoresistance values of ∼−1.1% were found for x = 0.5 near T{sub C}, and −7% for x = 1.5 near T = 80 K.

  18. About the mechanical stability of MnFe(P,Si,B) giant-magnetocaloric materials

    Energy Technology Data Exchange (ETDEWEB)

    Guillou, F., E-mail: f.guillou@tudelft.nl [FAME, Faculty of Applied Sciences, TU Delft, Mekelweg 15, 2629 JB Delft (Netherlands); Yibole, H.; Dijk, N.H. van [FAME, Faculty of Applied Sciences, TU Delft, Mekelweg 15, 2629 JB Delft (Netherlands); Zhang, L. [BASF Netherlands B.V., Strijkviertel 67, 3454 PK De Meern (Netherlands); Hardy, V. [CRISMAT, Ensicaen, UMR 6508 CNRS, 6 B" d Maréchal Juin, 14050 Caen Cedex (France); Brück, E. [FAME, Faculty of Applied Sciences, TU Delft, Mekelweg 15, 2629 JB Delft (Netherlands)

    2014-12-25

    Highlights: • Electrical resistivity and hardness show an evolution at T{sub C} with thermal cycling. • Degradation depends on the (c/a) lattice discontinuity at the transition. • Boron substituted materials present an improved mechanical stability. - Abstract: Due to its ability to control the latent heat and the hysteresis (thermal or magnetic) at the first-order transition (FOT) without deteriorating the saturation magnetisation, boron substitution in MnFe(P,Si) materials has recently been reported to be an ideal parameter to reach promising magnetocaloric performances: ΔS ≈ 10 Jkg{sup −1} K{sup −1} and cyclic ΔT of 2.6 K (and more) at a moderate magnetic field of ΔB = 1 T. Additionally, an interesting aspect for applications is the improvement of the mechanical stability in B doped materials compared to the pristine MnFe(P,Si) compounds. These improved mechanical properties were initially supported by naked-eye inspection and the observation of a constant ΔT during a few thousands of magnetic cycles. (Guillou et al., 2014) Here, the evolution upon cycling of MnFe(P,Si,B) materials is studied in a more quantitative and systematic manner. For that purpose transformation temperatures, electrical resistivity, micro-hardness and the microstructure are tracked as a function of the thermal cycling across the FOT for three prototypical compositions in the MnFe(P,Si,B) system. It turns out this set of data confirms the initial finding that B substitution has a positive effect on the mechanical stability. The origin of this improvement is discussed, in particular in respect to the lattice parameter discontinuities at the phase transition.

  19. Magnetocaloric properties of rapidly solidified Dy{sub 3}Co alloy ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez Llamazares, J. L., E-mail: jose.sanchez@ipicyt.edu.mx; Flores-Zúñiga, H.; Sánchez-Valdés, C. F. [Instituto Potosino de Investigación Científica y Tecnológica A.C., Camino a la Presa San José 2055 Col. Lomas 4" a, San Luis Potosí, S.L.P. 78216 (Mexico); Álvarez-Alonso, Pablo [Departamento de Electricidad y Electrónica, UPV/EHU, 48940 Leioa (Spain); Lara Rodríguez, G. A. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, México, D. F. 04510 (Mexico); Fernández-Gubieda, M. L. [Departamento de Electricidad y Electrónica, UPV/EHU, 48940 Leioa (Spain); BC Materials, Camino de Ibaizabal, Edificio 500, Planta 1, Parque Científico y Tecnológico de Zamudio, 48160 Derio (Spain)

    2015-05-07

    The magnetic and magnetocaloric (MC) properties of melt-spun ribbons of the Dy{sub 3}Co intermetallic compound were investigated. Samples were fabricated in an Ar environment using a homemade melt spinner system at a linear speed of the rotating copper wheel of 40 ms{sup −1}. X-ray diffraction analysis shows that ribbons crystallize into a single-phase with the Fe{sub 3}C-type orthorhombic crystal structure. The M(T) curve measured at 5 mT reveals the occurrence of a transition at 32 K from a first to a second antiferromagnetic (AFM) state and an AFM-to-paramagnetic transition at T{sub N} = 43 K. Furthermore, a metamagnetic transition is observed below T{sub N}, but the magnetization change ΔM is well below the one reported for bulk alloys. Below 12 K, large inverse MC effect and hysteresis losses are observed. This behavior is related to the metamagnetic transition. For a magnetic field change of 5 T (2 T) applied along the ribbon length, the produced ribbons show a peak value of the magnetic entropy change ΔS{sub M}{sup peak} of −6.5 (− 2.1) Jkg{sup −1}K{sup −1} occurring close to T{sub N} with a full-width at half-maximum δT{sub FWHM} of 53 (37) K, and refrigerant capacity RC = 364 (83) Jkg{sup −1} (estimated from the product |ΔS{sub M}{sup peak}| × δT{sub FWHM})

  20. Influence of random substitution on magnetocaloric effect in a spinel ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Mamiya, Hiroaki, E-mail: MAMIYA.Hiroaki@nims.go.j [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Terada, Noriki; Furubayashi, Takao; Suzuki, Hiroyuki S.; Kitazawa, Hideaki [National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2010-05-15

    Influence of random substitution of nonmagnetic ions on magnetocaloric effect is studied on manganese zinc ferrites from the viewpoints of Griffiths effects and frustration effects. The obtained results show that these side effects are insignificant at the ferrimagnetic transition in the range of zinc content below 70%. Consequently, the ferrite can keep a large magnetocaloric effect even when the transition temperature is lowered to a half of the original. This finding indicates that the nonmagnetic substitution is useful in adjusting the working temperature, if we utilize popular magnets such as ferrites with high Curie temperatures for the refrigerant consisting ubiquitous and nontoxic elements.

  1. Measuring the effect of demagnetization in stacks of gadolinium plates using the magnetocaloric effect

    DEFF Research Database (Denmark)

    Lipsø, Hans Kasper Wigh; Nielsen, Kaspar Kirstein; Christensen, Dennis

    2011-01-01

    The effect of demagnetization in a stack of gadolinium plates is determined experimentally by using spatially resolved measurements of the adiabatic temperature change due to the magnetocaloric effect. The number of plates in the stack, the spacing between them and the position of the plate...... on which the temperature is measured are varied. The orientation of the magnetic field is also varied. The measurements are compared to a magnetostatic model previously described. The results show that the magnetocaloric effect, due to the change in the internal field, is sensitive to the stack...

  2. Magnetocaloric effect in sandwich structures of La1- x K x MnO3 manganites

    Science.gov (United States)

    Gamzatov, A. G.; Aliev, A. M.; Kamilov, I. K.; Kaul', A. R.

    2016-07-01

    This paper reports on the results of the investigation into the magnetocaloric properties of sandwich structures of La1- x K x MnO3 manganites with x = 0.11 (LKM11), 0.13 (LKM13), and 0.15 (LKM15) in magnetic fields of up to 18 kOe. The results of the analysis of the field and temperature dependences of the magnetocaloric effect in the structures LKM11 + LKM13 and LKM13 + LKM15 have demonstrated that the use of sandwich structures increases the efficiency of magnetic cooling in a magnetic field of 18 kOe by 45%.

  3. Second Law Violation By Magneto-Caloric Effect Adiabatic Phase Transition of Type I Superconductive Particles

    Directory of Open Access Journals (Sweden)

    Peter Keefe

    2004-03-01

    Full Text Available Abstract: The nature of the thermodynamic behavior of Type I superconductor particles, having a cross section less than the Ginzburg-Landau temperature dependent coherence length is discussed for magnetic field induced adiabatic phase transitions from the superconductive state to the normal state. Argument is advanced supporting the view that when the adiabatic magneto-caloric process is applied to particles, the phase transition is characterized by a decrease in entropy in violation of traditional formulations of the Second Law, evidenced by attainment of a final process temperature below that which would result from an adiabatic magneto-caloric process applied to bulk dimensioned specimens.

  4. Optimal temperature range for determining magnetocaloric magnitudes from heat capacity

    Science.gov (United States)

    Moreno-Ramírez, L. M.; Blázquez, J. S.; Law, J. Y.; Franco, V.; Conde, A.

    2016-12-01

    The determination of the magnetocaloric magnitudes (specific magnetic entropy change, Δs M, and adiabatic temperature change, ΔT ad) from heat capacity (c H) measurements requires measurements performed at very low temperatures (~0 K) or data extrapolation when the low temperature range is unavailable. In this work we analyze the influence on the calculated Δs M and ΔT ad of the usually employed linear extrapolation of c H from the initial measured temperature down to 0 K. Numerical simulations have been performed using the Brillouin equation of state, the Debye model and the Fermi electron statistics to reproduce the magnetic, lattice and electronic subsystems, respectively. It is demonstrated that it is not necessary to reach experimentally temperatures very close to 0 K due to the existence of certain starting temperatures of the experiments, the same for Δs M and ΔT ad, that minimize the error of the results. A procedure is proposed to obtain the experimental magnitudes of Δs M and ΔT ad with a minimum error from c H data limited in temperature. It has been successfully applied to a GdZn alloy and results are compared to those derived from magnetization measurements.

  5. Review of magnetocaloric effect in perovskite-type oxides

    Institute of Scientific and Technical Information of China (English)

    Zhong Wei; Au Chak-Tong; Du You-Wei

    2013-01-01

    We survey the magnetocaloric effect in perovskite-type oxides (including doped ABO3-type manganese oxides,A3B2O7-type two-layered perovskite oxides,and A2B'B''O6-type ordered double-perovskite oxides).Magnetic entropy changes larger than those of gadolinium can be observed in polycrystalline La(Ⅰ)-xCaxMnO3 and alkali-metal (Na or K)doped La0.8Ca0.2MnO3 perovskite-type manganese oxides.The large magnetic entropy change produced by an abrupt reduction of magnetization is attributed to the anomalous thermal expansion at the Curie temperature.Considerable magnetic entropy changes can also be observed in two-layered perovskites La1.6Ca1.4Mn2O7 and La2.5-xK0.5+xMn2O7+δ(0 < x < 0.5),and double-perovskite Ba2Fe1+xMo1-xO6(0 ≤ x ≤ 0.3) near their respective Curie temperatures.Compared with rare earth metals and their alloys,the perovskite-type oxides are lower in cost,and they exhibit higher chemical stability and higher electrical resistivity,which together favor lower eddy-current heating.They are potential magnetic refrigerants at high temperatures,especially near room temperature.

  6. Effect of Gd polarization on the large magnetocaloric effect of GdCrO4 in a broad temperature range

    Science.gov (United States)

    Palacios, E.; Tomasi, C.; Sáez-Puche, R.; Dos santos-García, A. J.; Fernández-Martínez, F.; Burriel, R.

    2016-02-01

    The ferromagnetic zircon-type phase of GdCrO4 presents high values for the magnetocaloric (MC) parameters. This compound has large isothermal entropy changes Δ ST under the magnetic field action in a wide temperature range, from 5 to 35 K, reaching a maximum |Δ ST|=29.0 ±0.1 J /kg K at 22 K, for a field increment Δ B =9 T. It orders ferromagnetically at TC=21.3 K via the Cr-Cr exchange interaction and shows a second transition at 4.8 K due to the ordering of the Gd sublattice. The large MC effect is enhanced by the polarization of the Gd3 + ions by the Cr5 + ones via a weaker Gd-Cr interaction. This effect is an interesting feature to be considered in the search for new compounds with a high MC effect in the range of liquid hydrogen or natural gas, regarding the liquefaction of gases by magnetization-demagnetization cycles. This paper contains experimental measurements of magnetization, heat capacity, and direct determinations of the MC effect. The magnetic contribution to the heat capacity Cm has been obtained after subtracting the lattice component. Approximate values for the exchange constants J1 (Cr-Cr) and J3 (Gd-Cr) have been deduced from Cm.

  7. Magnetic Properties and Magnetocaloric Effect in Layered NdMn1.9V0.1Si2

    Directory of Open Access Journals (Sweden)

    Din M.F. Md

    2014-07-01

    Full Text Available The structural and magnetic properties of the compounds NdMn2-xVxSi2 have been studied by x-ray and high resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range 3-450 K. The Curie temperature and Néel temperature of layered NdMn1.9V0.1Si2 are been indicate at TC ~ 24 K and TN ~ 376 K respectively. The giant magnetocaloric effect (GMCE around TC is found in layered NdMn1.9V0.1Si2 associated with first order magnetic transition from antiferromagnetic [AFil-type] to ferromagnetic [F(Nd+Fmc]. This behaviorhas been confirmed as contribution of the magnetostructural coupling by using neutron powder diffraction. The magnetic entropy change −ΔSM ~ 25.4J kg-1 K-1 and adiabatic temperature change ΔTad~ 6.7 K have been determined using magnetization and specific heat measurement under 0-8 T field applied. This compound belongs with the small thermal ~ 0.8 K and magnetic ~ 0.1 T hysteresis characteristic providing high potential material for magnetic refrigerator.

  8. Giant rotating magnetocaloric effect in the region of spin-reorientation transition in the NdCo₅ single crystal.

    Science.gov (United States)

    Nikitin, S A; Skokov, K P; Koshkid'ko, Yu S; Pastushenkov, Yu G; Ivanova, T I

    2010-09-24

    We have investigated the anisotropy of the magnetocaloric effect in a NdCo₅ single crystal in a wide range of temperatures, including the spin-reorientation temperature region. In the field μ(0)H =1.3 T in the spin-reorientation region 250-310 K, we discovered a giant rotating magnetocaloric effect of ~ 1.6 K, caused by rotation of the magnetization vector. The calculations of the anisotropy magnetocaloric effect for the field μ(0)H =1.3 T have been carried out.

  9. Magnetic Properties of Nd12Co6Pb Compound

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The magnetic and magnetocaloric properties for the Nd12Co6Pb compound were investigated. The Curie temperature TC of the magnetic transition of Nd12Co6Pb compound is 194 K. The experimentally determined magnetic effective paramagnetic moment is μeff=12.36 μB per formula unit (3.49 μB per Nd atom). The maximum magnetic entropy change in the low magnetic field changes of 0~2 T for the Nd12Co6Pb compound is about 215.0 J·mole-1·K-1.

  10. Analysis of fitting metho ds for laser-triggered ultrafast magnetization dynamics in diluted magnetic semio cnductor (Ga, Mn)As film%稀磁半导体(Ga,Mn)As薄膜激光诱导超快磁化动力学过程拟合方法探究∗

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    Laser-triggered magnetization dynamics for diluted magnetic semiconductor (Ga, Mn)As has drawn great attention in recent years, aiming at studying the ultrafast manipulation of collective spin excitations towards spintronic information processing. In this work, different fitting methods for time-resolved magneto-optical Kerr effect (TR-MOKE) study of the laser-triggered magnetization dynamics in a diluted magnetic semiconductor (Ga, Mn)As are analyzed and compared. It is known that the exponentially damped cosine harmonic function and the numerical simulation based on Landau-Lifshitz-Gilbert (LLG) equation are usually applied to fit the laser-induced magnetization dynamics from TR-MOKE measurements. Under the specified experimental conditions, it is sometimes hard to fit the TR-MOKE response well with single-mode uniform precession by using the exponentially damped cosine harmonic function. Although the fitting with multiple precession frequencies may usually show much better fitting results, the numerical simulation based on LLG equation reveals that the multi-frequency precessional modes are caused by the superposition of three-dimensional trajectories of magnetization precession with different contributions from the in-plane and out-of-plane magneto-optical response in (Ga, Mn)As. Thus, the multi-frequency precessional modes obtained by adopting the fitting method with exponentially damped cosine harmonic function could be the fake ones. Meanwhile, it is important to note that though the LLG equation can be used to fit the macroscopic magnetization precession well with single frequency, the contribution of pulse-like background response from photo-generated polarized carriers at the above-bandgap excitation is strongly superimposed on the magnetization precession response, and the pulse-like background response cannot be described by LLG equation. Thus one should be cautious of applying LLG equation only to fit the entire TR-MOKE signal, especially when the

  11. Preparing Magnetocaloric LaFeSi Uniform Microstructures by Spark Plasma Sintering

    DEFF Research Database (Denmark)

    Vicente, N.; Ocanã, J.; Neves Bez, Henrique

    2014-01-01

    Spark Plasma Sintering (SPS) of LaFeSi alloy powders was conducted to prepare magnetocaloric La-Fe-Si-based uniform microstructures. Two electrically insulating discs made of alumina were interposed between the punches and powder sample inhibiting the flow of electric current across the powder......’s microhardness by means of ANOVA statistics....

  12. Spatially resolved measurements of the magnetocaloric effect and the local magnetic field using thermography

    DEFF Research Database (Denmark)

    Christensen, Dennis; Bjørk, Rasmus; Nielsen, Kaspar Kirstein

    2010-01-01

    The magnetocaloric effect causes a magnetic material to change temperature upon application of a magnetic field. Here, spatially resolved measurements of the adiabatic temperature change are performed on a plate of gadolinium using thermography. The adiabatic temperature change is used to extract...

  13. Modelling and simulation of regenerators with complex flow arrangements for active magnetocaloric refrigeration

    DEFF Research Database (Denmark)

    Lei, Tian; Nielsen, Kaspar Kirstein; Engelbrecht, Kurt

    2014-01-01

    Compared to a conventional vapor compression refrigera-tion system, a magnetocaloric refrigerator has many advantages, such as potentially high efficiency, low vibration and avoidance of refrigerants that deplete the ozone layer and cause the green-house effect. As a main component of the active...

  14. Nature of the first-order magnetic phase transition in giant-magnetocaloric materials

    NARCIS (Netherlands)

    Yibole

    2016-01-01

    This thesis reports on advanced characterizations of giant magnetocaloric materials that show a first order magnetic phase transition (FOMT). The results are of great interest not only for the design of new magnetic refrigerants, but also for a better understanding of the FOMT. This thesis paves the

  15. The effect of external pressure on the magnetocaloric effect of Ni-Mn-In alloy.

    Science.gov (United States)

    Sharma, V K; Chattopadhyay, M K; Roy, S B

    2011-09-14

    The martensitic transition in Ni(50)Mn(34)In(16) alloy has been studied by measuring the magnetization of the alloy as a function of temperature, magnetic field and pressure. Magnetic field and pressure have opposite effects on the martensitic transition in this alloy; the martensitic transition temperature decreases with increasing magnetic field but it increases with increasing pressure. The effect of pressure on the magnetocaloric properties of this large magnetocaloric effect alloy has been investigated in detail. The magnitude of the peak in the isothermal magnetic entropy change in Ni(50)Mn(34)In(16) increases with pressure. The temperature at which the magnetocaloric effect reaches the peak value in this alloy increases from near 240 K under ambient pressure to near 280 K under an external pressure of 9.5 kbar. The temperature corresponding to the peak in the isothermal magnetic entropy change increases with increasing pressure at a rate which matches the rate of increase of the martensite start temperature with increasing pressure. The temperature dependence of the isothermal magnetic entropy change under different pressures is found to follow a universal curve for a particular magnetic field change. These results show that pressure as a control parameter can be used to tune the temperature regime of the magnetocaloric effect in the alloy. The effect of pressure on the martensitic transition also gives a clue as regards the possibility of tuning this temperature regime with elemental substitution.

  16. Effects of relative orientation of magnetocaloric inserts with the magnetic flux

    Energy Technology Data Exchange (ETDEWEB)

    Risser, M.; Vasile, C. [National Institute of Applied Sciences (INSA) Strasbourg, 24 Bd de la Victoire, 67084 Strasbourg, Cedex (France); Laboratoire de Genie de la Conception (LGeCo), 24 Bd de la Victoire, 67084 Strasbourg, Cedex (France); Engel, T. [National Institute of Applied Sciences (INSA) Strasbourg, 24 Bd de la Victoire, 67084 Strasbourg, Cedex (France); Laboratoire des Systemes Photoniques (LSP), 24 Bd de la Victoire, 67084 Strasbourg, Cedex (France)

    2009-08-15

    This paper presents the study of the magnetic change of the magnetic flux density into the magnetocaloric materials (MCMs). The MCMs are shaped in thin parallel plates separated by a fluid forming together an insert. It is shown that keeping all the parameters equal, the unique modification of the orientation of the insert induces a change of the magnetic flux density into the magnetocaloric materials. Like all paramagnetic and ferromagnetic materials, the MCMs have variable magnetic permeability according to the density of flux that crosses them. The influence of a thermal circuit on a permanent magnetic circuit assembly is also evaluated. In order to ensure the heat exchange between the magnetocaloric materials and the outside space, the use of a heat transfer fluid is needed. The heat transfer fluid goes along the mini plates and is also placed inside the magnetic field. Because a fluid is generally a diamagnetic element, this increases the total magnetic reluctance of the assembly. Two different configurations named serial and parallel have been studied and evaluated in order to find the configuration that causes minimal disturbances to the magnetic flux and thus increases the magnetocaloric effect (MCE). Both configurations were also compared in respect to the induction obtained inside the vacuum gap of the magnet assembly. (author)

  17. Magnetization reversal behavior and magnetocaloric effect in SmCr0.85Mn0.15O3 chromites

    Science.gov (United States)

    Kumar, Surendra; Coondoo, Indrani; Vasundhara, M.; Patra, Ajit K.; Kholkin, Andrei L.; Panwar, Neeraj

    2017-01-01

    We have synthesized SmCr0.85Mn0.15O3 (SCMO) chromites through the ceramic route. The compound crystallized into a distorted orthorhombic structure with the Pnma space group, which was confirmed from the Rietveld refinement of x-ray powder diffraction patterns. Neel temperature, noticed at 168 K from the temperature variation of magnetisation, smaller than that reported for SmCrO3, indicated the influence of Mn3+ substitution on decreasing the antiferromagnetic ordering. A phenomenon of magnetization reversal was observed in the SCMO compound. At low magnetic fields, i.e., 500 Oe, a single compensation temperature (defined as the temperature where magnetization became zero) around 106 K was observed in the field cooled magnetization curve. However, with the application of higher magnetic fields, i.e., under an applied field of 1000 Oe, a second compensation temperature was noticed around 8 K. With a further increase in the magnetic field, the magnetization remained positive in both field cooled and zero field cooled protocols. A normal magnetocaloric effect was observed through an indirect method of field dependence of magnetisation measured in the temperature range of 2-152 K. The magnetic entropy change (-ΔS) of ˜11.36 J kg-1 K-1 along with the relative cooling power (RCP) of ˜175.89 J kg-1 was obtained in the temperature range of 10-20 K for an applied field of 90 kOe, and their values at 50 kOe applied field were, respectively, almost twenty and forty times larger in magnitude in comparison to those for the SmCrO3 compound. The relatively large values of ΔS and RCP make the studied compound a potential candidate for magnetic refrigeration applications at low temperatures.

  18. On the preparation of La(Fe,Mn,Si)13Hx polymer-composites with optimized magnetocaloric properties

    Science.gov (United States)

    Radulov, Iliya A.; Skokov, Konstantin P.; Karpenkov, Dmitriy Yu.; Gottschall, Tino; Gutfleisch, Oliver

    2015-12-01

    A successful use of the magnetocaloric material in an active magnetic regenerator (AMR) requires its machining into heat exchangers with good mechanical and chemical stability. Most of the magnetocaloric materials currently available for room temperature application do not meet those requirements, they are brittle and are susceptible to corrosion. Adhesive-bonding techniques can provide mechanical stability, corrosion protection and net shaped modules in a single step manufacturing process. However, the magnetocaloric properties of the composite materials can be significantly lowered during this process e.g. due to improper adhesion, dilution, and compaction pressure. We report on a comprehensive study of the influence of powder particle size, adhesive type, adhesive concentration and compaction pressure on the magnetocaloric properties of polymer-bonded La(Fe,Mn,Si)13Hx material.

  19. Review of the Magnetocaloric Effect in RMnO3 and RMn2O5 Multiferroic Crystals

    Directory of Open Access Journals (Sweden)

    Mohamed Balli

    2017-02-01

    Full Text Available It is known that some of RMnO3 and RMn2O5 (R = rare earth multiferroic crystals reveal a strong interplay between their magnetic and electric order parameters, paving the way for applications in spintronic technologies. Additionally, recent works have also pointed out their potential utilization as refrigerants in magnetocaloric cooling systems for cryogenic tasks. In this paper, recent advances regarding the magnetocaloric properties of both RMnO3 and RMn2O5 families of multiferroics are reviewed. With the aim of understanding the RMnO3 and RMn2O5 magnetocaloric features, their structural and magnetic properties are discussed. The physics behind the magnetocaloric effect as well as some of its key thermodynamic aspects are also considered.

  20. Magneto-caloric and magneto-resistive properties of La{sub 0.67}Ca{sub 0.33-x}Sr{sub x}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Reves Dinesen, Anders

    2004-08-01

    This thesis presents results of an experimental investigation of magneto-caloric and magneto-resistive properties of a series of polycrystalline Ca- and Sr-doped lanthanum manganites, La{sub 0.67}Ca{sub 0.33-x}Sr{sub x}MnO{sub 3} (0{<=} x {<=} 0.33), with the perovskite structure. The samples consisted of sintered oxide powders prepared the glycine-nitrate combustion technique. The compounds were ferromagnetic and showed a Curie transition in the temperature range 267370 K (T{sub C} increased with increasing x). An analysis of the structural properties was carried out by means of x-ray diffraction and the Rietveld technique. The variation of the Ca/Sr ratio was found to cause a transition from orthorhombic to rhombohedral symmetry in the composition range 0.110 < x < 0.165. The analysis suggested a strong correlation between structural properties and magnetism, for instance a relationship between the mean MnOMn bond angle and the Curie temperature. The MnOMn bonds mediate ferromagnetism and electrical transport in these materials via the double-exchange mechanism. The magnetocaloric effect of the La{sub 0.67}Ca{sub 0.33-x}Sr{sub x}MnO{sub 3} samples was measured directly and indirectly (by means of magnetization measurements). All the samples showed a magnetocaloric effect in the vicinity of T{sub C}. A model for the mag-netocaloric effect based on Weiss mean field theory and classical theories for heat capacities was developed. The model provided reasonable predictions of the magneto-caloric properties of the samples. The compounds with low Sr content showed a magnetocaloric effect comparable to that of Gadolinium, the prototypical working material for magnetic refrigeration at room temperature. A less comprehensive part of the investigation regarded the magneto-resistive properties of the La{sub 0.67}Ca{sub 0.33-x}Sr{sub x}MnO{sub 3} system. It was found that th polycrystalline nature of the compounds played a decisive role for the magnetotransport properties

  1. Magnetic and magnetocaloric properties of La0.7Ca0.3Mn1-xZnxO3

    Science.gov (United States)

    Ho, T. A.; Lim, S. H.; Tho, P. T.; Phan, T. L.; Yu, S. C.

    2017-03-01

    The magnetic Mn3+ ions in La0.7Ca0.3MnO3 are partially replaced by nonmagnetic Zn2+ ions to form La0.7Ca0.3Mn1-xZnxO3 compounds (x=0.0, 0.06, 0.08, and 0.1), and their magnetic and magnetocaloric properties are investigated. The Curie temperature decreases drastically from 245 to 70 K as x increases from 0 to 0.1. An analysis using the Banerjee's criterion of the experimental results for magnetization as a function of temperature and magnetic field indicates that the first-to-second order magnetic phase transformation occurs at a threshold composition of x=0.06, which is further supported by the universal curves of the normalized entropy change versus reduced temperature. The maximum magnetic entropy change measured at a magnetic field span of 50 kOe, which occurs near the Curie temperature, decreases from 10.30 to 2.15 J/kg K with the increase of x from 0.0 to 0.1. However, the relative cooling power, an important parameter for practical applications, shows a maximum value of 404 J/kg at x=0.08, which is 1.5 times greater than that observed for the undoped sample.

  2. Magnetocaloric effect in AlFe2B2: toward magnetic refrigerants from earth-abundant elements.

    Science.gov (United States)

    Tan, Xiaoyan; Chai, Ping; Thompson, Corey M; Shatruk, Michael

    2013-06-26

    AlFe2B2 was prepared by two alternative synthetic routes, arc melting and synthesis from Ga flux. In the layered crystal structure, infinite chains of B atoms are connected by Fe atoms into two-dimensional [Fe2B2] slabs that alternate with layers of Al atoms. As expected from the theoretical analysis of electronic band structure, the compound exhibits itinerant ferromagnetism, with the ordering temperature of 307 K. The measurement of magnetocaloric effect (MCE) as a function of applied magnetic field reveals isothermal entropy changes of 4.1 J kg(-1) K(-1) at 2 T and 7.7 J kg(-1) K(-1) at 5 T. These are the largest values observed near room temperature for any metal boride and for any magnetic material of the vast 122 family of layered structures. Importantly, AlFe2B2 represents a rare case of a lightweight material prepared from earth-abundant, benign reactants which exhibits a substantial MCE while not containing any rare-earth elements.

  3. Effect of Fe substitution on the structure and magnetocaloric effect of Mn5-xFexGeSi2 alloys

    Science.gov (United States)

    Sun, Y. W.; Yan, J. L.; Feng, E. L.; Tang, G. W.; Zhou, K. W.

    2017-01-01

    The structure and magnetocaloric effect of Mn5-xFexGeSi2 compounds were studied. Analysis of X-ray powder diffraction and energy dispersive X-Ray spectroscopy revealed that Mn5-xFexGeSi2 alloys with x<1 crystallize in the Mn5Si3-type structure (space group P63/mcm), maintaining the structure of Mn5Ge3; and alloys with x=1.5 and 2 consist of the major Mn5Si3-type phase and the minor Ni2In-type phase (space group P63/mmc). The results of Rietveld refinement showed that the cell parameters for the Mn5Si3-type phase decrease with increasing Fe content. The positive slopes in Arrott plots indicate that a second-order ferromagnetic to paramagnetic transition occurs. The Curie temperature increases with increasing Fe content from 182 K for x=0.6 to 224 K for x=2. The maximum magnetic entropy change of 3.7 J/(kg K) for x=0.8 was found under a magnetic field change of 0-20 kOe.

  4. Phase transitions, magnetotransport and magnetocaloric effects in a new family of quaternary Ni-Mn-In-Z Heusler alloys.

    Science.gov (United States)

    Kazakov, Alexander; Prudnikov, Valerii; Granovsky, Alexander; Perov, Nikolai; Dubenko, Igor; Pathak, Arjun Kumar; Samanta, Tapas; Stadler, Shane; Ali, Naushad; Zhukov, Arcady; Ilyin, Maxim; Gonzalez, Julian

    2012-09-01

    The magnetic, magnetotransport, and magnetocaloric properties near compound phase transitions in Ni50Mn35In14Z (Z = In, Ge, Al), and Ni48Co2Mn35In15 Heusler alloys have been studied using VSM and SQUID magnetometers (at magnetic fields (H) up to 5 T), four-probe method (at H = 0.005-1.5 T), and an adiabatic magnetocalorimeter (for H changes up to deltaH = 1.8 T), respectively. The martensitic transformation (MT) is accompanied by large magnetoresistance (up to 70%), a significant change in resistivity (up to 200%), and a sign reversal of the ordinary Hall effect coefficient, all related to a strong change in the electronic spectrum at the MT. The field dependences of the Hall resistance are complex in the vicinity of the MT, indicating a change in the relative concentrations of the austenite and martensite phases at strong fields. Negative and positive changes in adiabatic temperatures of about -2 K and +2 K have been observed in the vicinity of MT and Curie temperatures, respectively, for deltaH = 1.8 T.

  5. Magnetic Properties and Magnetocaloric Effect in Layered NdMn1.9Ti0.1Si2

    Directory of Open Access Journals (Sweden)

    M.F. Md Din

    2014-04-01

    Full Text Available The structural and magnetic properties of the NdMn1.9Ti0.1Si2 compund have been studied by high-intensity x-ray and high-resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range of 3-450 K. The Curie temperature and Néel temperature of layered NdMn1.9Ti0.1Si2 are indicated as TC ~ 22 K and TN ~ 374 K respectively. The first order magnetic transition from antiferromagnetic [AFil-type] to ferromagnetic [F(Nd+Fmc] around TC is found in layered NdMn1.9Ti0.1Si2 and is associated with large magnetocaloric effect. This behavior has been confirmed as a contribution of the magnetostructural coupling by using neutron and x-ray powder diffraction. The magnetic entropy change –ΔSM ~ 15.3 J kg-1 K-1 and adiabatic temperature change ΔTad ~ 4.7 K have been determined using magnetization and specific heat measurement under 0-5 T applied fields. This compound exhibits almost no thermal and magnetic hysteresis, thus potentially applicable in low temperature region for magnetic refrigerator material

  6. The influence of hydrostatic pressure on the magnetic and magnetocaloric properties of DyRu2Si2

    Science.gov (United States)

    Saleheen, Ahmad Us; Samanta, Tapas; Khan, Mojammel; Adams, Philip W.; Young, David P.; Dubenko, Igor; Ali, Naushad; Stadler, Shane

    2017-01-01

    We report the magnetic and magnetocaloric properties of the tetragonal rare-earth compound DyRu2Si2 under applied hydrostatic pressure. The isothermal entropy change ( ΔS ) and the adiabatic temperature change ( ΔTad ) were calculated from magnetization data collected at different applied pressures and from heat capacity measurements conducted at atmospheric pressure, respectively. The application of hydrostatic pressure significantly modified the multi-step magnetization curve and the saturation magnetization. A suppression of the magnetization was observed for P = 0.588 GPa and P = 0.654 GPa whereas, at about P ≈1 GPa, the saturation magnetization increased and the magnetization isotherms again resembled the curves measured at atmospheric pressure. A small thermal hysteresis was observed between the heating and cooling M(T) curves at Tt=3.4 K , with an applied magnetic field of H = 0.1 T. This thermal hysteresis indicates a first-order like transition which was also supported by the Arrott plot analysis. The volume magnetostriction was estimated from the pressure-dependent magnetization measurements using a Maxwell relation.

  7. Influence of extra La and annealing temperature on microstructure and magnetocaloric properties of La–Fe–Co–Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhongtian [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123 (China); He, Chun; Zhang, Mingxiao [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Liu, Jian, E-mail: liujian@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2015-11-01

    The microstructure, phase constitution and magnetocaloric properties of non-stoichiometric La{sub 1.7}Fe{sub 11}Co{sub 0.8}Si{sub 1.2} alloys were investigated. Compared with stoichiometric La(Fe,Co,Si){sub 13} alloys, a complex phase, including La(Fe,Co,Si){sub 13} phase, La{sub 5}Si{sub 3} phase, La(Fe,Co)Si phase, α-Fe phase and La oxide, can rapidly form upon annealing at 1323 K for 24 h in the present alloy. The resulting alloy exhibits a large magnetic entropy change of 7.5 J kg{sup −1} K{sup −1} at 271 K in a magnetic field change of 2 T. In addition, the annealed La{sub 1.7}Fe{sub 11}Co{sub 0.8}Si{sub 1.2} alloy shows a reversible magnetic phase transition with zero hysteresis. These characteristics indicate that the present La-rich La–Fe–Co–Si compounds have potential for the applications as ambient magnetic refrigeration materials.

  8. Investigation of magnetocaloric effect in La0.45Pr0.25Ca0.3MnO3 by magnetic, differential scanning calorimetry and thermal analysis

    Science.gov (United States)

    Aparnadevi, M.; Barik, S. K.; Mahendiran, R.

    2012-10-01

    We investigated magnetocaloric effect in La0.45Pr0.25Ca0.3MnO3 by direct methods (changes in temperature and latent heat) and indirect method (magnetization isotherms). This compound undergoes a first-order paramagnetic to ferromagnetic transition with TC=200 K upon cooling. The paramagnetic phase becomes unstable and it transforms into a ferromagnetic phase under the application of magnetic field, which results in a field-induced metamagnetic transition (FIMMT). The FIMMT is accompanied by release of latent heat and temperature of the sample as evidenced from differential scanning calorimetry and thermal analysis experiments. A large magnetic entropy change of ΔSm=-7.2 J kg-1 K-1 at T=212.5 K and refrigeration capacity of 228 J kg-1 are found for a field change of ΔH=5 T. It is suggested that destruction of magnetic polarons and growth of ferromagnetic phase accompanied by a lattice volume change with increasing magnetic field is responsible for the large magnetocaloric effect in this compound.

  9. Effect of trivalent rare earth doping on magnetic and magnetocaloric properties of Pr0.5(Ce,Eu,Y)0.1Sr0.4MnO3 manganites

    Science.gov (United States)

    Sakka, A.; M'nassri, R.; Chniba-Boudjada, N.; Ommezzine, M.; Cheikhrouhou, A.

    2016-06-01

    Experimental studies of the structural, magnetic and magnetocaloric properties of the three compounds Pr0.5X0.1Sr0.4MnO3 (X = Ce, Eu and Y) are reported. Our samples were synthesized using the Pechini sol-gel method. X-ray powder diffraction at room temperature indicates that our materials crystallize in the orthorhombic structure with Pbnm space group. The compounds undergo a second-order magnetic transition from paramagnetic to ferromagnetic state around their own Curie temperatures T C ~ 310, 270 and 230 K for X = Ce, Eu and Y, respectively. A considerable magnetocaloric effect (MCE) is observed around room temperature. The maximum values of magnetic entropy change ∆ S max are 3.54, 3.81 and 2.99 J/kgK for the samples with X = Ce, Eu and Y, respectively, when a magnetic field of 5 T was applied. The relative cooling power (RCP) values for the corresponding materials are 246.60, 261.66 and 298 J/kg. It is shown that for Pr0.5X0.1Sr0.4MnO3 the exponent n and the magnetic entropy change follow a master curve behavior. With the universal scaling curve, the experimental ∆ S at several temperatures and fields can be extrapolated.

  10. Reversible magnetocaloric effect in materials with first order phase transitions in cyclic magnetic fields: Fe48Rh52 and Sm0.6Sr0.4MnO3

    Science.gov (United States)

    Aliev, A. M.; Batdalov, A. B.; Khanov, L. N.; Kamantsev, A. P.; Koledov, V. V.; Mashirov, A. V.; Shavrov, V. G.; Grechishkin, R. M.; Kaul', A. R.; Sampath, V.

    2016-11-01

    The magnetocaloric effect (MCE) in an Fe48Rh52 alloy and Sm0.6Sr0.4MnO3 manganite was studied in cyclic magnetic fields. The adiabatic temperature change in the Fe48Rh52 alloy for a magnetic field change (ΔB) of 8 T and a frequency (f) of 0.13 Hz reaches the highest value of (ΔTad) of -20.2 K at 298 K. The magnitude of the MCE in Sm0.6Sr0.4MnO3 reaches ΔTad = 6.1 K at the same magnetic field change at 143 K. The temperature regions, where a strong MCE is exhibited in an alternating magnetic field, are bounded in both compounds. In the case of the Fe48Rh52 alloy, the temperature range for this phenomenon is bounded above by the ferromagnetic to antiferromagnetic transition temperature in the zero field condition during cooling. In the case of the Sm0.6Sr0.4MnO3 manganite, the temperature range for the MCE is bounded below by the ferromagnetic-paramagnetic transition temperature in zero field during heating. The presence of these phase boundaries is a consequence of the existence of areas of irreversible magnetic-field-induced phase transitions. It is found that the effect of long-term action of thousands of cycles of magnetization/demagnetization degrades the magnetocaloric properties of the Fe48Rh52 alloy. This can be explained by the gradual decrease in the size of the ferromagnetic domains and increasing role of the domain walls due to giant magnetostriction at the ferromagnetic to antiferromagnetic transition temperature. The initial magnetocaloric properties can be restored by heating of the material above their Curie temperature.

  11. Abnormal thermal expansion, multiple transitions, magnetocaloric effect, and electronic structure of Gd{sub 6}Co{sub 4.85}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jiliang [Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong (Hong Kong); Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States); Zheng, Zhigang [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Shan, Guangcun, E-mail: gshan2-c@my.cityu.edu.hk, E-mail: bobev@udel.edu, E-mail: apchshek@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong (Hong Kong); School of Instrumentation Science and Optoelectronics Engineering, Beihang University, Beijing 100191 (China); Bobev, Svilen, E-mail: gshan2-c@my.cityu.edu.hk, E-mail: bobev@udel.edu, E-mail: apchshek@cityu.edu.hk [Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States); Shek, Chan Hung, E-mail: gshan2-c@my.cityu.edu.hk, E-mail: bobev@udel.edu, E-mail: apchshek@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong (Hong Kong)

    2015-10-07

    The structure of known Gd{sub 4}Co{sub 3} compound is re-determined as Gd{sub 6}Co{sub 4.85}, adopting the Gd{sub 6}Co{sub 1.67}Si{sub 3} structure type, which is characterized by two disorder Co sites filling the Gd octahedral and a short Gd-Gd distance within the octahedra. The compound shows uniaxial negative thermal expansion in paramagnetic state, significant negative expansion in ferromagnetic state, and positive expansion below ca. 140 K. It also exhibits large magnetocaloric effect, with an entropy change of −6.4 J kg{sup −1} K{sup −1} at 50 kOe. In the lattice of the compound, Co atoms at different sites show different spin states. It was confirmed by the X-ray photoelectron spectra and calculation of electronic structure and shed lights on the abnormal thermal expansion. The stability of such compound and the origin of its magnetism are also discussed based on measured and calculated electronic structures.

  12. Mössbauer study of the magnetocaloric compound AlFe2 B 2

    Science.gov (United States)

    Cedervall, Johan; Häggström, Lennart; Ericsson, Tore; Sahlberg, Martin

    2016-12-01

    Mössbauer spectroscopy in the ferromagnetic AlFe2 B 2 reveals Tc=299 K and shows good agreement with magnetic measurements. The crystals are plate-shaped. The flakes are found from X-ray diffraction to be in the crystallographic ac-plane in the orthorhombic system. The axes of the principle electric field gradient tensor are, by symmetry, colinear with the crystal a-, b- and c-axes. By using information about the quadrupole splitting and line asymmetry in the paramagnetic regime together with the quadrupole shift of the resonance lines in the ferromagnetic regime the magnetic hyperfine field direction is found to be in the ab-plane having an angle =40° to the b-axis.

  13. Magnetocaloric and barocaloric effects in a Gd5Si2Ge2 compound

    Institute of Scientific and Technical Information of China (English)

    Zou Jun-Ding

    2012-01-01

    The first-order phase transition in Gd5Si2Ge2 is sensitive to both magnetic field and pressure.It may indicate that the influences of the magnetic field and the pressure on the phase transition are virtually equivalent.Moreover,theoretical analyses reveal that the total entropy change is almost definite at a certain Curie temperature no matter whether the applied external field is a magnetic field or a pressure. The entropy change curve can be broadened dramatically under pressure,and the refrigerant capacity is improved from 284.7 J/kg to 447.0 J/kg.

  14. Moment formation and giant magnetocaloric effects in hexagonal Mn-Fe-P-Si compounds

    NARCIS (Netherlands)

    Nguyen, H.D.

    2012-01-01

    Limited resources and the wish for improved prosperity call for efficient use of energy. The UN Advisory Group on Energy and Climate Change recommends a target of 40 % improved efficiency by 2030. Materials research can contribute significantly to reach this target. Magnetic refrigeration offers pot

  15. Magnetic hysterysis evolution of Ni-Al alloy with Fe and Mn substitution by vacuum arc melting to produce the room temperature magnetocaloric effect material

    Energy Technology Data Exchange (ETDEWEB)

    Notonegoro, Hamdan Akbar [PPS Materials Science, FMIPA-Universitas Indonesia, Depok 16424 (Indonesia); Mechanical Engineering Dept., FT-Universitas Sultan Ageng Tirtayasa, Cilegon 42435 (Indonesia); Kurniawan, Budhy; Manaf, Azwar, E-mail: azwar@sci.ui.ac.id [PPS Materials Science, FMIPA-Universitas Indonesia, Depok 16424 (Indonesia); Setiawan, Jan [Center for Nuclear Fuel Tecnology-Badan Tenaga Atom Nasional, Tangerang Selatan 15310 (Indonesia)

    2016-06-17

    The development of magnetocaloric effect (MCE) material is done in order to reduce the damage of the ozone layer caused by the chlorofluorocarbons (CFCs) emitted into the air. The research dealing with synthesis of magnetocaloric materials based of Ni-Al Heusler Alloy structure and by varying substitution some atoms of Ni with Fe and Al with Mn on Ni-Al Heusler Alloy structure to become Ni{sub 44}Fe{sub 6}Mn{sub 32}Al{sub 18}. Vacuum Arc Melting (VAM) equipment is used to form the alloys on vacuum condition and by flowing argon gas atmosphere and then followed by annealing process for 72 hours. X-Ray Diffraction (XRD) reveals that crystallite structure of material is observed. We define that Ni{sub 44}Fe{sub 6} as X{sub 2}, Mn{sub 25} as Y, and Al{sub 18}Mn{sub 7} as Z. Based on the XRD result, we observed that the general formula X{sub 2}YZ is not changed. The PERMAGRAF measurement revealed that there exists of magnetic hysterysis. The hysterysis show that the magnetic structures of the system undego evolution from diamagnetic to soft ferromagnetic material which all of the compound have the same crystallite structure. This evolution indicated that the change in the composition has led to changes the magnetic composition. Mn is the major element that gives strong magnetic properties to the sample. When Mn partially replaced position of Al, the sample became dominant to be influenced to improve their magnetic properties. In addition, substitution a part of Ni by Fe in the composition reveals a pinning of the domain walls in the sample.

  16. Magnetocaloric effect of Gd4(BixSb1-x)3 alloy series

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Xuejun [Iowa State Univ., Ames, IA (United States)

    1999-01-01

    Alloys from the Gd4(BixSb1-x)3 series were prepared by melting a stoichiometric amounts of pure metals in an induction furnace. The crystal structure is of the anti-Th3P4 type (space group I$\\bar{4}$3d) for all the compounds tested. The linear increase of the lattice parameters with Bi concentration is attributed to the larger atomic radius of Bi than that of Sb. Magnetic measurements show that the alloys order ferromagnetically from 266K to 330K, with the ordering temperature increasing with decreasing Bi concentration. The alloys are soft ferromagnets below their Curie temperatures, and follow the Curie-Weiss law above their ordering temperatures. The paramagnetic effective magnetic moments are low compared to the theoretical value for a free Gd3+, while the ordered magnetic moments are close to the theoretical value for Gd. The alloys exhibit a moderate magnetocaloric effect (MCE) whose maxima are located between 270K and 338K and have relatively wide peaks. The peak MCE temperature decreases with decreasing Bi concentration while the peak height increases with decreasing Bi concentration. The Curie temperatures determined from inflection points of heat capacity are in good agreement with those obtained from the magnetocaloric effect. The MCE results obtained from the two different methods (magnetization and heat capacity) agree quite well with each other for all of the alloys in the series.

  17. Normal and inverse magnetocaloric effect in magnetic multilayers with antiferromagnetic interlayer coupling.

    Science.gov (United States)

    Szałowski, Karol; Balcerzak, Tadeusz

    2014-09-24

    The thermodynamics of a spin-1/2 magnetic multilayer system with antiferromagnetic interplanar couplings is studied using the pair approximation method. Special attention is paid to magnetocaloric properties, quantified by isothermal entropy change. The multilayer consists of two kinds of magnetic planes, one of which is diluted. The intraplanar couplings in both planes have arbitrary anisotropy ranging between Ising and isotropic Heisenberg interactions. The phase diagram related to the occurrence of magnetic compensation phenomenon is constructed and discussed. Then the isothermal entropy change is discussed as a function of interaction parameters, magnetic component concentration and external magnetic field amplitude. The ranges of normal and inverse magnetocaloric effect are found and related to the presence or absence of compensation.

  18. Large magnetocaloric effect, moment, and coercivity enhancement after coating Ni nanoparticles with Ag.

    Science.gov (United States)

    Srinath, Sanyadanam; Poddar, Pankaj; Das, Raja; Sidhaye, Deepti; Prasad, Bhagavatula Lakshmi Vara; Gass, James; Srikanth, Hariharan

    2014-06-06

    We observe a large magnetocaloric effect in monodisperse Ni and Ni(core)Ag(shell) nanoparticles in the superparamagnetic region. The organically passivated Ni nanospheres show a large magnetic entropy change of 0.9 J kg(-1)  K for a 3 T magnetic field change. In comparison to the surfactant-coated Ni nanoparticles, the Ni(core)Ag(shell) nanoparticles show an enhanced coercivity, magnetization, and magnetocaloric effect (1.3 kg K for a 3 T magnetic field change). The coercivity at 10 K increases from 360 Oe for Ni nanoparticles to nearly 610 Oe for Ni(core)Ag(shell) particles. This large enhancement is attributed to the enhanced inter-particle interaction, which is mediated by the metallic shell, over the relatively weaker dipolar interaction in the surfactant-coated Ni nanoparticles, and to modification of the surface spin structure.

  19. Non-contact direct measurement of the magnetocaloric effect in thin samples.

    Science.gov (United States)

    Cugini, F; Porcari, G; Solzi, M

    2014-07-01

    An experimental setup, based on a non-contact temperature sensor, is proposed to directly measure the magnetocaloric effect of samples few micrometers thick. The measurement of the adiabatic temperature change of foils and ribbons is fundamental to design innovative devices based on magnetocaloric thin materials or micro-structuring bulk samples. The reliability of the proposed setup is demonstrated by comparing the measurements performed on a bulk gadolinium sample with the results obtained by an experimental setup based on a Cernox bare chip thermoresistance and by in-field differential scanning calorimetry. We show that this technique can measure the adiabatic temperature variation on gadolinium sheets as thin as 27 μm. Heat transfer simulations are added to describe the capability of the presented technique.

  20. Non-contact direct measurement of the magnetocaloric effect in thin samples

    Energy Technology Data Exchange (ETDEWEB)

    Cugini, F., E-mail: francesco.cugini1@difest.unipr.it; Porcari, G.; Solzi, M. [Department of Physics and Earth Sciences, University of Parma, Parco Area delle Scienze 7/A, 43124 Parma (Italy)

    2014-07-15

    An experimental setup, based on a non-contact temperature sensor, is proposed to directly measure the magnetocaloric effect of samples few micrometers thick. The measurement of the adiabatic temperature change of foils and ribbons is fundamental to design innovative devices based on magnetocaloric thin materials or micro-structuring bulk samples. The reliability of the proposed setup is demonstrated by comparing the measurements performed on a bulk gadolinium sample with the results obtained by an experimental setup based on a Cernox bare chip thermoresistance and by in-field differential scanning calorimetry. We show that this technique can measure the adiabatic temperature variation on gadolinium sheets as thin as 27 μm. Heat transfer simulations are added to describe the capability of the presented technique.

  1. (Magneto)caloric refrigeration: is there light at the end of the tunnel?

    Science.gov (United States)

    Pecharsky, Vitalij K; Cui, Jun; Johnson, Duane D

    2016-08-13

    Caloric cooling and heat pumping rely on reversible thermal effects triggered in solids by magnetic, electric or stress fields. In the recent past, there have been several successful demonstrations of using first-order phase transition materials in laboratory cooling devices based on both the giant magnetocaloric and elastocaloric effects. All such materials exhibit non-equilibrium behaviours when driven through phase transformations by corresponding fields. Common wisdom is that non-equilibrium states should be avoided; yet, as we show using a model material exhibiting a giant magnetocaloric effect, non-equilibrium phase-separated states offer a unique opportunity to achieve uncommonly large caloric effects by very small perturbations of the driving field(s).This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  2. The magnetocaloric effect at the first-order magneto-elastic phase transition.

    Science.gov (United States)

    Basso, Vittorio

    2011-06-08

    This paper presents a study of the magnetocaloric effect at the first-order magneto-elastic phase transition. The entropy change Δs at the transition temperature is given by the sum of the magnetic and the structural contributions. By using a thermodynamic model, it is shown that the sign and amplitude of the structural contribution to Δs are determined by the dimensionless parameter ζ (zeta) which depends on β, the steepness of the change of exchange forces with volume, and on α(p), the thermal expansion coefficient of the structural lattice. For ζ magnetocaloric effect. For 0 1 the structural entropy dominates and a transition occurs upon heating from a low temperature paramagnet to a high temperature ferromagnet.

  3. Magnetic refrigeration at room temperature - from magnetocaloric materials to a prototype

    DEFF Research Database (Denmark)

    Kuhn, Luise Theil; Pryds, Nini; Bahl, Christian Robert Haffenden

    2011-01-01

    materials, their shaping and graded composition for technological use. Modelling the performance of a permanent magnet with optimum use of the flux and relatively low weight, and designing and constructing a prototype continuous magnetic refrigeration device have also been major tasks in the project...... refrigeration machines have been presented worldwide and there are still many scientific and technological challenges to be overcome. We report here on the MagCool project, which spans all the way from basic materials studies to the construction of a prototype. Emphasis has been on ceramic magnetocaloric......Based on the magnetocaloric effect, magnetic refrigeration at room temperature has for the past decade been a promising, environmentally friendly new energy technology predicted to have a significantly higher efficiency than the present conventional methods. However, so far only a few prototype...

  4. Magnetocaloric effect in Sr2FeMoO6/Ag composites

    Directory of Open Access Journals (Sweden)

    Mahmoud A. Hamad

    2015-03-01

    Full Text Available The enhanced low-field magnetocaloric effect was investigated for double perovskite Sr2FeMoO6 - silver (SFMO/Ag composites with 0, 5 and 10 wt.% of Ag. A phenomenological model was used to predict magnetocaloric properties of SFMO/Ag composites, such as magnetic entropy change, heat capacity change and relative cooling power. It was shown that magnetic entropy change (∆S M peaks of SFMO/Ag span over a wide temperature region, which can significantly improve the global efficiency of the magnetic refrigeration. Furthermore, the ∆S M distribution of the SFMO/Ag composites is much more uniform than that of gadolinium. Through these results, SFMO/Ag composite has some potential application for magnetic refrigerants in an extended high-temperature range.

  5. Determining magnetic phase transitions temperatures in working magnetocaloric coolers bodies and gas cryorefrigerators regenerators

    Science.gov (United States)

    Karagusov, V. I.; Mayankov, I. V.

    2017-08-01

    Due to magnetic phase transitions rare-earth materials possess unique properties near the Curie and Neel temperatures, such as the magneto-caloric effect, the abnormally high heat capacity, the magnetic susceptibility and permeability extremes. Using rare earth materials in gas cryogenic refrigerators regenerators increases the efficiency, reduces the power consumption and allows reaching helium temperatures. The magneto-caloric effect has also extreme values near the Curie and Neel temperatures. The paper presents theoretical and experimental methods allowing to determine magnetic phase transitions temperatures in a wide range of low temperature materials with a various rare-earth components content and expected thermophysical properties of a certain rare-earth materials composition at the temperatures based on starting pure metals characteristics. The results analysis has shown that magnetic phase transitions temperatures are a linear function of the components concentration. Moreover, heat capacity values and MCE also depend linearly on the starting components concentration, which simplifies calculations significantly.

  6. A universal curve for the magnetocaloric effect: an analysis based on scaling relations

    Energy Technology Data Exchange (ETDEWEB)

    Franco, V; Conde, A; Blazquez, J S [Departamento de Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, PO Box 1065, 41080 Sevilla (Spain); Romero-Enrique, J M [Departamento de Fisica Atomica, Molecular y Nuclear, Area de Fisica Teorica, Universidad de Sevilla, PO Box 1065, 41080 Sevilla (Spain)

    2008-07-16

    The universal character of the recent experimentally found master curve for the magnetic entropy change, {delta}S{sub M}, in studies of the magnetocaloric response of materials is analytically justified by using scaling arguments. The validity of the obtained scaling relations is checked against experimental data as well as the mean field and Heisenberg models. The curves are unique for each universality class. It is shown that the universal curve can be practically constructed in two different ways, reducing the number of required parameters with respect to the previous phenomenological derivation. This opens the possibility of an inexpensive screening of the performance of magnetocaloric materials, as it allows extrapolations to magnetic fields or temperatures not available in some laboratories.

  7. Structural, microstructural and magnetocaloric investigations in high-energy ball milled NiMnGa powders

    Science.gov (United States)

    de Santanna, Y. V. B.; de Melo, M. A. C.; Santos, I. A.; Coelho, A. A.; Gama, S.; Cótica, L. F.

    2008-11-01

    In this paper, structural, microstrucutural and magnetocaloric properties of Ni 2.18Mn 0.82Ga alloys submitted to high-energy ball milling are reported. A 7-layered orthorhombic martensitic ( Pnnm) phase was detected in post-milling annealed samples, which reached a microstrucuture composed predominantly by nanograins. The magnetocaloric effect is strongly weakened in comparison with as-cast samples of similar composition. This effect can be attributed to the absence of the mesoscale twin-related martensitic variants in the nanostructurated powders. However, post-milled samples annealed at 1123 K for 4 h present relative cooling powers as high as those observed for manganites. Therefore, these materials can be considered as potential candidates for use as regenerators in prototypal magnetic refrigerators.

  8. Magnetocaloric response of amorphous and nanocrystalline Cr-containing Vitroperm-type alloys

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Ramírez, L.M.; Blázquez, J.S.; Franco, V.; Conde, A. [Dpto. Física de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Marsilius, M.; Budinsky, V.; Herzer, G. [Vacuumschmelze GmbH & Co KG, Grüner Weg 37, D-63450 Hanau (Germany)

    2016-07-01

    The broad compositional range in which transition metal (TM) based amorphous alloys can be obtained, yields an easily tunable magnetocaloric effect (MCE) in a wide temperature range. In some TM-based alloys, anomalous behaviors are reported, as a non-monotonous trend with magnetic moment (e.g. FeZrB alloys). Moreover, in certain Cr-containing Vitroperm alloys anomalously high values of the magnetic entropy change were published. In this work, a systematic study on MCE response of Cr-containing amorphous alloys of composition Fe{sub 74-x}Cr{sub x}Cu{sub 1}Nb{sub 3}Si{sub 15.5}B{sub 6.5} (with x=2, 8, 10, 12, 13, 14 and 20) has been performed in a broad Curie temperature range from 100 K to 550 K. Curie temperature and magnetic entropy change peak of the amorphous alloys decrease with the increase of Cr content at rates of −25.6 K/at% Cr and −54 mJ kg{sup −1} K{sup −1}/at% Cr, respectively, following a linear trend with the magnetic moment in both cases. The presence of nanocrystalline phases has been considered as a possible cause in order to explain the anomalies. The samples were nanocrystallized in different stages, however, the magnetocaloric response decreases as crystallization progresses due to the large separation of the Curie temperatures of the two phases. - Highlights: • Study of magnetocaloric effect of amorphous and nanocrystalline Cr-Vitroperm alloys. • Cr content decreases the magnetocaloric response and the Curie temperature. • Nanocrystallization reduces MCE and modifies T{sub C} in a non-monotonous way. • The large difference between T{sub C} of phases decreases MCE of composite.

  9. Tuning the metamagnetic transition in the (Co, Fe)MnP system for magnetocaloric purposes

    NARCIS (Netherlands)

    Guillou, F.; Brück, E.

    2013-01-01

    The inverse magnetocaloric effect taking place at the antiferro-to-ferromagnetic transition of (Co,Fe)MnP phosphides has been characterised by magnetic and direct ΔTad measurements. In Co0.53Fe0.47MnP, entropy change of 1.5 Jkg−1 K−1 and adiabatic temperature change of 0.6 K are found at room temper

  10. Enhancement of magnetocaloric effect in B-rich FeZrBCu amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kiss, L.F., E-mail: kissl@szfki.hu [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 49 (Hungary); Kemény, T. [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 49 (Hungary); Franco, V.; Conde, A. [Dpto. Física de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain)

    2015-02-15

    Highlights: • Magnetic properties and magnetocaloric effect were studied in FeZrBCu glasses. • An increase was found in the magnetic entropy change for high B content. • This correlates well with the anomalous increase of the magnetic moment. • The effect is attributed to the highly attractive B-Zr interaction. • This effect can have an impact on increasing the refrigeration capacity. - Abstract: Magnetic properties and magnetocaloric effect were studied in the Fe{sub 92−x}Zr{sub 7}B{sub x}Cu{sub 1} amorphous alloy series (x = 0-23 at.%). Enhancement of the magnetocaloric effect was observed in the B-rich side (x > 15 at.%) which correlates well with the anomalous increase of the saturation magnetic moment per Fe atom in this concentration range. Research into Fe{sub 2}(B{sub 1−y}ETM{sub y}) amorphous alloys (ETM = Zr, Nb, Ti and V; y = 0-0.55 atomic fraction for Zr and to 0.25 atomic fraction for the rest) reveals an unexpected increase of the iron magnetic moment when early transition metals are substituted for B up to y = 0.1-0.25 atomic fraction. This behavior is attributed to the highly attractive B-ETM interaction. Similar mechanism is thought to explain the anomalous increase of the iron magnetic moment and hence the magnetocaloric effect in the boron-rich Fe{sub 1−x}Zr{sub 7}B{sub x}Cu{sub 1} amorphous alloys. Universal scaling of the magnetic entropy change curves is also used to detect differences between Fe{sub 92−x}Zr{sub 7}B{sub x}Cu{sub 1} alloys.

  11. Direct measurement of the magnetocaloric effect in MnFe(P,X)(X = As, Ge, Si) materials

    Science.gov (United States)

    Yibole, H.; Guillou, F.; Zhang, L.; van Dijk, N. H.; Brück, E.

    2014-02-01

    An investigation of the magnetocaloric effect (MCE) displayed by three generations of MnFe(P,X) (X = As, Ge, Si) materials has been carried out by combining indirect ΔS and direct ΔTad measurements. To be able to compare the performances of the new Si-based system with the already well-known As- and Ge-based materials in optimal conditions, both the Mn/Fe and P/Si ratios of the MnxFe1.95-xP1-ySiy compounds were optimized to display the largest MCE around room temperature. Here, we show that the maximum values of ΔTad (ΔB = 1.1 T) and ΔS (ΔB = 1 T) are respectively ˜2.2 K and ˜8 J kg-1 K-1 in the Si-based material Mn1.25Fe0.7P0.49Si0.51. These values are very close to the MCE performances of the As-based and Ge-based compounds. A critical comparison of these three MnFe(P,X) series highlights the role played by the non-magnetic elements on the latent heat at the Curie temperature. The combination of: (i) large ΔS and ΔTad in intermediate magnetic fields, (ii) limited thermal/magnetic hysteresis, (iii) easy tunability of the Curie temperatures and (iv) practical advantages like cheap, non-critical and non-toxic starting materials; makes the MnxFe1.95-xP1-ySiy family highly promising for magnetic refrigeration applications.

  12. Influence of the transition width on the magnetocaloric effect across the magnetostructural transition of Heusler alloys.

    Science.gov (United States)

    Cugini, F; Porcari, G; Fabbrici, S; Albertini, F; Solzi, M

    2016-08-13

    We report a complete structural and magneto-thermodynamic characterization of four samples of the Heusler alloy Ni-Co-Mn-Ga-In, characterized by similar compositions, critical temperatures and high inverse magnetocaloric effect across their metamagnetic transformation, but different transition widths. The object of this study is precisely the sharpness of the martensitic transformation, which plays a key role in the effective use of materials and which has its origin in both intrinsic and extrinsic effects. The influence of the transition width on the magnetocaloric properties has been evaluated by exploiting a phenomenological model of the transformation built through geometrical considerations on the entropy versus temperature curves. A clear result is that a large temperature span of the transformation is unfavourable to the magnetocaloric performance of a material, reducing both isothermal entropy change and adiabatic temperature change obtainable in a given magnetic field and increasing the value of the maximum field needed to fully induce the transformation. The model, which is based on standard magnetometric and conventional calorimetric measurements, turns out to be a convenient tool for the determination of the optimum values of transformation temperature span in a trade-off between sheer performance and amplitude of the operating range of a material.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  13. The influence of magnetocrystalline anisotropy on the magnetocaloric effect: A case study on Co 2 B

    Science.gov (United States)

    Fries, M.; Skokov, K. P.; Karpenkov, D. Yu.; Franco, V.; Ener, S.; Gutfleisch, O.

    2016-12-01

    The influence of magnetocrystalline anisotropy on the magnetocaloric effect (MCE) was studied on single crystals of Co2B and compared to measurements on polycrystalline samples. Large differences in adiabatic temperature change Δ T a d and magnetic entropy change Δ S M were found along the different crystallographic directions. The magnetocaloric effect differs by 40% in the case of Δ T a d in a field change of 1.9 T when applying the field along the hard axis and easy plane of magnetization. In the case of Δ S M , the values differ 50% and 35% from each other in field changes of 1 and 1.9 T, respectively. It was found that this anisotropy effect does not saturate in fields up to 4 T, which is higher than the anisotropy field of Co2B ( ≈2 T). A simple model was developed to illustrate the possible effect on magnetocrystalline anisotropy, showing large differences especially in application relevant fields of about 1 T. The results strongly suggest that the MCE could be maximized when orienting single crystalline powders in an easy axis parallel to the applied field in active magnetocaloric regenerator structures, and therefore the overall device efficiency could be increased.

  14. Magnetocaloric effect in Ni-Zn ferrite nanoparticles prepared by using solution combustion

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K. D.; Kambale, R. C.; Hur, N. [Inha University, Incheon (Korea, Republic of)

    2014-12-15

    Ni{sub x}Zn{sub 1-x}Fe{sub 2}O{sub 4} (x = 0.2 and 0.3) ferrite nanoparticles with sizes ranging from 65 to 70 nm were synthesized employing the solution combustion route. The magnetocaloric behavior was investigated within the 50 K ≤ T ≤ 400 K range of temperatures (T). The entropy change (ΔS) and the adiabatic temperature change (ΔT) were derived from magnetization (M) and specific heat (C{sub P} ) measurements. Both compositions exhibited broad peaks for the isothermal entropy change. The magnetic field (H)-dependent ΔT was analyzed within the mean-field approximation scheme, and the observed magnetocaloric properties of the nanoparticle samples were compared with those of a bulk sample. Our study suggests that the magnetocaloric properties of magnetic oxides strongly depend on the particle size; thus, particle size should be considered as a key tuning parameter in the optimization of magnetic refrigeration.

  15. Large reversible magnetocaloric effect in a Ni-Co-Mn-In magnetic shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Huang, L.; Cong, D. Y.; Ma, L.; Nie, Z. H.; Wang, Z. L.; Suo, H. L.; Ren, Y.; Wang, Y. D.

    2016-01-18

    Reversibility of the magnetocaloric effect in materials with first-order magnetostructural transformation is of vital significance for practical magnetic refrigeration applications. Here, we report a large reversible magnetocaloric effect in a Ni49.8Co1.2Mn33.5In15.5 magnetic shape memory alloy. A large reversible magnetic entropy change of 14.6 J/(kg K) and a broad operating temperature window of 18 K under 5 T were simultaneously achieved, correlated with the low thermal hysteresis (-8 K) and large magnetic-field-induced shift of transformation temperatures (4.9 K/T) that lead to a narrow magnetic hysteresis (1.1 T) and small average magnetic hysteresis loss (48.4 J/kg under 5 T) as well. Furthermore, a large reversible effective refrigeration capacity (76.6 J/kg under 5 T) was obtained, as a result of the large reversible magnetic entropy change, broad operating temperature window, and small magnetic hysteresis loss. The large reversible magnetic entropy change and large reversible effective refrigeration capacity are important for improving the magnetocaloric performance, and the small magnetic hysteresis loss is beneficial to reducing energy dissipation during magnetic field cycle in potential applications.

  16. Magnetic phase transition and magnetocaloric properties of Mn1-xSnxCoGe alloys

    Science.gov (United States)

    Si, Xiaodong; Zhou, Keyi; Zhang, Rui; Liu, Yongsheng; Qi, Jing

    2017-05-01

    Magnetic phase transitions and the magnetocaloric effect of the polycrystalline Mn1-xSnxCoGe samples with x = 0.02, 0.04, and 0.06 have been investigated. The transformation temperature, room temperature magnetocaloric effect and magnetic orders of these alloys could be effectively tuned by Sn substitution. A detailed study on the critical behavior was performed by various techniques, such as modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis, to determine the critical exponents (β, γ, and δ). Those exponents calculated from the critical magnetization isotherm were found to obey the Widom scaling relation remarkably well and the validity of the obtained critical exponents was also verified by the prediction of the scaling theory in the critical region. All the results are similar to the theoretical values of the mean-field model, indicating the presence of long-range ferromagnetic coupling in this system. Moreover, we made an attempt to contrast the universal curve for magnetocaloric effect in the present system, finding that rescaled entropy data for all alloys collapse into a universal curve.

  17. Assessment of the magnetocaloric effect in La,Pr(Fe,Si) under cycling

    Science.gov (United States)

    Kaeswurm, B.; Franco, V.; Skokov, K. P.; Gutfleisch, O.

    2016-05-01

    The response of a magnetocaloric material to periodic variations of magnetic field and temperature corresponding to those occurring during a magnetic refrigeration process is studied. A series of simple measurement protocols are suggested which are used to obtain a value for the cyclic response of the magnetic entropy change associated with the magnetic transition. The entropy values are compared to direct measurements of the temperature change under adiabatic conditions. The procedure is illustrated on the first order magnetocaloric material La0.6Pr0.4Fe11.6Si1.4 and provides a basis for comparison of the suitability of different hysteretic magnetocaloric materials for application in a magnetic refrigerator. For the alloy studied here the peak magnetic entropy change of -28±1 J kg-1 K-1 in a field change of 2 T is not affected by cycling, but the full width at half maximum of the peak decreases from 8.7 K to 3.8 K.

  18. A two-dimensional investigation about magnetocaloric regenerator design: parallel plates or packed bed?

    Science.gov (United States)

    Aprea, C.; Greco, A.; Maiorino, A.; Masselli, C.

    2017-01-01

    Magnetic Refrigeration (MR) is a novel refrigeration technique based on eco-friendly solid materials as refrigerants, whom react to the application of magnetic fields, with warming and cooling by magnetocaloric effect. The thermodynamical cycle which best suits the magnetic refrigeration is Active Magnetic Regenerator cycle (AMR). Regenerator is the core of a magnetic refrigerator, since that it plays a dual-role: it operates both as refrigerant and regenerator in an AMR cycle. An AMR cycle consists of two adiabatic stages and two isofield stage. In this paper an investigation is conducted about the magnetocaloric refrigerator design through two-dimensional multiphysics numerical models of two different magnetocaloric regenerators: (1) a packed bed and (2) a parallel plates magnetic regenerators made of gadolinium, operating at room temperature under a 1.5T magnetic field induction. Both models employ water as secondary fluid. The tests were performed with variable fluid flow rate at fixed AMR cycle frequency. The results obtained are presented in terms of temperature span, cooling power, coefficient of performance and mechanical power of the circulation pump, and they indicate under which operating conditions packed bed configuration is to be preferred to parallel plates and vice versa.

  19. The metamagnetic behavior and giant inverse magnetocaloric effect in Ni–Co–Mn–(Ga, In, Sn) Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Entel, Peter [Faculty of Physics and CENIDE, University of Duisburg-Essen, 47048 Duisburg (Germany); Sokolovskiy, Vladimir V. [Condensed Matter Physics Department, Chelyabinsk State University, 454001 Chelyabinsk (Russian Federation); Buchelnikov, Vasiliy D., E-mail: buche@csu.ru [Condensed Matter Physics Department, Chelyabinsk State University, 454001 Chelyabinsk (Russian Federation); Ogura, Masako [Department of Physics, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043 (Japan); Gruner, Markus E.; Grünebohm, Anna; Comtesse, Denis [Faculty of Physics and CENIDE, University of Duisburg-Essen, 47048 Duisburg (Germany); Akai, Hisazumi [The Institute for Solid State Physics, Center of Computational Materials Science, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581 (Japan)

    2015-07-01

    The magnetic and magnetocaloric properties of Ni–Co–Mn–(Ga, In, Sn) Heusler intermetallics are discussed on the basis of ab initio and Monte Carlo calculations. The main emphasis is on the different reference spin states and magnetic exchange coupling constants of high-temperature austenite and low-temperature martensite which are very important for the calculation of magnetocaloric effect. The origin of metamagnetic behavior is considered in the framework of orbital resolved magnetic exchange parameters of austenite and martensite. The decomposition of exchange constants on orbital contributions has shown that a strong ferromagnetic interaction of magnetic moments in austenite is caused by the more itinerant d-electrons with t{sub 2g} states while a strong antiferromagnetic interaction in martensite is associated with the more localized e{sub g} states. In addition, the appearance of a paramagnetic gap between magnetically weak martensite and ferromagnetically ordered austenite can be realized because of strong competition of magnetic exchange interactions. As a result, large magnetization drop and giant inverse magnetocaloric effect can be achieved across the magnetostructural phase transition. - Highlights: • The magnetic and magnetocaloric properties of Ni–Co–Mn–(Ga, In, Sn) alloys are discussed. • The metamagnetic behavior results in a jump of magnetization. • The reason of metamagnetism is the antiferromagnetic interaction between Mn atoms. • The size of magnetocaloric effect is determined by the magnetic exchange parameters.

  20. Tuning structural instability toward enhanced magnetocaloric effect around room temperature in MnCo1−xZnxGe

    Science.gov (United States)

    Choudhury, D.; Suzuki, T.; Tokura, Y.; Taguchi, Y.

    2014-01-01

    Magnetocaloric effect is the phenomenon that temperature change of a magnetic material is induced by application of a magnetic field. This effect can be applied to environmentally-benign magnetic refrigeration technology. Here we show a key role of magnetic-field-induced structural instability in enhancing the magnetocaloric effect for MnCo1−xZnxGe alloys (x = 0–0.05). The increase in x rapidly reduces the martensitic transition temperature while keeping the ferromagnetic transition around room temperature. Fine tuning of x around x = 0.03 leads to the concomitant structural and ferromagnetic transition in a cooling process, giving rise to enhanced magnetocaloric effect as well as magnetic-field-induced structural transition. Analyses of the structural phase diagrams in the T-H plane in terms of Landau free-energy phenomenology accounts for the characteristic x-dependence of the observed magnetocaloric effect, pointing to the importance of the magnetostructural coupling for the design of high-performance magnetocalorics. PMID:25519919

  1. Tuning structural instability toward enhanced magnetocaloric effect around room temperature in MnCo(1-x)Zn(x)Ge.

    Science.gov (United States)

    Choudhury, D; Suzuki, T; Tokura, Y; Taguchi, Y

    2014-12-18

    Magnetocaloric effect is the phenomenon that temperature change of a magnetic material is induced by application of a magnetic field. This effect can be applied to environmentally-benign magnetic refrigeration technology. Here we show a key role of magnetic-field-induced structural instability in enhancing the magnetocaloric effect for MnCo(1-x)Zn(x)Ge alloys (x = 0-0.05). The increase in x rapidly reduces the martensitic transition temperature while keeping the ferromagnetic transition around room temperature. Fine tuning of x around x = 0.03 leads to the concomitant structural and ferromagnetic transition in a cooling process, giving rise to enhanced magnetocaloric effect as well as magnetic-field-induced structural transition. Analyses of the structural phase diagrams in the T-H plane in terms of Landau free-energy phenomenology accounts for the characteristic x-dependence of the observed magnetocaloric effect, pointing to the importance of the magnetostructural coupling for the design of high-performance magnetocalorics.

  2. Study of multi-layer active magnetic regenerators using magnetocaloric materials with first and second order phase transition

    Science.gov (United States)

    Lei, T.; Engelbrecht, K.; Nielsen, K. K.; Neves Bez, H.; Bahl, C. R. H.

    2016-09-01

    Magnetocaloric materials (MCM) with a first order phase transition (FOPT) usually exhibit a large, although sharp, isothermal entropy change near their Curie temperature, compared to materials with a second order phase transition (SOPT). Experimental results of applying FOPT materials in recent magnetocaloric refrigerators (MCR) demonstrated the great potential for these materials, but a thorough study on the impact of the moderate adiabatic temperature change and strong temperature dependence of the magnetocaloric effect (MCE) is lacking. Besides, comparing active magnetic regenerators (AMR) using FOPT and SOPT materials is also of fundamental interest. We present modeling results of multi-layer AMRs using FOPT and SOPT materials based on a 1D numerical model. First the impact of isothermal entropy change, adiabatic temperature change and shape factor describing the temperature dependence of the MCE are quantified and analyzed by using artificially built magnetocaloric properties. Then, based on measured magnetocaloric properties of La(Fe,Mn,Si)13H y and Gd, an investigation on how to layer typical FOPT and SOPT materials with different temperature spans is carried out. Moreover, the sensitivity of variation in Curie temperature distribution for both groups of AMRs is investigated. Finally, a concept of mixing FOPT and SOPT materials is studied for improving the stability of layered AMRs with existing materials.

  3. Effect of low temperature annealing on magneto-caloric effect of Ni–Mn–Sn–Al ferromagnetic shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Sandeep [Haldia Institute of Technology, Haldia 721657, West Bengal (India); LCMP, Department of Condensed Matter Physics and Material Sciences, S.N. Bose National Centre for Basic Sciences, JD Block, Salt Lake, Kolkata 700098 (India); Stern-Taulats, Enric; Mañosa, Lluís [Departament d’Estructura i Constituents de la Matèria, Facultat de Física, Universitat de Barcelona, 08028 Barcelona, Catalonia (Spain); Mukhopadhyay, P.K., E-mail: pkm@bose.res.in [LCMP, Department of Condensed Matter Physics and Material Sciences, S.N. Bose National Centre for Basic Sciences, JD Block, Salt Lake, Kolkata 700098 (India)

    2015-08-25

    Highlights: • Magnetic properties of the system changed after secondary heat treatment. • MCE was enhanced after Al was partially replaced with Sn in Ni–Mn–Al system. • Suitable heat treatment further increased overall MCE in the sample. • Change in magnetic properties occurred due to change in atomic ordering. - Abstract: We studied the effect of low temperature annealing on the atomic ordering and consequent changes in the magnetization and magnetocaloric effect of the sample. The annealing at lower temperatures initially decreased the magnetization and magnetocaloric effect in the sample, but at higher annealing temperatures both increased. The changes in magnetization and magnetocaloric effect arise from the change in atomic ordering. We have shown that post quenching heat treatment offers easy way of optimizing the alloy for magnetocaloric effect. In order to verify that there was no overestimation in the measurement of magnetocaloric effect we also performed an infield calorimetric measurements and compared them with those from the magnetization measurements. We did not find remarkable difference between them.

  4. Influence of Tb substitution on low-field magnetocaloric effect in Gd5Si1.72Ge2.28 alloy

    Institute of Scientific and Technical Information of China (English)

    DENG Jian-qiu; ZHUANG Ying-hong; WANG Ri-chu; YANG Zhen; XU Bin

    2008-01-01

    The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72-Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd5Si1.72Ge2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (Tc) of the compounds. The magnetic entropy change of (Gd1-xTbx)5Si1.72Ge2.28 alloys retains a large value in the low magnetic field of 1.0 T.The maximum magnetic entropy change for (Gd0.80Tb0.20)5Si1.72Ge2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K),which is nearly 4 times as large as that of (Gd0.3Dy0.7)5Si4 compound (|△Smax| = 2.24 J/(kg·K), TC = 198 K).

  5. Theoretical investigations on magnetocaloric effect in Er{sub 1−y}Tb{sub y}Al{sub 2} series

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, P.O., E-mail: paula.ribeiro@gmail.com [Instituto de Física, Universidade do Estado do Rio de Janeiro – UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil); Alho, B.P.; Alvarenga, T.S.T.; Nóbrega, E.P.; Sousa, V.S.R. de [Instituto de Física, Universidade do Estado do Rio de Janeiro – UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil); Carvalho, A. Magnus G. [Laboratório Nacional de Luz Síncrotron, CNPEM, 13083-970 Campinas, SP (Brazil); Caldas, A. [Sociedade Unificada de Ensino Superior e Cultura, SUESC, 20211-351 Rio de Janeiro, RJ (Brazil); Oliveira, N.A. de; Ranke, P.J. von [Instituto de Física, Universidade do Estado do Rio de Janeiro – UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil)

    2015-04-01

    We report on the magnetic and magnetocaloric effect calculations in rare earth Er{sub 1−y}Tb{sub y}Al{sub 2} compounds (y=0.00, 0.25, 0.5, 0.75 and 1.00). Our model Hamiltonian has contributions of the crystalline electrical field anisotropy in both Er and Tb magnetic sublattices, disorder in exchange interactions among Er–Er, Tb–Tb and Er–Tb magnetic ions and the Zeeman effect. The magnetization, the isothermal entropy change (ΔS{sub T}) and the adiabatic temperature change (ΔT{sub ad}) dependence on temperature were simulated and, compared with the experimental data available. - Highlights: • Modeling Er{sub (1−y)}Tb{sub y}Al{sub 2} intermetallic compounds. • Magnetic entropy changes in Er{sub (1−y)}Tb{sub y}Al{sub 2}. • Adiabatic temperature changes in Er{sub 0.75}Tb{sub 0.25}Al{sub 2} and Er{sub 0.65}Tb{sub 0.35}Al{sub 2} compounds.

  6. Sodium - Deficiency effects on the structural, magnetic and magnetocaloric properties of La0.8Na0.2-x□xMnO3 (0 ≤ x ≤ 0.15)

    Science.gov (United States)

    Choura-Maatar, S.; M'nassri, R.; Cheikhrouhou-Koubaa, W.; Koubaa, M.; Cheikhrouhou, A.; Hlil, E. K.

    2017-07-01

    In this paper, we report the magnetocaloric effect of Na vacancies in La0.8Na0.2-x□xMnO3 (0 ≤ x ≤ 0.15) powder samples synthesized using the sol-gel technique. Structural investigations using X-ray diffraction show that all the elaborated compounds crystallise in the rhombohedral structure with R 3 bar c space group. Magnetic measurements versus temperature reveal a magnetic transition from ferromagnetic (FM) to paramagnetic (PM) phase when increasing temperature. The Curie temperature TC shifts to lower values with increasing sodium-deficiency. The Arrott plots indicate that a second order phase transition takes place. The effect of sodium-deficiency on the magnetocaloric properties has also been investigated. The maximum values of the magnetic entropy changes, |-ΔSM|max, under a magnetic field change of 5T are found to be 4.74; 4.13; 6.14 and 4.55 J/kg K for x = 0; 0.05; 0.1 and x = 0.15 respectively. The relative cooling power (RCP) and its field dependence are also analyzed. The obtained magnetic entropy changes are compared to calculated ones based on the Landau theory and a good concordance is observed.

  7. Structural, magnetic and magnetocaloric properties of polycrystalline La{sub 0.67}Ba{sub 0.33-x}Zn{sub x}MnO{sub 3} (x = 0.15 and 0.2) manganites

    Energy Technology Data Exchange (ETDEWEB)

    Zaidi, Asma; Mohamed, Z.; Dhahri, J. [University of Monastir, Laboratory of Condensed Matter and Nanosciences, Monastir (Tunisia); Hlil, E.K. [CNRS, University of Joseph Fourier, Institut Neel, Grenoble (France); Alharbi, T.; Zaidi, M. [Majmaah University, College of Science of Zulfi, Al Majmaah (Saudi Arabia)

    2016-04-15

    We report on the structural, magnetic and magnetocaloric properties of manganite La{sub 0.67}Ba{sub 0.33-x}Zn{sub x}MnO{sub 3} (x=0.15 and 0.2). X-ray diffraction studies show that all samples crystallize with the rhombohedral symmetry within the space group R anti 3c. The magnetic and magnetocaloric properties of polycrystalline perovskite were investigated from the measured magnetization data of the samples as a function of the applied magnetic field. The associated magnetic entropy change close to their respective Curie temperature T{sub C} and the relative cooling power (RCP) have been determined. It was found that the maximum change in magnetic entropy of La{sub 0.67}Ba{sub 0.33-x}Zn{sub x}MnO{sub 3} samples reached 3.4 J/kg K at T{sub C}=260 K for a magnetic field of 5 T and RCP=223.77 J/kg. In view of these results, La{sub 0.67}Ba{sub 0.33-x}Zn{sub x}MnO{sub 3} compounds are potential candidates for magnetic refrigeration. (orig.)

  8. Structural, magnetic and magnetocaloric properties of polycrystalline La0.67Ba0.33- x Zn x MnO3 (x = 0.15 and 0.2) manganites

    Science.gov (United States)

    Zaidi, Asma.; Mohamed, Za.; Dhahri, J.; Hlil, E. K.; Alharbi, T.; Zaidi, M.

    2016-04-01

    We report on the structural, magnetic and magnetocaloric properties of manganite La0.67Ba0.33- x Zn x MnO3 (x = 0.15 and 0.2). X-ray diffraction studies show that all samples crystallize with the rhombohedral symmetry within the space Roverline{3} c. The magnetic and magnetocaloric properties of polycrystalline perovskite were investigated from the measured magnetization data of the samples as a function of the applied magnetic field. The associated magnetic entropy change close to their respective Curie temperature T C and the relative cooling power (RCP) have been determined. It was found that the maximum change in magnetic entropy of La0.67Ba0.33- x Zn x MnO3 samples reached 3.4 J/kg K at T C = 260 K for a magnetic field of 5 T and RCP = 223.77 J/kg. In view of these results, La0.67Ba0.33- x Zn x MnO3 compounds are potential candidates for magnetic refrigeration.

  9. Magnetic and magnetocaloric properties of La0.6Pr0.1Sr0.3Mn1-xFexO3 (0≤x≤0.3) manganites

    Science.gov (United States)

    Cherif, R.; Hlil, E. K.; Ellouze, M.; Elhalouani, F.; Obbade, S.

    2014-07-01

    The La0.6Pr0.1Sr0.3Mn1-xFexO3 (x=0, 0.1, 0.2 and 0.3) samples have been elaborated by the solid-state reaction method. X-ray powder diffraction shows that all the samples crystallize in a rhombohedric phase with R3barc space group. The variation of magnetization as a function of temperature and applied magnetic field was carried out. The samples for x=0 and 0.1 exhibit a FM-PM transition at the Curie temperature TC, however, for x=0.2 and 0.3 exhibit an AFM-PM one at the Neel temperature TN, when the temperature increases. A magneto-caloric effect has been calculated in terms of isothermal magnetic entropy change. A large magneto-caloric effect has been observed, the maximum entropy change, |ΔSMmax|, reaches the highest value of 3.28 J/kgK under a magnetic field change of 5 T with an RCP value of 220 J/kg for La0.6Pr0.1Sr0.3MnO3 composition, which will be an interesting compound for application materials working as magnetic refrigerants near room temperature.

  10. Magnetic and magnetocaloric properties of nanocrystalline Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) manganites.

    Science.gov (United States)

    Mahato, Rabindra Nath; Sethupathi, K; Sankaranarayanan, V; Nirmala, R; Malik, S K

    2011-03-01

    Structural, magnetic and magnetocaloric properties of sol-gel prepared, nanocrystalline oxides Pr(1-x)A(x)Mn(1-y)Co(y)O3 (A = Ca, Sr) (x = 0.3; y = 0.5) (cubic, space group Fm3m) have been studied. From the X-ray data, the crystallite size of Pro.7Ca0.3Mn0.5Co0,503 and Pr0.7Sr0.3Mn0.5Co0.5O3 samples is found to be approximately 24 nm and approximately15 nm respectively. High resolution transmission electron microscopy image shows average particle size of approximately 34 nm and approximately 20 nm. Magnetization measurements indicate a Curie temperature of approximately 153 K and approximately172 K in applied magnetic field of 100 Oe for Pr0.7Ca0.3Mn0.5Co0.5O3 and Pr0.7Sr0.3Mn0.5Co0.O3 compounds. The magnetization versus applied magnetic field curves obtained at temperatures below 150 K show significant hysteresis and magnetization is not saturated even in a field of 7 T. The magnetocaloric effect is calculated from M versus H data obtained at various temperatures. Magnetic entropy change shows a maximum near T(c) for both the samples and is of the order approximately 2.5 J/kg/K.

  11. High-resolution alternating-field technique to determine the magnetocaloric effect of metals down to very low temperatures.

    Science.gov (United States)

    Tokiwa, Y; Gegenwart, P

    2011-01-01

    The magnetocaloric effect or "magnetic Grüneisen ratio" Γ(H)=T(-1)(dT/dH)(S) quantifies the cooling or heating of a material when an applied magnetic field is changed under adiabatic conditions. Recently, this property has attracted considerable interest in the field of quantum criticality. Here, we report the development of a low-frequency alternating-field technique for measurements of the magnetocaloric effect down to very low temperatures, which is an important property for the study of quantum critical points. We focus, in particular, on highly conducting metallic samples and discuss the influence of eddy current heating. By comparison with magnetization and specific heat measurements, we demonstrate that our fast and accurate technique gives quantitatively correct values for the magnetocaloric effect under truly adiabatic conditions.

  12. The influence of hysteresis on the determination of the magnetocaloric effect in Gd5Si2Ge2

    DEFF Research Database (Denmark)

    von Moos, Lars; Bahl, Christian; Nielsen, Kaspar Kirstein

    2015-01-01

    We present a non-equilibrium Preisach-type hysteresis model based on the first order magnetocaloric material Gd5Si2Ge2. The model is developed from isofield magnetization measurements and first order reversal curves, both of which constitute a new and detailed approach to characterizing and model......We present a non-equilibrium Preisach-type hysteresis model based on the first order magnetocaloric material Gd5Si2Ge2. The model is developed from isofield magnetization measurements and first order reversal curves, both of which constitute a new and detailed approach to characterizing...... continuous magnetization cycles, which effectively limits the adiabatic temperature change by the amount of thermal hysteresis present. We suggest a straightforward method for realistic estimation of the magnetocaloric effect from indirect measurements....

  13. Investigations in MnAs{sub 1−x}Sb{sub x}: Experimental validation of a new magnetocaloric composite

    Energy Technology Data Exchange (ETDEWEB)

    Campos, A. de, E-mail: acampos@icte.uftm.edu.br [Instituto de Ciências Tecnológicas e Exatas, Universidade Federal do Triângulo Mineiro (UFTM), 38066-200 Uberaba (Brazil); Luz, M.S. da; Campos, Adriana de [Instituto de Ciências Tecnológicas e Exatas, Universidade Federal do Triângulo Mineiro (UFTM), 38066-200 Uberaba (Brazil); Coelho, A.A.; Cardoso, L.P. [Instituto deFísica Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP), 13083-970 Campinas (Brazil); Santos, A.O. dos [Centro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do Maranhão – (UFMA), 65900-000 Imperatriz, MA (Brazil); Gama, S. [Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo (UNIFESP), Diadema, 09971-270 SP (Brazil)

    2015-01-15

    An overview of the magnetocaloric properties of the MnAs{sub 1−x}Sb{sub x} is presented. The temperature dependence of the isothermal magnetic entropy, ΔS{sub mag}, and the refrigerant capacity, RC, have been investigated theoretically and experimentally in a composite based on second order MnAs{sub 1−x}Sb{sub x} phases. This work demonstrates the outstanding agreement between the experimental results and the continuous curves predicted by numerical calculations, indicating that this approach can be used to design magnetic refrigerant materials with enhanced magnetocaloric response in magnetic refrigerator performing an Ericsson cycle near room temperature. - Highlights: • This is the first report showing the magnetocaloric properties of the MnAs{sub 1−x}Sb{sub x} composite. • This work demonstrates a good agreement between experimental and the predicted by numerical calculations. The results indicating that this approach can be used to design magnetic refrigerant materials.

  14. Study of multi-layer active magnetic regenerators using magnetocaloric materials with first and second order phase transition

    DEFF Research Database (Denmark)

    Lei, Tian; Engelbrecht, Kurt; Nielsen, Kaspar Kirstein;

    2016-01-01

    Magnetocaloric materials (MCM) with a first order phase transition (FOPT) usually exhibit a large, although sharp, isothermal entropy change near their Curie temperature, compared to materials with a second order phase transition (SOPT). Experimental results of applying FOPT materials in recent...... FOPT and SOPT materials is also of fundamental interest. We present modeling results of multi-layer AMRs using FOPT and SOPT materials based on a 1D numerical model. First the impact of isothermal entropy change, adiabatic temperature change and shape factor describing the temperature dependence...... magnetocaloric refrigerators (MCR) demonstrated the great potential for these materials, but a thorough study on the impact of the moderate adiabatic temperature change and strong temperature dependence of the magnetocaloric effect (MCE) is lacking. Besides, comparing active magnetic regenerators (AMR) using...

  15. Manipulation of the magnetic properties in Er{sub 1−x}Co{sub 2} compounds by atomic vacancies

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Jun-Ding, E-mail: zoujd@zju.edu.cn [School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Key Laboratory of Novel Materials for Information Technology of Zhejiang Province, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Yan, Mi, E-mail: mse_yanmi@zju.edu.cn [School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Key Laboratory of Novel Materials for Information Technology of Zhejiang Province, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Yao, Jin-Lei [Research Center for Solid State Physics and Materials, School of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009 (China)

    2015-05-25

    Highlights: • The nonstoichiometric Er{sub 1−x}Co{sub 2} compounds are identified. • Er atomic vacancies lead to the volume contracting by 0.37% and enhance T{sub C} by 44%. • The anomalous susceptibility behavior is not exact the same with the Griffiths phase. • The refrigerant capacity of Er{sub 0.97}Co{sub 2} increases from 152 J/kg to 158 J/kg. - Abstract: ErCo{sub 2} compound is a well-known magnetocaloric material which shows giant magnetocaloric effect in the vicinity of first-order phase transition. We demonstrate a new way of fine tuning its crystal structure and magnetic properties. Er atomic vacancies are introduced in order to manipulate the local atomic environment, the phase transition characteristics, and the magnetocaloric effect as well. Er{sub 1−x}Co{sub 2} can be stable over a narrow homogenous range, and maintain the cubic structure. The Bragg peaks shift upward to higher angles, and the unit cell volume contracts with reduction of the Er content. The Curie temperatures in low magnetic field increase from 32 K (ErCo{sub 2}) to 46 K (Er{sub 0.97}Co{sub 2}), and linearly change with the magnetic field in nearly same slope. Er{sub 1−x}Co{sub 2} compounds exhibit anomalous susceptibility behaviors in the paramagnetic state, and deviate from the Curie–Weiss law at around 100 K. The temperature range of anomalous susceptibility behaviors also move upward to higher temperature with reduction of Er content. Er{sub 1−x}Co{sub 2} compounds also show anomalous coercivity behavior in the vicinity of phase transition. Er{sub 1−x}Co{sub 2} compounds exhibit large magnetocaloric effect and good refrigerant capacity in the vicinity of ferrimagnetic–paramagnetic phase transition.

  16. Applications of the Magnetocaloric Effect in Single-Stage, Multi-Stage and Continuous Adiabatic Demagnetization Refrigerators

    Science.gov (United States)

    Shirron, Peter J.

    2014-01-01

    Adiabatic demagnetization refrigerators (ADR), based on the magnetocaloric effect, are solid-state coolers that were the first to achieve cooling well into the sub-kelvin regime. Although supplanted by more powerful dilution refrigerators in the 1960s, ADRs have experienced a revival due to the needs of the space community for cooling astronomical instruments and detectors to temperatures below 100 mK. The earliest of these were single-stage refrigerators using superfluid helium as a heat sink. Their modest cooling power (magnetocaloric effect and its application in single-stage systems, and then describing the challenges and capabilities of multi-stage and continuous ADRs.

  17. Magnetocaloric effect in the spin-1/2 Ising-Heisenberg diamond chain with the four-spin interaction

    Directory of Open Access Journals (Sweden)

    L. Gálisová

    2014-03-01

    Full Text Available The magnetocaloric effect in the symmetric spin-1/2 Ising–Heisenberg diamond chain with the Ising four-spin interaction is investigated using the generalized decoration-iteration mapping transformation and the transfer-matrix technique. The entropy and the Grüneisen parameter, which closely relate to the magnetocaloric effect, are exactly calculated to compare an ability of the system to cool in the vicinity of different field-induced ground-state phase transitions during the adiabatic demagnetization.

  18. Giant and reversible extrinsic magnetocaloric effects in La0.7Ca0.3MnO3 films due to strain.

    Science.gov (United States)

    Moya, X; Hueso, L E; Maccherozzi, F; Tovstolytkin, A I; Podyalovskii, D I; Ducati, C; Phillips, L C; Ghidini, M; Hovorka, O; Berger, A; Vickers, M E; Defay, E; Dhesi, S S; Mathur, N D

    2013-01-01

    Large thermal changes driven by a magnetic field have been proposed for environmentally friendly energy-efficient refrigeration, but only a few materials that suffer hysteresis show these giant magnetocaloric effects. Here we create giant and reversible extrinsic magnetocaloric effects in epitaxial films of the ferromagnetic manganite La(0.7)Ca(0.3)MnO(3) using strain-mediated feedback from BaTiO(3) substrates near a first-order structural phase transition. Our findings should inspire the discovery of giant magnetocaloric effects in a wide range of magnetic materials, and the parallel development of nanostructured bulk samples for practical applications.

  19. Magnetic properties and magnetocaloric effect in Ni–Mn–Sn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dan, N.H., E-mail: dannh@ims.vast.ac.vn [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi (Viet Nam); Duc, N.H.; Yen, N.H.; Thanh, P.T. [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi (Viet Nam); Bau, L.V.; An, N.M. [Hong Duc University, 565 Quang Trung, Dong Ve, Thanh Hoa (Viet Nam); Anh, D.T.K.; Bang, N.A.; Mai, N.T. [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Hanoi (Viet Nam); Anh, P.K. [Vietnam Academy of Military Science, 322 Le Trong Tan, Thanh Xuan, Hanoi (Viet Nam); Thanh, T.D. [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi (Viet Nam); Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Phan, T.L. [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Yu, S.C., E-mail: scyu@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

    2015-01-15

    Magnetic and magnetocaloric properties in Ni{sub 50}Mn{sub 50−x}Sn{sub x} alloys with wide range of the Sn-concentration (x=0–40) were investigated. The alloys were prepared by arc-melting and subsequently annealing at 850 °C for 4 h. The X-ray diffraction analyses manifest the formation of the crystalline phases (Ni{sub 2}MnSn, NiMn, Ni{sub 3}Sn{sub 2}, Mn{sub 3}Sn, and MnSn{sub 2}) in the alloys with various compositions and fabrication conditions. With increasing x, the saturation magnetization first increases from near zero (at x=10) to above 40 emu/g (at x=20) and then decreases to below 10 emu/g (at x=40) for both the as-melted and annealed cases. The martensitic–austenitic transition was observed in the alloys with a narrow range of x (13–15). The magnetic transitions in the alloy can be controlled by changing Sn-concentration. The alloy reveals both the positive and negative entropy changes with quite large magnitude (∆S{sub m}>1 J/kg K with ∆H=12 kOe) with appropriate compositions and annealing conditions. - Highlights: • Crystalline phases and magnetic properties in Ni{sub 50}Mn{sub 50−x}Sn{sub x} alloys (x=0–40). • Simultaneous transitions of structural and magnetic phases. • Coexistence of positive and negative giant magnetocaloric effect in Heusler alloys. • Tuning giant magnetocaloric effect in room temperature region.

  20. Taming the first-order transition in giant magnetocaloric materials

    NARCIS (Netherlands)

    Guillou, F.; Porcari, G.; Yibole, H.; Van Dijk, N.H.; Brück, E.

    2014-01-01

    Large magnetically driven temperature changes are observed in MnFe(P,Si,B) materials simultaneously with large entropy changes, limited (thermal or magnetic) hysteresis, and good mechanical stability. The partial substitution of B for P in MnFe(P,Si) compounds is found to be an ideal parameter to co

  1. Excellent Magnetocaloric Effect in Er6oAl18Co22 Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    HUI Xi-Dong; XU Zhi-Yi; WANG En-Rui; CHEN Guo-Liang; LU Zhao-Ping

    2010-01-01

    @@ Excellent magnetocaloric effect with a maximum entropy change and refrigeration capacity of 17.6 J.kg-1.K-1 and 546 J.kg-1,respectively,has been discovered in the Er60Al18 Co22 bulk metallic glass under the fleld of 50 kOe in the temperature range of helium liquefaction.This MCE results from the second-order magnetic transition from the paramagnetic to the ferromagnetic state.Our analysis based on mean-field theory suggests that the excellent MCE is attributed to the strong exchange of magnetic moment in the glassy structure.

  2. Magnetic phase transitions and magnetocaloric effect in the Fe-doped MnNiGe alloys

    Institute of Scientific and Technical Information of China (English)

    Zhang Cheng-Liang; Wang Dun-Hui; Chen Jian; Wang Ting-Zhi; Xie Guang-Xi; Zhu Chun

    2011-01-01

    The magnetic phase transition and magnetocaloric effects in Fe-doped MnNiGe alloys are investigated. The substitution of Fe for Ni decreases the structural transition temperature remarkably,resulting in the magnetostructural transition occurring between antiferromagnetic and ferromagnetic states in MnNil-xFex Ge alloy. Owing to the enhanced ferromagnetic coupling induced by the substitution of Fe,metamagnetic behaviour is also observed in TiNiSi-type phase of MnNil_yFe.Ge alloys at temperature below the structural transition temperature.

  3. AC measurement of heat capacity and magnetocaloric effect for pulsed magnetic fields

    OpenAIRE

    2010-01-01

    International audience; A new calorimeter for measurements of the heat capacity and magnetocaloric effect of small samples in pulsed magnetic fields is discussed for the exploration of thermal and thermodynamic properties at temperatures down to 2 K. We tested the method up to 0H=50 T, but it could be extended to higher fields. For these measurements we used carefully calibrated bare-chip Cernox® and RuO2 thermometers, and we present a comparison of their performances. The monotonic temperatu...

  4. Magnetocaloric effect and slow magnetic relaxation in two only azido bridged ferromagnetic tetranuclear metal clusters.

    Science.gov (United States)

    Zhao, Jiong-Peng; Zhao, Ran; Yang, Qian; Hu, Bo-Wen; Liu, Fu-Chen; Bu, Xian-He

    2013-10-28

    Two M(II) tetranuclear complexes bridged only by azido, Mn4(N3)(7.3)Cl(0.7)L4 (1) and Co4(N3)8L4 (2) in which the four M(II) ions are precisely coplanar bridged only by six azido anions, were obtained by using 4,5-diazafluoren-9-one (L) as a corner ligand. Magnetic studies indicate that ferromagnetic coupling was conducted by the azido anions between M(II) ions. At low temperature, 1 exhibits a large magnetocaloric effect and 2 shows field-induced multiple magnetic relaxations.

  5. Theoretical investigation on the magnetocaloric effect in amorphous Eu80 Au20 system

    Science.gov (United States)

    Costa, S. S.; Roriz, O. A. V.; Silvano, N. de O.; von Ranke, P. J.; Nóbrega, E. P.

    2016-09-01

    In this work, we investigated the magnetic and magnetocaloric properties of the amorphous system Eu80 Au20. The magnetic state equation and entropy were considered in the framework of Handrich-Kaneyoshi model, which takes into account the amorphization through the symmetric exchange fluctuation in the mean field approximation. The exchange and structural fluctuations parameters were chosen based on the experimental data of Eu80 Au20. The isothermal entropy change was calculated for several variations of external magnetic field. Furthermore, the adiabatic temperature change and the refrigerant capacity were calculated for a magnetic field change from 0 to 5 T.

  6. Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

    Energy Technology Data Exchange (ETDEWEB)

    Nicholson, Don M [ORNL; Odbadrakh, Khorgolkhuu [ORNL; Shassere, Benjamin [ORNL; Rios, Orlando [ORNL; Hodges, Jason P [ORNL; Ludtka, Gerard Michael [ORNL; Porter, Wallace D [ORNL; Safa-Sefat, Athena [ORNL; Rusanu, Aurelian [ORNL; Brown, Greg [ORNL; Evans III, Boyd Mccutchen [ORNL

    2014-01-01

    Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations.

  7. Quantification of the effect of hysteresis on the adiabatic temperature change in magnetocaloric materials

    DEFF Research Database (Denmark)

    von Moos, Lars; Bahl, Christian R.H.; Nielsen, Kaspar Kirstein

    2014-01-01

    We quantify the effect of hysteresis on the performance of the magnetocaloric first order material Gd5Si2Ge2 undergoing an ideal active magnetic regenerator (AMR) cycle. The material is carefully characterized through magnetometry (VSM) and calorimetry (DSC) in order to enable an accurate model...... description of the phase transition at varying magnetic fields and temperatures. Using detailed experimental property data, a Preisach type model is used to describe the thermal hysteresis effects and simulate the material under realistic working conditions. We find that the adiabatic temperature change...... is limited by a significant fraction of the thermal hysteresis....

  8. Magnetocaloric properties of rare-earth substituted DyCrO3

    Science.gov (United States)

    McDannald, A.; Jain, M.

    2015-07-01

    Recently, there has been a focus on the need for efficient refrigeration technology without the use of expensive or harmful working fluids, especially at temperatures below 30 K. Solid state refrigeration, based on the magnetocaloric effect, provides a possible solution to this problem. The rare-earth chromites (RCrO3), especially DyCrO3, with its large magnetic moment dysprosium ion, are potential candidates for such an application. The Dy3+ ordering transition at low temperatures (cooling power of 237 J/kg at 40 kOe and 5 K) indicates that this material system is well suited for low temperature (<30 K) solid state refrigeration applications.

  9. Zero temperature non-plateau magnetization and magnetocaloric effect in an Ising-XYZ diamond chain structure

    Science.gov (United States)

    Torrico, J.; Rojas, M.; de Souza, S. M.; Rojas, Onofre

    2016-10-01

    Zero temperature non-plateau magnetization is a peculiar property of a quantum spin chain and it sometimes appears due to different gyromagnetic factors. In this study, we illustrate a quite unusual non-plateau magnetization property driven by XY-anisotropy in an Ising-XYZ diamond chain. Two particles with spin-1/2 are bonded by XYZ coupling and they are responsible for the emergence of non-plateau magnetization. These two quantum operator spins are bonded to two nodal Ising spins and this process is repeated infinitely to yield a diamond chain structure. Due to the non-plateau magnetization property, we focus our discussion on the magnetocaloric effect of this model by presenting the isentropic curves and the Grüneisen parameters, as well as showing the regions where the model exhibits an efficient magnetocaloric effect. Due to the existence of two phases located very close to each other, the strong XY-anisotropy exhibits a particular behavior with a magnetocaloric effect, with a wider interval in the magnetic field, where the magnetocaloric effect is efficient.

  10. Inverse magnetocaloric effect in Ce(Fe0.96Ru0.04)2: Effect of fast neutron irradiation

    Science.gov (United States)

    Dube, V.; Mishra, P. K.; Rajarajan, A. K.; Prajapat, C. L.; Sastry, P. U.; Thakare, S. V.; Singh, M. R.; Ravikumar, G.

    2013-02-01

    We have shown the effect of fast neutron irradiation on the magnetic phase transition and magnetocaloric effect (MCE) in a doped Ce(Fe0.96Ru0.04)2, intermettalic. We show that this leads to suppression of MCE and a to a disordered ferromagnetic phase.

  11. Correlation between electrical, magnetocaloric properties and critical behavior in (La0.75Nd0.25)2/3(Ca0.8Sr0.2)1/3MnO3

    Science.gov (United States)

    Khelifi, J.; Dhahri, E.; Hlil, E. K.

    2017-01-01

    An investigation of the critical behavior and magnetic entropy from resistivity of (La0.75Nd0.25)2/3(Ca0.8Sr0.2)1/3MnO3 is presented. The magnetocaloric properties of the polycrystalline manganite (La0.75Nd0.25)2/3(Ca0.8Sr0.2)1/3MnO3 based on resistivity measurements were investigated. Using, the equation ΔS = - α∫0H ∂Ln (ρ)/∂T) H dH relates magnetic order to the transport behavior of the compound, we measure the magnetic entropy change ΔSM from the resistivity which is similar to that calculated from the magnetic measurement. Moreover, we have found an excellent estimation of critical behavior from resistivity and magnetic analysis.

  12. Magnetocaloric Properties of Fe-Ni-Cr Nanoparticles for Active Cooling.

    Science.gov (United States)

    Chaudhary, V; Ramanujan, R V

    2016-10-11

    Low cost, earth abundant, rare earth free magnetocaloric nanoparticles have attracted an enormous amount of attention for green, energy efficient, active near room temperature thermal management. Hence, we investigated the magnetocaloric properties of transition metal based (Fe70Ni30)100-xCrx (x = 1, 3, 5, 6 and 7) nanoparticles. The influence of Cr additions on the Curie temperature (TC) was studied. Only 5% of Cr can reduce the TC from ~438 K to 258 K. These alloys exhibit broad entropy v/s temperature curves, which is useful to enhance relative cooling power (RCP). For a field change of 5 T, the RCP for (Fe70Ni30)99Cr1 nanoparticles was found to be 548 J-kg(-1). Tunable TCin broad range, good RCP, low cost, high corrosion resistance and earth abundance make these nanoparticles suitable for low-grade waste heat recovery as well as near room temperature active cooling applications.

  13. Direct observation of magnetocaloric effect by differential thermal analysis: Influence of experimental parameters

    Energy Technology Data Exchange (ETDEWEB)

    Rotstein Habarnau, Yamila; Bergamasco, Pablo [Departamento Materia Condensada, CAC, CNEA, Av. Gral Paz 1429, San Martin 1650 (Argentina); Departamento de Fisica, FCEN, Universidad de Buenos Aires, Ciudad Universitaria Pab. I, Buenos Aires 1428 (Argentina); Sacanell, Joaquin [Departamento Materia Condensada, CAC, CNEA, Av. Gral Paz 1429, San Martin 1650 (Argentina); Leyva, Gabriela [Departamento Materia Condensada, CAC, CNEA, Av. Gral Paz 1429, San Martin 1650 (Argentina); Escuela de Ciencia y Tecnologia, UNSAM, San Martin, Buenos Aires 1650 (Argentina); Albornoz, Cecilia [Departamento Materia Condensada, CAC, CNEA, Av. Gral Paz 1429, San Martin 1650 (Argentina); Quintero, Mariano, E-mail: mquinter@cnea.gov.ar [Departamento Materia Condensada, CAC, CNEA, Av. Gral Paz 1429, San Martin 1650 (Argentina); Escuela de Ciencia y Tecnologia, UNSAM, San Martin, Buenos Aires 1650 (Argentina)

    2012-08-15

    The magnetocaloric effect is the isothermal change of magnetic entropy and the adiabatic temperature change induced in a magnetic material when an external magnetic field is applied. In this work, we present an experimental setup to study this effect in metamagnetic transitions, using the differential thermal analysis technique, which consists in measuring simultaneously the temperatures of the sample of interest and a reference one while an external magnetic field ramp is applied. We have tested our system to measure the magnetocaloric effect in La{sub 0.305}Pr{sub 0.32}Ca{sub 0.375}MnO{sub 3}, which presents phase separation effects at low temperatures (T<200 K). We obtain {Delta}T vs H curves, and analyze how the effect varies by changing the rate of the magnetic field ramp. Our results show that the intensity of the effect increases with the magnetic field change rate. We also have obtained the effective heat capacity of the system without the sample by performing calorimetric measurements using a pulse heat method, fitting the temperature change with a two tau description. With this analysis, we are able to describe the influence of the environment and subtract it to calculate the adiabatic temperature change of the sample.

  14. Giant magnetocaloric effect near room temperature in the off-stoichiometric Mn-Co-Ge alloy

    Science.gov (United States)

    Sharma, V. K.; Manekar, M. A.; Srivastava, Himanshu; Roy, S. B.

    2016-12-01

    We report a giant magnetocaloric effect near room temperature in an off-stoichiometric Mn-Co-Ge alloy, across the magnetostructural transition. The isothermal entropy change accompanying this transition has a peak value of nearly 40 J kg-1 K-1 near 297 K for a field excursion of 70 kOe, and a refrigerant capacity of 270 J kg-1 with the hot end at 302.5 K and cold end at 293.5 K. We also present an experimental protocol to avoid spurious peaks in the magnetocaloric effect across a sharp first order magnetostructural transition, not confined to Mn-Co-Ge alone, where metastability during the transition could influence the measured magnetization and thus the estimated entropy change. The estimated entropy change in the present off-stoichiometric Mn-Co-Ge alloy is possibly the highest reported value near room temperature in undoped Mn-Co-Ge alloys and underlines the potential of the alloy for technological applications in room temperature magnetic refrigeration.

  15. Adiabatic magnetocaloric temperature change in polycrystalline gadolinium – A new approach highlighting reversibility

    Directory of Open Access Journals (Sweden)

    Mohammadreza Ghahremani

    2012-09-01

    Full Text Available The adiabatic temperature change (ΔT during the magnetization and demagnetization processes of bulk gadolinium is directly measured for several applied magnetic fields in the temperature range 285 K to 305 K. During the magnetization process, ΔT measurements display the same maximum for each applied field when plotted against the initial temperature (Ti. However, during the demagnetization process, the maximum ΔT varies for each applied field. This discrepancy between the magnetization and demagnetization measurements appears inconsistent with the reversibility of the magnetocaloric effect. A new approach is undertaken to highlight the reversibility of the magnetocaloric effect by plotting ΔT against the average temperature change (Tavg instead of Ti. The value of Tavg which corresponds to the maximum ΔT is found to increase linearly with the applied magnetic field, consistently for both the magnetization and demagnetization measurements. Solving the linear-fitting equations of these measurements gives a new, and more precise, Curie temperature measurement. This new approach confirmed that the relationship between the maximum adiabatic temperature change (ΔTpeak and the applied magnetic field is perfectly linear.

  16. Magnetocaloric effect in magnetothermally-responsive nanocarriers for hyperthermia-triggered drug release.

    Science.gov (United States)

    Li, Jianbo; Qu, Yang; Ren, Jie; Yuan, Weizhong; Shi, Donglu

    2012-12-21

    The magnetocaloric effects and lower critical solution temperature (LCST) were investigated in a magnetothermally-responsive nanocarrier for magnetothermal drug release under alternating magnetic field (AMF). The Mn(0.2)Zn(0.8)Fe(2)O(4) nanoparticles with low T(c) were dispersed in a polymeric matrix consisting of N-Isopropyl acrylamide (NIPAAm) and N-hydroxymethyl acrylamide (HMAAm). The magnetocaloric effects and LCST of the nanocarriers were characterized by using high-resolution electron transmission microscopy, thermogravimetric analyses, and vibrating sample magnetometer. The maximum self-heating temperature of 42.9 °C was achieved by optimizing the Mn(0.2)Zn(0.8)Fe(2)O(4) concentration in the polymer matrix. By adjusting the NIPAAm to HMAAm ratio, the LCST was controlled at an ideal level of 40.1 °C for efficient thermosensitive drug delivery. Magnetothermally responsive drug release of Doxorubicin, an anticancer drug, was significantly enhanced by application of an external AMF on the nanocarriers. The cytotoxicity experimental results in vitro show good biocompatibility and efficient therapeutic effects in cancer treatment.

  17. Magnetocaloric Evidence for FFLO Superconductivity in κ-(BEDT-TTF)2Cu(NCS)2

    Science.gov (United States)

    Fortune, Nathanael; Agosta, Charles; Hannahs, Scott; Park, Ju-Hyun; Gu, Shuyao; Liang, Lucy; Schleuter, John

    We present new magnetocaloric and calorimetric measurements of the high field superconducting state in the layered structure superconductor κ - (BEDT-TTF)2Cu(NCS)2. The strongly field-orientation dependent phase transition between the low field superconducting state and high field superconducting states is first order and is nearly temperature independent, occurring at the Clogston-Chandrasakar paramagnetic limit Hp. Magnetocaloric measurements dT / dH as a function of magnetic field reveal that the system becomes strongly paramagnetic at the cross over from the low field to high field state. At lower temperatures, we are able to resolve small changes at the phase boundary due to the absorption/release of latent heat when increasing/decreasing field, indicating that the high field state is higher entropy than the low field state. These results provide strong new evidence for the formation of paramagnetic spin domains within an inhomogeneous FFLO superconducting state. They also allow us to rule out alternative explanations involving the formation of spin density waves within a homogenous superconducting state. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490 and the State of Florida.

  18. Optimizing Magnetocaloric Properties of Heusler-Type Magnetic Shape Memory Alloys by Tuning Magnetostructural Transformation Parameters

    Science.gov (United States)

    Huang, Lian; Qu, Yuhai; Cong, Daoyong; Sun, Xiaoming; Wang, Yandong

    2017-08-01

    Heusler-type magnetic shape memory alloys show a magnetostructural transformation from the low-magnetization phase to the high-magnetization phase upon the application of external magnetic fields. As a result, these alloys exhibit fascinating multifunctional properties, such as magnetic shape memory effect, magnetocaloric effect, magnetoresistance, and magnetic superelasticity. All these functional properties are intimately related to the coupling of the structural and magnetic transitions. Therefore, deliberate tuning of the magnetostructural transformation parameters is essential for obtaining optimal multifunctional properties. Here, we show that by tuning the magnetostructural transformation parameters, we are able to achieve a variety of novel magnetocaloric properties with different application potentials: (1) large magnetic entropy change of 31.9 J kg-1 K-1 under a magnetic field of 5 T; (2) giant effective magnetic refrigeration capacity (251 J kg-1) with a broad operating temperature window (33 K) under a magnetic field of 5 T; (3) large reversible field-induced entropy change (about 15 J kg-1 K-1) and large reversible effective magnetic refrigeration capacity (77 J kg-1) under a magnetic field of 5 T. The balanced tuning of magnetostructural transformation parameters of magnetic shape memory alloys may provide an instructive reference to the shape memory and magnetic refrigeration communities.

  19. Room temperature magnetocaloric effect in Ni-Mn-In-Cr ferromagnetic shape memory alloy thin films

    Science.gov (United States)

    Akkera, Harish Sharma; Singh, Inderdeep; Kaur, Davinder

    2017-02-01

    The influence of Cr substitution for In on the martensitic phase transformation and magnetocaloric effect (MCE) has been investigated in Ni-Mn-Cr-In ferromagnetic shape memory alloy (FSMA) thin films fabricated by magnetron sputtering. Temperature dependent magnetization (M-T) measurements demonstrated that the martensitic transformation temperatures (TM) monotonously increase with the increase of Cr content due to change in valence electron concentration (e/a) and cell volume. From the study of isothermal magnetization curves (M-H), magnetocaloric effect around the martensitic transformation has been investigated in these FSMA thin films. The magnetic entropy change ∆SM of 7.0 mJ/cm3-K was observed in Ni51.1Mn34.9In9.5Cr4.5 film at 302 K in an applied field of 2 T. Further, the refrigerant capacity (RC) was also calculated for all the films in an applied field of 2 T. These findings indicate that the Cr doped Ni-Mn-In FSMA thin films are potential candidates for room temperature micro-length-scale magnetic refrigeration applications.

  20. Magnetocaloric Properties of Fe-Ni-Cr Nanoparticles for Active Cooling

    Science.gov (United States)

    Chaudhary, V.; Ramanujan, R. V.

    2016-10-01

    Low cost, earth abundant, rare earth free magnetocaloric nanoparticles have attracted an enormous amount of attention for green, energy efficient, active near room temperature thermal management. Hence, we investigated the magnetocaloric properties of transition metal based (Fe70Ni30)100‑xCrx (x = 1, 3, 5, 6 and 7) nanoparticles. The influence of Cr additions on the Curie temperature (TC) was studied. Only 5% of Cr can reduce the TC from ~438 K to 258 K. These alloys exhibit broad entropy v/s temperature curves, which is useful to enhance relative cooling power (RCP). For a field change of 5 T, the RCP for (Fe70Ni30)99Cr1 nanoparticles was found to be 548 J-kg‑1. Tunable TCin broad range, good RCP, low cost, high corrosion resistance and earth abundance make these nanoparticles suitable for low-grade waste heat recovery as well as near room temperature active cooling applications.

  1. Investigation of magnetocaloric effect in La{sub 0.45}Pr{sub 0.25}Ca{sub 0.3}MnO{sub 3} by magnetic, differential scanning calorimetry and thermal analysis

    Energy Technology Data Exchange (ETDEWEB)

    Aparnadevi, M.; Barik, S.K. [Department of Physics, 2 Science Drive 3, National University of Singapore, Lower Kent Ridge Road, Singapore-117 452 (Singapore); Mahendiran, R., E-mail: phyrm@nus.edu.sg [Department of Physics, 2 Science Drive 3, National University of Singapore, Lower Kent Ridge Road, Singapore-117 452 (Singapore)

    2012-10-15

    We investigated magnetocaloric effect in La{sub 0.45}Pr{sub 0.25}Ca{sub 0.3}MnO{sub 3} by direct methods (changes in temperature and latent heat) and indirect method (magnetization isotherms). This compound undergoes a first-order paramagnetic to ferromagnetic transition with T{sub C}=200 K upon cooling. The paramagnetic phase becomes unstable and it transforms into a ferromagnetic phase under the application of magnetic field, which results in a field-induced metamagnetic transition (FIMMT). The FIMMT is accompanied by release of latent heat and temperature of the sample as evidenced from differential scanning calorimetry and thermal analysis experiments. A large magnetic entropy change of {Delta}S{sub m}=-7.2 J kg{sup -1} K{sup -1} at T=212.5 K and refrigeration capacity of 228 J kg{sup -1} are found for a field change of {Delta}H=5 T. It is suggested that destruction of magnetic polarons and growth of ferromagnetic phase accompanied by a lattice volume change with increasing magnetic field is responsible for the large magnetocaloric effect in this compound. - Highlights: Black-Right-Pointing-Pointer We report magnetic entropy change measured by indirect and direct methods in La{sub 0.45}Pr{sub 0.25}Ca{sub 0.3}MnO{sub 3.} Black-Right-Pointing-Pointer Anomalous field-induced induced metamagnetic transition is found in the paramagnetic state. Black-Right-Pointing-Pointer A large reversible magnetic entropy change ({Delta}S{sub m}=7.2 J kg{sup -1} K{sup -1} for {Delta}H=5 T). Black-Right-Pointing-Pointer A large refrigeration capacity (RC=228 J kg{sup -1}). Black-Right-Pointing-Pointer Collapse of magnetic polarons is suggested as possible origin of the large MCE.

  2. The influence of gallium on the magnetocaloric properties of Gd{sub 5}Si{sub 2}Ge{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Aksoy, Seda [Department of Engineering Physics, Faculty of Engineering, University of Ankara, Besevler 06100, Ankara (Turkey); Fachbereich Physik, Experimentalphysik, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany)], E-mail: seda.aksoy@uni-due.de; Yucel, Atila [Department of Physics, Faculty of Science and Letters, University of Mugla, TR-48000 Mugla (Turkey); Elerman, Yalcin [Department of Engineering Physics, Faculty of Engineering, University of Ankara, Besevler 06100, Ankara (Turkey); Krenke, Thorsten [ThyssenKrupp Electrical Steel, F and E Ge, KurtSchumacher Str. 95, D-45881 Gelsenkirchen (Germany); Acet, Mehmet [Fachbereich Physik, Experimentalphysik, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany); Moya, Xavier; Manosa, Lluis [Departament d' Estructura i Constituents de la Materia, Facultat de Fisica Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

    2008-07-28

    Gd{sub 5}Si{sub 2}Ge{sub 2} was alloyed with varying amounts of Ga to study its influence on the giant magnetocaloric effect. Investigations on Gd{sub 5}(Si{sub 2-x}Ge{sub 2-x})Ga{sub 2x} with 2x = 0.03, 0.05 and 0.13 were carried out using X-ray powder diffraction, temperature and magnetic field dependent magnetization measurements, and differential scanning calorimetry. We observe that as the Ga content increases, the temperature stability range of the monoclinic phase narrows, and the orthorhombic structure gains stability. This is expected to be related to the decrease in the (Si/Ge)-(Si/Ge) bond distance in the monoclinic phase. The maximum entropy change for the parent compound at 270 K was found to be 9.8 J kg{sup -1} K{sup -1} in an applied field of 5 T. For 2x = 0.03, this value reduces to 8.5 J kg{sup -1} K{sup -1}, and the temperature corresponding to the maximum entropy change shifts marginally to 278 K. For other 2x values, the maximum entropy change further decreases.

  3. Magnetic and calorimetric studies of magnetocaloric effect in La0.7-xPrxCa0.3MnO3

    Science.gov (United States)

    Barik, S. K.; Aparnadevi, M.; Rebello, A.; Naik, V. B.; Mahendiran, R.

    2012-04-01

    We report magnetocaloric effect in La0.7-xPrxCa0.3MnO3 (x = 0, 0.2, 0.3, and 0.4). All these compounds undergo first-order paramagnetic to ferromagnetic transition upon cooling and show field-induced metamagnetic transition (FIMMT) in the paramagnetic state. The FIMMT is accompanied by a release of latent heat and change in temperature of the sample as evidenced from differential scanning calorimetry and thermal analysis data for x = 0.3. The magnetic entropy decreases (-ΔSm = 8.23, 8.1, 7, and 5.38 Jkg-1 K-1 for a field change of ΔH = 5 T, for x = 0, 0.2, 0.3, and 0.4, respectively) and refrigeration capacity (RC) increases with increasing x (RC = 197, 215, 240, and 259 J/kg for x = 0, 0.2, 0.3, and 0.4, respectively). We suggest that collapse of magnetic polarons in the paramagnetic state and magnetovolume effect are responsible for the observed FIMMT and large -ΔSm values.

  4. Magnetic entropy change plateau in a geometrically frustrated layered system: FeCrAs-like iron-pnictide structure as a magnetocaloric prototype.

    Science.gov (United States)

    Florez, J M; Vargas, P; Garcia, C; Ross, C A

    2013-06-05

    Monte Carlo modeling suggests that the magnetothermal features of the Fe2P-structured FeCrAs-like compound offer a promising route for the design of magnetocaloric materials. The prototype structure is modeled as antiferromagnetically coupled layered Heisenberg systems mimicking the distorted Kagome/triangular stacked architecture of FeCrAs iron-pnictide. The magnetic entropy change ΔSm(T) presents a plateau-like behavior which can be tailored by tuning either the JCr-Fe/JCr-Cr exchange energy ratio or the magnetic field. The plateau is defined by cooperative spin ordering within a ferrimagnetic region which exists between two critical temperatures separating at the lower bound (Tac) a canted antiferromagnetic phase and at the upper bound (Tdc) the thermally disordered phase. The refrigerant capacity and adiabatic change of temperature are A(H)(Tdc - Tac) and A(H)Tp/Cm respectively, with Tac heat, whose critical behavior is related to the T(a,d)(c) values.

  5. Magnetic entropy change plateau in a geometrically frustrated layered system: FeCrAs-like iron-pnictide structure as a magnetocaloric prototype

    Science.gov (United States)

    Florez, J. M.; Vargas, P.; Garcia, C.; Ross, C. A.

    2013-06-01

    Monte Carlo modeling suggests that the magnetothermal features of the Fe2P-structured FeCrAs-like compound offer a promising route for the design of magnetocaloric materials. The prototype structure is modeled as antiferromagnetically coupled layered Heisenberg systems mimicking the distorted Kagome/triangular stacked architecture of FeCrAs iron-pnictide. The magnetic entropy change ΔSm(T) presents a plateau-like behavior which can be tailored by tuning either the JCr-Fe/JCr-Cr exchange energy ratio or the magnetic field. The plateau is defined by cooperative spin ordering within a ferrimagnetic region which exists between two critical temperatures separating at the lower bound ({T}_{{c}}^{a}) a canted antiferromagnetic phase and at the upper bound ({T}_{{c}}^{d}) the thermally disordered phase. The refrigerant capacity and adiabatic change of temperature are A(H)({T}_{{c}}^{d}-{T}_{{c}}^{a}) and A(H)Tp/Cm respectively, with {T}_{{c}}^{a}\\lt {T}_{{p}}\\lt {T}_{{c}}^{d}, A(H) an increasing positive function of the field defining the height of the plateau and Cm the magnetic specific heat, whose critical behavior is related to the {T}_{{c}}^{a,d} values.

  6. Basics and prospective of magnetic Heusler compounds

    Directory of Open Access Journals (Sweden)

    Claudia Felser

    2015-04-01

    Full Text Available Heusler compounds are a remarkable class of materials with more than 1000 members and a wide range of extraordinary multi-functionalities including halfmetallic high-temperature ferri- and ferromagnets, multi-ferroics, shape memory alloys, and tunable topological insulators with a high potential for spintronics, energy technologies, and magneto-caloric applications. The tunability of this class of materials is exceptional and nearly every functionality can be designed. Co2-Heusler compounds show high spin polarization in tunnel junction devices and spin-resolved photoemission. Manganese-rich Heusler compounds attract much interest in the context of spin transfer torque, spin Hall effect, and rare earth free hard magnets. Most Mn2-Heusler compounds crystallize in the inverse structure and are characterized by antiparallel coupling of magnetic moments on Mn atoms; the ferrimagnetic order and the lack of inversion symmetry lead to the emergence of new properties that are absent in ferromagnetic centrosymmetric Heusler structures, such as non-collinear magnetism, topological Hall effect, and skyrmions. Tetragonal Heusler compounds with large magneto crystalline anisotropy can be easily designed by positioning the Fermi energy at the van Hove singularity in one of the spin channels. Here, we give a comprehensive overview and a prospective on the magnetic properties of Heusler materials.

  7. The influence of substitution of Mn by Fe and Co on magnetocaloric effect and magnetoresistance properties of SmMn{sub 2}Ge{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Dincer, I., E-mail: idincer@eng.ankara.edu.tr [Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Besevler, Ankara (Turkey); Elerman, Y. [Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Besevler, Ankara (Turkey)

    2013-01-15

    Magnetocaloric and magnetoresistance properties of SmMn{sub 2-x}Fe{sub x}Ge{sub 2} (x=0.05 and 0.10) and SmMn{sub 2-x}Co{sub x}Ge{sub 2} (x=0.05 and 0.15) compounds have been studied by magnetic and resistance measurements in the temperature range between 30 and 350 K. All compounds exhibit metamagnetic transition from antiferromagnetism to ferromagnetism around the Sm moments ferromagnetic ordering temperature-T{sub Sm} and Mn moments antiferromagnetic ordering temperature-T{sub N1}. The magnetic entropy changes of these compounds are estimated from the Maxwell equation, Maxwell Clausius Clapeyron equation, Landau theory and mean-field theory. The maximum magnetic entropy change values of SmMn{sub 1.90}Fe{sub 0.10}Ge{sub 2} and SmMn{sub 1.85}Co{sub 0.15}Ge{sub 2} compounds are -8.1 J kg{sup -1} K{sup -1} and -5.1 J kg{sup -1} K{sup -1} in a magnetic field change of 5 T, respectively. These compounds show negative magnetoresistance around the magnetic phase transition temperatures. The magnetoresistance value of SmMn{sub 1.95}Fe{sub 0.05}Ge{sub 2} is -23% at T{sub Sm} which is bigger than the magnetoresistance value of SmMn{sub 2}Ge{sub 2} (-15%). - Highlights: Black-Right-Pointing-Pointer Magnetic entropy changes of these compounds are estimated from the Maxwell equation, Maxwell Clausius Clapeyron equation, Landau theory and mean-field theory. Black-Right-Pointing-Pointer Our results exhibit that the Maxwell Clausius Clapeyron equation should be used for compounds that have a first-order phase transition instead of using the Maxwell equation. Black-Right-Pointing-Pointer As a result, in the antiferromagnetic state, the resistance is higher than that in the ferromagnetic state, suggesting that the MR in compounds from the RMn{sub 2}X{sub 2} family may arise on the basis of a spin-valve mechanism.

  8. Magnetocaloric properties of manganese(III) porphyrins bearing 2,6-di-tert-butylphenol groups

    Energy Technology Data Exchange (ETDEWEB)

    Korolev, V.V., E-mail: vvk@isc-ras.ru [G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Akademicheskaya str., 1, Ivanovo 153045 (Russian Federation); Lomova, T.N.; Maslennikova, A.N.; Korolev, D.V. [G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Akademicheskaya str., 1, Ivanovo 153045 (Russian Federation); Shpakovsky, D.B.; Zhang, Jianwei; Milaeva, E.R. [Lomonosov Moscow State University, Department of Medicinal Chemistry and Fine Organic Synthesis, Moscow 119991 (Russian Federation)

    2016-03-01

    Magnetocaloric effect (MCE) and heat capacity during the magnetization of (5,10,15,20-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphynato) manganese (III) chloride (1), (5-(4-hydroxyphenyl)-10,15,20-tris(3,5-di-tert-butyl-4-hydroxyphenyl) porphynato) manganese (III) chloride (2), and (5-(4-palmitoyloxyphenyl)-10,15,20-tris(3,5-di-tert-butyl-4-hydroxyphenyl) porphynato) manganese (III) chloride (3) in their aqueous suspensions were determined by the microcalorimetric method over the temperature range of 278–320 K and in magnetic fields from 0 to 1 T. MCE was positive for all complexes studied, i.e. the magnetic field impression under adiabatic conditions led to an increase in temperature of the complexes suspensions. MCE increased with an increase in the magnetic field induction at all temperatures studied. Dependences of MCE on temperature had weak maxima at 298 K at all magnetic induction values. The disturbance of the intermolecular hydrogen-bonding of hydroxyl groups is one of probable reasons for such dependences type. MCE values increased under the palmitoyl substituent incorporation into one of the phenol groups at all temperatures. The heat capacity of the studied complexes rose slightly with temperature growth. Dependences of the heat capacity on temperature showed that the magnetic component of the heat capacity did not appear due to the presence of the manganese atom acting as a paramagnetic center in complexes 1, 2, and 3. The relation between the complexes structure and their magnetothermal properties was analyzed. It was justified that the changes of magnetothermal properties were caused by electronic substitution effects and, to an even greater degree, by the conditions of intermolecular hydrogen bonds formation in the paramagnetic materials. - Highlights: • The magnetocaloric effect and heat capacity of 3 manganese porphyrin were determined. • Temperature dependences of magnetocaloric effect has been studied. • The relation between the

  9. From first-order magneto-elastic to magneto-structural transition in (Mn,Fe)1.95P0.50Si0.50 compounds

    NARCIS (Netherlands)

    Dung, N. H.; Zhang, L.; Ou, Z. Q.; Brück, E.

    2011-01-01

    We report on structural, magnetic, and magnetocaloric properties of MnxFe1.95−xP0.50Si0.50 (x ≥ 1.10) compounds. With increasing the Mn:Fe ratio, a first-order magneto-elastic transition gradually changes into a first-order magneto-structural transition via a second-order magnetic transition. The st

  10. Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe{sub 11.6}Si{sub 1.4}

    Energy Technology Data Exchange (ETDEWEB)

    Shamba, P.; Morley, N.A.; Reaney, I.M.; Rainforth, W.M. [University of Sheffield, Department of Materials Science and Engineering, Sheffield (United Kingdom); Cespedes, O. [University of Leeds, School of Physics and Astronomy, Leeds (United Kingdom)

    2016-08-15

    LaFe{sub 11.6}Si{sub 1.4} alloy has been synthesized in polycrystalline form using both arc melting and spark plasma sintering (SPS). The phase formation, hysteresis loss and magnetocaloric properties of the LaFe{sub 11.6}Si{sub 1.4} alloys synthesized using the two different techniques are compared. The annealing time required to obtain the 1:13 phase is significantly reduced from 14 days (using the arc melting technique) to 30 min (using the SPS technique). The magnetic entropy change (ΔS{sub M}) for the arc-melted LaFe{sub 11.6}Si{sub 1.4} compound, obtained for a field change of 5 - 0T (decreasing field), was estimated to be 19.6 J kg{sup -1} K{sup -1}. The effective RCP at 5T of the arc-melted LaFe{sub 11.6}Si{sub 1.4} compound was determined to be 360 J kg{sup -1} which corresponds to about 88 % of that observed in Gd. A significant reduction in the hysteretic losses in the SPS LaFe{sub 11.6}Si{sub 1.4} compound was observed. The ΔS{sub M}, obtained for a field change of 5 - 0T (decreasing field), for the SPS LaFe{sub 11.6}Si{sub 1.4} compound decreases to 7.4 J kg{sup -1} K{sup -1}. The T{sub C} also shifts from 186 (arc-melted) to 230 K (SPS) and shifts the order of phase transition from first to second order, respectively. The MCE of the SPS LaFe{sub 11.6}Si{sub 1.4} compound spreads over a larger temperature range with the RCP value at 5T reaching 288 J kg{sup -1} corresponding to about 70 % of that observed in Gd. At low fields, the effective RCP values of the arc-melted and spark plasma-sintered LaFe{sub 11.6}Si{sub 1.4} compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe{sub 11.6}Si{sub 1.4} compounds in low-field magnetic refrigeration applications. (orig.)

  11. Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe11.6Si1.4

    Science.gov (United States)

    Shamba, P.; Morley, N. A.; Cespedes, O.; Reaney, I. M.; Rainforth, W. M.

    2016-08-01

    LaFe11.6Si1.4 alloy has been synthesized in polycrystalline form using both arc melting and spark plasma sintering (SPS). The phase formation, hysteresis loss and magnetocaloric properties of the LaFe11.6Si1.4 alloys synthesized using the two different techniques are compared. The annealing time required to obtain the 1:13 phase is significantly reduced from 14 days (using the arc melting technique) to 30 min (using the SPS technique). The magnetic entropy change (Δ S M) for the arc-melted LaFe11.6Si1.4 compound, obtained for a field change of 5 - 0 T (decreasing field), was estimated to be 19.6 J kg-1 K-1. The effective RCP at 5 T of the arc-melted LaFe11.6Si1.4 compound was determined to be 360 J kg-1 which corresponds to about 88 % of that observed in Gd. A significant reduction in the hysteretic losses in the SPS LaFe11.6Si1.4 compound was observed. The Δ S M, obtained for a field change of 5 - 0 T (decreasing field), for the SPS LaFe11.6Si1.4 compound decreases to 7.4 J kg-1 K-1. The T C also shifts from 186 (arc-melted) to 230 K (SPS) and shifts the order of phase transition from first to second order, respectively. The MCE of the SPS LaFe11.6Si1.4 compound spreads over a larger temperature range with the RCP value at 5 T reaching 288 J kg-1 corresponding to about 70 % of that observed in Gd. At low fields, the effective RCP values of the arc-melted and spark plasma-sintered LaFe11.6Si1.4 compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe11.6Si1.4 compounds in low-field magnetic refrigeration applications.

  12. MnFe1-xTixP0.63Ge0.12Si0.25(x=0,0.01,0.02,0.03)系列化合物的磁热效应%Magnetocaloric Effect of MnFe1 -xTixP0.63Ge0.12Si0.25 (x =0, 0.01, 0.02, 0.03) Compounds

    Institute of Scientific and Technical Information of China (English)

    王冬梅; 松林; 王耀辉; 张伟; 耿遥祥; 特古斯

    2012-01-01

    通过X射线衍射分析(XRD)和振动磁强计(VSM)磁性测量,研究了替代元素Ti替代Fe元素含量的MnFe1-xTixP0.63Ge0.12Si0.25(x=0,0.01,0.02,0.03)系列化合物的物相结构与磁热效应的影响.结果表明:该系列化合物的结构为Fe2P型六角晶系结构,空间群为P62m.主相均为( Mn,Fe)2(P,Ge,Si),并含有少量的第二相(Mn,Fe)3Si相.随着Ti原子替代Fe原子的增加化合物的晶格常数a增大,晶格常数c略有减小,晶胞体积V基本保持不变.随着Ti含量增加居里温度(TC)减小,热滞△Thys的大小改进不太明显.MnFeP0.63Ge0.12Si0.25的TC为305 K,当外磁场变化为0~1.5T时最大磁熵变的绝对值为14.8 J·(kg·K)-1.%The substitution effect of Ti for Fe on the structure and magnetoealoric properties in the MnFe1-xTixP0.63Ge0.12Si0.25(x= 0, 0.01, 0.02, 0.03) compounds was investigated by means of X-ray diffraction (XRD) and magnetic measurements. Analysis showed that the MnFe1-xTixP0.63Ge0.12Si0.25(x= 0, 0. 01, 0. 02, 0. 03) compounds mainly crystallized in the Fe2P-type hexagonal structure, and a small second phase of ( Mn,Fe)3Si was detected in all compounds. It was found that the lattice parameter a increased and the lattice parameter c slightly decreased with increasing x, and the unit cell volume did not obviously change. The Curie temperature decreased with the increase of Ti content and thermal hysteresis did not obviously change. Curie temperature of MnFeP0.63Ge0.12 Si0.25 was 305 K and the maximum magnetic entropy was 14. 8 J·( kg·K)-1 for a field change from 0 to 1.5 T.

  13. Electrical, magnetic and magnetocaloric properties of polycrystalline Pr0.63A0.07Sr0.3MnO3 (A=Pr, Sm and Bi)

    Science.gov (United States)

    Elghoul, A.; Krichene, A.; Boujelben, W.

    2016-11-01

    We studied the effects of the partial substitution (10%) of praseodymium by samarium and bismuth, on the structural, magnetic, magnetocaloric and electrical properties of the Pr0.63A0.07Sr0.3MnO3 (A=Pr, Sm and Bi) manganites prepared using the solid state reaction. Refinement of the X-ray diffraction patterns shows that all our samples are single phase and crystallize in the orthorhombic structure with Pnma space group. Magnetic studies indicate that all the samples exhibit a ferromagnetic-paramagnetic transition with increasing temperature. Curie temperature TC decreases by substitution. M(H) curves indicate the presence of some antiferromagnetic domains in the substituted samples testifying the phase-separated nature of these samples. The magnetic entropy curves -ΔS(T) show a maximum in vicinity of TC. Important values of maximum of -ΔS are recorded for our compounds. For the parent compound, we found 4.59 J/kg K for an applied magnetic field of 2 T at TC=266 K which raises the possibility of using this compound as a magnetic refrigerant. The temperature dependence of the electrical resistivity ρ(T) indicates that all compounds exhibit a metal-insulator transition with increasing temperature. Electrical study suggests the presence of a correlation between electrical and magnetic properties.

  14. Modelling and comparison studies of packed screen regenerators for active magnetocaloric refrigeration

    DEFF Research Database (Denmark)

    Lei, Tian; Engelbrecht, Kurt; Nielsen, K. K.

    2011-01-01

    such as relatively large pressure drop and almost fixed porosity make loss reductions and further optimization challenging. This paper proposes and focuses on packed screen regenerators, which may exhibit lower pressure drop and equivalent heat transfer performance to packed sphere regenerators. A 1D AMR model......In active magnetic regeneration (AMR) systems, not only the magnetocaloric properties of materials, but also the regenerator geometry plays an important role in the system performance. Packed sphere regenerators are often employed in existing prototypes, however, the characteristics...... is improved and applied to simulate the regenerators. The performance of the new regenerators is studied and compared with that of the packed sphere regenerators. Possible fabrication methods of the packed screen regenerators are also discussed....

  15. Large reversible magnetocaloric effect in HoMn2O5

    Institute of Scientific and Technical Information of China (English)

    Ge Heng; Zhang Xiang-Qun; Ke Ya-Jiao; Jin Jin-Ling; Liao Zhi-Xin; Cheng Zhao-Hua

    2013-01-01

    Magnetocaloric effect (MCE) in polycrystalline HoMn2O5 was investigated by isothermal magnetization curves from 2 K to 50 K.A relatively large magnetic entropy change,ASM =7.8 J/(kg.K),was achieved with the magnetic field up to 70 kOe (1 Oe =79.5775 A·m-1).The magnetic entropy change is reversible in the whole range of temperature.The contributions of elastic and magnetoelastic energy to the changing of the magnetic entropy are discussed in terms of the Landau theory.The reversibility of MCE with maximal refrigerant capacity Rc =216.7 J/kg makes polycrystalline HoMn2O5 promising as a magnetic refrigerant.

  16. The thermomechanical stability of Fe-based amorphous ribbons exhibiting magnetocaloric effect

    Science.gov (United States)

    Shishkin, D. A.; Volegov, A. S.; Baranov, N. V.

    2016-12-01

    The Fe-Nb-B and Fe71.5Cr2Si13.5B9Nb3Cu1 alloys have been prepared by rapid quenching from the melt, and the magnetic properties of alloys in the vicinity of the magnetic ordering have been studied before and after thermomechanical processing. It has been shown that change in the Fe:Nb:B ratio allows tuning the magnetic ordering temperature and the position of maximum of the isothermal magnetic entropy change | { - Δ Sm } | from 256 to 333 K. The thermomechanical treatment of alloys at 623 K under applied tensile stresses observed does not affect remarkably the magnetocaloric properties of alloys. The combination of high thermomechanical stability, good electrical, anti-corrosive and thermomagnetic properties makes these alloys promising for use in magnetic refrigeration devices.

  17. Achieving tailorable magneto-caloric effect in the Gd-Co binary amorphous alloys

    Directory of Open Access Journals (Sweden)

    C. Wu

    2016-03-01

    Full Text Available Tailorable magnetic properties and magneto-caloric effect were achieved in the Gd-Co binary amorphous alloys. It was found that the Curie temperature (Tc of the GdxCo100-x (x=50, 53, 56, 58, 60 metallic glasses can be tuned by changing the concentration of Gd as Tc =708.8-8.83x, and the mechanism involved was investigated. On the other hand, a linear correlation between the peak value of magnetic entropy change (-Δ Smpeak and Tc-2/3 is found in the amorphous alloys with a linear correlation coefficients of above 0.992. Therefore, the -ΔSmpeak of the Gd-Co binary amorphous alloys under different magnetic fields can be easily tailored by adjusting the composition of the alloy.

  18. Magnetocaloric Effect of Alloys Gd(Al1-xCox)2

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The magnetocaloric effect in alloys Gd(Al1-xCox)2 with x=0, 0.05, and 0.10 were investigated using X-ray diffraction (XRD) and magnetization measurements.It was found that three alloys crystallized in a single phase with MgCu2-type structure.The lattice parameter and Curie temperature decreased with increasing Co content, whereas the magnetic-entropy change increased.With a magnetic-field change of 2 T, the maximum of the magnetic-entropy change reached 4.6 J·kg-1·K-1 near Curie temperature at approximately 95 K in the alloy GdAl1.8Co0.2, which appeared to be an alternative candidate for active magnetic refrigerants working in the temperature range centered at 100 K.

  19. The giant magnetocaloric effect in Gd5Si2Ge2 with low purity gadolinium

    Institute of Scientific and Technical Information of China (English)

    ZHANG Tiebang; CHEN Yungui; FU Hao; TENG Baohua; TANG Yongbai; TU Mingjing

    2005-01-01

    The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Powder XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1 h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J·kg-1·K-1 under a magnetic field change of 0―5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment.

  20. Large room-temperature rotating magnetocaloric effect in NdCo4Al polycrystalline alloy

    Science.gov (United States)

    Hu, Y.; Hu, Q. B.; Wang, C. C.; Cao, Q. Q.; Gao, W. L.; Wang, D. H.; Du, Y. W.

    2017-01-01

    The magnetic refrigeration based on rotating magnetocaloric effect (MCE) is promising to build a simplified magnetic cooling system. Until now, most magnetic refrigerants for rotating MCE are single crystal and work at low temperature, which hinder the development of this refrigeration technology. In present paper, we report a large room-temperature rotating MCE in a magnetic-field-aligned NdCo4Al polycrystalline alloy. A large rotating magnetic entropy change of 1.3 J kg-1 K-1 under 10 kOe and a broad operating temperature window of 52 K are achieved. The origin of large rotating MCE in NdCo4Al polycrystalline alloy and its advantages for rotating magnetic refrigeration are discussed.

  1. Switching of the magnetocaloric effect of Mn(II) glycolate by water molecules.

    Science.gov (United States)

    Chen, Yan-Cong; Guo, Fu-Sheng; Liu, Jun-Liang; Leng, Ji-Dong; Vrábel, Peter; Orendáč, Martin; Prokleška, Jan; Sechovský, Vladimír; Tong, Ming-Liang

    2014-03-10

    The transformation of Mn(II) glycolates (glc) between the three-dimensional coordination polymer [Mn(glc)2]n (1) and discrete mononuclear phase [Mn(glc)2 (H2O)2] (2) can be reversibly switched by water molecules, which dramatically change the magnetocaloric effect (MCE) of Mn(II) glycolates from the maximum of 6.9 J kg(-1)  K(-1) in 1 to 60.3 J kg(-1)  K(-1) in 2. This case example reveals that the effect of magnetic coupling on MCE plays a dominant role over that of other factors such as magnetic density for 3d-type magnetic refrigerants.

  2. Multifunctional Hydrogels with Temperature, Ion, and Magnetocaloric Stimuli-Responsive Performances.

    Science.gov (United States)

    Wang, Xiao-Qiao; Yang, Shengyang; Wang, Cai-Feng; Chen, Li; Chen, Su

    2016-05-01

    In this work, multifunctional hydrogels with vivid color change and shrinking-swelling response to temperature, ion strength, and alternating magnetic field are fabricated via magnetic assembly. The hydrogels show gradual shift colors from yellowish green to green, cyan, blue, purple, and even reddish violet in response to temperature or ion strength. In the response process, the whole color modulation process is fully reversible and transferable along with a relative short response time. Especially, the magnetism and porous structure of the hybrid hydrogel enable it to be a potential carrier for hydrophobic molecules. Taking advantage of the magnetocaloric responsiveness, the dyed oil loaded hydrogel exhibits a controllable release behavior in each reversible shrinking-swelling cycle under an alternating magnetic field. This multi-responsive hydrogel can hold promise for practical engineering applications, including sensors, displays, and controlled release.

  3. Giant magnetocaloric effect, magnetization plateaux and jumps of the regular Ising polyhedra

    Energy Technology Data Exchange (ETDEWEB)

    Strečka, Jozef, E-mail: jozef.strecka@upjs.sk [Institute of Physics, Faculty of Science, P.J. Šafárik University, Park Angelinum 9, 040 01 Košice (Slovakia); Karľová, Katarína [Institute of Physics, Faculty of Science, P.J. Šafárik University, Park Angelinum 9, 040 01 Košice (Slovakia); Madaras, Tomáš [Institute of Mathematics, Faculty of Science, P.J. Šafárik University, Jesenná 5, 040 01 Košice (Slovakia)

    2015-06-15

    Magnetization process and adiabatic demagnetization of the antiferromagnetic Ising spin clusters with the shape of regular polyhedra (Platonic solids) are exactly examined within the framework of a simple graph-theoretical approach. While the Ising cube as the only unfrustrated (bipartite) spin cluster shows just one trivial plateau at zero magnetization, the other regular Ising polyhedra (tetrahedron, octahedron, icosahedron and dodecahedron) additionally display either one or two intermediate plateaux at fractional values of the saturation magnetization. The nature of highly degenerate ground states emergent at intermediate plateaux owing to a geometric frustration is clarified. It is evidenced that the regular Ising polyhedra exhibit a giant magnetocaloric effect in a vicinity of magnetization jumps, whereas the Ising octahedron and dodecahedron belong to the most prominent geometrically frustrated spin clusters that enable an efficient low-temperature refrigeration by the process of adiabatic demagnetization.

  4. Phase structure and magnetocaloric effect of (Tb1-xDyx)Co2 alloys

    Institute of Scientific and Technical Information of China (English)

    ZHUANG Yinghong; CHEN Xiang; ZHOU Kaiwen; LI Kefeng; MA Chunhua

    2008-01-01

    Phase structure and magnetocaloric effect of (Tb1-xDyx)Co2 alloys with x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were investigated using X-ray diffraction analysis, differential thermal analysis, and magnetization measurement. The samples were single phase with cubic MgCu2- type structure; with the increase of Dy content, Tc decreased from 240 K (TbCo2) to 130 K (DyCo2), and the maximum magnetic entropy change |ΔSM,max| increased from 3.133 to 8.176 J/kg-K under low magnetic field of 0-2 T. The Arrott plot and the change of |ΔSM,max| showed that magnetic phase transition from second order to first order occurred with the increase of Dy content between x=0.6 and 0.8.

  5. Magnetic, magnetocaloric and magnetoresistive properties of cubic Laves phase HoAl2 single crystal.

    Science.gov (United States)

    Patra, M; Majumdar, S; Giri, S; Xiao, Y; Chatterji, T

    2014-01-29

    We report the magnetization (M) and magnetoresistance (MR) results of HoAl2 single crystals oriented along the ⟨100⟩ and ⟨110⟩ directions. Although HoAl2 has cubic Laves phase structure, a large anisotropy is observed in M and MR below the Curie temperature (TC). A satisfactory correlation between magnetic entropy change (ΔSM) and MR could be established along ⟨110⟩ and also ⟨100⟩, except for the temperature (T) region around which spin reorientation takes place. Large inverse magnetocaloric effect is observed at low T, which is associated with the spin reorientation process in the ⟨100⟩ direction. A theoretical model based on the Landau theory of phase transition can describe the T-variation of -ΔSM for T > TC.

  6. Magnetocaloric cycle with six stages: Possible application of graphene at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Reis, M. S., E-mail: marior@if.uff.br [Instituto de Física, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza s/n, 24210-346 Niterói, RJ (Brazil)

    2015-09-07

    The present work proposes a thermodynamic hexacycle based on the magnetocaloric oscillations of graphene, which has either a positive or negative adiabatic temperature change depending on the final value of the magnetic field change. For instance, for graphenes at 25 K, an applied field of 2.06 T/1.87 T promotes a temperature change of ca. −25 K/+3 K. The hexacycle is based on the Brayton cycle and instead of the usual four steps, it has six stages, taking advantage of the extra cooling provided by the inverse adiabatic temperature change. This proposal opens doors for magnetic cooling applications at low temperatures.

  7. Magnetization Process and Magnetocaloric Effect of the Spin-1/2 XXZ Heisenberg Cuboctahedron

    Science.gov (United States)

    Karľová, Katarína; Strečka, Jozef

    2016-10-01

    Magnetic properties of the spin-1/2 XXZ Heisenberg cuboctahedron are examined using exact numerical diagonalization depending on a relative strength of the exchange anisotropy. While the Ising cuboctahedron exhibits in a low-temperature magnetization curve only one-third magnetization plateau, the XXZ Heisenberg cuboctahedron displays another four intermediate plateaux at zero, one-sixth, one-half and two-thirds of the saturation magnetization. The novel magnetization plateaux generally extend over a wider range of magnetic fields with increasing of a quantum (xy) part of the XXZ exchange interaction. It is shown that the XXZ Heisenberg cuboctahedron exhibits in the vicinity of all magnetization jumps anomalous thermodynamic behavior accompanied by an enhanced magnetocaloric effect.

  8. Large magnetocaloric effects in magnetic intermetallics: First-principles and Monte Carlo studies

    Directory of Open Access Journals (Sweden)

    Entel Peter

    2015-01-01

    Full Text Available We have performed ab initio electronic structure calculations and Monte Carlo simulations of frustrated ferroic materials where complex magnetic configurations and chemical disorder lead to rich phase diagrams. With lowering of temperature, we find a ferromagnetic phase which transforms to an antiferromagnetic phase at the magnetostructural (martensitic phase transition and to a cluster spin glass at still lower temperatures. The Heusler alloys Ni-(Co-Mn-(Cr-(Ga, Al, In, Sn, Sb are of particular interest because of their large inverse magnetocaloric effect associated with the magnetostructural transition and the influence of Co/Cr doping. Besides spin glass features, strain glass behavior has been observed in Ni-Co-Mn-In. The numerical simulations allow a complete characterization of the frustrated ferroic materials including the Fe-Rh-Pd alloys.

  9. Octanuclear [Ni(II)₄Ln(III)₄] complexes. Synthesis, crystal structures and magnetocaloric properties.

    Science.gov (United States)

    Pasatoiu, Traian D; Ghirri, Alberto; Madalan, Augustin M; Affronte, Marco; Andruh, Marius

    2014-06-28

    Two original heterooctanuclear [Ni(II)4Ln(III)4] complexes (Ln(III) = Sm(III), Gd(III)) have been obtained starting from the [Ni(II)(valpn)(H2O)2] mononuclear precursor [H2valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)] and the corresponding lanthanide nitrates, in the presence of azide anions, through slow capture of atmospheric CO2. Three weak and competitive exchange interactions, J(GdGd), J(GdNi), J(NiNi), make the ground state of this magnetic system degenerate at cryogenic temperature and zero field. This, along with the high spin of Gd(III), lead to a significant magnetocaloric effect spread in the temperature range 1 to 20 K (ΔSm[0-7 T, 3.5 K] = 19 J kg(-1) K(-1)).

  10. Acoustic Detection of the Magnetocaloric Effect in Gadolinium Thin Films: Influence of the Substrate

    Science.gov (United States)

    Nogal, U.; Mansanares, A. M.; Gandra, F. C. G.; Soffner, M. E.; Guimarães, A. O.; da Silva, E. C.; Vargas, H.; Marín, E.; Calderón, A.

    2015-06-01

    The magnetocaloric effect (temperature change) in gadolinium thin films is investigated as a function of the external magnetic field using the magnetoacoustic technique. The measured signal evidences the magnetic anisotropy of the sample, and it is in good agreement with results obtained from magnetization measurements. The thermal coupling of the film with the substrate invalidates the adiabatic condition usually achieved when measuring bulk magnetic samples using the magnetoacoustic technique. The influence of the substrate on the temperature of the film is therefore investigated using a simple model for the heat diffusion within the sample. The temperature distribution is calculated as a function of the thermal parameters of the substrate and the results compared to the magnetoacoustic measurements.

  11. Universally diverging Grüneisen parameter and the magnetocaloric effect close to quantum critical points.

    Science.gov (United States)

    Zhu, Lijun; Garst, Markus; Rosch, Achim; Si, Qimiao

    2003-08-08

    At a generic quantum critical point, the thermal expansion alpha is more singular than the specific heat c(p). Consequently, the "Grüneisen ratio," Gamma=alpha/c(p), diverges. When scaling applies, Gamma approximately T(-1/(nu z)) at the critical pressure p=p(c), providing a means to measure the scaling dimension of the most relevant operator that pressure couples to; in the alternative limit T-->0 and p not equal p(c), Gamma approximately 1/(p-p(c)) with a prefactor that is, up to the molar volume, a simple universal combination of critical exponents. For a magnetic-field driven transition, similar relations hold for the magnetocaloric effect (1/T) partial differential T/ partial differential H|(S). Finally, we determine the corrections to scaling in a class of metallic quantum critical points.

  12. Estimation of magnetocaloric properties by using Monte Carlo method for AMRR cycle

    Science.gov (United States)

    Arai, R.; Tamura, R.; Fukuda, H.; Li, J.; Saito, A. T.; Kaji, S.; Nakagome, H.; Numazawa, T.

    2015-12-01

    In order to achieve a wide refrigerating temperature range in magnetic refrigeration, it is effective to layer multiple materials with different Curie temperatures. It is crucial to have a detailed understanding of physical properties of materials to optimize the material selection and the layered structure. In the present study, we discuss methods for estimating a change in physical properties, particularly the Curie temperature when some of the Gd atoms are substituted for non-magnetic elements for material design, based on Gd as a ferromagnetic material which is a typical magnetocaloric material. For this purpose, whilst making calculations using the S=7/2 Ising model and the Monte Carlo method, we made a specific heat measurement and a magnetization measurement of Gd-R alloy (R = Y, Zr) to compare experimental values and calculated ones. The results showed that the magnetic entropy change, specific heat, and Curie temperature can be estimated with good accuracy using the Monte Carlo method.

  13. Magnetocaloric and magnetic properties of La2NiMnO6 double perovskite

    Science.gov (United States)

    Masrour, R.; Jabar, A.

    2016-08-01

    The magnetic effect and the magnetocaloric effect in La2NiMnO6(LNMO) double perovskite are studied using the Monte Carlo simulations. The magnetizations, specific heat values, and magnetic entropies are obtained for different exchange interactions and external magnetic fields. The adiabatic temperature is obtained. The transition temperature is deduced. The relative cooling power is established with a fixed value of exchange interaction. According to the master curve behaviors for the temperature dependence of predicted for different maximum fields, in this work it is confirmed that the paramagnetic-ferromagnetic phase transition observed for our sample is of a second order. The near room-temperature interaction and the superexchange interaction between Ni and Mn are shown to be due to the ferromagnetism of LNMO.

  14. Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

    Energy Technology Data Exchange (ETDEWEB)

    Nicholson, Don M [ORNL; Odbadrakh, Khorgolkhuu [ORNL; Rios, Orlando [ORNL; Hodges, Jason P [ORNL; Ludtka, Gerard Michael [ORNL; Porter, Wallace D [ORNL; Sefat, Athena Safa [ORNL; Rusanu, Aurelian [ORNL; Evans III, Boyd Mccutchen [ORNL

    2012-01-01

    Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system have been explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering (LSMS) method to explore the magnetic states responsible for the magnet-caloric effect in this material. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy were investigated using differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). Neutron scattering experiments were performed to observe the structural and magnetic phase transformations at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on alloys of Ni-Mn-Ga and Ni-Mn-Ga-Cu-Fe. Data from the observations are discussed in comparison with the computational studies.

  15. Large rotating magnetocaloric effect in ErAlO3 single crystal

    Directory of Open Access Journals (Sweden)

    X. Q. Zhang

    2017-05-01

    Full Text Available Magnetic and magnetocaloric properties of ErAlO3 single crystal were investigated. Magnetization of ErAlO3 shows obvious anisotropy when magnetic field is applied along the a, b and c axes, which leads to large anisotropic magnetic entropy change. In particular, large rotating field entropy change from the b to c axis within the bc plane is obtained and reaches 9.7 J/kg K at 14 K in a field of 5 T. This suggests the possibility of using ErAlO3 single crystal for magnetic refrigerators by rotating its magnetization vector rather than moving it in and out of the magnet.

  16. Tailored inter and intra layer exchange coupled superlattices for optimized magnetocaloric effect

    Science.gov (United States)

    Mukherjee, Tathagata; Michalski, S.; Skomski, R.; Sellmyer, D. J.; Binek, Ch.

    2012-02-01

    We explore Magnetocaloric (MC) properties of Fe/Cr superlattices with tailored inter- and intra-layer interaction using simple 3d metals. Our multilayers are fabricated by pulsed-laser deposition with emphasis on maximizing magnetic entropy changes near room temperature. NanostructuringootnotetextT. Mukherjee, S. Sahoo, R. Skomski, D. J. Sellmyer, and Ch. Binek, Phys. Rev. B 79, 144406 (2009). allows tailoring ferromagnetic and antiferromagnetic coupling. This in concert with finite size scaling of the ferromagnetic Fe films has the potential to lead to optimized MC materials. Thermodynamic and MC properties of such Fe/Cr superlattices are studied with the help of SQUID magnetometry. Entropy changes are deduced via the Maxwell relation in single phase regions, X-ray diffraction and X-ray reflectivity are used to correlate structural data with the magnetic properties.

  17. Magnetization and Magnetocaloric Effect in Sol-Gel Derived Nanocrystalline Copper-Zinc Ferrite.

    Science.gov (United States)

    Anwar, M S; Ahmed, Faheem; Koo, Bon Heun

    2015-02-01

    We report the sol-gel synthesis and magnetocaloric effect in nanocrystalline copper-zinc ferrite (Cu0.5Zn0.5Fe2O4). The synthesized powder was characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and magnetization measurements. The XRD results confirm the formation of single phase spinel structure. The average particle size was found to be ~58 nm. FE-SEM results suggested that the nanoparticles are agglomerated and spherical in shape. Magnetization measurement reveals that Cu0.5Zn0.5Fe2O4 nanoparticles exhibit transition temperature (Tc) above room temperature. The maximum magnetic entropy change (ΔSM)max shows interesting behaviour and was found to vary with the applied magnetic field. This nanopowder can be considered as potential material for magnetic refrigeration above room temperature.

  18. Giant magnetocaloric effect in Gd5(Si2Ge2 alloy with low purity Gd

    Directory of Open Access Journals (Sweden)

    Cleber Santiago Alves

    2004-12-01

    Full Text Available Gd5(Ge1-xSi x, x < 4 based alloys are potential candidates for magnetic refrigeration in the range ~20 - ~290 K. However, one of the greatest obstacles for the use of that technology in large scale is the utilization of high pure Gd metal (99.99 wt. (% to produce the GdGeSi alloys, since the impurity elements decrease the intensity of the magnetocaloric effect (EMC¹. In this work, we prove that annealing of the Gd5Ge2Si2 can promote remarkable values for the EMC in comparison to those obtained for the alloy with high pure Gd. Also, the as cast alloy and the annealed alloy are not monophasic, but have at least two crystalline phases in their microstructure. Results for X-ray analysis, optical and electronic microscopy and magnetization measurements are reported.

  19. Amorphization Induced High Magneto-Caloric Effect of Gd55A120Ni25 Ternary Alloy

    Institute of Scientific and Technical Information of China (English)

    DING Ding; XIA Lei; YU Zhong-Hua; DONG Yuan-Da

    2008-01-01

    We report the amorphization induced high magneto-caloric effect (MCE) of recently developed Gd55Al15Ni30 bulk metallic glass (BMG). The magnetic properties of the Gd55Al15Ni30 BMG are investigated in comparison with that of its crystalline counterpart. It is found that amorphization can increase the saturation magnetization and decrease the hysteresis of Gd55Al15Ni30 alloys, which indicate the possible enhancement of MCE. The magnetic entropy changes and the refrigerant capacity of the BMG as well as the crystalline samples is calculated directly from isothermal magnetic measurements. The results show the amorphization induced high MCE of the alloy and the excellent refrigerant efficiency of Gd55A115Ni30 bulk metallic glass.

  20. Fluctuating local moments, itinerant electrons, and the magnetocaloric effect: Compositional hypersensitivity of FeRh

    Science.gov (United States)

    Staunton, J. B.; Banerjee, R.; Dias, M. dos Santos; Deak, A.; Szunyogh, L.

    2014-02-01

    We describe an ab initio disordered local moment theory for materials with quenched static compositional disorder traversing first-order magnetic phase transitions. It accounts quantitatively for metamagnetic changes and the magnetocaloric effect. For perfect stoichiometric B2-ordered FeRh, we calculate the transition temperature of the ferromagnetic-antiferromagnetic transition to be Tt= 495 K and a maximum isothermal entropy change in 2 T of |ΔS|=21.1 J K-1 kg-1. A large (40%) component of |ΔS| is electronic. The transition results from a fine balance of competing electronic effects which is disturbed by small compositional changes; e.g., swapping just 2% Fe of "defects" onto the Rh sublattice makes Tt drop by 290 K. This hypersensitivity explains the narrow compositional range of the transition and impurity doping effects.

  1. Atomic ordering effect in Ni{sub 50}Mn{sub 37}Sn{sub 13} magnetocaloric ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Wu Dianzhen; Xue Sichuang [Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Frenzel, Jan; Eggeler, Gunther [Institute of Materials, Ruhr University Bochum, Bochum 44801 (Germany); Zhai Qijie [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Zheng Hongxing, E-mail: hxzheng@shu.edu.cn [Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China)

    2012-02-01

    Highlights: Black-Right-Pointing-Pointer High-performance Ni-Mn-Sn magnetocaloric materials are produced. Black-Right-Pointing-Pointer Ni{sub 50}Mn{sub 37}Sn{sub 13} demonstrates great potential for magnetic refrigeration applications. Black-Right-Pointing-Pointer A strong atomic order dependence is revealed in Ni{sub 50}Mn{sub 37}Sn{sub 13} materials. - Abstract: High-performance Ni{sub 50}Mn{sub 37}Sn{sub 13} magnetocaloric materials are produced using melt spinning technique in the present work and the atomic order dependence of phase transition behaviors and magnetic properties is established. The effective refrigeration capacity of the melt-spun ribbon annealed at 1273 K for 15 min reaches 95.27 J/kg for a magnetic field change of 18 kOe, demonstrating great potential for magnetic refrigeration applications near ambient temperature.

  2. Structural, magnetic and magnetocaloric properties of Heusler alloys Ni50Mn38Sb12 with boron addition

    DEFF Research Database (Denmark)

    Van Nong, Ngo; Tai, N.T.; Huy, N.T.;

    2011-01-01

    We report on the structural, magnetic and magnetocaloric properties of the Ni50Mn38Sb12Bx alloys in term of boron addition with x=1, 3 and 5. We have found that both the paramagnetic–ferromagnetic austenitic transition (TC) and the ferromagnetic–antiferromagnetic martensitic transition (TM......) are sensitively influenced by the boron addition: TC tends to increase, while TM decreases with increasing boron concentration. Temperature dependent X-ray diffraction in the range of 200–500K clearly shows an evolution of the structural transformation from orthorhombic to cubic structure phase transition...... on heating for the x=1 and 3 samples. Strikingly, the addition of boron atoms into the lattice favours the ferromagnetic ordering relatively to the antiferromagnetic arrangement below TM. This consequently affects on the magneto-structural transition as well as on the size of magnetocaloric effect....

  3. Magnetic Grüneisen parameter and magnetocaloric properties of a coupled spin–electron double-tetrahedral chain

    Energy Technology Data Exchange (ETDEWEB)

    Gálisová, Lucia, E-mail: galisova.lucia@gmail.com [Department of Applied Mathematics and Informatics, Faculty of Mechanical Engineering, Technical University, Letná 9, 042 00 Košice (Slovakia); Strečka, Jozef, E-mail: jozef.strecka@upjs.sk [Department of Theoretical Physics and Astrophysics, Faculty of Science, P.J. Šafárik University, Park Angelinum 9, 040 01 Košice (Slovakia)

    2015-10-16

    Magnetocaloric effect in a double-tetrahedral chain, in which nodal lattice sites occupied by the localized Ising spins regularly alternate with three equivalent lattice sites available for mobile electrons, is exactly investigated by considering the one-third electron filling and the ferromagnetic Ising exchange interaction between the mobile electrons and their nearest Ising neighbours. The entropy and the magnetic Grüneisen parameter, which closely relate to the magnetocaloric effect, are exactly calculated in order to investigate the relation between the ground-state degeneracy and the cooling efficiency of the hybrid spin–electron system during the adiabatic demagnetization. - Highlights: • A double-tetrahedral chain of mobile electrons and localized Ising spins is studied. • Magnetic Grüneisen parameter for the system is exactly derived. • Macroscopically degenerate phases FRU and FM constitute the ground state. • MCE is three times higher nearby FRU–FM transition than in FRU phase at small fields.

  4. Improved magneto-caloric effect of the Gd50Co50 metallic glass by minor Si addition

    Science.gov (United States)

    Tang, B. Z.; Yu, P.; Ding, D.; Wu, C.; Xia, L.

    2017-02-01

    In the present work, we studied the effect of minor Si addition on the magneto-caloric effect (MCE) of the Gd50Co50 metallic glass. The Gd50Co50-xSix (x=2, 5) as-spun ribbons show typical amorphous characteristics in structure and magneto-caloric behaviors. The peak values for the magnetic entropy change (-ΔSmpeak) of the Gd50Co50-xSix (x=0, 2, 5) metallic glasses increase significantly with the addition of Si. The mechanism for the enhanced MCE by minor addition of Si was investigated by revealing the relationship between -ΔSmpeak and the Curie temperature in the Gd-Co-based amorphous ribbons.

  5. A Preisach approach to modeling partial phase transitions in the first order magnetocaloric material MnFe(P,As)

    DEFF Research Database (Denmark)

    von Moos, Lars; Bahl, C.R.H.; Nielsen, Kaspar Kirstein;

    2014-01-01

    . Such materials are potential candidates for application in magnetic refrigeration devices. However, the first order materials often have adverse properties such as hysteresis, making actual performance troublesome to quantify, a subject not thoroughly studied within this field.Here we investigate the behavior...... of MnFe(P,As) under partial phase transitions, which is similar to what materials experience in actual magnetic refrigeration devices. Partial phase transition curves, in the absence of a magnetic field, are measured using calorimetry and the experimental results are compared to simulations......Magnetic refrigeration is an emerging technology that could provide energy efficient and environmentally friendly cooling. Magnetocaloric materials in which a structural phase transition is found concurrently with the magnetic phase transition are often termed first order magnetocaloric materials...

  6. 不同工艺和原料对Mn1.2Fe0.8P0.48Si0.52化合物磁热效应的影响%Influence of Different Preparation Techniques and Raw Materials on Magnetocaloric Effect in Mn1.2Fe0.8P0.48Si0.52 Compound

    Institute of Scientific and Technical Information of China (English)

    耿遥祥; 特古斯; 毕力格; 王伟; 哈斯朝鲁; 松林

    2011-01-01

    用不同的工艺和原料制备了3个名义成分相同的Mn1.2Fe0.8P0.48Si0.52化合物.X射线衍射结果表明,3个化合物均为Fe2P型六角结构(空间群为P-62m),并且存在少量的(Fe,Mn)3Si相.通过磁性测量发现,3个样品的居里温度有所不同,但是都在室温附近(270~290K).以Fe2P为原料制备的化合物具有较大的磁熵变,在1.5 T的磁场变化下其最大磁熵变为13.6 J·(kg·K)-1.以行星样品球磨机制备的化合物具有较小的热滞,最小热滞为6.7 K.这些表明不同的制备工艺和原料对化合物的居里温度、热滞和磁熵变都具有一定的影响.同时低成本的原料、简单的制备工艺、较小的热滞和较大的磁熵变使得Mn1.2Fe0.8P0.48Si0.52化合物成为一种理想的室温磁致冷候选材料.%The three samples of Mn1.2Fe0.8 P0.48Si0.52 were prepared by different preparation techniques and raw materials. The powder X-ray diffraction patterns showed that all samples crystallized in the hexagonal Fe2P-type structure (space group P-62m), with minor (Fe, Mn)3Si as a second phase. The magnetic measurements showed that the Curie temperatures of three samples were different, but they were near room temperature. The samples with Fe2 P as raw materials exhibited large magnetic entropy change, and the maximum magnetic entropy change of samples was about 13.6 J·(kg·K)-1 in a field change of 1.5 T. The samples prepared by plate high energy ball milling possessed smaller thermal hysteresis, and the minimum thermal hysteresis was about 6.7 K. The different preparation techniques and raw materials had certain influence on the Curie temperature, thermal hysteresis and magnetic entropy change of Mn1.2Fe0.8P0.48 Si0.52 compound. The low-cost raw materials, simple preparation techniques, smaller thermal hysteresis and large magnetic entropy change made compound Mn1.2 Fe0.8 P0.48 Si0.52 an excellent candidate material for room-temperature magnetic refrigeration applications.

  7. Magnetocaloric properties of LaFe13−x−yCoxSiy and commercial grade Gd

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Katter, M.

    2010-01-01

    The magnetocaloric properties of three samples of LaFe13−x−yCoxSiy have been measured and compared to measurements of commercial grade Gd. The samples have (x=0.86, y=1.08), (x=0.94, y=1.01) and (x=0.97, y=1.07) yielding Curie temperatures in the range 276–288 K. The magnetization, specific heat...

  8. Co and In Doped Ni-Mn-Ga Magnetic Shape Memory Alloys: A Thorough Structural, Magnetic and Magnetocaloric Study

    Directory of Open Access Journals (Sweden)

    Simone Fabbrici

    2014-04-01

    Full Text Available In Ni-Mn-Ga ferromagnetic shape memory alloys, Co-doping plays a major role in determining a peculiar phase diagram where, besides a change in the critical temperatures, a change of number, order and nature of phase transitions (e.g., from ferromagnetic to paramagnetic or from paramagnetic to ferromagnetic, on heating can be obtained, together with a change in the giant magnetocaloric effect from direct to inverse. Here we present a thorough study of the intrinsic magnetic and structural properties, including their dependence on hydrostatic pressure, that are at the basis of the multifunctional behavior of Co and In-doped alloys. We study in depth their magnetocaloric properties, taking advantage of complementary calorimetric and magnetic techniques, and show that if a proper measurement protocol is adopted they all merge to the same values, even in case of first order transitions. A simplified model for the estimation of the adiabatic temperature change that relies only on indirect measurements is proposed, allowing for the quick and reliable evaluation of the magnetocaloric potentiality of new materials starting from readily available magnetic measurements.

  9. Magneto-caloric effect of FexZryB100-x-y metallic ribbons for room temperature magnetic refrigeration

    Science.gov (United States)

    Guo, D. Q.; Chan, K. C.; Xia, L.; Yu, P.

    2017-02-01

    Among various amorphous magnetic materials, even though Fe-based materials do not have high magnetocaloric effect (MCE), their advantages of tunable Curie temperature (TC) and low cost have attracted considerable attention in regard to room temperature magnetic refrigeration applications. With the aim of enhancing the MCE, the influence of boron addition on Fe-based amorphous materials was investigated in this study. Fe94-xZr6Bx (x=5, 6, 8 and 10), Fe91-yZr9By (y=3, 4, 5, 6, 8 and 10) and Fe89-zZr11Bz (z=3, 4, 5, 6, 8 and 10) specimens were made in ribbon form and their magnetocaloric effect was investigated. The Curie temperature (TC) of all three series of ribbons underwent an almost linear increase, and the peak magnetic entropy change, | Δ SMpeak | (obtained in a magnetic field of 1.5 T), generally increases with increasing boron content. The results further show that the Fe86Zr9B5 ribbon exhibits a relatively large | Δ SMpeak | value of 1.13 J/kgK at 330 K and a large refrigerant capacity value of 135.6 J/kg under 1.5 T. On the basis of these results, although there is still much scope for improvement before totally replacing the conventional cooling method, the Fe-based amorphous ribbon can be seen as a promising magnetocaloric material for room temperature magnetic refrigeration applications.

  10. Study of magnetic and magnetocaloric properties of monoclinic and triclinic spin chain CoV2O6

    Science.gov (United States)

    Nandi, Moumita; Mandal, Prabhat

    We have investigated magnetic and magnetocaloric properties of both monoclinic and triclinic phases of CoV2O6 from magnetization and heat capacity measurements. Conventional and inverse magnetocaloric effects have been observed in both phases of CoV2O6. For a field change from 0 to 7 T, maximum values of magnetic entropy change and adiabatic temperature change reach 11.8 J kg-1 K-1 and 9.5 K respectively for monoclinic CoV2O6 while the corresponding values reach 12.1 J kg-1 K-1 and 13.1 K for triclinic CoVO6. Particularly for triclinic CoVO6, the magnetocaloric parameters are quite large in low or moderate field range. Apart from this, we have constructed magnetic phase diagram of monoclinic CoV2O6 where field-induced complex magnetic phases appear below a certain critical temperature 6 K when external magnetic field is applied along crystallographic easy axis.

  11. Study of Magnetic and Magnetocaloric Behaviour of (1 - Y)La0.7Ca0.3MnO3/(Y)MnFe2O4, (1 - Y)La0.7Ca0.3MnO3/(Y)Ni0.9Zn0.1Fe2O4 Composites.

    Science.gov (United States)

    Anwar, M S; Jung-Il; Lee, S R; Koo, Bon Heun

    2015-11-01

    We report the structural, magnetic and magnetocaloric properties of (1 - Y)La0.7Ca0.3MnO3/ (Y)MnFe2O4 (LCMO/MFO) and (1 - Y)La0.7Ca0.3MnO3/(Y)Ni0.9Zn0.1Fe2O4 (LCMO/NZFO) composites. Polycrystalline LCMO/MFO samples were prepared using the conventional solid-state reaction technique. The results of X-ray diffraction indicates mainly LCMO phase without characteristic lines of the MFO and NZFO phase. The magnetic study has revealed that the Curie temperature was influenced by the concentration of MFO and NZFO phases. A large magnetic entropy change has been observed for La0.7Ca0.3MnO3 compound. The value of the maximum magnetic entropy change was found to decrease in the composites samples with increasing the concentration of the MFO and NZFO phases. This investigation suggests that LCMO/MFO and LCMO/NZFO types of composites can give a new kind of refrigeration candidates, which can easily provide the tunable magnetocaloric effect.

  12. Tailoring of Magnetocaloric Effect in Ni45.5Mn43.0In11.5 Metamagnetic Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    W. O. Rosa

    2012-01-01

    Full Text Available We investigate the direct and inverse magnetocaloric effect in Ni45.5Mn43.0In11.5 Heusler alloy ribbons comparing the results obtained for the as-quenched sample with the ones after different annealing procedures. An enhancement and shift of the entropy maximum to near room temperature is observed in all annealed samples. A remarkable magnetocaloric effect is observed in samples with short-time treatment (10 minutes and at the lowest annealing temperature. We show that the suppressing of uncompensated martensitic transition and thermal hysteresis are both influenced by the heat treatment. Also, an improvement on Curie’s temperature is observed and, at low magnetic field, it has been risen up to 310 K. Our results demonstrate that the martensitic transformation is highly sensitive to the applied magnetic field and also to the annealing treatment, which means that the magnetocaloric effect can be tuned showing different behaviors for each sample.

  13. Magnetocaloric effect in (La1-xAx)2/3Ba1/3Mn1.05O3-δ

    DEFF Research Database (Denmark)

    Ancona-Torres, Carlos Eugenio; Menon, Mohan; Bahl, Christian Robert Haffenden

    Recently, a large magnetocaloric effect has been reported in La2/3Ba1/3MnO3-δ at about 300 K. In this paper, we investigate the effect of the ion size distribution at the A site on the magnetocaloric effect of this perovskite material. This is accomplished by replacing the lanthanum by Ce, Pr......, and Nd, which allows us to study the effect of both the average size, , and the distribution, σrA, on the magnetic properties of the system. Using magnetization and heat capacity measurements, we determine the important magnetocaloric parameters ΔSM and ΔTad of (La1-xAx)2/3Ba1/3Mn1.05O3-δ powders...

  14. Magnetocaloric effect and magnetothermopower in the room temperature ferromagnet Pr0.6Sr0.4MnO3

    Science.gov (United States)

    Maheswar Repaka, D. V.; Tripathi, T. S.; Aparnadevi, M.; Mahendiran, R.

    2012-12-01

    We have investigated magnetization (M), magnetocaloric effect (MCE), and magnetothermopower (MTEP) in polycrystalline Pr0.6Sr0.4MnO3, which shows a second-order paramagnetic to ferromagnetic transition near room temperature (TC = 305 K). However, field-cooled M(T) within the long range ferromagnetic state shows an abrupt decrease at TS = 86 K for μ0H inverse MCE) at TS. ΔSm = -2.185 J/kg K (-3.416 J/kg K) with refrigeration capacity RC = 43.4 J/kg (103.324 J/kg) for field change of μ0ΔH = 1.5 T (3 T) at TC = 304 K is one of the largest values reported in manganites near room temperature. Thermopower (Q) is negative from 350 K to 20 K, which shows a rapid decrease at TC and a small cusp around TS in zero field. The MTEP [ΔQ/Q(0)] reaches a maximum value of 25% for μ0ΔH = 3 T around TC, which is much higher than 15% dc magnetoresistance for the same field change. A linear relation between MTEP and magnetoresistance and between ΔSm and ΔQ are found near TC. Further, ac magnetotransport in low dc magnetic fields (μ0 H ≤ 0.1 T), critical analysis of the paramagnetic to ferromagnetic transition, and scaling behavior of ΔSm versus a reduced temperature under different magnetic fields are also reported. Coexistence of large magnetic entropy change and magnetothermopower around room temperature makes this compound interesting for applications.

  15. Magnetocaloric effect in pristine and Bi-doped Pr0.6Sr0.4MnO3 manganite

    Science.gov (United States)

    Daivajna, Mamatha D.; Rao, Ashok

    2016-11-01

    Near room temperature, magnetocaloric effect in pristine and Bi-doped Pr0.6Sr0.4MnO3 manganites has been studied using in-field heat capacity measurements. The Debye temperature (θD) for the pristine sample was estimated to be 522 K and its value increases to 530 K for the Bi-doped sample with x=0.05. The entropy associated with paramagnetic (PM) to ferromagnetic (FM) transition is found to be 2.4 J/mol K and 2.3 J/mol K for x=0 and 0.05 compositions respectively. The estimated values of adiabatic temperature ∆Tad for the samples with x=0 and x=0.05 are respectively 2.2 K and 1.9 K for 0-6 Tesla. The maximum isothermal change in entropy, ∆SM for the sample Pr0.6Sr0.4MnO3 with transition temperature 306 K is found to be 2.7 J/kg-K with application of external magnetic field of 2 T and for Bi-doped sample (with x=0.05) the isothermal change in entropy reduces to 2.0 J/kg-K. The calculated maximum values of the isothermal entropy changes, ∆SM for the pristine sample, vary in the range 1.7-3.9 J/kg-K for a magnetic field change of 1-6 T. The present results suggest that these compounds can be possible candidates as magnetic refrigerants. This results in a large relative cooling power (RCP) around 93.5 J kg-1 K for the pristine sample under an application of magnetic field of 2 T. On contrary, with Bi-doping, RCP decreases to 56 J kg-1 K at external field of 2 T.

  16. Magnetocaloric Effect in Colossal Magnetoresistance Material (La0.6Dy0.1)Sr0.3MnO3

    Institute of Scientific and Technical Information of China (English)

    Cai Zhirang; Xu Sujun; Liu Ning; Sun Yong; Tong Wei; Zhang Yuheng

    2005-01-01

    The magnetocaloric effect in the A-site doping colossal magnetoresistance material (La0.6Dy0.1)Sr0.3MnO3 was studied. From the measurement and calculation of isothermal magnetization (M-H) curves under various temperatures, a large magnetocaloric effect with ferromagnetic-paramagnetic transition, additional magnetism exchange action introduces additional magnetic entropy change was discovered. This result suggests that (La0.6Dy0.1)Sr0.3MnO3 is a suitable candidate as working substance at room temperature in magnetic refrigeration technology.

  17. Reentrant phenomenon and inverse magnetocaloric effect in a generalized spin-(1/2,  s) Fisher’s super-exchange antiferromagnet

    Science.gov (United States)

    Gálisová, Lucia

    2016-11-01

    The thermodynamic and magnetocaloric properties of a generalized spin-(1/2,  s) Fisher’s super-exchange antiferromagnet are investigated precisely by using the decoration-iteration mapping transformation. Besides the critical temperature, sublattice magnetization, total magnetization, entropy and specific heat, the isothermal entropy change and adiabatic temperature change are also rigorously calculated in order to examine the cooling efficiency of the model in the vicinity of the first- and second-order phase transitions. It is shown that an enhanced inverse magnetocaloric effect occurs around the temperature interval {{T}\\text{c}}(B\

  18. Effects of the Mn/Co ratio on the magnetic transition and magnetocaloric properties of Mn1+χCo1-χGe alloys

    Institute of Scientific and Technical Information of China (English)

    Ma Sheng-Can; Wang Dun-Hui; Xuan Hai-Cheng; Shen Ling-Jia; Cao Qing-Qi; Du You-Wei

    2011-01-01

    We have investigated the magnetic transition and magnetocaloric effects of Mn1+χCo1-χGe alloys by tuning the ratio of Mn/Co. With increasing Mn content, a series of first-order magnetostructural transitions from ferromagnetic to paramagnetic states with large changes of magnetization are observed at room temperature. Further increasing the content of Mn (χ = 0.11) gives rise to a single second-order magnetic transition. Interestingly, large low-field magnetic entropy changes with almost zero magnetic hysteresis are observed in these alloys. The effects of Mn/Co ratio on magnetic transition and magnetocaloric effects are discussed in this paper.

  19. Magnetocaloric effect and magnetostructural coupling in Mn0.92Fe0.08CoGe compound

    Science.gov (United States)

    Wang, J. L.; Shamba, P.; Hutchison, W. D.; Gu, Q. F.; Md Din, M. F.; Ren, Q. Y.; Cheng, Z. X.; Kennedy, S. J.; Campbell, S. J.; Dou, S. X.

    2015-05-01

    The structural properties of Mn0.92Fe0.08CoGe have been investigated in detail using synchrotron x-ray diffraction in zero and applied pressure (p = 0-10 GPa). A ferromagnetic transition occurs around TC = 300 K and a large magnetic-entropy change -ΔSM = 17.3 J/kg K detected at TC for a field change of ΔB = 5 T. The field dependence of -ΔSMmax can be expressed as -ΔSMmax ∝ B. At ambient temperature and pressure, Mn0.92Fe0.08CoGe exhibits a co-existence of the orthorhombic TiNiSi-type structure (space group Pnma) and hexagonal Ni2In-type structure (space group P63/mmc). Application of external pressure drives a structure change from the orthorhombic TiNiSi-type structure to the hexagonal Ni2In-type structure. A large anomaly in heat capacity around TC is detected and the Debye temperature θD (=319(±10) K) has been derived from analyses of the low temperature heat capacity, T ≲ 10 K.

  20. Review on magnetic and related properties of RTX compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sachin, E-mail: gsachin55@gmail.com; Suresh, K.G., E-mail: suresh@phy.iitb.ac.in

    2015-01-05

    RTX (R = rare earths, T = 3d/4d/5d, transition metals such as Sc, Ti, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, and X = p-block elements such as Al, Ga, In, Si, Ge, Sn, As, Sb, Bi) series is a huge family of intermetallics compounds. These compounds crystallize in different crystal structures depending on the constituents. Though these compounds have been known for a long time, they came to limelight recently in view of the large magnetocaloric effect (MCE) and magnetoresistance (MR) shown by many of them. Most of these compounds crystallize in hexagonal, orthorhombic and tetragonal crystal structures. Some of them show crystal structure modification with annealing temperature; while a few of them show iso-structural transition in the paramagnetic regime. Their magnetic ordering temperatures vary from very low temperatures to temperatures well above room temperature (∼510 K). Depending on the crystal structure, they show a variety of magnetic and electrical properties. These compounds have been characterized by means of a variety of techniques/measurements such as X-ray diffraction, neutron diffraction, magnetic properties, heat capacity, magnetocaloric properties, electrical resistivity, magnetoresistance, thermoelectric power, thermal expansion, Hall effect, optical properties, XPS, Mössbauer spectroscopy, ESR, μSR, NMR, and NQR. Some amount of work on theoretical calculations on electronic structure, crystal field interaction and exchange interactions has also been reported. The interesting aspect of this series is that they show a variety of physical properties such as Kondo effect, heavy fermion behavior, spin glass state, intermediate valence, superconductivity, multiple magnetic transitions, metamagnetism, large MCE, large positive as well as negative MR, spin orbital compensation, magnetic polaronic behavior, and pseudo gap effect. Except Mn, no other transition metal in these compounds possesses considerable magnetic moments. Because of this

  1. Practical system for the direct measurement of magneto-caloric effect by micro-thermocouples.

    Science.gov (United States)

    Kamarád, J; Kaštil, J; Arnold, Z

    2012-08-01

    A system for direct measurements of the magneto-caloric effect (MCE) exploits a rapid transport of a sample into or from magnetic field in permanent Halbach-type (1 T) or superconducting (4.7 T) magnets. Time dependence of induced changes of the sample temperature, ΔT(t), is detected directly by the differential Cu-Constantan-Cu micro-thermocouples with time steps of 300 ms. A sample placed inside an evacuated simple LN(2) cryostat is either totally isolated (adiabatic conditions) or partly connected with the copper sample holder (non-adiabatic conditions). The last arrangement (a model of the Brayton cycle) is used to simulate an application of MCE in refrigeration techniques. The relations describing ΔT(t) that allow an analysis of MCE of the studied materials are based on the general cooling law. The effect of the first-order magnetic transition on MCE of selected sample is also demonstrated by non-standard ΔT(t) curves measured in the last mentioned experimental arrangements.

  2. Critical behavior and reversible magnetocaloric effect in multiferroic MnCr2O4

    Science.gov (United States)

    Dey, K.; Indra, A.; Majumdar, S.; Giri, S.

    2017-08-01

    Magnetocaloric effect (MCE) in multiferroic cubic spinel MnCr2O4 (space group Fd 3 bar m, no. 227, cF56), has been investigated using dc magnetization studies. The values of maximum magnetic entropy change (ΔSMmax) and the adiabatic temperature change (Δ Tad) are ∼5.3 J kg-1 K-1 and ∼2 K, respectively, at ∼42.8 K for the magnetic field change of 50 kOe. The dc magnetization data near the transition temperature were analyzed by the modified Arrott plots, the Kouvel-Fisher method, log M vs log H, and the scaling analysis. Critical exponents β = 0.3932 ± 0.0287, γ = 1.0256 ± 0.0239, and δ = 3.55 ± 0.26 are obtained around the critical temperature ∼ 42.88 K. The critical exponents are in excellent agreement with the single scaling equation of state M (H, ɛ) =ɛ 0.3932 ± 0.0287 f± (H /ɛ ((0.3932 ± 0.0287) + (1.0256 ± 0.0239))); with f+ for T > 42.88 K, f- for T model, while values of γ and δ are close to those of the mean field model. So the values of critical exponents indicate that the critical behavior of MnCr2O4 cannot be described within the framework of existing universality classes and probably belong to a separate class.

  3. Adiabatic magnetocaloric effect in Ni50Mn35In15 ribbons

    Science.gov (United States)

    Álvarez-Alonso, P.; Aguilar-Ortiz, C. O.; Camarillo, J. P.; Salazar, D.; Flores-Zúñiga, H.; Chernenko, V. A.

    2016-11-01

    Heusler-type Ni-Mn-based metamagnetic shape memory alloys (MetaMSMAs) are promising candidates for magnetic refrigeration. To increase heat exchange rate and efficiency of cooling, the material should have a high surface/volume ratio. In this work, the typical Ni50Mn35In15 MetaMSMA was selected to fabricate thin ribbons by melt-spinning. The characteristic transformations of the ribbons were determined by calorimetry, X-ray diffraction, scanning electron microscopy and thermomagnetization measurements. The inverse and conventional magnetocaloric effects (MCEs) associated with the martensitic transformation (MT) and the ferromagnetic transition of the austenite (TCA), respectively, were measured directly by the adiabatic method (ΔTad) and indirectly by estimating the magnetic entropy change from magnetization measurements. It is found that the ribbons exhibit large values of ΔTad = -1.1 K at μ0ΔH = 1.9 T, in the vicinity of the MT temperature of 300 K for inverse MCE, and ΔTad = 2.3 K for conventional MCE at TCA = 309 K. This result strongly motivates further development of different MetaMSMA refrigerants shaped as ribbons.

  4. Structure and Magnetocaloric Effect in Tb( Co1-xSnx )2 Alloys

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The phases and magnetocaloric effect in the alloys Tb (Co1 - xSnx) 2 with x = 0, 0.025, 0.050, 0.075, 0.100were investigated by X-ray diffraction analysis and magnetization measurement. The substitution of Sn in TbCo2 was limited. The cubic MgCu2-type structure for the sample of TbCo2 was confirmed by the results of X-ray powder diffraction and the rest samples consist of the TbCo2 phase mainly, together with some TbCo3 and Tb5Sn3 impurity phases. The impurity phases increase with the increase of Sn contents. The magnetic phase transition in all samples keeps second-order transition. TC increases slightly by Sn substitution from 230 K of the alloy with x = 0 to 233 K of the alloy with x = 0. 050 and then a slight decrease for higher concentration of x. The maximum magnetic entropy change in the samples Tb (Co1- x change from 0 to 2.0 T.

  5. Consecutive magnetic and magnetocaloric transitions in herringbone nanostructured Heusler Mn50Ni41Sn9 alloy.

    Science.gov (United States)

    Prasanna, A A; Ram, S; Fecht, H J

    2013-08-01

    A herringbone nanostructured Mn-rich Heusler Mn50Ni50-Sndelta (8 - 9) alloy exhibits tailored magnetocaloric properties in the martensite and ferro paramagnetic transitions concur in a narrow temperature window. In a Sn --> Ni substitution 8 - 9, the martensite (M) A approximately equal to 282 mJ/g (deltaC(P)(M A) approximately equal to 0.025 mJ/g-K in the heat capacity), i.e., the M A transition process lacks a complete reversibility. Warming a zero-field cooled sample retains lower magnetization (sigma) at low fields B, e.g., by 58% over the field cooled value at 5 mT, wherein merely low field magnetic susceptibility imparts the magnetization process. A reversible thermal hysteresis thus the transition traces in cooling and heating. The field diminishes difference in two sigma-values progressively, e.g., only - 12% lasts at 5 T. The two curves bifurcate below 160 K (B-5 mT) and the gap grows exponentially over lower temperatures before sigma(M or = 250 K) before a ferromagnetic A-state lines-up the successive transitions. Temperature and frequency dependence ac and dc susceptibilities describe the surface spins dynamics.

  6. Magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys

    Directory of Open Access Journals (Sweden)

    T. Thanveer

    2016-05-01

    Full Text Available A study of magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys is reported. Amorphous Fe40Ni38Mo4B18, near its magnetic ordering temperature (600K showed a magnetic entropy change ΔSM of 1.1 J/KgK and a relative cooling power of 36J/Kg in a field change of 10 kOe. Amorphous samples were partially crystallized by annealing at 700 K at different time intervals. Partially crystallized samples showed two distinct magnetic ordering temperature, one corresponding to the precipitated FeNi nanocrystals and the other one corresponding to the boron rich amorphous matrix. Magnetic ordering temperature of the residual amorphous matrix got shifted to the lower temperatures on increasing the annealing duration. Partially crystallised samples showed a magnetic entropy change of about 0.27J/kgK near the magnetic ordering temperature of the amorphous matrix (540K in a field change of 10 kOe. The decrease in ΔSM on partial crystallisation is attributed to the biphasic magnetic nature of the sample.

  7. Magnetocaloric effect of (Gd1-xNdx)Co2 alloys in low magnetic field

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiang; ZHUANG Yinghong; YAN Jialin; ZHOU Kaiwen; LI Kefeng

    2008-01-01

    The phases and magnetocaloric effect in the alloys (Gd1-xNdx)Co2 with x = 0,0.1,0.2,0.3,and 0.4 were investigated by X-ray diffraction analysis and magnetization measurement.The samples are single phase with a cubic MgCu2-type structure.The Tc decreases obviously with increasing Nd content from 404 K of the alloy with x = 0 to 272 K of the alloy with x = 0.4;for x = 0.3,the Tc is 296 K,which is near room temperature.In the samples (Gd1-xNdx)Co2 with x = 0.0,0.1,0.2,0.3,and 0.4,the maximum magnetic entropy change is 1.471,1.228,1.280,1.381 and 1.610 J.kg-1.K-1,respectively,in the applied field range of 0-2.0 T.The results of Arrott plots confirmed that the transition type were second order magnetic transition for x = 0,0.3,and 0.4.

  8. Magnetocaloric effect (MCE): Microscopic approach within Tyablikov approximation for anisotropic ferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Kotelnikova, O.A.; Prudnikov, V.N. [Physical Faculty, Lomonosov State University, Department of Magnetism, Moscow (Russian Federation); Rudoy, Yu.G., E-mail: rudikar@mail.ru [People' s Friendship University of Russia, Department of Theoretical Physics, Moscow (Russian Federation)

    2015-06-01

    The aim of this paper is to generalize the microscopic approach to the description of the magnetocaloric effect (MCE) started by Kokorina and Medvedev (E.E. Kokorina, M.V. Medvedev, Physica B 416 (2013) 29.) by applying it to the anisotropic ferromagnet of the “easy axis” type in two settings—with external magnetic field parallel and perpendicular to the axis of easy magnetization. In the last case there appears the field induced (or spin-reorientation) phase transition which occurs at the critical value of the external magnetic field. This value is proportional to the exchange anisotropy constant at low temperatures, but with the rise of temperature it may be renormalized (as a rule, proportional to the magnetization). We use the explicit form of the Hamiltonian of the anisotropic ferromagnet and apply widely used random phase approximation (RPA) (known also as Tyablikov approximation in the Green function method) which is more accurate than the well known molecular field approximation (MFA). It is shown that in the first case the magnitude of MCE is raised whereas in the second one the MCE disappears due to compensation of the critical field renormalized with the magnetization.

  9. Tricarboxylate-based Gd(III) coordination polymers exhibiting large magnetocaloric effects.

    Science.gov (United States)

    Liu, Sui-Jun; Cao, Chen; Xie, Chen-Chao; Zheng, Teng-Fei; Tong, Xiao-Lan; Liao, Jin-Sheng; Chen, Jing-Lin; Wen, He-Rui; Chang, Ze; Bu, Xian-He

    2016-05-31

    Two Gd(III) coordination polymers with the formula [Gd(cit)(H2O)]∞ () and [Gd(nta)(H2O)2]∞ () (H4cit = citric acid, H3nta = nitrilotriacetic acid) have been successfully prepared under hydrothermal conditions. Complex exhibits a three-dimensional (3D) structure based on carboxylate-bridged layers, while complex is a double-layer structure containing eight-coordinated Gd(III). Magnetic investigations reveal that weak antiferromagnetic couplings between adjacent Gd(III) ions in both and with different Weiss values result in large cryogenic magnetocaloric effects. It is notable that the maximum entropy changes (-ΔS) of and reach 31.3 J kg(-1) K(-1) and 32.2 J kg(-1) K(-1) at 2 K for a moderate field change (ΔH = 3 T), and a remarkable -ΔS (41.5 J kg(-1) K(-1) for and 42.0 J kg(-1) K(-1) for ) could be obtained for ΔH = 7 T.

  10. Size-dependent structure and magnetocaloric properties of Fe-based glass-forming alloy powders

    Directory of Open Access Journals (Sweden)

    Qiang Luo

    2016-04-01

    Full Text Available We investigated the influence of particle size on the microstructure and magnetocaloric effect of Fe-based alloy powders (11 μm to 100 μm in diameter. The degree of structure order varies with the powder size. The 11 μm to 18 μm powders show the largest peak magnetic entropy change (MEC. Increasing the degree of structure order tends to decrease the maximum MEC. Nevertheless, enhancement of refrigerant capacity and MEC (above 70 K is achieved when the crystalline phase content is ∼50% (above 75 μm in the 75 μm to 100 μm powders. Exponent n of the field dependence of MEC increases with the decrease in powder size above 22.5 K. The size dependence of the structure and properties is associated with the fact that a larger particle has a slower cooling rate and takes a longer time to form medium-to-long range ordered structures.

  11. Giant magnetocaloric effect in MnCoGe with minimal Ga substitution

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Danlu [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Nie, Zhihua, E-mail: zhihua_nie@yahoo.com [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Wang, Zilong; Huang, Lian; Zhang, Qinghua [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Wang, Yan-dong, E-mail: ydwang@mail.neu.edu.cn [The State Key Laboratory of Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-08-01

    The effects of Ga-doping on the phase transition behaviors and magnetocaloric properties of MnCoGe alloys are systematically investigated through calorimetry and magnetic measurements. The magneto-structural coupling between the structural and magnetic transitions is achieved in the MnCoGe{sub 1–x}Ga{sub x} alloys by decreasing the structural transition temperature via Ga substitution. An 80 K Curie-temperature window is established between Curie temperatures of austenite and martensite phases. Within the window, a magnetic entropy change of 34 J kg{sup −1} K{sup −1} can be obtained near room temperature under the application of a 5 T magnetic field. - Highlights: • The magnetostructural coupling is achieved in MnCoGe alloys with Ga substitution. • An 80 K Curie-temperature window is established in MnCoGe{sub 1–x}Ga{sub x} alloys. • A magnetic entropy change of 34 J kg{sup −1} K{sup −1} is obtained under magnetic field of 5 T.

  12. Anisotropic Magnetocaloric Effect in Single Crystalline NiTa2O6

    Science.gov (United States)

    Schye, Aaron T.; Masunaga, Sueli H.; Christian, Aaron B.; Neumeier, John J.; Yu, Yi-Kuo

    2015-03-01

    Magnetic susceptibility and heat capacity measurements were made on the low-dimensional antiferromagnet NiTa2O6. The antiferromagnetic structure most consistent with our measurements is the two sub-lattice model proposed by Law et al.[1] in which magnetic moments in the z = 0 plane are aligned parallel to [110] and those in the z = 1/2 plane are aligned parallel to [1 1 0]. Applying a magnetic field along [110] causes the peak in the heat capacity to split into two with one remaining at TN and the other shifting to lower temperatures as the field is increased with a maximum ΔT ~ 3 K at 8 T. This splitting indicates that each sub-lattice orders at different Néel temperatures. Calculation of the magnetic entropy change associated with an increase in magnetic field(ΔSm (T , ΔH)) reveals ΔSm (T , ΔH) ~ 0.7 J/kg K for H ∥ [110] and ΔSm (T , ΔH) ~ 0 J/kg K for H ∥ [001] if ΔH = 8 T. This anisotropy in the magnetocaloric effect suggests that rotating the sample in constant magnetic field will result in a change in sample temperature. Supported by NSF Grant DMR-0907036.

  13. Indirect measurement of the magnetocaloric effect using a novel differential scanning calorimeter with magnetic field.

    Science.gov (United States)

    Jeppesen, S; Linderoth, S; Pryds, N; Kuhn, L Theil; Jensen, J Buch

    2008-08-01

    A simple and high-sensitivity differential scanning calorimeter (DSC) unit operating under magnetic field has been built for indirect determination of the magnetocaloric effect. The principle of the measuring unit in the calorimeter is based on Peltier elements as heat flow sensors. The high sensitivity of the apparatus combined with a suitable calibration procedure allows very fast and accurate heat capacity measurements under magnetic field to be made. The device was validated from heat capacity measurements for the typical DSC reference material gallium (Ga) and a La(0.67)Ca(0.33)MnO(3) manganite system and the results were highly consistent with previous reported data for these materials. The DSC has a working range from 200 to 340 K and has been tested in magnetic fields reaching 1.8 T. The signal-to-noise ratio is in the range of 10(2)-10(3) for the described experiments. Finally the results have been compared to results from a Quantum Design(R) physical properties measuring system. The configuration of the system also has the advantage of being able to operate with other types of magnets, e.g., permanent magnets or superconducting coils, as well as the ability to be expanded to a wider temperature range.

  14. Determination of the magnetocaloric entropy change by field sweep using a heat flux setup

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, J. C. B., E-mail: jolmiui@gmail.com; Reis, R. D. dos; Mansanares, A. M.; Gandra, F. G. [Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin, Campinas, SP 13083-859 (Brazil)

    2014-08-18

    We report on a simple setup using a heat flux sensor adapted to a Quantum Design Physical Property Measurement System to determine the magnetocaloric entropy change (ΔS). The major differences for the existing setups are the simplicity of this assembly and the ease to obtain the isothermal entropy change either by a field sweep or a temperature sweep process. We discuss the use of these two processes applied to Gd and Gd{sub 5}Ge{sub 2}Si{sub 2} samples. The results are compared to the temperature sweep measurements and they show the advantages of this setup and of the field sweep procedure. We found a significant reduction of ΔS and on the refrigerating cooling power (RCP) at low field changes in a field sweep process when the sample is not driven to the same initial state for each temperature. We show that the field sweep process without any measuring protocol is the only correct way to experimentally determine ΔS and RCP for a practical regenerative refrigerator.

  15. Magnetocaloric effect in In doped YbMnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Sattibabu, Bhumireddi, E-mail: bsb.satti@gmail.com [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); Department of Electronics and Physics, Institute of Science, GITAM University, Visakhapatnam 530045 (India); Bhatnagar, A.K., E-mail: anilb42@gmail.com [School of Physics, University of Hyderabad, Hyderabad 500046 (India); Vinod, K.; Mani, Awadhesh [Condensed Matter Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2017-06-01

    Magnetic and magnetocaloric (MCE) properties of Yb{sub 0.9}In{sub 0.1}MnO{sub 3} and Yb{sub 0.8}In{sub 0.2}MnO{sub 3} polycrystalline samples are presented in this paper. Isothermal magnetization measurements reveal a field induced magnetic transition. Magnetic entropy change of 2.34±0.35 J/mole-K for Yb{sub 0.9}In{sub 0.1}MnO{sub 3} and 2.64±0.38 J/mole-K for Yb{sub 0.8}In{sub 0.2}MnO{sub 3} field change ΔH =10 KOe is observed around the ferromagnetic ordering temperature of Yb{sup 3+}. Values of relative cooling power for the same field change are found to be 38.03±9 J /mol, and 40.90±10 J/mol for Yb{sub 0.9}In{sub 0.1}MnO{sub 3} and Yb{sub 0.8}In{sub 0.2}MnO{sub 3}, respectively. These values suggest In doped YbMnO{sub 3} may be a potential candidate for magnetic refrigerant at low temperatures.

  16. Magnetostructural transition and magnetocaloric effect in highly textured Ni-Mn-Sn alloy

    Science.gov (United States)

    Czaja, P.; Chulist, R.; Szczerba, M. J.; Przewoźnik, J.; Olejnik, E.; Chrobak, A.; Maziarz, W.; Cesari, E.

    2016-04-01

    Ni49.4Mn38.5Sn12.1 near single crystal was obtained by the Bridgman method. At room temperature, it consisted of a mixture of the parent austenite phase with the cubic L21 Heusler structure (ac = 5.984 Å) and modulated, tetragonal martensite phase 4M (at = 4.337 Å, ct = 5.655 Å). Under the application of a magnetic field, the specimen undergoes field induced reverse martensitic transformation, which combined with the Curie transition in austenite leads to the coexistence of direct and inverse magnetocaloric effects. The maximum entropy change at 280 K and under 5 T amounts to 3.4 J.kg-1.K-1 for the structural transition and at 316 K reaches -2.7 J.kg-1.K-1 for the magnetic transformation. The magnetic entropy change occurs over a wide temperature span leading to improved refrigerant capacity of 101 J.kg-1 (5 T). Hysteretic losses are considerably reduced, which is promising with respect to improved cyclic stability of such a material.

  17. Giant magnetocaloric effect and temperature induced magnetization jump in GdCrO3 single crystal

    Science.gov (United States)

    Yin, L. H.; Yang, J.; Kan, X. C.; Song, W. H.; Dai, J. M.; Sun, Y. P.

    2015-04-01

    We report on a systematic study of the single-crystal GdCrO3, which shows various novel magnetic features, such as temperature-induced magnetization reversal (TMR), temperature-induced magnetization jump (TMJ), spin reorientation, and giant magnetocaloric effect (MCE). In the field-cooled cooling process with modest magnetic field along the c axis, GdCrO3 first shows a TMR at T c o m p ˜ 120 - 130 K and then an abrupt TMJ with a sign change of magnetization at T j u m p ˜ 52 - 120 K , and finally a spin reorientation at T S R ˜ 4 - 7 K . Interestingly, the remarkable TMJ behavior, which was not reported ever before, persists at higher fields up to 10 kOe even when TMR disappears. In addition, giant MCE with the maximum value of magnetic entropy change reaching ˜31.6 J/kg K for a field change of 44 kOe was also observed in GdCrO3 single crystal, suggesting it could be a potential material for low-T magnetic refrigeration. A possible mechanism for these peculiar magnetic behaviors is discussed based on the various competing magnetic interactions between the 3d electrons of Cr3+ ions and 4f electrons of Gd3+ ions.

  18. Electrical and morphological properties of magnetocaloric nano ZnNi ferrite

    Science.gov (United States)

    Hemeda, O. M.; Mostafa, Nasser Y.; Abd Elkader, Omar H.; Hemeda, D. M.; Tawfik, A.; Mostafa, M.

    2015-11-01

    A series of Zn1-xNixFe2O4 nano ferrite (with x=0, 0.2, 0.4, 0.6, 0.8, and 1) compositions were synthesized using the combustion technique. The powder samples were characterized by XRD. The X-ray analysis showed that the samples were single phase spinel cubic structure. The AC resistivity decreases by increasing the frequency from 1 kHz to 10 kHz. As the frequency of the applied field increases the hopping of charge carrier also increase, thereby decreasing the resistivity. A shift in dielectric maximum is observed toward higher temperature with increasing the Ni content from 536 K to 560 K at 1 kHz. The HRTEM (high resolution TEM) images of four compositions have lattice spacing which confirms the crystalline nature of the samples. The surface morphology SEM of the sample consists of some grains with relatively homogenies distribution with an average size varying from 0.85 to 0.92 μm. The values for entropy change in this work are still small but are significally higher than the values that have been reported for iron oxide nanoparticle. The magnetic entropy change was calculated from measurements of M (H, T) where H is the magnetic field and T is the temperature. The maximum value of entropy change (∆S) obtained near Curie temperature which makes these material candidates for magnetocaloric applications.

  19. Effect of Milling Time on the Blocking Temperature of Nanoparticles of Magnetocaloric Gd5Si4

    Science.gov (United States)

    Hadimani, Ravi; Gupta, Shalbh; Harstad, Shane; Pecharsky, Vitalij; Jiles, David; David C Jiles Team; Vitalij Pecharsky Collaboration

    Extensive research has been done on giant magnetocaloric material Gd5(SixGe1-x)4 to improve adiabatic temperature/isothermal entropy change. However, there have been only a few reports on fabrication of nanostructure/nanoparticles that can be used to tune various properties by changing the length scale. Recently we have reported fabrication of room temperature ferromagnetic nanoparticles of Gd5Si4 using high energy ball milling. These nanoparticles have potential applications in biomedical engineering such as better T2 MRI contrast agents and in hypothermia. Here we report the effect of milling time on the blocking temperature, micro-structure, crystal structure, and magnetic properties of these nanoparticles. Magnetization vs. temperature at an applied field of 100 Oe is measured for all the ball milled samples. Bulk Gd5Si4 has a transition temperature of ~340 K. There are two phase transitions observed in the nanoparticles, one near 300 K corresponding to the Gd5Si4 phase and another between 75-150 K corresponding to Gd5Si3. Zero Field Cooling (ZFC) and Field Cooling (FC) were measured. The blocking temperatures for the nanoparticles increase with decrease in milling time.

  20. Impact of cycle-hysteresis interactions on the performance of giant magnetocaloric effect refrigerants

    Science.gov (United States)

    Brown, T. D.; Karaman, I.; Shamberger, P. J.

    2016-07-01

    Magnetic refrigeration technology based on the giant magnetocaloric effect in solid-state refrigerants is known qualitatively to be limited by dissipative mechanisms accompanying hysteresis in the magneto-structural solid-solid phase transition. In this paper, we quantitatively explore the dependence of cycle performance metrics (cooling power, temperature span, work input, and fractional Carnot efficiency) on hysteresis properties (thermal hysteresis, one-way transition width) of the magneto-structural phase transition in a Ni45Co5Mn36.6In13.4 alloy system. We investigate a variety of Ericsson-type magnetic refrigeration cycles, using a Preisach-based non-equilibrium thermodynamic framework to model the evolution of the alloy's magnetic and thermal properties. Performance metrics are found to depend strongly on hysteresis parameters, regardless of the cycle chosen. However, for a given hysteresis parameter set, the material's transformation temperatures determine a unique cycle that maximizes efficiency. For the model system used undergoing Ericsson cycles with 5 and 1.5 {{T}} maximum field constraint, fractional Carnot efficiencies in excess of 0.9 require thermal hysteresis below 1.5 {{K}} and 0.5 {{K}}, respectively. We conclude briefly with some general materials considerations for mitigating these hysteresis inefficiencies through microstructure design and other materials processing strategies.

  1. Criticality-Enhanced Magnetocaloric Effect in Quantum Spin Chain Material Copper Nitrate

    Science.gov (United States)

    Xiang, Jun-Sen; Chen, Cong; Li, Wei; Sheng, Xian-Lei; Su, Na; Cheng, Zhao-Hua; Chen, Qiang; Chen, Zi-Yu

    2017-01-01

    In this work, a systematic study of Cu(NO3)2·2.5 H2O (copper nitrate hemipentahydrate, CN), an alternating Heisenberg antiferromagnetic chain model material, is performed with multi-technique approach including thermal tensor network (TTN) simulations, first-principles calculations, as well as magnetization measurements. Employing a cutting-edge TTN method developed in the present work, we verify the couplings J = 5.13 K, α = 0.23(1) and Landé factors g∥= 2.31, g⊥ = 2.14 in CN, with which the magnetothermal properties have been fitted strikingly well. Based on first-principles calculations, we reveal explicitly the spin chain scenario in CN by displaying the calculated electron density distributions, from which the distinct superexchange paths are visualized. On top of that, we investigated the magnetocaloric effect (MCE) in CN by calculating its isentropes and magnetic Grüneisen parameter. Prominent quantum criticality-enhanced MCE was uncovered near both critical fields of intermediate strengths as 2.87 and 4.08 T, respectively. We propose that CN is potentially a very promising quantum critical coolant. PMID:28294147

  2. Effect of Fe substitution on magnetocaloric effect in La 0.7Sr 0.3Mn 1- xFe xO 3 (0.05≤ x≤0.20)

    Science.gov (United States)

    Barik, S. K.; Krishnamoorthi, C.; Mahendiran, R.

    2011-04-01

    We have studied the effect of Fe substitution on magnetic and magnetocaloric properties in La0.7Sr0.3Mn1-xFexO3 (x=0.05, 0.07, 0.10, 0.15, and 0.20) over a wide temperature range (T=10-400 K). It is shown that substitution by Fe gradually decreases the ferromagnetic Curie temperature (TC) and saturation magnetization up to x=0.15 but a dramatic change occurs for x=0.2. The x=0.2 sample can be considered as a phase separated compound in which both short-range ordered ferromagnetic and antiferromagnetic phases coexist. The magnetic entropy change (-ΔSm) was estimated from isothermal magnetization curves and it decreases with increase of Fe content from 4.4 J kg-1 K-1 at 343 K (x=0.05) to 1.3 J kg-1 K-1 at 105 K (x=0.2), under ΔH=5 T. The La0.7Sr0.3Mn0.93Fe0.07O3 sample shows negligible hysteresis loss, operating temperature range over 60 K around room temperature with refrigerant capacity of 225 J kg-1, and magnetic entropy of 4 J kg-1 K-1 which will be an interesting compound for application in room temperature refrigeration.

  3. New 3d-4f heterometallic clusters built from mixed glycine and iminodiacetate acid: dioctahedron {La2Ni9} and onion-like {Gd5}⊂{Ni12} with interesting magnetocaloric effect.

    Science.gov (United States)

    Li, Zhong-Yi; Zhu, Jiang; Wang, Xiao-Qun; Ni, Jun; Zhang, Jian-Jun; Liu, Shu-Qin; Duan, Chun-Ying

    2013-04-28

    The preparation, structures and properties of 3d-4f compounds, undecanuclear [La2Ni9(Gly)12(IDA)3(μ3-OH)3][La(H2O)9][Na3(H2O)7(ClO4)3](ClO4)6·5H2O (1) and isostructural heptadecanuclear [Ln5Ni12(Gly)12(IDA)6(μ3-OH)9(H2O)3](ClO4)6·11H2O (Ln = Gd (2); Nd (3); Sm (4); Tb (5); Dy (6); Y (7)) based on mixed glycine (HGly) and iminodiacetate acid (H2IDA) ligands were described. The structure of the [La2Ni9(μ3-OH)3(IDA)3(Gly)12](3+) cationic cluster in 1 can be described as a face-shared and La-centered dioctahedron. However, the [Ln5Ni12(Gly)12(IDA)6(μ3-OH)9(H2O)3](6+) cationic clusters in 2-7 bear an onion-like {Ln5}⊂{Ni12} structure, where the trigonal bipyramid {Ln5} core is encapsulated by the outer triangular orthobicupola {Ni12} shell. Magnetic studies have been performed for these compounds, and 2 displays dominant ferromagnetic coupling and has a large magnetocaloric effect (21.8 J kg(-1) K(-1), ΔH = 7 T).

  4. Magnetic Properties of AIIBIVCV2 Compounds Doped with Mn

    Directory of Open Access Journals (Sweden)

    A.V. Kochura

    2013-12-01

    Full Text Available Mn-doped AIIBIVCV2 semiconductors bulk crystals were grown by direct melting of base components with fast cooling. Structural and magnetic properties of samples were investigated. Analysis of the temperature dependence of the magnetization reveals three types of magnetic species: the substitutional Mn ions making Mn complexes (especially dimers, the MnAs micro- and nanosize precepitates.

  5. Influence of cobalt on the structural, magnetic and magnetocaloric properties of La{sub 0.67}Ca{sub 0.33}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Nisha, P.; Pillai, S. Savitha [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695 019, Kerala (India); Varma, Manoj Raama, E-mail: manoj@niist.res.in [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695 019, Kerala (India); Suresh, K.G. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India)

    2013-02-15

    The critical properties and magnetocaloric effect of perovskite manganite La{sub 0.67}Ca{sub 0.33}Mn{sub 1-x}Co{sub x}O{sub 3} (x=0.03, 0.1 and 0.15) are investigated. Structural study using Reitveld refinement of X-ray diffraction pattern indicates an orthorhombic structure with Pnma space group for all compositions. The Curie temperature and magnetic moment decrease with increase of cobalt doping concentration and the samples exhibit characteristics of spin/cluster glass state which is evident from magnetization (zero field cooled and field cooled) vs temperature curves. The magnetic data is analyzed in the critical region using the modified Arrott plot method. The obtained values of critical exponents are in agreement with the values predicted by mean field interaction model. LCMCo{sub 0.03} compound shows a large magnetic entropy change ({Delta}S{sub M}) of 4 J/kg K at a magnetic field of 50 kOe. The relative cooling power (RCP) is found to be about {approx}184 J/kg for LCMCo{sub 0.03} and {approx}114 J/kg in the case of LCMCo{sub 0.1} in a magnetic field change of 50 kOe. The field dependance of {Delta}S{sub M} and RCP are showing a power dependence at their respective transition temperatures. An increase in resistance and a diminution of magnetic entropy change were observed as a consequence of Co doping. An enhanced magnetoresistance up to 87% and considerable magnetic entropy change were observed for these cobalt doped compounds. - Highlights: Black-Right-Pointing-Pointer The magnetic results show that the MCE property of LCMO is affected by doping of Co for Mn sites. Black-Right-Pointing-Pointer An increase in MR, a decrease of MCE and Curie temperatures are observed with increase in Co doping. Black-Right-Pointing-Pointer Relatively large value and broad temperature interval of MCE are observed in LCMCo{sub 0.03} compound. Black-Right-Pointing-Pointer LCMCo{sub 0.03} is found to be a candidate for magnetic refrigerators at sub-room temperatures.

  6. Influence of partial substitution of cerium for lanthanum on magnetocaloric properties of La1-xCexFe11.44Si1.56 and their hydrides

    Institute of Scientific and Technical Information of China (English)

    慕利娟; 黄焦宏; 张文佳; 刘翠兰; 王高峰; 赵增祺

    2014-01-01

    The structure and magnetocaloric properties of La1–xCexFe11.44Si1.56 and their hydrides La1–xCexFe11.44Si1.56Hy (x=0, 0.1, 0.2, 0.3, 0.4) were investigated. The samples crystallized mainly in the cubic NaZn13-type structure with a small amount ofα-Fe phase as impurity. The lattice constants and Curie temperature presented the same change tendency with increasing of Ce content. For the hydrides, the influence of Ce content on lattice constants was weakened and the values of H concentration y were approximate to be 1.56. The La1–xCexFe11.44Si1.56 compounds exhibited large values of isothermal entropy change –ΔSm around the Curie tem-perature TC under a low magnetic field change of 1.5 T. The value of–ΔSm increased and then decreased with increasing Ce con-tent, reached the maximum, 26.07 J/kg·K for x=0.3. TC increased up to the vicinity of room temperature by hydrogen absorption for the Ce substituted compounds, but TC only slightly decreased with increasing Ce content. The first-order metamagnetic transi-tion was still kept in the hydrides and the maximum values of–ΔSm were lower than those of the La1–xCexFe11.44Si1.56 compounds, but still remained large values, about 10.5 J/kgK under a magnetic field change of 1.5 T. The values of–ΔSm were nearly inde-pendent of the Ce content and did not increase with increasing x for the hydrides. The La1–xCexFe11.44Si1.56Hy (x=0–0.4) hydrides exhibited large magnetic entropy changes, small hysteresis loss and effective refrigerant capacity covered the room temperature range from 305 to 317 K. These hydrides are very useful for the magnetic refrigeration applications near room temperature under low magnetic field change.

  7. Structural, magnetic and magnetocaloric properties of La{sub 0.8}Ca{sub 0.2−x}Na{sub x}MnO{sub 3} manganites (0≤x≤0.2)

    Energy Technology Data Exchange (ETDEWEB)

    Choura Maatar, S. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); M’nassri, R. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Institut NEEL, CNRS, B.P.166, 38042 Grenoble Cedex 9 (France); Cheikhrouhou Koubaa, W., E-mail: wissem.koubaa@yahoo.fr [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Koubaa, M. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Cheikhrouhou, A. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Sfax University, B.P. 1171, 3000 Sfax (Tunisia); Centre de Recherche en Informatique, Multimédia et Traitement Numérique des Données, Technopole de Sfax, Cité El Ons, Route de Tunis, Km 9, Sfax. B.P. 275, Sakiet Ezzit, 3021 Sfax (Tunisia)

    2015-05-15

    In this work, we report the effect of Na doping on the structural, magnetic and magnetocaloric properties in La{sub 0.8}Ca{sub 0.2−x}Na{sub x}MnO{sub 3} powder samples. Our polycristalline samples have been synthesized using the solid-state reaction method at high temperatures. The parent compound La{sub 0.8}Ca{sub 0.2}MnO{sub 3} crystallizes in the orthorhombic system with Pbnm space group. Na doping induces a structural transition from orthorhombic (Pbnm space group) to rhombohedral (R-3C space group) symmetry. Magnetization measurements versus temperature in a magnetic applied field of 50 mT showed that all our investigated samples display a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature T{sub C} increases with Na content from 240 K for x=0 to 330 K for x=0.2. A large magnetocaloric effect has been observed in all samples, the maximum entropy change, |∆S{sub M}|{sub max}, shifts to smaller values with increasing Na content, from4.56 J/kg K (x=0.05) to 2.3 J/kg K (x=0.2) under a magnetic field change ∆µ{sub 0}H of 2 T. For the same applied magnetic field of 2 T, the Relative Cooling Power (RCP) values are found to be constant around 91 J/kg. - Graphical abstract: Sodium doping induces an increase of T{sub C} from 240 K for x=0 to 330 K for x=0.2. - Highlights: • La{sub 0.8}Ca{sub 0.2−x}Na{sub x}MnO{sub 3} are synthesized using the ceramic method at high temperatures. • Na doping induces a structural transition from Pbnm to R-3C space group. • T{sub C} increases with Na content from 240 K for x=0 to 330 K for x=0.2. • RCP is constant around 91 J/kg for all compounds under 2 T.

  8. Effect of Fe substitution on magnetocaloric effect in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (0.05{<=}x{<=}0.20)

    Energy Technology Data Exchange (ETDEWEB)

    Barik, S.K.; Krishnamoorthi, C. [Department of Physics and NUS Nanoscience and Nanotechnology Initiative, 2 Science Drive 3, National University of Singapore, Singapore 117542, Singapore. (Singapore); Mahendiran, R., E-mail: phyrm@nus.edu.s [Department of Physics and NUS Nanoscience and Nanotechnology Initiative, 2 Science Drive 3, National University of Singapore, Singapore 117542, Singapore. (Singapore)

    2011-04-15

    We have studied the effect of Fe substitution on magnetic and magnetocaloric properties in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (x=0.05, 0.07, 0.10, 0.15, and 0.20) over a wide temperature range (T=10-400 K). It is shown that substitution by Fe gradually decreases the ferromagnetic Curie temperature (T{sub C}) and saturation magnetization up to x=0.15 but a dramatic change occurs for x=0.2. The x=0.2 sample can be considered as a phase separated compound in which both short-range ordered ferromagnetic and antiferromagnetic phases coexist. The magnetic entropy change (-{Delta}S{sub m}) was estimated from isothermal magnetization curves and it decreases with increase of Fe content from 4.4 J kg{sup -1} K{sup -1} at 343 K (x=0.05) to 1.3 J kg{sup -1} K{sup -1} at 105 K (x=0.2), under {Delta}H=5 T. The La{sub 0.7}Sr{sub 0.3}Mn{sub 0.93}Fe{sub 0.07}O{sub 3} sample shows negligible hysteresis loss, operating temperature range over 60 K around room temperature with refrigerant capacity of 225 J kg{sup -1}, and magnetic entropy of 4 J kg{sup -1} K{sup -1} which will be an interesting compound for application in room temperature refrigeration. - Research highlights: > We report magnetocaloric effect in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (x=0-0.2). > Magnetic entropy change ({Delta}S{sub m}) decreases with increasing x. > A large {Delta}S{sub m} and refrigeration capacity are found around 300 K in x=0.07.

  9. Understanding the role played by Fe on the tuning of magnetocaloric effect in Tb5Si2Ge2

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Andre [University of Porto, Portugal; Moreira Dos Santos, Antonio F [ORNL; Magen Dominguez, Cesar [ORNL; Sousa, Joao Bessa [University of Porto, Portugal; Algarabel, Pedro A. [University of Zaragoza, Spain; Ren, Yang [Argonne National Laboratory (ANL); Ritter, Clemens [Institut Laue-Langevin (ILL); Morellon, Luis [University of Zaragoza, Spain; Ibarra, M. Ricardo [University of Zaragoza, Spain; Araujo, Joao Pedro [University of Porto, Portugal

    2011-01-01

    In this work, it is shown that when replacing Ge by Fe in Tb5Si2Ge2 the structural transition still occurs and enhances the Magnetocaloric effect (up to 66%) with maximum of MCE at a critical Fe amount where the magnetic and structural transitions become fully coupled. It is observed that Fe concentration is able to mimic the e?ect of external pressure as it induces a complex microstructure, that tunes long range strain ?elds. This knowledge is crucial for the development of strategies towards materials with improved performance for e?cient magnetic refrigeration applications.

  10. Direct and indirect measurement of the magnetocaloric effect in a La0.6Ca0.4MnO3 ceramic perovskite

    DEFF Research Database (Denmark)

    Dinesen, A.R.; Linderoth, Søren; Mørup, Steen

    2002-01-01

    The adiabatic temperature change DeltaT(ad) due to a change of the external magnetic field (the magnetocaloric effect) for a perovskite-type La0.6Ca0.4MnO3 sample has been measured directly and indirectly (from the entropy change) and the results are compared. From the indirect method, involving...

  11. Reversible crystal-to-amorphous-to-crystal phase transition and a large magnetocaloric effect in a spongelike metal organic framework material.

    Science.gov (United States)

    Tian, Chong-Bin; Chen, Rui-Ping; He, Chao; Li, Wei-Jin; Wei, Qi; Zhang, Xu-Dong; Du, Shao-Wu

    2014-02-21

    Reversible crystal-to-amorphous-to-crystal phase transition accompanied by changes in magnetic and NLO properties was first observed in a rigid non-porous spongelike MOF material. The crystal phase exhibits a high magnetocaloric effect, while the amorphous phase has potential application as a magnetic DMF sensor.

  12. Magnetocaloric and thermomagnetic properties of Ni2.18Mn0.82Ga Heusler alloy in high magnetic fields up to 140 kOe

    Science.gov (United States)

    Kamantsev, Alexander P.; Koledov, Victor V.; Mashirov, Alexey V.; Dilmieva, Elvina T.; Shavrov, Vladimir G.; Cwik, Jacek; Los, Anton S.; Nizhankovskii, Victor I.; Rogacki, Krzysztof; Tereshina, Irina S.; Koshkid'ko, Yuriy S.; Lyange, Maria V.; Khovaylo, Vladimir V.; Ari-Gur, Pnina

    2015-04-01

    Measurements of the adiabatic temperature change (ΔT) and the specific heat transfer (ΔQ) of Ni2.18Mn0.82Ga Heusler alloy were taken in order to quantify the direct giant magnetocaloric effect of the alloy when it is in the vicinity of magneto-structural phase transition (PT) from paramagnetic austenite to ferromagnetic martensite, and their results are presented. A new vacuum calorimeter was used to simultaneously measure ΔT and ΔQ of magnetocaloric materials with a Bitter coil magnet in fields of up to H = 140 kOe. Other thermomagnetic properties of this alloy were investigated using standard differential scanning calorimetry and PPMS equipment. The maximal values of magnetocaloric effect in H = 140 kOe were found to be ΔT = 8.4 K at initial temperature 340 K and ΔQ = 4900 J/kg at 343 K. Using this direct method, we show that the alloy indeed demonstrates the largest value of ΔQ as compared with previously published results for direct measurements of magnetocaloric materials, even though at 140 kOe the magnetic field-induced magnetostructural PT is still not complete.

  13. Inverse magnetocaloric effect in Ce(Fe{sub 0.96}Ru{sub 0.04}){sub 2}: Effect of fast neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Dube, V.; Mishra, P. K.; Prajapat, C. L.; Singh, M. R.; Ravikumar, G. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai-4000085 (India); Rajarajan, A. K.; Sastry, P. U. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai-4000085 (India); Thakare, S. V. [Radio Pharmaceuticals Division, Bhabha Atomic Research Centre, Mumbai-4000085 (India)

    2013-02-05

    We have shown the effect of fast neutron irradiation on the magnetic phase transition and magnetocaloric effect (MCE) in a doped Ce(Fe{sub 0.96}Ru{sub 0.04}){sub 2}, intermettalic. We show that this leads to suppression of MCE and a to a disordered ferromagnetic phase.

  14. Gd{sub 90}Co{sub 2.5}Fe{sub 7.5} alloy displaying enhanced magnetocaloric properties

    Energy Technology Data Exchange (ETDEWEB)

    Provenzano, V., E-mail: virgil12@nist.gov [Materials Science and Engineering Division, NIST, Gaithersburg, MD 20899-8552 (United States); Shull, R.D., E-mail: robert.shull@nist.gov [Materials Science and Engineering Division, NIST, Gaithersburg, MD 20899-8552 (United States); Kletetschka, G., E-mail: kletetschka@gmail.com [Faculty of Science, Charles University, Prague 12843 (Czech Republic); Institute of Geology, Academy of Science of the Czech Republic, v.v.i., Prague 16500 (Czech Republic); Stutzman, P.E., E-mail: paul.stutzman@nist.gov [Materials and Structural Systems Division, NIST, Gaithersburg, MD 20899-861 (United States)

    2015-02-15

    Highlights: • The Gd{sub 90}Co{sub 2.5}Fe{sub 7.5} alloy displays superior magnetocaloric properties than Gd. • Alloy’s superior properties at relatively low field values: 400, 800 kA/m (0.5, 1 T). • We proposed two possible mechanisms for the Gd-based alloy enhanced properties. • We indicated a pathway for further improving the alloy magnetocaloric properties. - Abstract: We report on the discovery of a new Gd{sub 90}Co{sub 2.5}Fe{sub 7.5} alloy exhibiting superior magnetocaloric properties compared to those of gadolinium. We present magnetically-derived entropy change, ΔS{sub M}, computed from magnetic data, and thermally-derived temperature change, ΔT{sub ad}, obtained from direct thermal measurements together with their respective MCE peaks for the alloy and gadolinium. The MCE peaks of the alloy are taller and broader than the corresponding MCE peaks of gadolinium. Correspondingly, the refrigeration capacity (RC) values of the alloy computed from magnetic and thermal MCEs for field changes, ΔH, of 400 kA/m (0.5 T) and 800 kA/m (1 T) are about 20% larger than those of gadolinium. Two possible mechanisms are proposed to account for the improved magnetocaloric properties of gadolinium alloyed with small amounts of Co and Fe, thereby pointing out a different methodology to use in the search for improved low field magnetic refrigerants.

  15. Impacts of nanostructuring and magnetic ordering of Nd{sup 3+} on the magnetic and magnetocaloric response in NdMnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Sayan, E-mail: schandr5@mail.usf.edu; Biswas, Anis, E-mail: biswas.anis@gmail.com; Phan, Manh-Huong, E-mail: phanm@usf.edu; Srikanth, Hariharan, E-mail: sharihar@usf.edu

    2015-06-15

    Magnetocaloric properties of NdMnO{sub 3} were investigated in its bulk polycrystalline and nanocrystalline forms. The nanocrystalline sample (average particle size ∼40 nm) exhibits a maximum in the temperature dependence of magnetic entropy change [−ΔS{sub M}(T)] at ∼70 K due to the paramagnetic to ferromagnetic transition, which is absent in case of its bulk counterpart. The absence of peak in −ΔS{sub M}(T) in the bulk sample is attributed to the co-existence of antiferromagnetic and ferromagnetic phases. A canted magnetic state (CMS) is stabilized at low temperature for both the samples due to the ordering of Nd{sup 3+} giving rise to a peak in −ΔS{sub M}(T) at ∼15 K. Interestingly −ΔS{sub M}(T) for these two samples show a universal behavior near their transitions at low temperature although their temperature dependence of magnetization is markedly different around those transitions. A detailed analysis of magnetocaloric data conclusively establishes the existence of a canted magnetic state, which is not obvious from magnetometry, demonstrating the usefulness of this method for probing phase coexistence and multiple magnetic states in complex oxide systems. - Highlights: • Effect of reduction of particle size on magnetocaloric properties of NdMnO{sub 3} has been investigated. • The roles of Nd{sup 3+}-ordering and self-doping effect on magnetic and magnetocaloric properties of NdMnO{sub 3} have been discussed. • Nanocrystalline NdMnO{sub 3} exhibits large magnetocaloric effect (MCE) in two temperature regimes in contrary to bulk sample. • We emphasize how MCE study can be exploited to explore fundamental physics of magnetism.

  16. Adiabatic Magnetooptical and Magnetocaloric Effects of Tb3GasO12 at Low Temperature in Strong Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guo-Ying; CHEN Hui; YANG Dan; HU Feng; LIU Hai-Shun

    2012-01-01

    In a strong magnetic field, the magnetic susceptibility χ and equivalent magnetic susceptibility λχ of some paramagnetic materials depend sensitively on the applied field He. Here A is the coefficient of the effective field Hm, which relates to the superexchange interaction between the electrons in different magnetic ions. We present the forms of the adiabatic equivalent λχ and the effective field Hm. The adiabatic magneto-caloric and magneto-optical effects of paramagnetic terbium gallate garnet Tb3 Ga5 O12 are calculated at 6K in strong magnetic fields. Our calculated results are in agreement with the experimental data.%In a strong magnetic field,the magnetic susceptibility χ and equivalent magnetic susceptibility λχ of some paramagnetic materials depend sensitively on the applied field He.Here λ is the coefficient of the effective field Hm,which relates to the superexchange interaction between the electrons in different magnetic ions.We present the forms of the adiabatic equivalent λχ and the effective field Hm.The adiabatic magneto-caloric and magnetooptical effects of paramagnetic terbium gallate garnet Tb3Ga5O12 are calculated at 6 K in strong magnetic fields.Our calculated results are in agreement with the experimental data.

  17. Magnetic and magnetocaloric properties of quasi-one-dimensional Ising spin chain CoV2O6

    Science.gov (United States)

    Nandi, M.; Mandal, P.

    2016-04-01

    We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV2O6 by magnetization and heat capacity measurements. Both monoclinic α-CoV2O6 and triclinic γ-CoV2O6 exhibit field-induced metamagnetic transitions from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to the field-induced metamagnetic transitions, these systems show large conventional as well as inverse magnetocaloric effects. In α-CoV2O6, we observe field-induced complex magnetic phases and multiple magnetization plateaus below 6 K when the field is applied along c axis. Several critical temperatures and fields have been identified from the temperature and field dependence of magnetization, magnetic entropy change, and heat capacity to construct the H-T phase diagram. As compared to α-CoV2O6, γ-CoV2O6 displays a relatively simple magnetic phase diagram. Due to the large magnetic entropy change and adiabatic temperature change at low or moderate applied magnetic field, γ-CoV2O6 may be considered as a magnetic refrigerant in the low-temperature region below 20 K.

  18. Searching the conditions for a table-like shape of the magnetic entropy in magneto-caloric materials

    Energy Technology Data Exchange (ETDEWEB)

    Álvarez, Pablo, E-mail: pablo.alvarez@ehu.es [Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48940 Leioa (Spain); Departamento de Física, Universidad de Oviedo, c/ Calvo Sotelo, s/n, 33007 Oviedo (Spain); Gorria, Pedro, E-mail: pgorria@uniovi.es [Departamento de Física, Universidad de Oviedo, c/ Calvo Sotelo, s/n, 33007 Oviedo (Spain); Sánchez Llamazares, José L. [División de Materiales Avanzados, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la presa San José 2055, CP 78216 San Luis Potosí (Mexico); Blanco, Jesús A. [Departamento de Física, Universidad de Oviedo, c/ Calvo Sotelo, s/n, 33007 Oviedo (Spain)

    2013-08-15

    Highlights: •The magnetic entropy change for two-ribbon (amorphous) composite materials is investigated. •The conditions to obtain a table-like shape of the magnetic entropy change are specified. •We give the essential ingredients to maximize the effective refrigerant capacity and the efficiency. •Our findings could be used in other magneto-caloric materials to tune the temperature range for the table-like behavior. -- Abstract: We show a systematic study of the magneto-caloric response carried out on a series of FeZrB(Cu) amorphous ribbons with different Curie temperature values in the 210–320 K interval. The main aim of the work is to investigate the conditions to obtain, from the isothermal magnetic entropy change vs. temperature curves, ΔS{sub M}(T), a table-like behavior of the entropy using two-ribbon composites. Even though the maximum value of ΔS{sub M} for the composite is lower than those of the single components, the existence of a table-like behavior maximizes the effective refrigerant capacity, reaching values around 80 J/kg for an applied magnetic field change of 2 T. Furthermore, we discuss how the temperature range for such a table-like behavior can be tuned and the refrigerant capacity enhanced in terms of energy efficiency.

  19. MAGNETOCALORIC RESPONSE OF NON-STOICHIOMETRIC Ni2MnGa ALLOYS AND THE INFLUENCE OF CRYSTALLOGRAPHIC TEXTURE

    Science.gov (United States)

    McLeod, M.V.; Giri, A. K.; Paterson, B. A.; Dennis, C. L.; Zhou, L.; Vogel, S.C.; Gourdon, O.; Reiche, H. M.; Cho, K.C.; Sohn, Y. H.; Shull, R. D.; Majumdar, B.S.

    2016-01-01

    Currently, there is significant interest in magnetocaloric materials for solid state refrigeration. In this work, polycrystalline Heusler alloys belonging to the Ni2+xMn1−xGa family, with x between 0.08 and 0.24, were evaluated for the purpose of finding composition(s) with an enhanced magnetocaloric effect (MCE) close to room temperature. Differential scanning calorimetry (DSC) was successfully used to screen alloy composition for simultaneous magnetic and structural phase transformations; this coupling needed for a giant MCE. The alloy with x = 0.16 showed an excellent match of transformation temperatures and exhibited the highest magnetic entropy change, ΔSM, in the as-annealed state. Furthermore, the MCE increased by up to 84 % with a 2 Tesla (T) field change when the samples were thermally cycled through the martensite to austenite transformation temperature while held under a constant mechanical load. The highest ΔSM measured for our x = 0.16 alloy for a 2 T magnetic field change was −18 J/kg-K. Texture measurements suggest that preferential orientation of martensite variants contributed to the enhanced MCE in the stress-assisted thermally cycled state. PMID:27099566

  20. Magnetocaloric properties of manganese(III) porphyrins bearing 2,6-di-tert-butylphenol groups

    Science.gov (United States)

    Korolev, V. V.; Lomova, T. N.; Maslennikova, A. N.; Korolev, D. V.; Shpakovsky, D. B.; Zhang, Jianwei; Milaeva, E. R.

    2016-03-01

    Magnetocaloric effect (MCE) and heat capacity during the magnetization of (5,10,15,20-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphynato) manganese (III) chloride (1), (5-(4-hydroxyphenyl)-10,15,20-tris(3,5-di-tert-butyl-4-hydroxyphenyl)porphynato) manganese (III) chloride (2), and (5-(4-palmitoyloxyphenyl)-10,15,20-tris(3,5-di-tert-butyl-4-hydroxyphenyl)porphynato) manganese (III) chloride (3) in their aqueous suspensions were determined by the microcalorimetric method over the temperature range of 278-320 K and in magnetic fields from 0 to 1 T. MCE was positive for all complexes studied, i.e. the magnetic field impression under adiabatic conditions led to an increase in temperature of the complexes suspensions. MCE increased with an increase in the magnetic field induction at all temperatures studied. Dependences of MCE on temperature had weak maxima at 298 K at all magnetic induction values. The disturbance of the intermolecular hydrogen-bonding of hydroxyl groups is one of probable reasons for such dependences type. MCE values increased under the palmitoyl substituent incorporation into one of the phenol groups at all temperatures. The heat capacity of the studied complexes rose slightly with temperature growth. Dependences of the heat capacity on temperature showed that the magnetic component of the heat capacity did not appear due to the presence of the manganese atom acting as a paramagnetic center in complexes 1, 2, and 3. The relation between the complexes structure and their magnetothermal properties was analyzed. It was justified that the changes of magnetothermal properties were caused by electronic substitution effects and, to an even greater degree, by the conditions of intermolecular hydrogen bonds formation in the paramagnetic materials.