Staging structures of the intercalation compounds Ag/sub x/TiS2

International Nuclear Information System (INIS)

Bardhan, K.K.; Kirczenow, G.; Jackle, G.; Irwin, J.C.

1986-01-01

An extensive investigation of the structure, and in particular the staging, of powdered samples of the intercalation compounds Ag/sub x/TiS 2 (0 0 C. The (T,x) phase diagram contains three phases: a high-x (dense) stage-1 phase, a stage-disordered phase, which at low x or high temperatures appears to become a pure low-x (dilute) stage-1 phase, and a simple stage-2 phase. On the high-x side of its stability region the stage-2 phase undergoes an apparent first-order transition to the dense stage-1 phase, but on the high-temperature side it proceeds continuously, through stage-disordered states, to a dilute stage-1 phase. On the low-x side of the stage-2 region there is also a dilute stage-1 phase. At sufficiently high temperatures a novel coexistence of the two stage-1 phases is observed. This is the first time that the high-temperature stability limit of the stage-2 region has been probed in any intercalation compound. The results are compared with recent theoretical models

Conduction anisotropy of the Bechgaard salts

International Nuclear Information System (INIS)

Kezsmarki, I.; Zamborszky, F.; Mihaly, G.; Montgomery, L.K.; Indiana Univ., Bloomington, IN

1999-01-01

We report the results of a systematic study on the temperature dependence of the normal state conductivity, measured along the a, b', and c * axis, in a representative set of Bechgaard salts. The anisotropic electron transport of four compounds are compared: (TMTSF) 2 ClO 4 , (TMTSF) 2 PF 6 , (TMTTF) 2 Br and (TMTTF) 2 PF 6 . We analyze the tendency, following this order of the compounds, of the metallic ab' plane conductivity change to a semiconductor like behavior, and we discuss the mechanism of inter- and intra-chain transport. The c * -direction conduction is determined by the nature of the counter-ion and seems to be irrelevant in this comparison. (orig.)

(Gd1−xErx)5Si2Ge2 compounds

Indian Academy of Sciences (India)

Gd metal (3 N) by arc melting, and then annealed at 1523 K (3 h). The phase, microstructure, Curie ... The temperature of magnetic transition decreases linearly from 281 K to 177 K with the increase of Er content from x = 0–0·2. ... Gd5Si2Ge2 serial compounds, different rare earth elements substituted for Gd in Gd5(Six ...

Magnetic properties and magnetocaloric effects in Mn1.2Fe0.8P1-xGex compounds

International Nuclear Information System (INIS)

Ou, Z Q; Wang, G F; Lin Song; Tegus, O; Brueck, E; Buschow, K H J

2006-01-01

We have studied the magnetic properties and magnetocaloric effects in the Mn 1.2 Fe 0.8 P 1-x Ge x compounds with x = 0.2, 0.22, 0.3, 0.4 and 0.5. X-ray diffraction patterns show that the Mn 1.2 Fe 0.8 P 1-x Ge x compounds crystallize in the hexagonal Fe 2 P-type crystal structure. The magnetic moments of the Mn 1.2 Fe 0.8 P 1-x Ge x compounds measured at 5 K and 5 T increase with increasing Ge content. The Curie temperature increases strongly and the magnetic entropy change has a maximum around 233 K for the compound with x = 0.22, which is about 19 and 31 J kg -1 K -1 for a field change of 2 and 5 T, respectively

Crystal structure and magnetic properties of PrCo6.8-xCuxHf0.2 compounds

International Nuclear Information System (INIS)

Luo, J; Liang, J K; Guo, Y Q; Liu, Q L; Liu, F S; Yang, L T; Zhang, Y; Rao, G H

2004-01-01

The effects of Cu substitution on the crystal structure and magnetic properties of PrCo 6.8-x Cu x Hf 0.2 (x = 0-1.0) compounds were investigated by means of x-ray powder diffraction and magnetic measurements. The as-cast PrCo 6.8-x Cu x Hf 0.2 compounds crystallize in the TbCu 7 -type structure with the space group P6/mmm. The Curie temperature and magnetic anisotropy field decrease with increasing Cu content. A spin reorientation behaviour has been observed in the PrCo 6.8-x Cu x Hf 0.2 compounds. The addition of Cu weakens the anisotropy of the Co sublattice, leading to an increase in the spin reorientation temperature with increasing content of Cu

Impurity induced antiferromagnetic order in Haldane gap compound SrNi2-xMgxV2O8

International Nuclear Information System (INIS)

Pahari, B.; Ghoshray, K.; Ghoshray, A.; Samanta, T.; Das, I.

2007-01-01

The effect of nonmagnetic Mg 2+ doping in SrNi 2 V 2 O 8 , a Haldane gap system with a disordered ground state, was investigated using DC magnetic susceptibility and heat capacity measurements in polycrystalline samples of SrNi 2-x Mg x V 2 O 8 with x=0.03, 0.05, 0.07, 0.1 and 0.14. The results clearly reveal that the substitution of Ni 2+ (S=1) ion by Mg 2+ (S=0) ion induces a magnetic phase transition with the ordering temperatures lying in the range 3.4-4.3K, for the samples with lowest and highest value of x. The intrachain exchange constant (J/k B ) and the Haldane gap (Δ) for all the compounds were estimated to be ∼98+/-2 and 25K, respectively, which are close to that of the undoped compound. The magnetization data further suggest that the compounds exhibit metamagnetic behavior below T N , supporting a picture of antiferromagnet with significant magnetic anisotropy and competing intrachain and interchain interactions

X-Ray Absorption Near-Edge Structure (XANES) of Calcium L3,2 Edges of Various Calcium Compounds and X-Ray Excited Optical Luminescence (XEOL) Studies of Luminescent Calcium Compounds

International Nuclear Information System (INIS)

Ko, J. Y. Peter; Zhou Xingtai; Sham, T.-K.; Heigl, Franziskus; Regier, Tom; Blyth, Robert

2007-01-01

X-ray absorption at calcium L3,2 edges of various calcium compounds were measured using a high resolution Spherical Grating Monochromator (SGM) at the Canadian Light Source (CLS). We observe that each compound has its unique fine structure of L3,2 edges. This uniqueness is due to differences in local structure of compounds. We also performed (X-ray Excited Optical Luminescence) XEOL of selected luminescent calcium compounds to investigate their optical properties. XEOL is a photon-in-photon-out technique in which the optical luminescence that is excited by tunable x-rays from a synchrotron light source is monitored. Depending on excitation energy of the x-ray, relative intensities of luminescence peaks vary. Recent findings of the results will be presented here

Hydrogen absorption in Zr(Alsub(x)Bsub(1-x))2 (B = Fe, Co) Laves phase compounds

International Nuclear Information System (INIS)

Jacob, I.; Shaltiel, D.

1978-01-01

The hydrogen absorption capacity of the systems Zr(Alsub(x)Fesub(1-x)) 2 and Zr(Alsub(x)Cosub(1-x)) 2 (0 = 2 (A = V, Cr, Mn; B = Fe, Co; 0 =< x =< 1). The maximum hydrogen content in both systems is achieved for x approximately 2/12 at 40 atm and 80 K. Further increase of the Al content leads, however, to a steep decrease in the hydrogen capacity. This general behaviour is well described by a phenomenological model, recently proposed by the authors, thus supporting the importance of short-range neighbouring effects for the hydrogen absorption capacity. The influence of Al on the hydrogen sorption properties in different intermetallic compounds is discussed. (author)

Pressure induced magneto-structural phase transitions in layered RMn2X2 compounds (invited)

International Nuclear Information System (INIS)

Kennedy, Shane; Wang, Jianli; Campbell, Stewart; Hofmann, Michael; Dou, Shixue

2014-01-01

We have studied a range of pseudo-ternaries derived from the parent compound PrMn 2 Ge 2 , substituting for each constituent element with a smaller one to contract the lattice. This enables us to observe the magneto-elastic transitions that occur as the Mn-Mn nearest neighbour distance is reduced and to assess the role of Pr on the magnetism. Here, we report on the PrMn 2 Ge 2−x Si x , Pr 1−x Y x Mn 2 Ge 2 , and PrMn 2−x Fe x Ge 2 systems. The pressure produced by chemical substitution in these pseudo-ternaries is inherently non-uniform, with local pressure variations dependent on the local atomic distribution. We find that concentrated chemical substitution on the R or X site (e.g., in Pr 0.5 Y 0.5 Mn 2 Ge 2 and PrMn 2 Ge 0.8 Si 1.2 ) can produce a separation into two distinct magnetic phases, canted ferromagnetic and canted antiferromagnetic, with a commensurate phase gap in the crystalline lattice. This phase gap is a consequence of the combination of phase separation and spontaneous magnetostriction, which is positive on transition to the canted ferromagnetic phase and negative on transition to the canted antiferromagnetic phase. Our results show that co-existence of canted ferromagnetic and antiferromagnetic phases depends on chemical pressure from the rare earth and metalloid sites, on local lattice strain distributions and on applied magnetic field. We demonstrate that the effects of chemical pressure bear close resemblance to those of mechanical pressure on the parent compound

Elastic, vibration and thermodynamic properties of Cu1‑x Ag x InTe2 (x = 0, 0.25, 0.5, 0.75 and 1) chalcopyrite compounds via first principles

Science.gov (United States)

Zhong, Yuhan; Wang, Peida; Mei, Huayue; Jia, Zhenyuan; Cheng, Nanpu

2018-06-01

CuInTe2 chalcopyrite compound is widely used in the fields of optoelectronics and pyroelectricity, and doping atoms can further improve the physical properties of the CuInTe2 compound. For all we know, this is the first time that the elastic behaviors and lattice dynamical properties of Ag-doped CuInTe2 compounds with the tetragonal system are determined theoretically. The elastic, lattice dynamical and thermal properties of Cu1‑x Ag x InTe2 (x = 0, 0.25, 0.5, 0.75 and 1) compounds have been investigated by using density functional theory. The obtained elastic constants of Cu1‑x Ag x InTe2 compounds indicate that these compounds are mechanically stable and elastic anisotropic. The anisotropy of the {001} plane is more obvious than those of the {100} and {010} planes. Additionally, with increasing Ag doping concentrations, the bulk and shear moduli of Cu1‑x Ag x InTe2 compounds decrease and their toughness improves. The phonon spectra and density of states reveal that Cu (or Ag) atoms in Cu1‑x Ag x InTe2 compounds form chemical bonds with Te atoms, and Cu-Te bonds are gradually replaced by Ag-Te bonds with increasing Ag doping concentration. Vibration modes of Cu1‑x Ag x InTe2 compounds at the {{Γ }} point in the Brillouin zone show that each Cu1‑x Ag x InTe2 (x = 0 and 1) crystal includes five irreducible representations (A1, A2, B1, B2 and E). As for Cu1‑x Ag x InTe2 (x = 0.25, 0.5 and 0.75) compounds, each crystal has three irreducible representations (A, B and E). The atomic displacements of several typical phonon modes in CuInTe2 crystals have been analyzed to deepen the understanding of lattice vibrations in Cu1‑x AgxInTe2 compounds. With increasing Ag doping concentration, the Debye temperatures of Cu1‑x Ag x InTe2 compounds decrease, while their heat capacities increase.

Magnetocaloric effect and transport properties of Gd5Ge2(Si1-x Sn x )2 (x=0.23 and 0.40) compounds

International Nuclear Information System (INIS)

Campoy, J.C.P.; Plaza, E.J.R.; Nascimento, F.C.; Coelho, A.A.; Pereira, M.C.; Fabris, J.D.; Raposo, M.T.; Cardoso, L.P.; Persiano, A.I.C.; Gama, S.

2007-01-01

We report a study about the structural properties of polycrystalline samples of nominal composition Gd 5 Ge 2 (Si 1- x Sn x ) 2 (x=0.23, 0.40) that closely influence their physical behavior particularly related to electric resistivity and magnetocaloric (MCE) effect. The samples were characterized by X-ray diffraction (XRD) using the Rietveld refinement method, metallographic analyses, 119 Sn Moessbauer spectroscopy, DC magnetization and electrical transport measurements. It was identified a Gd 5 Si 2 Ge 2 -monoclinic phase for x=0.23 and a Sm 5 Sn 4 -orthorhombic phase (type II) for x=0.40, both with two non-equivalent crystallographic sites for the Sn ions. We were able to infer on the role of tin on the magnetic and transport properties in these compounds

NMR study of Y2(Co1-xFex)14B compounds

International Nuclear Information System (INIS)

Maruyama, F.; Ichinose, K.; Nagai, H.; Adachi, K.; Misawa, M.; Tsujimura, A.

1992-01-01

59 Co and 89 Y NMR of Y 2 (Co 1-x Fe x ) 14 B compounds has been measured at 4.2 K. The line positions shift rapidly to higher frequency for x≤0.3 and are almost constant for 0.3 1 and 8j 2 sites give a large contribution to the anisotropy of the 3d sublattice. (orig.)

Magnetic properties of the HoMn6-xFe xSn6 compounds

International Nuclear Information System (INIS)

Cakir, O.; Dincer, I.; Duman, E.; Krenke, T.; Elmali, A.; Elerman, Y.

2007-01-01

Intermetallic compounds of HoMn 6-x Fe x Sn 6 (0 ≤ x ≤ 1.2) were studied by means of field-cooled (FC) and zero-field-cooled (ZFC) magnetization measurements in the temperature range 5 K ≤ T ≤ 600 K. The unit cell parameters decrease with the increasing of Fe content. The compounds with x = 0 and 0.3 behave ferrimagnetically in the whole temperature range and spin reorientation transition is observed at 200 and 185 K, respectively. The x = 0.5 and 0.6 compounds show ferrimagnetic-helimagnetic-ferrimagnetic phase transitions with decreasing temperature while the compounds with x = 0.9 and 1.2 only show helimagnetic-ferrimagnetic phase transitions. Additionally, for the x = 0.6 compound the metamagnetic phase transition from helimagnetism to ferrimagnetism is induced by an applied field 20 kOe

Fe-moment instability in Ti{sub 1-x}Sc{sub x}Fe{sub 2} Laves-phase compounds

Energy Technology Data Exchange (ETDEWEB)

Ouladdiaf, B. [Institut Laue-Langevin, BP 156, 38042 GRENOBLE Cedex 09 (France); Deportes, J. [Lab. Louis Neel, CNRS, BP 166, 38042 GRENOBLE Cedex 09 (France); Saoudi, M. [Centre Universitaire de Guelma, GUELMA 24 000 (Algeria)

2002-07-01

The magnetic properties of the pseudo-binary Laves-phase compounds Ti{sub 1-x}Sc{sub x}Fe{sub 2} were investigated by means of magnetisation and high-resolution powder neutron diffraction techniques. For x<0.2 a transition from an antiferromagnetic state to a canted one with a ferromagnetic component in the basal plane is observed, while for 0.2<x<0.27 the transition is from a collinear ferromagnetic state along the c-axis to a canted one. For x{proportional_to}0.3, an additional first-order transition is observed at low temperature accompanied by a large magnetovolume anomaly due to the increase of the intrinsic moment of the Fe atoms at the 2a site. (orig.)

Mild hydrothermal synthesis, crystal structure, spectroscopic and magnetic properties of the [MxIIM2.5-xIII(H2O)2(HPIIIO3)y(PVO4)2-yF] [M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds

International Nuclear Information System (INIS)

Orive, Joseba; Mesa, Jose L.; Legarra, Estibaliz; Plazaola, Fernando; Arriortua, Maria I.; Rojo, Teofilo

2009-01-01

The [M x II M 2.5-x III (H 2 O) 2 (HP III O 3 ) y (P V O 4 ) 2-y F] [M=Fe (1), x=2.08, y=1.58; M=Co (2), x=2.5, y=2; Ni (3), x=2.5, y=2] compounds have been synthesized using mild hydrothermal conditions at 170 deg. C during five days. Single-crystals of (1) and (2), and polycrystalline sample of (3) were obtained. These isostructural compounds crystallize in the orthorhombic system, space group Aba2, with a=9.9598(2), b=18.8149(4) and c=8.5751(2) A for (1), a=9.9142(7), b=18.570(1) and c=8.4920(5) A for (2) and a=9.8038(2), b=18.2453(2) and c=8.4106(1) A for (3), with Z=8 in the three phases. An X-ray diffraction study reveals that the crystal structure is composed of a three-dimensional skeleton formed by [MO 5 F] and [MO 4 F 2 ] (M=Fe, Co and Ni) octahedra and [HPO 3 ] tetrahedra, partially substituted by [PO 4 ] tetrahedra in phase (1). The IR spectra show the vibrational modes of the water molecules and those of the (HPO 3 ) 2- tetrahedral oxoanions. The thermal study indicates that the limit of thermal stability of these phases is 195 deg. C for (1) and 315 deg. C for (2) and (3). The electronic absorption spectroscopy shows the characteristic bands of the Fe(II), Co(II) and Ni(II) high-spin cations in slightly distorted octahedral geometry. Magnetic measurements indicate the existence of global antiferromagnetic interactions between the metallic centers with a ferromagnetic transition in the three compounds at 28, 14 and 21 K for (1), (2) and (3), respectively. Compound (1) exhibits a hysteresis loop with remnant magnetization and coercive field values of 0.72 emu/mol and 880 Oe, respectively. - Abstract: Polyhedral view of the crystal structure of the [M x II M 2.5-x III (H 2 O) 2 (HP III O 3 ) y (P IV O 4 ) 2-y F] [M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds showing the sheets along the [001] direction.

Half-metallic ferromagnetism in full-Heusler compounds ACaX2 (A = K and Rb; X = N and O)

International Nuclear Information System (INIS)

Umamaheswari, R.; Vijayalakshmi, D.; Yogeswari, M.; Kalpana, G.

2014-01-01

Electronic structure and magnetic properties of hypothetical ACaX 2 (A = K and Rb; X= N and O) compounds in full-Heusler phase have been investigated based on density functional theory (DFT) within the local density approximation (LDA). The electronic band structures and density of states of these compounds show that the spin-down electrons have metallic, and the spin-up electrons have a semi conducting gap resulting in stable half-metallic ferromagnetic behaviour. The strong spin polarization of 2p states of N and O atoms is found to be the origin of ferromagnetism which results in a total magnetic moment of 3 μB and 1 μB respectively

Electronic response of rare-earth magnetic-refrigeration compounds GdX2 (X = Fe and Co)

Science.gov (United States)

Bhatt, Samir; Ahuja, Ushma; Kumar, Kishor; Heda, N. L.

2018-05-01

We present the Compton profiles (CPs) of rare-earth-transition metal compounds GdX2 (X = Fe and Co) using 740 GBq 137Cs Compton spectrometer. To compare the experimental momentum densities, we have also computed the CPs, electronic band structure, density of states (DOS) and Mulliken population (MP) using linear combination of atomic orbitals (LCAO) method. Local density and generalized gradient approximations within density functional theory (DFT) along with the hybridization of Hartree-Fock and DFT (B3LYP and PBE0) have been considered under the framework of LCAO scheme. It is seen that the LCAO-B3LYP based momentum densities give a better agreement with the experimental data for both the compounds. The energy bands and DOS for both the spin-up and spin-down states show metallic like character of the reported intermetallic compounds. The localization of 3d electrons of Co and Fe has also been discussed in terms of equally normalized CPs and MP data. Discussion on magnetization using LCAO method is also included.

Giant magnetoresistance associated with a first-order transition between two ferrimagnetic states in Mn2-xZnxSb (x < 0.3) compounds

International Nuclear Information System (INIS)

Zhang, Q; Zhang, Y Q; Li, Y B; Du, J; Feng, W J; Li, D; Zhang, Z D

2008-01-01

A giant magnetoresistance (GMR) is observed in the Mn 2-x Zn x Sb (x 1.9 Zn 0.1 Sb compound. Different from other Mn 2 Sb-based compounds, the GMR in Mn 2-x Zn x Sb is closely correlated with a field-induced transition from a weak ferrimagnetic (WFI) state to a ferrimagnetic (FI) state. It is understood that the influences of both super-zone gap and spin-dependent scattering are responsible for GMR in the present system. Magnetic hysteresis and phase coexistence of the WFI and the FI phases suggest that this WFI-FI transition is of first order. The different mechanisms responsible for butterfly loops of magnetization/resistivity curves in different magnetic states are discussed

Nuclear magnetic resonance study of (Y[sub 1-x]R[sub x])[sub 2]Co[sub 14]B compounds (R=Gd, Tb)

Energy Technology Data Exchange (ETDEWEB)

Myojin, T. (Takamatsu National Coll. of Technology, Takamatsu (Japan)); Hayashi, M. (Takamatsu Coll. (Japan)); Ohno, T. (Faculty of Engineering, Tokushima Univ. (Japan)); Imaeda, Y. (Faculty of Engineering, Tokushima Bunri Univ., Shido (Japan)); Ushida, T. (Faculty of Engineering, Tokushima Bunri Univ., Shido (Japan)); Tsujimura, A. (Faculty of Engineering, Tokushima Bunri Univ., Shido (Japan)); Hihara, T. (Faculty of Integrated Arts and Sciences, Hiroshima Univ. (Japan))

1993-03-15

Influence of the Gd spin on the Co hyperfine field has been studied by [sup 59] Co nuclear magnetic resonance (NMR) in (Y[sub 1-x]Gd[sub x])[sub 2]Co[sub 14]B compounds. It is shown that the hyperfine coupling constants from the Gd spin for 8j[sub 1] and 8j[sub 2] sites are negative while those for 16k[sub 1] and 16k[sub 2] sites are positive. The dependence of the spin orientation temperature on the non-magnetic Y concentration in (Y[sub 1-x]Tb[sub x])[sub 2]Co[sub 14]B is also investigated by magnetization and [sup 59]Co NMR measurements. A spin phase diagram for this compound is proposed. (orig.)

Magnetic, transport and magnetocaloric properties in the Laves phase intermetallic Ho (Co1−xAlx)2 compounds

International Nuclear Information System (INIS)

Ivanova, T.I.; Nikitin, S.A.; Tskhadadze, G.A.; Koshkid’ko, Yu.S.; Suski, W.; Iwasieczko, W.; Badurski, D.

2014-01-01

Highlights: • The Al influence on magnetic properties of the Ho (Co 1-x Al x ) 2 compounds is analyzed. • The first-order magnetic transition appears in sample with Al concentrations x ≤ 0.06. • The MCE and Curie temperature TC demonstrate complex Al concentration dependences. • The magnetoresistance for sample with Al concentration x = 0.06 (58%) is maximum. • High magnetic fields changes the Curie temperature T c of the Ho (Co 1−x Al x ) 2 compounds. - Abstract: The magnetization, magnetoresistivity and magnetocaloric effect (MCE) of the Ho (Co 1−x Al x ) 2 Laves phase intermetallic compounds for x ⩽ 0.2 have been investigated. Complex measurements have been carried out in order to determine the influence of substitution in the Co sublattice by Al on the Co moment, type of the magnetic transition and related properties of these compounds. A comparative analysis of the magnetic, transport and magnetocaloric properties of Ho (Co 1−x Al x ) 2 alloys under various Al concentration is represented. Substitutions at the Co site by Al are found to result in the appearance of itinerant electron metamagnetism (IEM) at the small Al concentrations and in positive magnetovolume effect, leading to an initial increase in the ordering temperature; on the other hand the magnetic phase transition temperature as well as ΔT (MCE) do not depend in direct way on the Al concentration. The 16% increase of magnetocaloric effect for the alloy with x = 0.02 is detected in relation to maternal HoCo 2 . A giant value of magnetoresistivity (58%) is observed for the alloy with the same Al concentration

Study of the CdX-B2X3-X (X=S, Se), CdTe-B-Te systems

International Nuclear Information System (INIS)

Odin, I.N.; Grin'ko, V.V.; Safronov, E.V.; Kozlovskij, V.F.

2001-01-01

Liquidus surfaces of the CdX-B 2 X 3 -X (X=S, Se), CdTe-B-Te systems are plotted for the first time. It is shown that in equilibrium solid solutions on the basis of ternary Cd 2 B 2 X 5 compounds and binary B 2 X 3 , CdX, BS 2 compounds take part with liquid phases. p gen -T and T-x projects of p-T-x phase diagram of B-S (59-100 at. % S), B-Se (59-100 at. % Se), B-Te systems are plotted . B 2 X 3 , BS 2 compounds are formed in that regions of compositions of B-X systems . In the B-Te system compounds are not formed. Ternary compounds are not formed in the CdTe-B-Te system [ru

Investigation of structural imitation and lattice vibrations of Pr{sub 2}Fe{sub 17-} {sub x} Mn {sub x} compounds

Energy Technology Data Exchange (ETDEWEB)

Shen Jiang [Institute of Applied Physics, University of Science and Technology Beijing, 30 Xueyuou Road, HaiDian District, Beijing 100083 (China)]. E-mail: shenj@sas.ustb.edu.cn; Qian Ping [Institute of Applied Physics, University of Science and Technology Beijing, 30 Xueyuou Road, HaiDian District, Beijing 100083 (China); Chen Nanxian [Institute of Applied Physics, University of Science and Technology Beijing, 30 Xueyuou Road, HaiDian District, Beijing 100083 (China); Department of Physics, Tsinghua University, Beijing 100084 (China)

2005-03-15

We have investigated the structural properties of Pr{sub 2}Fe{sub 17-} {sub x} Mn {sub x} compounds by using quasi-ab initio pair potentials {phi} {sub Fe-Fe}(r), {phi} {sub Pr-Fe}(r), {phi} {sub Pr-Pr}(r), {phi} {sub Pr-Mn}(r), {phi} {sub Fe-Mn}(r) and {phi} {sub Mn-Mn}(r). In Pr{sub 2}Fe{sub 17-} {sub x} Mn {sub x} , the ternary elements Mn substitute for Fe atoms without changing the crystal structure. The calculated cohesive energy curves show that for all values of x, Mn preferentially substitutes for Fe in the 6c site and randomly substitutes for Fe in the 18f and 18h site. The calculated lattice constants coincide quite well with experimental values. Furthermore, the phonon density, specific heat and vibrational entropy of these compounds are also calculated. It is interesting that simple pair potentials can describe these extremely anisotropic materials.

Compound refractive X-ray lens

International Nuclear Information System (INIS)

Nygren, D.R.; Cahn, R.; Cederstrom, B.; Danielsson, M.; Vestlund, J.

2000-01-01

An apparatus and method are disclosed for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point

Compound refractive X-ray lens

Science.gov (United States)

Nygren, David R.; Cahn, Robert; Cederstrom, Bjorn; Danielsson, Mats; Vestlund, Jonas

2000-01-01

An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point.

Band metamagnetism and peculiarities of magnetic structure of (Er1-xYx)Co2 compounds

International Nuclear Information System (INIS)

Baranov, N.V.; Kozlov, A.I.; Pirogov, A.N.; Sinitsyn, E.V.

1989-01-01

A study of the magnetization, electric resistance, and thermal expansion as well as neutron diffraction data are used to show that in Er 1-x Y x Co 2 compounds the splitting of the d=zone of cobalt disappears as yttrium concentration grows up to x=0.4 and that simultaneously disordering of the Er subssystem sets in due to a phase transition of the first kind. It is discovered that at x∼0.45 the introduction of a weak external magnetic field with μ 0 H∼0.4 T causes the magnetization of the partially disordered Er subsystem to grow, which is accompanied by an irreversible splitting of the d-zone and an increase in the magnetic moment of cobalt from 0.3μ B to 0.9μ B . The presence of minima on the temperature curves for the electric resistance, observed in Er 1-x Y x Co 2 compounds (.2≤x≤0.6) at temperatures above the magnetic ordering temperature, is related to spin density fluctuations in the Co subsystem

Magnetocaloric effect in the La0.8Ce0.2Fe11.4-xCoxSi1.6 compounds

International Nuclear Information System (INIS)

Wang, G.F.; Song, L.; Li, F.A.; Ou, Z.Q.; Tegus, O.; Brueck, E.; Buschow, K.H.J.

2009-01-01

The effects of substitution of Co for Fe on the magnetic and magnetocaloric properties of La 0.8 Ce 0.2 Fe 11.4-x Co x Si 1.6 (0, 0.2, 0.4, 0.6, 0.8 and 1.0) compounds have been investigated. X-ray diffraction shows that all compounds crystallize in the NaZn 13 -type structure. Magnetic measurements show that the Curie temperature (T C ) can be tuned between 184 and 294 K by changing the Co content from 0 to 1. A field-induced methamagnetic transition occurs in samples with x=0, 0.2 and 0.4. The magnetic entropy changes of the compounds have been determined from the isothermal magnetization measurements by using the Maxwell relation.

Structure and magnetic transition of LaFe13-xSix compounds

International Nuclear Information System (INIS)

Bo Liuxu; Altounian, Z; Ryan, D H

2003-01-01

Structure and magnetic transitions were investigated by x-ray diffraction and Moessbauer spectroscopy in LaFe 13-x Si x compounds with x = 1.6, 2.0 and 2.6. With increasing Si content, the La-Fe interatomic distance decreased while the average Fe-Fe distance increased. These changes affect the structural stability and the magnetic properties of the compounds. The temperature dependence of the hyperfine field for the compound with x = 2.6 can be fitted very well using a mean field model with a Brillouin function (BF) while that for the compounds with x = 1.6 and 2.0 changes more sharply than that predicted by the BF relation near the Curie temperature. The different nature of the magnetic transition with different Si content originates from the spatial distribution of the Si atoms and related variation of the La-(Fe, Si) and the Fe-Fe distances in the cubic NaZn 13 structure

Projection-type X-ray microscope based on a spherical compound refractive X-ray lens

OpenAIRE

Dudchik, Yu. I.; Gary, C. K.; Park, H.; Pantell, R. H.; Piestrup, M. A.

2007-01-01

New projection- type X-ray microscope with a compound refractive lens as the optical element is presented. The microscope consists of an X-ray source that is 1-2 mm in diameter, compound X-ray lens and X-ray camera that are placed in-line to satisfy the lens formula. The lens forms an image of the X-ray source at camera sensitive plate. An object is placed between the X-ray source and the lens as close as possible to the source, and the camera shows a shadow image of the object. Spatial resol...

The relation of the broad band with the E2g phonon and superconductivity in the Mg(B1-xCx)2 compound

International Nuclear Information System (INIS)

Parisiades, P.; Lampakis, D.; Palles, D.; Liarokapis, E.; Karpinski, J.

2007-01-01

We have carried out an extensive micro-Raman study on Mg(B 1-x C x ) 2 single crystals, for carbon concentrations up to x=0.15. The E 2g symmetry broad band for pure MgB 2 at ∼600cm -1 disappears even for small doping levels (x=0.027) and two well-defined peaks in the high-energy side of this band play a major role in the Raman spectra of the substituted compounds. We propose that a two-mode behavior of the compound might be present, induced by the coupling of the observed phonons with the electronic bands

NMR study of (Y1-xLax) Mn2X2 (X = Ge, Si) compounds

International Nuclear Information System (INIS)

Ichinose, K.; Nagai, H.; Tsujimura, A.; Oyasato, M.

1988-01-01

Nuclear magnetic resonances of 55 Mn and 139 La nuclei in (Y 1-x La x ) Mn 2 X 2 (X = Ge, Si) have been observed at 4.2 K in their ferromagnetic state for 0.3 ≤ x ≤ 1. The hyperfine fields at these nuclei are independent of La concentration. This result shows that Mn moment is almost constant when replacing Y with La

Structural stability of ternary C22–Zr6X2Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and C22–Zr6Sn2T′ (T′=Fe, Co, Ni, Cu) compounds

International Nuclear Information System (INIS)

Colinet, Catherine; Crivello, Jean-Claude; Tedenac, Jean-Claude

2013-01-01

The crystal and electronic structures, and the thermodynamic properties of Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu) ternary compounds in the Fe 2 P-type structure have been investigated by means of first principle calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the ternary Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu) compounds. - Graphical abstract: Valence charge electronic localization function (ELF) calculated for Zr 6 Sb 2 Co compound. Display Omitted - Highlights: • Structural stability of Zr 6 X 2 T′ compounds (X: p element, T′: late transition metal) in the Fe 2 P-type structure. • First principles calculation of lattice parameters and enthalpies of formation. • Electronic densities of state in the series Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu). • Electronic densities of state in the series Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te)

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.

Enthalpies of formation of layered LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} (0 ≤ x ≤ 0.5) compounds as lithium ion battery cathode materials

Energy Technology Data Exchange (ETDEWEB)

Masoumi, Maryam; Cupid, Damian M.; Reichmann, Thomas L.; Seifert, Hans J. [Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany). Inst. for Applied Materials - Applied Materials Physics; Chang, Keke; Music, Denis; Schneider, Jochen M. [RWTH Aachen Univ. (Germany). Materials Chemistry

2017-11-15

Layer-structured mixed transition metal oxides with the formula LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} (0 ≤ x ≤ 0.5) are considered as important cathode materials for lithium-ion batteries. In an effort to evaluate the relative thermodynamic stabilities of individual compositions in this series, the enthalpies of formation of selected stoichiometries are determined by high temperature oxide melt drop solution calorimetry and verified by ab-initio calculations. The measured and calculated data are in good agreement with each other, and the results show that LiCoO{sub 2}-LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} solid solution approaches ideal behavior. By increasing x, i.e. by equimolar substitution of Mn{sup 4+} and Ni{sup 2+} for Co{sup 3+}, the enthalpy of formation of LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} from the elements becomes more exothermic, implying increased energetic stability. This conclusion is in agreement with the literature results showing improved structural stability and cycling performance of Ni/Mn-rich LiNi{sub x}Mn{sub x}Co{sub 1-2x}O{sub 2} compounds cycled to higher cut-off voltages.

Measurement of pressure effects on the magnetic and the magnetocaloric properties of the intermetallic compounds DyCo2 and Er(Co1-xSix)2

International Nuclear Information System (INIS)

Singh, Niraj K; Kumar, Pramod; Suresh, K G; Nigam, A K; Coelho, A A; Gama, S

2007-01-01

The effect of external pressure on the magnetic properties and magnetocaloric effect of polycrystalline compounds DyCo 2 and Er(Co 1-x Si x ) 2 (x = 0,0.025 and 0.05) has been studied. The ordering temperatures of both the parent and the Si-substituted compounds are found to decrease with pressure. In all the compounds, the critical field for metamagnetic transition increases with pressure. It is seen that the magnetocaloric effect in the parent compounds is almost insensitive to pressure, while there is considerable enhancement in the case of Si-substituted compounds. Spin fluctuations arising from the magnetovolume effect play a crucial role in determining the pressure dependence of the magnetocaloric effect in these compounds. The variation of the magnetocaloric effect is explained on the basis of the Landau theory of magnetic phase transitions

Synthesis and structural investigation of new Co1-xNixTeO4 (x = 0, 0.2, 0.5, 0.8 and 1) compounds

Science.gov (United States)

Patel, Akhilesh K.; Singh, Harishchandra; Suresh, K. G.

2018-05-01

The new polycrystalline compounds Co1-xNixTeO4 (x = 0, 0.2, 0.5, 0.8 and 1) were prepared by sol-gel method and their structural properties have been studied. Structural investigation through Rietveld method shows monoclinic structure with space group P21/c for all compounds. All compounds polyhedral structure found to be in octahedral form with cations (M) at the center and six oxygen atoms at corner of octahedral structure. The lattice parameters variation with Ni substitution are found to be decreasing with Ni substitution.

Electric resistivity of Y (Fe1-xAlx)2 compounds in the spin glass region (0,10<x<0,35)

International Nuclear Information System (INIS)

Souza, G.P. de.

1985-01-01

Measurements of electric resistivity in function of the temperature (1.5 1-x Al x2 pseudobinary intermetallic compounds in the region of concentration where there is a spin-glass behaviour, were carried out. The obtained results distinguished two behaviours. In certain cocentration, the minimum of resistivity at low temperatures was observed and in the others, a decrease of resistivity with increase of temperature up to environment temperature was found out. Magnetometry measurements, were carried out aiming to determine freezing critical temperature and of the order of long range, making possible to obtain more accurate measurements in the temperature range where the spin-glass, ferromagnetic and paramagnetic states occur in the compounds. (M.C.K.) [pt

X-ray powder diffraction data on miscellaneous lanthanide compounds

International Nuclear Information System (INIS)

Ferguson, I.F.; Hughes, T.E.

1978-08-01

Recent work on neutron absorbing materials has produced various new X-ray diffraction powder patterns of compounds of the lanthanides. Various inconsistencies in previously published data have been noted, and accurate measurements have been made of the lattice parameters of the rare earth oxides Sm 2 0 3 , Eu 2 0 3 , Gd 2 0 3 which have the monoclinic rare earth type B- structure, as well as Eu0. These data are recorded for reference. The optimum conditions for obtaining X-ray powder diffraction data from europium compounds are also noted. (author)

Enthalpies of formation of layered LiNixMnxCo1-2xO2 (0 ≤ x ≤ 0.5) compounds as lithium ion battery cathode materials

International Nuclear Information System (INIS)

Masoumi, Maryam; Cupid, Damian M.; Reichmann, Thomas L.; Seifert, Hans J.; Chang, Keke; Music, Denis; Schneider, Jochen M.

2017-01-01

Layer-structured mixed transition metal oxides with the formula LiNi x Mn x Co 1-2x O 2 (0 ≤ x ≤ 0.5) are considered as important cathode materials for lithium-ion batteries. In an effort to evaluate the relative thermodynamic stabilities of individual compositions in this series, the enthalpies of formation of selected stoichiometries are determined by high temperature oxide melt drop solution calorimetry and verified by ab-initio calculations. The measured and calculated data are in good agreement with each other, and the results show that LiCoO 2 -LiNi 0.5 Mn 0.5 O 2 solid solution approaches ideal behavior. By increasing x, i.e. by equimolar substitution of Mn 4+ and Ni 2+ for Co 3+ , the enthalpy of formation of LiNi x Mn x Co 1-2x O 2 from the elements becomes more exothermic, implying increased energetic stability. This conclusion is in agreement with the literature results showing improved structural stability and cycling performance of Ni/Mn-rich LiNi x Mn x Co 1-2x O 2 compounds cycled to higher cut-off voltages.

Study of the magnetic properties of Tb(Cosub(1-x)Nisub(x))sub(5) compounds

International Nuclear Information System (INIS)

Pirogov, A.N.; Kelarev, V.V.; Ermolenko, A.S.; Chuev, V.V.; Sidorov, S.K.; Artamonova, A.M.

1982-01-01

The crystal and magnetic structures of Tb(Cosub(1-x)Nisub(x))sub(5) compounds are investigated by neutron-diffraction and magnetic techniques. It is shown that the Ni ions occupy predominantly the 2c positions and the Co ions 3g positions in the crystal unit of the CaCu 5 type of structure. The magnetic phase diagram is set up. From an analysis of the concentration dependence of the magnetizations of the 2c- and 3g-sublattices it is concluded that the magnetic moments at the Co ions are constant. The magnetic moment of the Ni ions in the compounds studied are found to depend on the concentration x. Estimations based on the assumption of constancy of the R-R and R-Co exchange interaction energies indicate that Co-Co interactions contribute significantly to the Curie temperature of compounds with a low Co content (x=0.8). It is found that the temperature dependence of the magnetization of the 2c-sublattice is related to the direction of the easy magnetization axis of the crystal, a consequence being a jump of the magnetization in the easy plane - easy axis transition. On this basis it is concluded that Co atoms in the 2c positions give the major contribution to the magnetic anisotropy of Co sublattice for compounds of the RCo 5 type

Satelite structure in 59Co NMR spectrum of magnetically ordered Dysub(1-x)Ysub(x)Co2 intermetallic compound

International Nuclear Information System (INIS)

Yoshimura, Kazuyoshi; Hirosawa, Satoshi; Nakamura, Yoji

1984-01-01

The magnetic environment effect of cobalt in Dysub(1-x)Ysub(x)Co 2 has been studied by means of bulk magnetization and 59 Co spin-echo NMR measurements at 4.2K. Clearly resolved satellite structures of the NMR spectra have been observed. The hyperfine field distributions of 59 Co are decomposed into contributions of Co atoms in various nearest neighbor configurations of rare earth atoms. In this analysis the dipole field due to nearest neighbor rare earth moments plays an important role. The result indicates that the magnetic moment of Co in the RCo 2 cubic Laves phase pseudobinary compounds is quite sensitive to the nearest neighbor rare earth environment. (author)

On ternary intermetallic aurides. CaAu{sub 2}Al{sub 2}, SrAu{sub 2-x}Al{sub 2+x} and Ba{sub 3}Au{sub 5+x}Al{sub 6-x}

Energy Technology Data Exchange (ETDEWEB)

Stegemann, Frank [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Benndorf, Christopher [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Mineralogie, Kristallographie und Materialwissenschaften, Universitaet Leipzig (Germany); Zhang, Yuemei; Fokwa, Boniface P.T. [Department of Chemistry, University of California, Riverside, CA (United States); Bartsch, Manfred; Zacharias, Helmut [Physikalisches Institut, Westfaelische Wilhelms-Universitaet Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos, SP (Brazil); Janka, Oliver [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Chemie, Carl von Ossietzky Universitaet Oldenburg (Germany)

2017-11-17

The intermetallic compound CaAu{sub 2}Al{sub 2}, and the members of the solid solutions SrAu{sub 2-x}Al{sub 2+x} (0 ≤ x ≤ 0.33) and Ba{sub 3}Au{sub 5+x}Al{sub 6-x} (x = 0, 0.14, 0.49) were synthesized from the elements in sealed tantalum ampoules. The Ca compound crystallizes with the orthorhombic ThRu{sub 2}P{sub 2} type structure, whereas the targeted SrAu{sub 2}Al{sub 2} was found to form a solid solution according to SrAu{sub 2-x}Al{sub 2+x}. For the Ba system no ''BaAu{sub 2}Al{sub 2}'' was found, however, Ba{sub 3}Au{sub 5+x}Al{sub 6-x} was discovered to crystallize in the monoclinic space group C2/c with its own structure type. The samples were investigated by powder X-ray diffraction and their crystal structures were refined on the basis of single-crystal X-ray diffraction data. All compounds were characterized furthermore by susceptibility measurements. The crystallographic aluminum sites of CaAu{sub 2}Al{sub 2} and Ba{sub 3}Au{sub 5}Al{sub 6} can be differentiated by {sup 27}Al solid state NMR spectra on the basis of their different electric field gradients, in agreement with theoretical calculations. The electron transfer from the alkaline earth metals and the aluminum atoms onto the gold atoms was investigated by X-ray photoelectron spectroscopy (XPS) classifying these intermetallics as aurides, in full agreement with the calculated Bader charges. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Infrared absorption in pseudobinary InSb1-xBix compounds

International Nuclear Information System (INIS)

El-Den, M.B.; Mina, N.K.; Samy, A.M.; El-Mously, M.K.

1988-08-01

The group III-V pseudobinary InSb 1-x Bi x compounds, with x = 0, 0.2 and 0.04, were prepared in thin ribbon forms (30 μ) by splat cooling in air. The optical absorption α(λ) was measured in the wavelength range from 4 to 15 μm. The optical energy gap E opt. , was calculated for the three compounds. A shift of the absorption edge towards longer wavelengths with increasing Bi content was observed. (author). 7 refs, 4 figs

Structural stability of ternary C22–Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and C22–Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds

Energy Technology Data Exchange (ETDEWEB)

Colinet, Catherine, E-mail: ccolinet@simap.grenoble-inp.fr [Science et Ingénierie des Matériaux et Procédés, Grenoble INP, UJF, CNRS, 38402 Saint Martin d’Hères, Cedex (France); Crivello, Jean-Claude [ICMPE-CMTR, CNRS UMR-7182, 2-8 rue Henri Dunant, 94320 Thiais (France); Tedenac, Jean-Claude [Institut de Chimie Moléculaire et des Matériaux I.C.G., UMR-CNRS 5253, Université Montpellier II, Place E. Bataillon, 34095 Montpellier Cedex 5 (France)

2013-09-15

The crystal and electronic structures, and the thermodynamic properties of Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) ternary compounds in the Fe{sub 2}P-type structure have been investigated by means of first principle calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the ternary Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds. - Graphical abstract: Valence charge electronic localization function (ELF) calculated for Zr{sub 6}Sb{sub 2}Co compound. Display Omitted - Highlights: • Structural stability of Zr{sub 6}X{sub 2}T′ compounds (X: p element, T′: late transition metal) in the Fe{sub 2}P-type structure. • First principles calculation of lattice parameters and enthalpies of formation. • Electronic densities of state in the series Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu). • Electronic densities of state in the series Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te)

Magnetic properties of compounds Ba/sub 3/Fesub(2-x)Msub(x)UO/sub 9/ with M=Y, Sc, In and rare earth

Energy Technology Data Exchange (ETDEWEB)

Grenet, J C; Berthon, J [Paris-11 Univ., 91 - Orsay (France); Poix, P [Ecole Nationale Superieure de Chimie, 67 - Strasbourg (France)

1979-01-01

The compounds Ba/sub 3/Fesub(2-x)Msub(x)UO/sub 9/ crystallize in the perovskite type system. The magnetic behavior of these compounds is different when M/sup 3 +/ is dia- or paramagnetic. When M/sup 3 +/ is diamagnetic, the magnetic exchange interaction between A and B sublattices is strongly antiferromagnetic, the (UO/sub 6/)/sup 6 -/ clusters having a special effect. When M/sup 3 +/ is paramagnetic, the perovskite compounds have three magnetic sublattices. In the third one are placed rare earth ions M/sup 3 +/; in this case the A-B exchange interactions are antiferromagnetic but the interactions with the third sublattice are probably slightly ferromagnetic. This special feature and the fact that a temperature of compensation is missing differentiate these perovskites from the garnets.

Electronic and magnetic properties study of neptunium compounds: NpX{sub 3} and Np{sub 2}T{sub 2}X by Moessbauer effect, neutrons diffraction and Squid magnetometry; Etude des proprietes magnetiques et electroniques de composes de neptunium NpX{sub 3} et Np{sub 2}T{sub 2}X par spectrometrie mossbauer, diffraction de neutrons et magnetometrie squid

Energy Technology Data Exchange (ETDEWEB)

Colineau, E.

1996-07-11

This work is a contribution to the study of magnetic and electronic properties of the intermetallic compounds: NpX{sub 3} (X= Al, Ga, In, Sn) and Np{sub 2}T{sub 2}X (T= Co, Ni, Ru, Rh, Pd, Pt; X= In, Sn). These properties have been determined by Moessbauer effect, neutron diffraction and Squid magnetometry. The obtained results for NpX{sub 3} show particularly that NpAl{sub 3} orders in a type II (k= 1/2 1/2 1/2) antiferromagnetic structure at T{sub N} {approx_equal} 37 K. The antiferromagnetic phase NpGa{sub 3} orders in a type II too and the magnetic moments carried by neptunium in the ferromagnetic phase are oriented along the (111) axes. The two NpIN{sub 3} magnetic phases observed by Moessbauer effect (4.2 K-10 K and 10 K- 14 K) are identified by neutron diffraction as ferromagnetic and antiferromagnetic (k= 3/8 3/8 3/8). In this last phase the moments are oriented along the (111) axes. The magnetization measures on monocrystals show a weak anisotropy with (111) at all the temperatures and reveal the presence of a third magnetic phase between 8.2 and 10 K. At last, the fundamental state of the compounds NpAl{sub 3}, NpGa{sub 3} and NpIn{sub 3} is attributed to the {Gamma}{sub 5} crystal field and the strong reduction of the ordered moment in NpSn{sub 3} to a Kondo effect. Concerning the Np{sub 2}T{sub 2}X compounds, the Moessbauer effect measures have revealed that eight of these compounds order and three do not order. (O.M.). 239 refs.

Magnetism and superconductivity in Ru{sub 1-x}Sr{sub 2}RECu{sub 2+x}O{sub 8-d} (RE=Gd, Eu) and RuSr{sub 2}Gd{sub 1-y}Ce{sub y}Cu{sub 2}O{sub 8} compounds

Energy Technology Data Exchange (ETDEWEB)

Klamut, P.W. [Dept. of Physics, Northern Illinois Univ., DeKalb, IL (United States)]|[Inst. of Low Temperature and Structure Research of Polish Academy of Sciences, Wroclaw (Poland); Dabrowski, B.; Mini, S.M.; Kolesnik, S.; Maxwell, M.; Mais, J. [Dept. of Physics, Northern Illinois Univ., DeKalb, IL (United States); Shengelaya, A.; Keller, H. [Physik-Inst., Univ. Zuerich, Zuerich (Switzerland); Khazanov, R. [Physik-Inst., Univ. Zuerich, Zuerich (Switzerland)]|[Lab. for Muon-Spin Spectroscopy, Paul Scherrer Inst., Villigen PSI (Switzerland); Savic, I. [Physik-Inst., Univ. Zuerich, Zuerich (Switzerland)]|[Faculty of Physics, Univ. of Belgrade, Belgrade (Yugoslavia); Sulkowski, C.; Wlosewicz, D.; Matusiak, M. [Inst. of Low Temperature and Structure Research of Polish Academy of Sciences, Wroclaw (Poland); Wisniewski, A.; Puzniak, R.; Fita, I. [Inst. of Physics of Polish Academy of Sciences, Warszawa (Poland)

2002-07-01

We discuss the properties of new superconducting compositions of ruthenocuprates Ru{sub 1-x}Sr{sub 2}RECu{sub 2+x}O{sub 8-d} (RE=Gd, Eu) that were synthesized at 600 atm. of oxygen at 1080 C. By changing ratio between the Ru and Cu, the temperature of superconducting transition (T{sub C}) raises up to T{sub C}{sup max} = 72 K for x=0.3, 0.4. The hole doping achieved along the series increases with Cu{yields}Ru substitution. For x {ne} 0, T{sub C} can be subsequently tuned between T{sub C}{sup max} and 0 K by changing oxygen content in the compounds. The magnetic characteristics of the RE=Gd and Eu based compounds are interpreted as indicative of constrained dimensionality of the superconducting phase. Muon spin rotation experiments reveal the presence of the magnetic transitions at low temperatures (T{sub m}=14-2 K for x=0.1-0.4) that can originate in the response of Ru/Cu sublattice. RuSr{sub 2}Gd{sub 1-y}Ce{sub 1-y}Cu{sub 2}O{sub 8} (0 {<=} y {<=} 0.1) compounds show the simultaneous increase of T{sub N} and decrease of T{sub C} with y. The effect should be explained by the electron doping that occurs with Ce{yields}Gd substitution. Properties of these two series allow us to propose phase diagram for 1212-type ruthenocuprates that links their properties to the hole doping achieved in the systems. Non-superconducting single-phase RuSr{sub 2}GdCu{sub 2}O{sub 8} and RuSr{sub 2}EuCu{sub 2}O{sub 8} are reported and discussed in the context of the properties of substituted compounds. (orig.)

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

International Nuclear Information System (INIS)

Tegus, O.; Bao Li-Hong; Song Lin

2013-01-01

Since the discovery of giant magnetocaloric effect in MnFeP 1−x As x compounds, much valuable work has been performed to develop and improve Fe 2 P-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 Fe 2 P-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 MnFeP 1−x Si(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. (topical review - magnetism, magnetic materials, and interdisciplinary research)

Structural and magnetic properties of MnCo1-xVxGe compounds

International Nuclear Information System (INIS)

Meng, G.H.; Tegus, O.; Zhang, W.G.; Song, L.; Huang, J.H.

2010-01-01

The structural and magnetic properties of MnCo 1-x V x Ge (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20 and 0.30) compounds were investigated by means of X-ray diffraction, scanning electron microscopy and magnetization measurements. The MnCo 1-x V x Ge compounds crystallize in the orthorhombic TiNiSi-type crystal structure for x ≤ 0.02 and in the hexagonal Ni 2 In-type structure for x > 0.02. The magnetization measurements show that the MnCo 1-x V x Ge compounds exhibit a complex magnetic behavior. The Curie temperature can be tuned from 360 K to 148 K by increasing x. The maximal magnetic-entropy change is 3.9 J/kg K for x = 0.06 at a field change from 0 to 1.5 T at about 265 K.

Electronic and magnetic structure of RENi{sub 2}Mn{sub x}-compounds (RE = rare earth, x = 0, 0.25, 0.5, 0.75, 1, 1.25) with respect to ErNi{sub 2}Mn{sub x}

Energy Technology Data Exchange (ETDEWEB)

Balinski, Kamil; Kuepper, Karsten [Department of Physics, Osnabrueck University (Germany); Chrobak, Artur [Department of Physics, University of Silesia in Katowice (Poland); Kuznetzsova, T.V.; Mushnikov, N.V.; Marchenkov, V.V. [Institute of Metal Physics, 620990 Ekaterinburg (Russian Federation)

2015-07-01

Rare earth (RE) and transition metal (T) compounds are research field since the 1960s. Because of huge magnetocalorical effect and giant magnetostriction the RE-T-compounds are excellent for applications like magnetic cooling or hydrogen storage devices. Besides of that RE-Ni{sub 2}-type of alloys are, due to the relatively simple crystal structure and the fact that Ni{sub 2} does not indicate any %behavior with result in an magnetic moment, excellent candidates for studies of magnetic behavior of RE's and their binding partners. The electronic structure of ErNi{sub 2}Mn{sub x} (x = 0, 0.25, 0.5, 0.75, 1, 1.25) is characterized by XPS and ResPES, the magnetic structure is investigated by SQUID and PPMS techniques, and resistivity measurements are made. Variation in Mn concentration revealed the position of Mn 3d-states at 1.7 eV. The XPS intensity at 1.7 eV can be correlated with the behavior of the Curie temperature and the resistivity. While similar RENi{sub 2}Mn{sub x}-systems, where RE had been replaced by Gd and Tb, highest resistivity, Curie temperature and the highest Mn 3d-valence band state intensity were observed at x = 0.5. ErNi{sub 2}Mn{sub x}-system behave different and show the mentioned maxima at x = 1.25.

Crystal structures of orthorhombic, hexagonal, and cubic compounds of the Sm(x)Yb(2−x)TiO5 series

International Nuclear Information System (INIS)

Aughterson, Robert D.; Lumpkin, Gregory R.; Reyes, Massey de los; Sharma, Neeraj; Ling, Christopher D.; Gault, Baptiste; Smith, Katherine L.; Avdeev, Maxim; Cairney, Julie M.

2014-01-01

A series of single phase compounds with nominal stoichiometry Sm (x) Yb (2−x) TiO 5 (x=2, 1.4, 1, 0.6, and 0) have been successfully fabricated to generate a range of crystal structures covering the most common polymorphs previously discovered in the Ln 2 TiO 5 series (Ln=lanthanides and yttrium). Four of the five samples have not been previously fabricated in bulk, single phase form so their crystal structures are refined and detailed using powder synchrotron and single crystal x-ray diffraction, neutron diffraction and transmission electron microscopy. Based on the phase information from diffraction data, there are four crystal structure types in this series; orthorhombic Pnma, hexagonal P6 3 /mmc, cubic (pyrochlore-like) Fd-3m and cubic (fluorite-like) Fm-3m. The cubic materials show modulated structures with variation between long and short range ordering and the variety of diffraction techniques were used to describe these complex crystal structure types. - Graphical abstract: A high resolution image of the compound Sm 0.6 Yb 1.4 TiO 5 showing contrast from lattice fringes and the corresponding fast Fourier transform (FFT) of the HREM image with pyrochlore related diffraction spots marked “P” and fluorite marked “F”. The crystal is oriented down the [1 1 0] zone axis based on the Fd-3m structure. The ideal crystal structure (no vacancies) of the cubic, pyrochlore-like (Sm 0.6 Yb 1.4 TiO 5 ). - Highlights: • First fabrication of bulk single-phase material with stoichiometry Sm 2 TiO 5 . • Systematic study of crystal structure types within Ln 2 TiO 5 series (Ln=lanthanides). • A novel technique using IFFT of HREM images to study cubic structures

In situ X-ray and neutron diffraction of the Ruddlesden-Popper compounds (RE2-xSrx)0.98(Fe0.8Co0.2)1-yMgyO4-δ (RE=La, Pr): Structure and CO2 stability

DEFF Research Database (Denmark)

Chatzichristodoulou, Christodoulos; Hauback, B.C.; Hendriksen, Peter Vang

2013-01-01

The crystal structure of the Ruddlesden-Popper compounds (La 1.0Sr1.0)0.98Fe0.8Co 0.2O4-δ and (La1.2Sr0.8) 0.98(Fe0.8Co0.2)0.8Mg 0.2O4-δ was investigated at 1000 °C in N 2 (aO2=1×10-4) by in-situ powder neutron diffraction. In-situ powder X-ray diffraction (PXD) was also employed to investigate....... The equivalent pseudo-cubic thermal and chemical expansion coefficients are in agreement with values determined by dilatometry. The chemical stability in CO2 containing environments of various Ruddlesden-Popper compounds with chemical formula (RE2-xSr x)0.98(Fe0.8Co0.2) 1-yMgyO4-δ (RE=La, Pr), as well...

Metastable phases freezing from melts of reciprocal systems PbX + CdI2=CdX + PbI2 (X=S, Se, Te)

International Nuclear Information System (INIS)

Odin, I.N.; Chukichev, M.V.

2001-01-01

The transformations in the mutual PbX + CdI 2 =CdX + PbI 2 (X=S, Se, Te) systems leading to the crystallization of metastable polytypical modifications of lead iodide in metastable ternary compounds are studied for the first time. Microstructural and X-ray diffraction analyses were conducted. Their phase diagrams were constructed. The luminescence properties of the stable and metastable modifications of the lead iodide and the metastable compound Pb 4 SeI 6 were investigated. The lines 504 and 512 nm are noted in the 2H-PbI 2 cathodoluminescence spectra. The close lines - 508 and 516 nm provide for the 6R-PbI 2 modification. The metastable compound Pb 4 SeI 6 is characterized by the 769 and 868 nm lines [ru

X-ray absorption spectroscopy on high-temperature superconductors and related compounds

International Nuclear Information System (INIS)

Pellegrin, E.J.H.A.

1995-07-01

The electronic structure of the cuprate high-temperature superconductors La 2-x Sr x CuO 4+δ , Tl 2 Ba 2 CaCu 2 O 8 and Tl 2 Ba 2 Ca 2 Cu 3 O 10 has been investigated using polarization-dependent near-edge X-ray absorption fine structure spectroscopy (NEXAFS). In addition, La 2-x Sr x NiO 4+δ has been included in the actual study as an isostructural analogue to the La 2-x Sr x CuO 4+δ system. It appears that the electronic structure of these compounds corresponds to that of a p-type doped charge-transfer insulator including electron-electron interactions on the Cu(Ni) sites and a strong hybridization between Cu(Ni) and O atoms. It is concluded that the low-energy excitations in these compounds can be described on the basis of an effective one-band Mott-Hubbard model. The polarization-dependence of the above spectra gives evidence for the strong in-plane character of the intrinsic and the doped holes. The small amount and the doping-dependence of the out-of-plane character of these charge carriers rule out models for a microscopic mechanism of superconductivity based on a large amount of hole states in the corresponding Apex-O2p z /Cu3d 3z 2 -r 2 orbitals. On the other hand, the reduction of this anisotropy in the overdoped compounds together with similar findings in the macroscopic properties seems to indicate a detrimental influence of non-planar orbitals on the superconducting properties. The differences in the energetic ordering and atomic character of the states close to the Fermi level between the undoped compounds La 2 CuO 4+δ , La 2 NiO 4+δ , and NiO have been determined from the NEXAFS data. It is found that these differences can be explained by the different size of the tetragonal crystal field splitting E Z compared to that of the Hund's rule interaction J H in these systems. This gives evidence for the high-spin d 8 ground state of the undoped nickelates (i.e. J H >E Z ). It is suggested that the polarons in La 2-x Sr x NiO 4+δ can be seen as non

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.

The (x, T) magnetic phase diagram of Y2Co17-xCrx (1.17-bar x-bar 3) compounds by neutron diffraction

International Nuclear Information System (INIS)

Schobinger-Papamantellos, P.; Buschow, K.H.J.; Fuquan, B.; Tegus, O.; Brueck, E.; Boer, F.R. de; Ritter, C.

2006-01-01

We present the (x, T) phase diagram of the ferromagnetic Y 2 Co 17-x Cr x (x=1.17, 1.76, 2.34, 3) compounds with rhombohedral structure (space group R3-bar m, Th 2 Zn 17 -type), determined for the entire magnetically ordered regime from high-resolution neutron-diffraction data. Substitution of small amounts of Cr for Co was found to have drastic effects on the magnetic properties such as a decrease of the Curie (T C ) and spin reorientation (T SR ) temperatures as well as a decrease of the ordered-moment values. These effects could be brought into connection to the fact that Cr was found to have a preference for the four Co sites in the following order 6c>18f>9d>18h. The number of Cr atoms found occupying the latter two sites, however, is within experimental error negligible. The magnetic phase diagram comprises three distinct regions of magnetic order in addition to the paramagnetic state: (a) the HT range (easy axis) (b) the LT (easy plane) for 0 C and T SR . It also leads to the formation of varying portions of the hexagonal Th 2 Ni 17 -modification (with similar magnetic properties) in samples with x>=1.76. The crystal and magnetic structure of both modifications were refined simultaneously

Magnetocaloric effects in Mn1.35Fe0.65P1−xSix compounds

International Nuclear Information System (INIS)

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

2012-01-01

The structural and magnetocaloric properties of Mn 1.35 Fe 0.65 P 1−x Si x compounds are investigated. The Si-substituted compounds, Mn 1.35 Fe 0.65 P 1−x Si x 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 Fe 2 P-type hexagonal structure with space group P6-bar2m. 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 Mn 1.35 Fe 0.65 P 1−x Si x compound decreases with the Si content increasing. The maximal value of the magnetic-entropy change is about 7.0 J/kg·K in the Mn 1.35 Fe 0.65 P 0.48 Si 0.52 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 Mn 1.35 Fe 0.65 P 0.45 Si 0.55 compound with a field change of 1.48 T. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Correlation between magnetostriction and magnetic structure in pseudobinary compounds Tb(Co1-xFex2

Directory of Open Access Journals (Sweden)

Yue Wang

2017-07-01

Full Text Available Giant low-field magnetostriction has been achieved in pseudobinary Laves phase compounds RR’T2 (R and R’: rare earth elements; T: transition metal elements around the ferromagnetic - ferromagnetic (ferro.-ferro. transition temperature. Evolution of the magnetic structure across such transition requires comprehensive investigation. In this work, pseudobinary system Tb(Co1-xFex2 is selected to investigate the evolution of local magnetic moment, for which two end terminals TbCo2 and TbFe2 possess the rhombohedral (R structure at the ferromagnetic state but with different magnetic ordering temperatures (TC. Magnetometry measurements reveal that a composition independent ferromagnetic - ferromagnetic transition occurs at ∼100 K despite the increased Curie temperature TC with raised Fe concentration in the Tb(Co1-xFex2. Synchrotron XRD data reveal that both the lattice parameter and the lattice strain along the direction are abnormally temperature dependent, accompanied with experimentally observed magnetostriction abnormality at 100 K. In-situ neutron powder diffraction (NPD results show that the local magnetic moments of T2 (9e site atoms are also abnormally temperature dependent, which is larger at 100 K than that at a lower temperature 50 K. Such findings indicate close correlations between the magnetic structure and the magnetostrictive effect in the pseudobinary RT2 compounds.

Magnetic properties and tunable magneto-caloric effect in La0.8Ce0.2Fe11.5-xCoxSi1.5C0.2 (x = 0.3, 0.5, and 0.7) compounds

Science.gov (United States)

Wu, Qiming; Wang, Xiangjie; Ding, Zan; Li, Lingwei

2018-05-01

The magnetic and magneto-caloric properties in the ternary elementals doped La0.8Ce0.2Fe11.5-xCoxSi1.5C0.2 (x = 0.3, 0.5, and 0.7) compounds were studied. With the increases of Co content x, the Curie temperature TC increases and the thermal hysteresis decreases. All the compounds undergo a second-order magnetic phase transition and exhibit a considerable reversible tunable magneto-caloric effect. The values of maximum magnetic entropy change (-ΔSMmax) and the Relative Cooling Power (RCP) are kept at same high level with different Co content. Under a magnetic field change of 0-5 T, the values of -ΔSMmax for La0.8Ce0.2Fe11.5-xCoxSi1.5C0.2 are 10.5, 10.7, and 9.8 J/kg K for x = 0.3, 0.5, and 0.7, respectively. The corresponding values of RCP are 267.1, 289.9, and 290.2 J/kg.

Study of electrical transport properties of (U 1- xY x)RuP 2Si 2

Science.gov (United States)

Radha, S.; Park, J.-G.; Roy, S. B.; Coles, B. R.; Nigam, A. K.; McEwen, K. A.

1996-02-01

Electrical resistivity and magnetoresistance ( {δϱ}/{ϱ}) measurements on a series of (U 1- xY x)Ru 2Si 2 (0 ⩽ x ⩽ 0.9) compounds in the temperature range 4.2-300 K and in magnetic fields up to 45 kOe are reported. The resistivity measurements do not show any signature of antiferromagnetism for x > 0.5. The compound URu 2Si 2 exhibits a large, positive ( {δϱ}/{ϱ}) presumably due to destruction of Kondo coherence as well as due to antiferromagnetism. The presence of even 5% Y at U-site weakens the Kondo coherence and reduces the magnetoresistance considerably.

Transformation characteristics of LaV/sub x/Nb/sub 1-x/O4 compounds

International Nuclear Information System (INIS)

Nevitt, M.V.; Aldred, A.T.

1983-06-01

X-ray diffractometry measurements were made as a function of temperature on a series of polycrystalline LaV/sub x/Nb/sub 1-x/O 4 compounds (0 4 compounds that are either candidates or are appropriate models for candidate materials for hosting nuclear-waste ions. Partial substitution of V 5+ on the Nb 5+ site significantly lowers the tetragonal scheelite (I4 1 /a) to monoclinic fergusonite (I2/c) transformation, from 770 0 K in LaNbO 4 to approximately 215 0 K for LaV 0 25 Nb 0 75 O 4 (the solubility limit is close to x = 0.35). The transformation is displacive, of second order, involving two coupled order parameters. Heat capacity measurements on LaV 0 25 Nb 0 75 O 4 showed that the specific heat anamoly at the transformation point is extremely small. It is concluded that the two polymorphic forms of LaV/sub x/Nb/sub 1-x/O 4 have very nearly the same free energies over a substantial range of temperature below the transformation

Effect of Si substitution on structural, electronic and optical properties of YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds

Energy Technology Data Exchange (ETDEWEB)

Maurya, Dinesh Kumar; Saini, Sapan Mohan, E-mail: smsaini.phy@nitrr.ac.in

2016-10-15

We employed first principle calculations for investigation of structural, electronic and optical properties of YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds. These properties are studied first time on YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} compounds. The exchange and correlation potential is treated by the Coulomb corrected local spin density approximation (LSDA+U) method for better accounting of the correlation between the 4f electrons. The optimized lattice constants and internal cell parameters are in agreement with the available data. Self consistence band structure calculations show that Ni-3d states remains in valance band and dominant below the E{sub F}, while Dy-5d and 4f states mainly contributes above Fermi Energy (E{sub F}) in DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds. We also find that when silicon for nickel substitution takes place (DyNi{sub 4}Si), there is a gradual hybridization of Ni-3d and Si-3p states results, nickel moments decrease rapidly in agreement with the experiment. Optical spectra shows the main absorption peak around 4 eV depends on the substituent concentration and could be due to transition from hybridized band (Ni-3d and Si-3p), below E{sub F} to free Dy-4d states. Frequency-dependent refractive index, n(ω), and the extinction coefficient, k(ω), of DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) are also calculated for the radiation up to 14 eV. - Highlights: • Calculated DOS revels that Ni-3d states are dominated below Fermi level (E{sub F}). • Spin down Dy-4f states show significant contribution to DOS above E{sub F.} • Nickel moments decrease rapidly with substitution of silicon for nickel (DyNi{sub 4}Si). • Most significant peak is found around 7eV in optical conductivity. • Nickel moments decrease rapidly with substitution of silicon for nickel (DyNi{sub 4}Si). • Peak indicates the possibility of transitions from Ni-3d states to empty spin down Dy-4f states.

Readily-accessible oxidation of d0 organozirconium compounds: The electronic structure of (η5-C5H5)3ZrX compounds

International Nuclear Information System (INIS)

Strittmatter, R.J.; Bursten, B.E.; Rhodes, L.F.; Morris, D.E.; Rogers, R.D.

1990-01-01

In an effort to obtain a comparison between organotransition metal and organoactinide complexes, a series of Cp 3 ZrX compounds have been synthesized. A single crystal X-ray crystallographic study of Cp 3 ZrCl reveals that all three Cp ligands are bound in an η 5 fashion. Electrochemical investigations of this series show a first oxidation of these d 0 compounds approximately one volt less positive than the d 0 Cp 2 ZrX 2 compounds and approximately one-half volt less positive than the d 0 f 0 Cp 3 ThCl compound. These results will be presented along with a discussion of the electronic structure of this series, as determined by Xα-SW and Fenske-Hall calculations

Sequential evolution of different phases in metastable Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 (0.0 ≤ x ≤ 2.0) system: crucial role of reaction conditions.

Science.gov (United States)

Shukla, Rakesh; Sayed, Farheen N; Phapale, Suhas; Mishra, Ratikant; Tyagi, Avesh K

2013-07-15

The Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 (0.0 ≤ x ≤ 2.0) series was synthesized by the gel combustion method. This system exhibited the presence of a fluorite-type phase, along with a narrow biphasic region, depending upon the Ce/Gd content in the sample. Thermal stability of these new compounds under oxidizing and reducing conditions has been investigated. The products obtained on decomposition of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 in oxidizing and reducing conditions were found to be entirely different. It was observed that in air the fluorite-type solid solutions of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 composition undergo phase separation into perovskite GdAlO3 and fluorite-type solid solutions of Gd-Ce-Zr-O or Ce-Zr-Al-O depending upon the extent of Ce and Al substitution. On the other hand, Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 samples on heating under reducing conditions show a phase separation to CeAlO3 perovskite and a defect-fluorite of Gd2Zr2O7. The extent of metastability for a typical composition of Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (nano), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O(6.6) (heated under reduced conditions), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (heated in air at 1200 °C) has been experimentally determined employing a high temperature Calvet calorimeter. On the basis of thermodynamic stability data, it could be inferred that the formation of a more stable compound in the presence of two competing cations (i.e., Gd(3+) and Ce(3+)) is guided by the crystallographic stability.

Thermodynamics of the (Sm{sub 2}Fe{sub 17-x}Ga{sub x}+H{sub 2}) system

Energy Technology Data Exchange (ETDEWEB)

Kubis, M.; Handstein, A.; Gebel, B.; Gutfleisch, O.; Mueller, K.H.; Schultz, L. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe

2000-08-10

Sm{sub 2}Fe{sub 17-x}Ga{sub x} samples (with x=0, 0.5, 1, and 2) were disproportionated into SmH{sub 2} and {alpha}-(Fe,Ga) by heating the samples in 4 MPa hydrogen up to 650 C. It was possible to disproportionate even the more stable compounds with a higher Ga content under these conditions. The recombination into the original 2:17 phase was carried out by annealing in low hydrogen pressures of 2.5, 12 and 60 kPa. The values of the hydride formation enthalpy, {delta}H, and of the change of entropy, {delta}S, for the Sm{sub 2}Fe{sub 17-x}Ga{sub x} compounds were obtained by using the Van't Hoff relation. It was found that the negative {delta}H increases monotonically from 141 to 229 kJ/mol H{sub 2} and the negative {delta}S increases monotonically from 112 to 258 J/Kmol H{sub 2} for x=0 to x=2, respectively. These results show that the higher stability for the compounds with increasing Ga content is mainly attributed to the increasing negative change of entropy -{delta}S and not, as expected before, to a decrease of -{delta}H. (orig.)

Magnetic and transport properties of EuNi(Si1-xGex)3 compounds

International Nuclear Information System (INIS)

Uchima, K; Takaesu, Y; Akamine, H; Kakihana, M; Tomori, K; Uejo, T; Teruya, A; Nakamura, A; Hedo, M; Nakama, T; Yagasaki, K; Matsubayashi, K; Uwatoko, Y

2014-01-01

The magnetization M, electrical resistivity ρ, thermopower S and specific heat C of EuNi(Si 1-x Ge x ) 3 compounds have been measured at temperatures from 2 to 300 K. For the compounds of EuNi(Si 1-x Ge x ) 3 , we obtained an effective magnetic moment of μ eff ∼ 7.7 μ B , which is close to the divalent Eu value of μ eff =7.94 μ B . All compounds of EuNi(Si 1-x Ge x ) 3 order antiferromagnetically. The Néel temperature T N decreases monotonously with increasing the Ge concentration x from T N =49 K for EuNiSi 3 to T N =14 K for EuNiGe 3 . In the low temperature region below T N , anomalies corresponding to an additional magnetic phase transition into ferromagnetic state for compounds with x < 0.3, and into another antiferromagnetic for x > 0.3 were observed. The Curie temperature T C rapidly decreases with increasing x and vanishes at x ≈ 0.3. It is found that the magnetic phase transition temperatures of T N and T C in EuNi(Si 1-x Ge x ) 3 are strongly connected with the change of volume induced by the atomic substitution of Si by Ge

The structure and band gap design of high Si doping level Ag1−xGa1−xSixSe2 (x=1/2)

International Nuclear Information System (INIS)

Zhang, Shiyan; Mei, Dajiang; Du, Xin; Lin, Zheshuai; Zhong, Junbo; Wu, Yuandong; Xu, Jingli

2016-01-01

Ag 1−x Ga 1−x Si x Se 2 solutions with high Si doping level (x=1/2) are considered and new compound AgGaSiSe 4 has been synthesized. It crystallizes in space group Aea2 and possesses very long axis of a=63.06(1)Å. The three-dimensional framework in AgGaSiSe 4 is composed of AgSe 3 trigonal planar units, AgSe 4 tetrahedra and MSe 4 (M=Si, Ga) tetrahedra. AgGaSiSe 4 is a congruently melting compound with the melt temperature of 759 °C. The diffuse reflectance measurements reveal the band gap of 2.63 eV in AgGaSiSe 4 and the value is 0.33 eV larger than that of Ag 3 Ga 3 SiSe 8 (2.30 eV). - Graphical abstract: The Ag 1−x Ga 1−x Si x Se 2 with high Si doping level (x=1/2) has been studied and the new compound AgGaSiSe 4 was synthesized for the first time. AgGaSiSe 4 crystallizes in a new structure type in space group Aea2 and adopts a three-dimensional framework consisting of AgSe 3 trigonal planar units, AgSe 4 tetrahedra and MSe 4 (M=Si, Ge) tetrahedra. Display Omitted - Highlights: • Study of Ag 1−x Ga 1−x Si x Se 2 with high Si doping level (x=1/2). • Successful synthesis of new compound named AgGaSiSe 4 . • AgGaSiSe 4 crystallizes in space group Aea2 and adopts a three-dimensional framework. • The energy band gap of AgGaSiSe 4 is enlarged compared with Ag 3 Ga 3 SiSe 8 .

Hydrogen isotope effect on muonic x-ray spectra of (CH2)/sub x/ and H2O

International Nuclear Information System (INIS)

Mausner, L.F.; Knight, J.D.; Orth, C.J.; Schillaci, M.E.; Naumann, R.A.

1977-01-01

We have measured the muonic x-ray intensity patterns of C in (CH 2 )/sub x/ and (CD 2 )/sub x/ and of O in H 2 O and D 2 O. In both cases the relative intensities of the higher Lyman series members are significantly lower in the deuterium compounds, indicating that the initial angular momentum distribution of the muons captured on C and O is weighted to higher l states compared to the normal hydrogen compounds. This isotope effect has not been predicted by any model of negative-meson capture

The structure, magnetism, and electrical-transport properties of the Heusler alloys Co2Cr1-xFexAl (x=0.2-0.6)

International Nuclear Information System (INIS)

Zhang Ming; Wolf, Anne L.; Zhang, L.; Tegus, O.; Brueck, Ekkes; Wu Guangheng; Boer, Frank R. de

2005-01-01

We synthesize the polycrystalline Heusler compounds Co 2 Cr 1-x Fe x Al (x=0.2-0.6). The x-ray diffraction patterns show A2 structure rather than L2 1 structure. The magnetic moment and the Curie temperature increase with increasing x. The electrical resistivity characterizes the Co 2 Cr 1-x Fe x Al compounds to be not typical metals and the temperature dependence of the resistivity changes from metallic to semiconductinglike behavior with increasing Cr concentrations. We attribute the fact, which we observe for most of the compounds smaller magnetic moments than the theoretical values and the low magnetoresistance in these alloys, to the considerably high level of Co-(Cr, Fe)-type disorder

Accessing alkali-free NASICON-type compounds through mixed oxoanion sol–gel chemistry: Hydrogen titanium phosphate sulfate, H{sub 1−x}Ti{sub 2}(PO{sub 4}){sub 3−x}(SO{sub 4}){sub x} (x=0.5–1)

Energy Technology Data Exchange (ETDEWEB)

Mieritz, Daniel; Davidowski, Stephen K.; Seo, Dong-Kyun, E-mail: dseo@asu.edu

2016-10-15

We report a direct sol–gel synthesis and characterization of new proton-containing, rhombohedral NASICION-type titanium compounds with mixed phosphate and sulfate oxoanions. The synthetic conditions were established by utilizing peroxide ion as a decomposable and stabilizing ligand for titanyl ions in the presence of phosphates in a strong acidic medium. Thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), induction-coupled plasma optical emission spectroscopic (ICP-OES) elemental analysis, and Raman and {sup 1}H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopic studies have determined the presence of sulfate and proton ions in the structure, for which the compositional range has been found to be H{sub 1−x}Ti{sub 2}(PO{sub 4}){sub 3−x}(SO{sub 4}){sub x} (x=0.5–1). The particulate products exhibit a nanocrystalline nature observed through characterization with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The N{sub 2} sorption isotherm measurements and subsequent Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses confirmed the presence of the textural meso- and macropores in the materials. Future studies would determine the potential of the new compounds in various applications as battery materials, proton conductors and solid acid catalysts. - Graphical abstract: A series of proton-containing NASICON-type compounds, H{sub 1−x}Ti{sub 2}(PO{sub 4}){sub 3−x}(SO{sub 4}){sub x} (x=0.5–1), were discovered through a new sol–gel synthetic method that utilizes peroxide ion as a decomposable and stabilizing ligand for titanyl ions in the presence of phosphates in a strong acidic medium.

The structure and band gap design of high Si doping level Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} (x=1/2)

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shiyan [College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Mei, Dajiang, E-mail: meidajiang718@pku.edu.cn [College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Du, Xin [Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Lin, Zheshuai [Center for Crystal Research and Development, Key Laboratory of Functional Crystals and Laser Technology, Chinese Academy of Sciences, Beijing 100190 (China); Zhong, Junbo [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Wu, Yuandong, E-mail: wuyuandong2013@outlook.com [College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Xu, Jingli [College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China)

2016-06-15

Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} solutions with high Si doping level (x=1/2) are considered and new compound AgGaSiSe{sub 4} has been synthesized. It crystallizes in space group Aea2 and possesses very long axis of a=63.06(1)Å. The three-dimensional framework in AgGaSiSe{sub 4} is composed of AgSe{sub 3} trigonal planar units, AgSe{sub 4} tetrahedra and MSe{sub 4}(M=Si, Ga) tetrahedra. AgGaSiSe{sub 4} is a congruently melting compound with the melt temperature of 759 °C. The diffuse reflectance measurements reveal the band gap of 2.63 eV in AgGaSiSe{sub 4} and the value is 0.33 eV larger than that of Ag{sub 3}Ga{sub 3}SiSe{sub 8} (2.30 eV). - Graphical abstract: The Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} with high Si doping level (x=1/2) has been studied and the new compound AgGaSiSe{sub 4} was synthesized for the first time. AgGaSiSe{sub 4} crystallizes in a new structure type in space group Aea2 and adopts a three-dimensional framework consisting of AgSe{sub 3} trigonal planar units, AgSe{sub 4} tetrahedra and MSe{sub 4} (M=Si, Ge) tetrahedra. Display Omitted - Highlights: • Study of Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} with high Si doping level (x=1/2). • Successful synthesis of new compound named AgGaSiSe{sub 4}. • AgGaSiSe{sub 4} crystallizes in space group Aea2 and adopts a three-dimensional framework. • The energy band gap of AgGaSiSe{sub 4} is enlarged compared with Ag{sub 3}Ga{sub 3}SiSe{sub 8}.

Phase formation and magnetic properties of YFe12-xNbx (x=0.70-0.90) compounds

International Nuclear Information System (INIS)

Fuquan, B.; Wang, J.L.; Tegus, O.; Dagula, W.; Tang, N.; Yang, F.M.; Wu, G.H.; Brueck, E.; Boer, F.R. de; Buschow, K.H.J.

2005-01-01

The phase formation and the magnetic properties of YFe 12-x Nb x (x=0.70-0.90) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that all compounds investigated crystallize single phase in the tetragonal ThMn 12 -type of structure. The lattice parameters and the unit-cell volume increase slightly with increasing Nb content, but the Curie temperature does not change. The X-ray-diffraction patterns of aligned powders of the samples show that all the compounds investigated have uniaxial anisotropy at room temperature. At 1.5K, the spontaneous magnetization, the anisotropy field and the anisotropy constant K 1 decrease with increasing Nb content

Elastic properties of LaSnxNi5-x compounds

International Nuclear Information System (INIS)

Yeheskel, O.; Nattrass, C.E.; Leisure, R.G.; Jacob, I.; Bowman, R.C. Jr.

2004-01-01

Ultrasonic methods were used to measure the room-temperature elastic moduli of polycrystalline LaSn x Ni 5-x compounds for 0≤x≤0.5. These materials are of great importance for their hydrogen storage properties. The samples, prepared by a hot isostatic pressing method, had near-theoretical densities with calculated porosities ranging from 0 to 1.5%. The porosity-corrected moduli decreased with increasing x. Poisson's ratio was approximately constant at 0.314 for all the compounds. The Debye temperature, calculated from the RT polycrystalline moduli, decreased from 359 to 344 K as x increased from 0 to 0.5. The results were used to calculate the elastic interaction energy of an interstitial hydrogen atom with the strain fields of all the other interstitial hydrogen. This energy was in turn used to calculate the critical temperature below which phase separation occurs in LaM x Ni 5-x H y compounds (M=Sn or Al). It was found that the critical temperature decreases with increasing x, confirming in a more general way a conclusion drawn for a specific case from earlier thermodynamic measurements. It is suggested that the lowering of the critical temperature plays a role in limiting the width of the plateaus in pressure-composition isotherms for the two-phase regions of these compounds. This suggestion implies a relation between the elastic properties and the maximum hydrogen capacity

Polymorphism in 2-X-adamantane derivatives (X = Cl, Br).

Science.gov (United States)

Negrier, Philippe; Barrio, María; Tamarit, Josep Ll; Mondieig, Denise

2014-08-14

The polymorphism of two 2-X-adamantane derivatives, X = Cl, X = Br, has been studied by X-ray powder diffraction and normal- and high-pressure (up to 300 MPa) differential scanning calorimetry. 2-Br-adamantane displays a low-temperature orthorhombic phase (space group P212121, Z = 4) and a high-temperature plastic phase (Fm3̅m, Z = 4) from 277.9 ± 1.0 K to the melting point at 413.4 ± 1.0 K. 2-Cl-adamantane presents a richer polymorphic behavior through the temperature range studied. At low temperature it displays a triclinic phase (P1̅, Z = 2), which transforms to a monoclinic phase (C2/c, Z = 8) at 224.4 ± 1.0 K, both phases being ordered. Two high-temperature orientationally disordered are found for this compound, one hexagonal (P63/mcm, Z = 6) at ca. 241 K and the highest one, cubic (Fm3̅m, Z = 4), being stable from 244 ± 1.0 K up to the melting point at 467.5 ± 1.0 K. No additional phase appears due to the increase in pressure within the studied range. The intermolecular interactions are found to be weak, especially for the 2-Br-adamantane compound for which the Br···Br as well as C-Br···H distances are larger than the addition of the van der Waals radii, thus confirming the availability of this compound for building up diamondoid blocks.

Growth and magnetotransport properties of epitaxial films of the layered perovskite La2-2xSr1+2xMn2O7

International Nuclear Information System (INIS)

Philipp, J.B.; Alff, L.; Gross, R.; Klein, J.; Recher, C.

2002-01-01

Epitaxial thin films of the bilayered perovskite La 2-2x Sr 1+2x Mn 2 O 7 (x=0.3, 0.4) have been grown by laser molecular beam epitaxy on NdGaO 3 substrates. Magnetotransport measurements with the current in the ab-plane and along the c-axis direction showed an intrinsic c-axis tunneling magnetoresistance effect associated with nonlinear current-voltage-characteristics for the x=0.3 compound. Besides the colossal magnetoresistance effect around the Curie temperature T C , at temperatures below about 40 K an additional high-field magnetoresistance was found most likely due to a strain and disorder induced re-entrant spin glass state in both the x=0.3 and 0.4 compounds. Our experiments show that the substrate induced coherency strain in the high quality epitaxial films results in magnetotransport properties that show markedly different behavior from those of single crystals. (orig.)

NpX3 compounds under high pressure

International Nuclear Information System (INIS)

Zwirner, S.; Kalvius, G.M.

1993-01-01

The systematics of hyperfine interactions and the ordering temperature T ord in isostructural NpX 3 compounds (X=Al, Si, Ga, Ge, ln, Sn) are briefly reviewed. NpSn 3 has been viewed as a Kondo lattice system, similar to CeAl 2 , NpIn 3 shows a modulated magnetic structure including low moment and nonmagnetic contributions at ambient pressure and 4.2 K. Preliminary results of recent 237 Np Moessbauer studies on NpIn 3 at ambient pressure and various temperatures and at 4.0(8) GPa and 4.2 K are reported. At 4.0(8) GPa, T ord rises from 17 to 22 K, the low-moment contributions of the modulated structure are reduced and the non-magnetic site is lost below T ord . The variation of the hyperfine parameters and of T ord with pressure is similar to the behavior observed in NpSn 3 . (orig.)

Low-temperature heat-capacity study of the U6X (XequivalentMn, Fe, Co, Ni) compounds

International Nuclear Information System (INIS)

Yang, K.N.; Maple, M.B.; DeLong, L.E.; Huber, J.G.; Junod, A.

1989-01-01

Measurements of the superconducting- and normal-state heat capacity of U 6 X (XequivalentMn, Fe, Co, Ni) compounds have been performed over a temperature range 1 Kapprox. 6 X compounds have strong renormalizations of the free-carrier effective mass m/sup */ in the range 10m/sub e/approx. 6 X heat capacities suggest the presence of high densities of low-energy excitations of undetermined nature. The results are analyzed in terms of models appropriate to heavy-fermion liquids, and anisotropic or strong-coupled superconductors. The U 6 X compounds form a link between relatively low-m/sup */, high-transition-temperature A15 compounds and the more extreme examples of heavy-fermion superconductors such as UBe/sub 13/, UPt 3 , and CeCuSi 2 for which m/sup */∼10 2 m/sub e/. .AE

Metamagnetic behaviour of La1-xGdxFe12B6 compounds

International Nuclear Information System (INIS)

Li, Q.A.; Groot, C.H. de; Boer, F.R. de; Buschow, K.H.J.

1997-01-01

The magnetic properties of compounds of the type La 1-x Gd x Fe 12 B 6 have been studied in high magnetic fields at 4.2 K. LaFe 12 B 6 is a compound with Fe moments close to magnetic instability and values not larger than about 0.5 μ B . Substitution of Gd for part of the La and application of high magnetic fields enhance the Fe moments to values in excess of 2 μ B . The high-moment state in LaFe 12 B 6 is reached via a metamagnetic transition. This first-order transition is associated with an extremely large hysteresis of nearly 7 T at 4.2 K. (orig.)

Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

Science.gov (United States)

Lee, Jonathan A.

2009-01-01

In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

In situ X-ray and neutron diffraction of the Ruddlesden–Popper compounds (RE2−xSrx)0.98(Fe0.8Co0.2)1−yMgyO4−δ (RE=La, Pr): Structure and CO2 stability

International Nuclear Information System (INIS)

Chatzichristodoulou, C.; Hauback, B.C.; Hendriksen, P.V.

2013-01-01

The crystal structure of the Ruddlesden–Popper compounds (La 1.0 Sr 1.0 ) 0.98 Fe 0.8 Co 0.2 O 4−δ and (La 1.2 Sr 0.8 ) 0.98 (Fe 0.8 Co 0.2 ) 0.8 Mg 0.2 O 4−δ was investigated at 1000 °C in N 2 (a O2 =1×10 −4 ) by in-situ powder neutron diffraction. In-situ powder X-ray diffraction (PXD) was also employed to investigate the temperature dependence of the lattice parameters of the compounds in air and the oxygen activity dependence of the lattice parameters at 800 °C and 1000 °C. The thermal and chemical expansion coefficients, determined along the two crystallographic directions of the tetragonal unit cell, are highly anisotropic. The equivalent pseudo-cubic thermal and chemical expansion coefficients are in agreement with values determined by dilatometry. The chemical stability in CO 2 containing environments of various Ruddlesden–Popper compounds with chemical formula (RE 2−x Sr x ) 0.98 (Fe 0.8 Co 0.2 ) 1−y Mg y O 4−δ (RE=La, Pr), as well as their stability limit in H 2 /H 2 O=4.5 were also determined by in-situ PXD for x=0.9, 1.0 and y=0, 0.2. - Graphical abstract: Influence of electronic configuration on bond length, lattice parameters and anisotropic thermal and chemical expansion. Highlights: ► The thermal and chemical expansion coefficients are largely anisotropic. ► The expansion of the perovskite layers is constrained along the a direction. ► The studied compositions show remarkable thermodynamic stability upon reduction. ► The thermal and chemical expansion coefficients are lower than related perovskites. ► The investigated materials decompose in CO 2 containing atmospheres

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

Magnetic properties of the Ce2Fe17-x Mn x helical magnets up to high magnetic fields

International Nuclear Information System (INIS)

Kuchin, A.G.; Mushnikov, N.V.; Bartashevich, M.I.; Prokhnenko, O.; Khrabrov, V.I.; Lapina, T.P.

2007-01-01

Magnetic properties of the Ce 2 Fe 17- x Mn x , x=0-2, alloys in magnetic fields up to 40 T are reported. The compounds with x=0.5-1 are helical antiferromagnets and those with 1 B that couple antiparallelly to the Fe moments. Easy-plane magnetic anisotropy in the Ce 2 Fe 17- x Mn x compounds weakens upon substitution of Mn for Fe. The absolute value of the first anisotropy constant in the Ce 2 Fe 17- x Mn x helical ferromagnets decreases slower with increasing temperature than that calculated from the third power of the spontaneous magnetization. Noticeable magnetic hysteresis in the Ce 2 Fe 17- x Mn x , x=0.5-2, helical magnets over the whole range of magnetic fields reflects mainly irreversible deformation of the helical magnetic structure during the magnetization of the compounds. A contribution from short-range order (SRO) magnetic clusters to the magnetic hysteresis of the helical magnets has been also estimated

Magnetism and large magnetocaloric effect in HoFe{sub 2-x}Al{sub x}

Energy Technology Data Exchange (ETDEWEB)

Mican, S., E-mail: sever.mican@ubbcluj.ro [Babes-Bolyai University Cluj-Napoca, RO-400084 Cluj-Napoca (Romania); Benea, D., E-mail: diana.benea@phys.ubbcluj.ro [Babes-Bolyai University Cluj-Napoca, RO-400084 Cluj-Napoca (Romania); Tetean, R., E-mail: romulus.tetean@phys.ubbcluj.ro [Babes-Bolyai University Cluj-Napoca, RO-400084 Cluj-Napoca (Romania)

2013-02-05

Highlights: Black-Right-Pointing-Pointer Structural, magnetic and magnetocaloric properties of HoFe{sub 2-x}Al{sub x} compounds are reported. Black-Right-Pointing-Pointer Electronic structure calculations show a good agreement between theory and experiment. Black-Right-Pointing-Pointer Magnetic transitions close to room temperature for the Fe-rich samples. Black-Right-Pointing-Pointer High values of the relative cooling power for all of the investigated samples. Black-Right-Pointing-Pointer No hysteresis losses in applied fields of up to 4 T. - Abstract: The structural, magnetic and magnetocaloric properties of several HoFe{sub 2-x}Al{sub x} compounds were investigated. The compounds in the Fe-rich region (0.36 Less-Than-Or-Slanted-Equal-To x Less-Than-Or-Slanted-Equal-To 0.4) crystallize in the cubic MgCu{sub 2} (C15) structure, while for the ones in the intermediate region (0.75 Less-Than-Or-Slanted-Equal-To x Less-Than-Or-Slanted-Equal-To 1.125) the hexagonal MgZn{sub 2} (C14) structure was observed. Electronic structure calculations were performed, showing a good agreement between theory and experiment. The Curie temperatures were found to decrease with Al content. For the Fe-rich compounds, these are close to room temperature, while for the compounds in the intermediate region, transition temperatures are well below 300 K. No magnetic hysteresis was found around the Curie temperature for applied magnetic fields of up to 4 T. All of the investigated compounds undergo a second-order magnetic phase transition at the Curie temperature. A maximum magnetic entropy change value of 7.6 J/kg K was obtained for the sample with x = 1.125, all of the samples displaying rather large RCP values. The possibility of incorporating these materials in magnetic refrigeration devices is discussed.

X-ray imaging with compound refractive lens and microfocus X-ray tube

OpenAIRE

Pina, Ladislav; Dudchik, Yury; Jelinek, Vaclav; Sveda, Libor; Marsik, Jiri; Horvath, Martin; Petr, Ondrej

2008-01-01

Compound refractive lenses (CRL), consisting of a lot number in-line concave microlenses made of low-Z material were studied. Lenses with focal length 109 mm and 41 mm for 8-keV X-rays, microfocus X-ray tube and X-ray CCD camera were used in experiments. Obtained images show intensity distribution of magnified microfocus X-ray source focal spot. Within the experiments, one lens was also used as an objective lens of the X-ray microscope, where the copper anode X-ray microfocus tube served as a...

Crystal structures and electronic properties of UTixNb3-xO10 (x=0,1/3,1) and of the intercalation compound Li0.9UTiNb2O10

International Nuclear Information System (INIS)

Dickens, P.G.; Flynn, G.J.; Patat, S.; Stuttart, G.P.

1997-01-01

Complete crystal structures of the related phases UTi x Nb 3-x O 10 (x=0,1/3,1) and of the intercalation compound Li 0.9 UTiNb 2 O 10 have been determined by Rietveld analysis of room-temperature powder neutron diffraction data. The new structural data combined with magnetic susceptibility measurements made in the range 5 y 1 U V 1+y-x U VI x-y Ti IV x Nb V 3-x O 10 (y≤ x ≤1) with U V (f 1 ) being the only paramagnetic species present. (Author)

The determination of the crystal structures of some uranium compounds by means of x-ray and neutron diffraction

International Nuclear Information System (INIS)

Adrian, H.W.W.

1977-10-01

In industrial uranium processing or reprocessing procedures, aqueous uranyl nitrate solutions are an intermediate product. The compounds, whose structures are reported, might prove valuable as alternative crystallization products to existing methods of extracting the uranium from solution. The compounds are obtained by the addition of hydroxylammonium to the uranyl nitrate solution and are of the general formula UO 2 (NH 2 0) 2 .xH 2 0, where x can take the values zero, two, three and four. In addition a compound of the formula UO 2 (NH 2 0) 2 .2(NH 2 CH).2H 2 0 was obtained. The UO 2 (NH 2 0) compound crystallized in a monoclinic crystal form. Crystals large enough for neutron diffraction were not obtained. The structure of the UO 2 (NH 2 0) 2 .2H 2 0 could not be solved because only disordered crystalline material was available. The structure of UO 2 (NH 2 0) 2 .3H 2 0 was solved by means of room- and low-temperature neutron diffraction. The unit cell is orthorhombic. The structure of α-UO 2 (NH 2 0) 2 .4H 2 0 was investigated by means of room-temperature x-ray and room- and low-temperature neutron diffraction. The unit cell is triclinic. This compound strongly resembles the trihydrate. The UO 2 (NH 2 0) 2 .2(NH 2 0H).2H 2 0 compound gave crystals large enough for single crystal x-ray but not neutron diffraction. The unit cell is orthorhombic. The characteristic powder patterns (indexed except for the dihydrate compound) of the above compounds are reported [af

Magnetic properties and magnetocaloric effect in the HoNi1−xCuxIn (x=0, 0.1, 0.3, 0.4) intermetallic compounds

International Nuclear Information System (INIS)

Mo, Zhao-Jun; Shen, Jun; Yan, Li-Qin; Tang, Cheng-Chun; He, Xiao-Nan; Zheng, Xinqi; Wu, Jian-Feng; Sun, Ji-Rong; Shen, Bao-Gen

2014-01-01

The magnetic properties and magnetocaloric effect (MCE) in HoNi 1−x Cu x In (x=0, 0.1, 0.3, 0.4) compounds have been investigated. With the substitution of Cu for Ni, the Ho magnetic moment will cant from the c-axis, and form a complicated magnetic structure. These compounds exhibit two successive magnetic transitions with the increase in temperature. The large reversible magnetocaloric effects have been observed in HoNi 1−x Cu x In compounds around T ord , with no thermal and magnetic hysteresis loss. The large reversible isothermal magnetic entropy change (−ΔS M ) is 20.2 J/kg K and the refrigeration capacity (RC) reaches 356.7 J/kg for field changes of 5 T for HoNi 0.7 Cu 0.3 In. Especially, the value of −ΔS M (12.5 J/kg K) and the large RC (132 J/kg) are observed for field changes of 2 T for HoNi 0.9 Cu 0.1 In. Additionally, the values of RC are improved to 149 J/K for the field changes of 2 T due to a wide temperature span for the mix of HoNi 0.9 Cu 0.1 In and HoNi 0.7 Cu 0.3 In compounds with the mass ratio of 1:1. These compounds with excellent MCE are expected to have effective applications in magnetic refrigeration around 20 K. - Highlights: • For magnetic-field changes of 2 T, the values of RC are improved to 149 J/K. • MCEs of these compounds show no thermal and magnetic hysteresis. • Compounds show two successive magnetic transitions with the increase in temperature. • With the substitution of Cu for Ni, compounds form a complicated magnetic structure

Crystal structure and magnetic state of pseudo-binary intermetallic compounds Ho(Cosub(1-x)Nisub(x))sub(5)

International Nuclear Information System (INIS)

Chuev, V.V.; Kelarev, V.V.; Pirogov, A.N.; Sidorov, S.K.; Koryakova, V.S.

1983-01-01

In the range of 1.8-1000 K intermetallic compounds Ho(Cosub(1-x)Nisub(x))sub(5) have been investigated neutronographically and roentgenographically. Crystal structure of two series of samples: HoCosub(5.5-5.5x)Nisub(5x) and HoCosub(5-5x)Nisub(5x) is studied. It is shown that Ni atoms mainly occupy positions 2c, Co atoms - positions 3g; coordinates of atoms and position occupation of TbCu 7 type structure are specified. Analysis of magnetic structure is made, angles of magnetic momenta orientation as to crystallographic axes are determined. Magnetic phase diagram is built. Concentrational dependences of sublattice magnetization: Msub(Ho)(x), Mdsub(2c)(x), Mdsub(3g)(x) are determined

Effect of Pressure on Valence and Structural Properties of YbFe₂Ge₂ Heavy Fermion Compound A Combined Inelastic X-ray Spectroscopy, X-ray Diffraction, and Theoretical Investigation

Energy Technology Data Exchange (ETDEWEB)

Kumar, Ravhi S.; Svane, Axel; Vaitheeswaran; #8741; , Ganapathy; Kanchana, Venkatakrishnan; Antonio, Daniel; Cornelius, Andrew L.; Bauer, Eric D.; Xiao, Yuming; Chow, Paul (Aarhus); (CIW); (Hyderabad - India); (IIT-India); (LANL); (UNLV)

2016-06-03

The crystal structure and the Yb valence of the YbFe₂Ge₂ heavy fermion compound was measured at room temperature and under high pressures using high-pressure powder X-ray diffraction and X-ray absorption spectroscopy via both partial fluorescence yield and resonant inelastic X-ray emission techniques. Furthermore, the measurements are complemented by first-principles density functional theoretical calculations using the self-interaction corrected local spin density approximation investigating in particular the magnetic structure and the Yb valence. While the ThCr₂Si₂-type tetragonal (I4/mmm) structure is stable up to 53 GPa, the X-ray emission results show an increase of the Yb valence from v = 2.72(2) at ambient pressure to v = 2.93(3) at ~9 GPa, where at low temperature a pressure-induced quantum critical state was reported.

Crystallographic and 119Sn and 155Gd Moessbauer analyses of Gd5Ge2(Si1-xSnx)2 (x = 0.23 and x = 0.40)

International Nuclear Information System (INIS)

Campoy, J. C. P.; Santos, A. O. dos; Cardoso, L. P.; Paesano, A.; Raposo, M. T.; Fabris, J. D.

2010-01-01

We report the structural characterization of Gd 5 Ge 2 (Si 1-x Sn x ) 2 (x = 0.23 and x = 0.40) compounds by means of 100 and 298 K-X-ray diffractometry (XRD) and 4 K- 155 Gd and 298 K- 119 Sn Moessbauer spectroscopy. These compounds order ferromagnetically at 218.4 and 172.7 K, respectively. At ∼100 K, it was identified the Gd 5 Si 4 -orthorhombic phase (type I) for both samples. At ∼298 K, it was identified a Gd 5 Si 2 Ge 2 -monoclinic phase, for x = 0.23 and a Sm 5 Sn 4 -orthorhombic phase (type II), for x 0.40. The Rietveld analysis of XRD data suggests a first order magneto-structural transition at Curie temperature for both compositions. Moessbauer results are well consistent with the proposed crystallographic models for these systems.

Lessons learned from participating in D3R 2016 Grand Challenge 2: compounds targeting the farnesoid X receptor

Science.gov (United States)

Duan, Rui; Xu, Xianjin; Zou, Xiaoqin

2018-01-01

D3R 2016 Grand Challenge 2 focused on predictions of binding modes and affinities for 102 compounds against the farnesoid X receptor (FXR). In this challenge, two distinct methods, a docking-based method and a template-based method, were employed by our team for the binding mode prediction. For the new template-based method, 3D ligand similarities were calculated for each query compound against the ligands in the co-crystal structures of FXR available in Protein Data Bank. The binding mode was predicted based on the co-crystal protein structure containing the ligand with the best ligand similarity score against the query compound. For the FXR dataset, the template-based method achieved a better performance than the docking-based method on the binding mode prediction. For the binding affinity prediction, an in-house knowledge-based scoring function ITScore2 and MM/PBSA approach were employed. Good performance was achieved for MM/PBSA, whereas the performance of ITScore2 was sensitive to ligand composition, e.g. the percentage of carbon atoms in the compounds. The sensitivity to ligand composition could be a clue for the further improvement of our knowledge-based scoring function.

Bonding in inorganic compounds: a study by x-ray photoelectron spectroscopy

International Nuclear Information System (INIS)

Avanzino, S.C.

1978-10-01

Core electron binding energies were measured for a variety of inorganic and organometallic compounds using gas-phase X-ray photoelectron spectroscopy (XPS). The atomic charge distributions in these molecules are deduced from the binding energies, often leading to a better understanding of the bonding in these compounds. The XPS spectra of fifteen volatile tin compounds were recorded. The data suggest that the metal d orbitals are not significantly involved in the bonding. The oxygen ls XPS spectra of gaseous CH 3 Mn(CO) 5 , [π-C 5 H 5 Fe(CO) 2 ] 2 , and Co 4 (CO) 12 can be readily resolved into separate peaks due to bridging and terminal carbonyl groups. The C ls spectrum of Fe(CO) 5 consists of a single symmetric peak. The carbonyl ligand core binding energies of transition-metal carbonyl complexes are sensitive to differences in the metal-to-CO ligand bonding. Both C ls and O ls carbonyl binding energies correlate well with average C-O stretching force constants or average C-O stretching frequencies. The metal and carbonyl binding energies in a series of pentacarbonylmanganese complexes LMn(CO) 5 are a good measure of the relative electronegativities of the ligands L. High-quality X-ray photoelectron spectra have been obtained for compounds dissolved in glycerin solutions, and aqueous solutions were converted into glycerin solutions which gave good XRSspectra of the solutes. The technique appears promising as a future analytical application of X-ray photoelectron spectroscopy. The shifts in the binding energies of oxygen, chlorine, and carbon atoms in some isoelectronic isostructural compounds can be explained in terms of simple trends in atomic charges

Synthesis, structure and chemical bonding of CaFe{sub 2−x}Rh{sub x}Si{sub 2} (x=0, 1.32, and 2) and SrCo{sub 2}Si{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Hlukhyy, Viktor, E-mail: viktor.hlukhyy@lrz.tu-muenchen.de; Hoffmann, Andrea V.; Fässler, Thomas F.

2013-07-15

The finding of superconductivity in Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2} put the attention on the investigation of compounds that crystallize with ThCr{sub 2}Si{sub 2} structure type such as AT{sub 2}X{sub 2} (A=alkali/alkaline earth/rare earth element; T=transition metal and X=element of the 13–15th group). In this context the silicides CaFe{sub 2}Si{sub 2}, CaFe{sub 0.68(6)}Rh{sub 1.32(6)}Si{sub 2}, CaRh{sub 2}Si{sub 2} and SrCo{sub 2}Si{sub 2} have been synthesized by reaction of the elements under an argon atmosphere. Single crystals were obtained by special heat treatment in welded niobium/tantalum ampoules. The compounds were investigated by means of powder and single crystal X-ray diffraction. All compounds crystallize in the ThCr{sub 2}Si{sub 2}-type structure with space group I4/mmm (No. 139): a=3.939(1) Å, c=10.185(1) Å, R{sub 1}=0.045, 85 F{sup 2} values, 8 variable parameters for CaFe{sub 2}Si{sub 2}; a=4.0590(2) Å, c=9.9390(8) Å, R{sub 1}=0.030, 90 F{sup 2} values, 10 variable parameters for CaFe{sub 0.68(6)}Rh{sub 1.32(6)}Si{sub 2}; a=4.0695(1) Å, c=9.9841(3) Å, R{sub 1}=0.031, 114 F{sup 2} values, 9 variable parameters for CaRh{sub 2}Si{sub 2}; and a=3.974(1) Å, c=10.395(1) Å, R{sub 1}=0.036, 95 F{sup 2} values, 8 variable parameters for SrCo{sub 2}Si{sub 2}. The structure of SrCo{sub 2}Si{sub 2} contains isolated [Co{sub 2}Si{sub 2}]{sup 2−} 2D-layers in the ab-plane whereas in CaFe{sub 2−x}Rh{sub x}Si{sub 2} the [T{sub 2}Si{sub 2}] layers (T=Fe and Rh) are interconnected along the c-axis via Si3Si bonds resulting in a three-dimentional (3D) [T{sub 2}Si{sub 2}]{sup 2−} polyanions and therefore belong to the so-called collapsed form of the ThCr{sub 2}Si{sub 2}-type structure. The SrCo{sub 2}Si{sub 2} and CaRh{sub 2}Si{sub 2} are isoelectronic to the parent 122 iron–pnictide superconductors AeFe{sub 2}As{sub 2} (Ae=alkaline earth elements), whereas CaFe{sub 2}Si{sub 2} is a full substituted variant (As/Si) of CaFe{sub 2}As{sub 2

X-ray electron investigation of technetium compounds

International Nuclear Information System (INIS)

Gerasimov, V.N.; Kryuchkov, S.V.; Kuzina, A.F.; Kulakov, V.M.; Pirozhkov, S.V.; Spitsyn, V.I.; Gosudarstvennyj Komitet po Ispol'zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Atomnoj Ehnergii)

1982-01-01

Investigation results of a number of technetium compounds using the method of X-ray electron spectroscopy have been presented for the first time. Calculation of effective charge for compounds without Tc-Tc bond and cluster complexes with strong Tc-Tc bond is made. Strong interdependence of effective charge and properties of technetium clusters is shown. Binding energies for certain cluster complexes of technetium with halides are given

Synthesis, structure and chemical bonding of CaFe2−xRhxSi2 (x=0, 1.32, and 2) and SrCo2Si2

International Nuclear Information System (INIS)

Hlukhyy, Viktor; Hoffmann, Andrea V.; Fässler, Thomas F.

2013-01-01

The finding of superconductivity in Ba 0.6 K 0.4 Fe 2 As 2 put the attention on the investigation of compounds that crystallize with ThCr 2 Si 2 structure type such as AT 2 X 2 (A=alkali/alkaline earth/rare earth element; T=transition metal and X=element of the 13–15th group). In this context the silicides CaFe 2 Si 2 , CaFe 0.68(6) Rh 1.32(6) Si 2 , CaRh 2 Si 2 and SrCo 2 Si 2 have been synthesized by reaction of the elements under an argon atmosphere. Single crystals were obtained by special heat treatment in welded niobium/tantalum ampoules. The compounds were investigated by means of powder and single crystal X-ray diffraction. All compounds crystallize in the ThCr 2 Si 2 -type structure with space group I4/mmm (No. 139): a=3.939(1) Å, c=10.185(1) Å, R 1 =0.045, 85 F 2 values, 8 variable parameters for CaFe 2 Si 2 ; a=4.0590(2) Å, c=9.9390(8) Å, R 1 =0.030, 90 F 2 values, 10 variable parameters for CaFe 0.68(6) Rh 1.32(6) Si 2 ; a=4.0695(1) Å, c=9.9841(3) Å, R 1 =0.031, 114 F 2 values, 9 variable parameters for CaRh 2 Si 2 ; and a=3.974(1) Å, c=10.395(1) Å, R 1 =0.036, 95 F 2 values, 8 variable parameters for SrCo 2 Si 2 . The structure of SrCo 2 Si 2 contains isolated [Co 2 Si 2 ] 2− 2D-layers in the ab-plane whereas in CaFe 2−x Rh x Si 2 the [T 2 Si 2 ] layers (T=Fe and Rh) are interconnected along the c-axis via Si3Si bonds resulting in a three-dimentional (3D) [T 2 Si 2 ] 2− polyanions and therefore belong to the so-called collapsed form of the ThCr 2 Si 2 -type structure. The SrCo 2 Si 2 and CaRh 2 Si 2 are isoelectronic to the parent 122 iron–pnictide superconductors AeFe 2 As 2 (Ae=alkaline earth elements), whereas CaFe 2 Si 2 is a full substituted variant (As/Si) of CaFe 2 As 2 . The crystal chemistry and chemical bonding in the title compounds are discussed in terms of LMTO band structure calculations and a topological analysis using the Electron Localization Function (ELF). - Graphical abstract: The SrCo 2 Si 2 and CaFe 2−x Rh x Si

Novel organophosphorus compounds; synthesis, spectroscopy and X-ray crystallography

Czech Academy of Sciences Publication Activity Database

Shariatinia, Z.; Sohrabi, M.; Yousefi, M.; Kovaľ, Tomáš; Dušek, Michal

2012-01-01

Roč. 11, č. 2 (2012), s. 125-133 ISSN 1024-1221 Grant - others:AV ČR(CZ) AP0701 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : organophosphorus compounds * NMR * X-ray crystallography * hydrogen bond Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.686, year: 2012

Magnetic anisotropy of (Sm, Y)2Fe17Ny compounds

International Nuclear Information System (INIS)

Lu, Y.; Tegus, O.; Li, Q.A.; Tang, N.; Yu, M.J.; Zhao, R.W.; Kuang, J.P.; Yang, F.M.; Zhou, G.F.; Li, X.; Boer, F.R. de

1992-01-01

A study of the crystal structure and the magnetic properties, especially the magnetocrystalline anisotropy of (Sm 1-x Y x ) 2 Fe 17 N y compounds (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0, 2 2 Zn 17 - or Th 2 Ni 17 -type structure as the original compounds. The Curie temperatures decrease from 750 to 700 K as x increases from 0 to 1. The anisotropy field decreases linearly with increasing yttrium content. The spin reorientation has been investigated by means of high field magnetization measurements, AC-susceptibility measurements and thermomagnetic analysis, combined with X-ray diffraction. The anisotropy constants K 1 , K 2 and K 3 were derived by a phenomenological analysis, using magnetization curves measured in high fields, applied perpendicular to the alignment direction of the powder samples. A tentative spin phase diagram of the series is presented. (orig.)

Magnetostriction of rare earth-Fe2 Laves phase compounds

International Nuclear Information System (INIS)

Clark, A.E.; Abbundi, R.; Savage, H.T.

1977-01-01

Single crystal magnetostriction measurements were made as a function of temperature on TbFe 2 and DyFe 2 . From these, the intrinsic magnetoelastic coupling coefficients were determined for the rare earth-Fe 2 compounds. Employing X-ray techniques, certain multicomponent rare earth-Fe 2 compounds were identified to maximize the magnetostriction to anisotropy ratio. (Auth.)

Magnetic and crystallographic properties of Gd(Cu/sub 1-x/Ni/sub x/)2 and Gd(Cu/sub 1-x/Al/sub x/)2 intermetallic compounds

International Nuclear Information System (INIS)

Borombaev, M.K.; Levitin, R.Z.; Markosyan, A.S.; Snegirev, V.V.

1986-01-01

Magnetization, paramagnetic susceptibility, and temperature dependence of lattice parameters of Gd(Cu/sub 1-x/Ni/sub x/) 2 (0 2 (0 2 -type structure have been studied in a wide range of temperatures. Below the ordering temperature anomalies in thermal expansion along the crystallographic axes a, b, and c enabled to distinguish between various types of magnetic arrangements. The Gd(Cu/sub 1-x/Ni/sub x/) 2 system has two types of antiferromagnetic phases: AF1 (0 = 0.13 the system orders ferromagnetically. In the Gd(Cu/sub 1-x/Al/sub x/) 2 system two magnetic phases AF1 and AF3 occur in the concentration regions 0 <= x <= 0.035 and 0.04 <= x <= 0.07, respectively. The obtained results are discussed in terms of the RKKY model via the changing conduction electron concentration. (author)

An electrochemical study of the systems Li1+-xV2O4 and Li1-xVO2 (0≤x≤1)

International Nuclear Information System (INIS)

De Picciotto, L.A.; Thackeray, M.M.; Pistoia, G.

1988-01-01

Electrochemical properties of the systems Li 1±x V 2 O 4 (0≤x≤1), Li 1-x VO 2 (0≤x 2 O 4 is reversible, which confirms that lithium may be cycled, topotactically, in and out of the Li 1+x V 2 O 4 spinel structure. Delithiation of the LiV 2 O 4 spinel is irreversible; during this process the vanadium ions migrate through the oxide layers. This results in a defect rocksalt phase, which can, in turn, be relithiated by a different mechanism. Lithium extraction for the layered compound LiVO 2 yields a structure similar to the delithiated LiV 2 O 4 product. The spinel-derived compounds Li 1 +-x/V 2 O 4 (0 -3 Ω -1 cm -1 at x=0 and 10 -6 Ω -1 cm -1 at x=1. Lithium diffusion rates in Li 1±x V 2 O 4 samples increase with lithiation from D=4x10 -10 cm 2 /s in LiV 2 O 4 to D=6x10 -8 cm 2 /s in Li 2 V 2 O 4 . Intermediate values of D are obtained in the delithiated compound Li 0.28 V 2 O 4 and in the layered oxide LiVO 2 ; significantly lower values of D, viz. 1x10 -11 cm 2 /s and 4x10 -11 cm 2 /s , are found in the spinels LiMn 2 O 4 and Fe 3 O 4 respectively. 28 refs.; 5 figs.; 1 table

Phase relations in the pseudobinary systems RAO3-R2Ti2O7 (R: rare earth element and Y, A: Fe, Ga, Al, Cr and Mn) and syntheses of new compounds R(A1-xTix)O3+x/2 (2/3≤x≤3/4) at elevated temperatures in air

Science.gov (United States)

Brown, Francisco; Jacobo-Herrera, Ivan; Alvarez-Montaño, Victor; Kimizuka, Noboru; Kurashina, Keiji; Michiue, Yuichi; Matsuo, Yoji; Mori, Shigeo; Ikeda, Naoshi; Medrano, Felipe

2017-07-01

Phase relations in the pseudo-binary systems RFeO3-R2Ti2O7 (R: Lu, Ho and Dy), RGaO3-R2Ti2O7 (R: Lu and Er), LuAlO3-Lu2Ti2O7 and RAO3-R2Ti2O7 (R: Lu and Yb. A: Cr and Mn) at elevated temperatures in air were determined by means of a classic quenching method. There exist Lu(Fe1-xTix)O3+x/2, R(Ga1-xTix)O3+x/2 (R: Lu and Er) and Lu(Al1-xTix)O3+x/2 (2/3≤ x≤3/4) having the Yb(Fe1-xTix)O3+x/2-type of crystal structure (x=0.72, space group: R3m, a(Å)=17.9773 and c(Å)=16.978 as a hexagonal setting) in these pseudo binary systems. Eighteen compounds R(A1-xTix)O3+x/2 (R: Lu-Sm and Y, A: Fe, Ga and Al) were newly synthesized and their lattice constants as a hexagonal setting were measured by means of the X-ray powder diffraction method. The R occupies the octahedral site and both A and Ti does the trigonalbipyramidal one in these compounds. Relation between lattice constants for the rhombic R(A1-xTix)O3+x/2 and the monoclinic In(A1-xTix)O3+x/2 are as follows, ah≈5 x bm, ch≈3 x cm x sin β and am=31/2 x bm, where ah and ch are the lattice constants as a hexagonal setting for R(A1-xTix)O3+x/2 and am, bm, cm and β are those of the monoclinic In(A1-xTix)O3+x/2. Crystal structural relationships among α-InGaO3 (hexagonal, high pressure form, space group: P63/mmc), InGaO3 (rhombic, hypothetical), (RAO3)n(BO)m and RAO3(ZnO)m (R: Lu-Ho, Y and In, A: Fe, Ga, and Al, B: divalent cation element, m, n: natural number), the orthorhombic-and monoclinic In(A1-xTix)O3+x/2 (A: Fe, Ga, Al, Cr and Mn) and the hexagonal-and rhombic R(A1-xTix)O3+x/2 (R: Lu-Sm and Y, A: Fe, Ga and Al) are schematically presented. We concluded that the crystal structures of both the α-InGaO3 (high pressure form, hexagonal, space group: P63/mmc) and the hypothetical InGaO3 (rhombic) are the key structures for constructing the crystal structures of these compounds having the cations with CN=5.

Features of magnetic and thermal properties of R(Co{sub 1−x}Fe{sub x}){sub 2} (x≤0.16) quasibinary compounds with R=Dy, Ho, Er

Energy Technology Data Exchange (ETDEWEB)

Anikin, Maksim; Tarasov, Evgeniy; Kudrevatykh, Nikolay [Institute of Natural Sciences, Ural Federal University, Ekaterinburg 620002 (Russian Federation); Inishev, Aleksander [Institute of Metal Physics, Ekaterinburg 620137 (Russian Federation); Semkin, Mikhail; Volegov, Aleksey; Zinin, Aleksander [Institute of Natural Sciences, Ural Federal University, Ekaterinburg 620002 (Russian Federation)

2016-11-15

In this work the results of measurements of high field susceptibility, paraprocess susceptibility and thermal properties of R(Co{sub 1−x}Fe{sub x}){sub 2} intermetallic compounds (R=Dy, Ho, Er and x=(0−0.16)) are presented (heat capacity and magnetocaloric effect (MCE)). A magnetic structure of the Ho(Co{sub 0.88}Fe{sub 0.12}){sub 2} at 293 K and 78 K was studied by neutron powder diffraction. Some peculiarities of a high-field susceptibility were revealed at low temperatures and around the Curie point (T{sub C}). In temperature range lower than T{sub C} by (100–150) K, magnetic contributions to a zero-field heat capacity were found. Studying MCE in wide temperatures range, the large change of the entropy magnetic contribution (∆S) was observed which correlates with ∆T phenomenon. In particular, for the Er(Co{sub 0.84}Fe{sub 0.16}){sub 2} compound the ∆S value at low temperatures is six times higher than that at Curie point. The possible reasons of such behavior were discussed. - Highlights: • Magnetic and magnetocaloric properties of R(Co–Fe){sub 2} compounds have been studied. • Fe introduction induces the disorientation effect in Ho-ions magnetic ordering. • Emergence of magnetic contribution to a heat capacity at temperatures less T{sub C}. • The existence of a broad maximum on a temperature dependence of the MCE. • Direct MCE measurements at magnetic field of (0–17.5) kOe have been performed.

X-ray diffraction studies of the Tl(GaS{sub 2}){sub 1–x}(InSe{sub 2}){sub x} solid solutions

Energy Technology Data Exchange (ETDEWEB)

Sheleg, A. U.; Hurtavy, V. G., E-mail: hurtavy@physics.by; Chumak, V. A. [National Academy of Sciences of Belarus, Scientific-Practical Materials Research Center (Belarus); Mustafaeva, S. N.; Kerimova, E. M. [Azerbaijan National Academy of Sciences, Institute of Physics (Azerbaijan)

2016-07-15

The unit-cell parameters of crystals obtained in the Tl(GaS{sub 2}){sub 1–x}(InSe{sub 2}){sub x} system are measured by X-ray diffraction. The relationship between these parameters and composition is determined. It is shown that, with growing x, the a, b, and c parameters increase and the β angle decreases. Two types of solid solutions are found in the Tl(GaS{sub 2}){sub 1–x}(InSe{sub 2}){sub x} system: one is based on compound TlGaS{sub 2} with monoclinic structure and the other is based on TlInSe{sub 2} with tetragonal structure.

Structure and magnetic properties of (Nd1-xErx)3Fe25Cr4.0 (0 ≤ x ≤ 0.8) compounds

International Nuclear Information System (INIS)

Luo Hongzhi; Jia Lin; Li Yangxian; Meng Fanbin; Shen Jiang; Chen Nanxian; Wu Guangheng; Yang Fuming

2004-01-01

The structure and magnetic properties of (Nd 1-x Er x ) 3 Fe 25 Cr 4.0 compounds with x = 0-0.8 have been investigated using x-ray powder diffraction (XRD) and magnetic measurements. It has been found that all the compounds crystallize in a Nd 3 (Fe,Ti) 29 -type structure. Substitution of Er for Nd leads to a contraction of the unit-cell volume. The Curie temperature, T c , and the saturation magnetization, M s , of (Nd 1-x Er x ) 3 Fe 25 Cr 4.0 decrease monotonically with increasing Er content. The easy magnetization direction (EMD) of Nd 3 Fe 25 Cr 4.0 at room temperature is close to the [040] direction but may be a little out of the basal plane. With increasing Er content, the EMD changes closer to the [40-2] direction and the tilt angle increases. Both the XRD patterns and ac susceptibility indicate the appearance of a spin reorientation for x = 0-0.4 as the temperature decreases from room temperature to 77 K. The spin reorientation temperature, T sr , increases monotonically with increasing Er content from 158 K for x = 0 to 198 K for x = 0.4. A first order magnetization process (FOMP) occurs for all the compounds, and the critical field of the FOMP decreases with increasing Er content from 6.6 T for x = 0 to 2.0 T for x = 0.7

Crystalline and Electronic Structures and Magnetic and Electrical Properties of La-Doped Ca2Fe2O5 Compounds

Science.gov (United States)

Phan, T. L.; Tho, P. T.; Tran, N.; Kim, D. H.; Lee, B. W.; Yang, D. S.; Thiet, D. V.; Cho, S. L.

2018-01-01

Brownmillerite Ca2Fe2O5 has been observed to exhibit many outstanding properties that are applicable to ecotechnology. However, very little work on doped Ca2Fe2O5 compounds has been carried out to widen their application scope. We present herein a detailed study of the crystalline/geometric and electronic structures and magnetic and electrical properties of Ca2- x La x Fe2O5 ( x = 0 to 1) prepared by conventional solid-state reaction. X-ray diffraction patterns indicated that the compounds with x = 0 to 0.05 exhibited brownmillerite-type single phase. La doping with higher content ( x ≥ 0.1) stimulated additive formation of Grenier- (LaCa2Fe3O8) and perovskite-type (LaFeO3) phases. Extended x-ray absorption fine structure spectroscopy at the Fe K-edge and electron spin resonance spectroscopy revealed presence of Fe3+ in the parent Ca2Fe2O5 ( x = 0) and both Fe3+ and Fe4+ in the doped compounds ( x ≥ 0.05). The Fe4+ content tended to increase with increasing x. This stimulates ferromagnetic exchange interactions between Fe3+ and Fe4+ ions and directly influences the magnetic properties of Ca2- x La x Fe2O5. Electrical resistivity ( ρ) measurements in the temperature range of T = 20 K to 400 K revealed that all the compounds exhibit insulator behavior; the ρ( T) data for x ≥ 0.1 could be described based on the adiabatic small polaron hopping model.

Magnetic properties and magnetocaloric effect of MnFeP0.5Ge0.5-xSix compounds

International Nuclear Information System (INIS)

Song, L.; Wang, G.F.; Ou, Z.Q.; Haschaolu, O.; Tegus, O.; Brueck, E.; Buschow, K.H.J.

2009-01-01

We have studied the magnetic properties and magnetic-entropy changes of the MnFeP 0.5 Ge 0.5-x Si x compounds with x = 0.1, 0.2, 0.3, 0.4 and 0.45. X-ray diffraction shows that the compounds crystallize in the Fe 2 P-type hexagonal structure. The lattice parameter a and the Curie temperature decreases with increasing x. The maximal magnetic-entropy changes for x = 0.4 and 0.45 derived from the magnetization data are about 6.0 J/kg K and 5.8 J/kg K, respectively, for a field change from 0 to 1.5 T

Lattice and Valence Electronic Structures of Crystalline Octahedral Molybdenum Halide Clusters-Based Compounds, Cs2[Mo6X14] (X = Cl, Br, I), Studied by Density Functional Theory Calculations.

Science.gov (United States)

Saito, Norio; Cordier, Stéphane; Lemoine, Pierric; Ohsawa, Takeo; Wada, Yoshiki; Grasset, Fabien; Cross, Jeffrey S; Ohashi, Naoki

2017-06-05

The electronic and crystal structures of Cs 2 [Mo 6 X 14 ] (X = Cl, Br, I) cluster-based compounds were investigated by density functional theory (DFT) simulations and experimental methods such as powder X-ray diffraction, ultraviolet-visible spectroscopy, and X-ray photoemission spectroscopy (XPS). The experimentally determined lattice parameters were in good agreement with theoretically optimized ones, indicating the usefulness of DFT calculations for the structural investigation of these clusters. The calculated band gaps of these compounds reproduced those experimentally determined by UV-vis reflectance within an error of a few tenths of an eV. Core-level XPS and effective charge analyses indicated bonding states of the halogens changed according to their sites. The XPS valence spectra were fairly well reproduced by simulations based on the projected electron density of states weighted with cross sections of Al K α , suggesting that DFT calculations can predict the electronic properties of metal-cluster-based crystals with good accuracy.

Colossal magnetoresistance in layered manganite Nd2−2xSr1+ ...

Indian Academy of Sciences (India)

starting compounds, have been obtained. Except for x=0.4, which is found to be an antiferromagnetic insulator, all other x values yielded metal–insulator transition and ferromagnetic ordering. Keywords. Colossal magnetoresistance; layered manganites; Nd2−2x Sr1+2x Mn2O7. PACS Nos 75.30.Vn; 71.30.+h. 1. Introduction.

High field magnetization process of (Sm, Nd)2Fe17Ny compounds

International Nuclear Information System (INIS)

Yu, M.J.; Tang, N.; Liu, Y.L.; Tegus, O.; Lu, Y.; Kuang, J.P.; Yang, F.M.; Li, X.; Zhou, G.F.; Boer, F.R. de

1992-01-01

The crystal structure and high-field magnetization process of (Sm 1-x Nd x ) 2 Fe 17 N y compounds (x = 0.0, 0.1, ..., 1.0, 2 1-x Nd x ) 2 Fe 17 N y compounds were found to crystallize in the rhombohedral Th 2 Zn 17 structure. As x increases, the Curie temperature decreases. The anisotropy fields and easy magnetization direction were investigated from 1.5 K to room temperature by means of high-field magnetization measurements and AC-susceptibility measurements, combined with X-ray diffraction on random and magnetically aligned powder samples. The anisotropy field decreases with increasing x and approaches a minimum value at about x = 0.6, then increases again. A tentative spin phase diagram for the (Sm 1-x Nd x ) 2 Fe 17 N y series is presented. At room temperature, the easy magnetization direction remains along the c-axis up to x = 0.6. (orig.)

Structural and magnetic properties of transition metal substituted BaFe₂As₂ compounds studied by x-ray and neutron scattering

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Gyu [Iowa State Univ., Ames, IA (United States)

2012-01-01

The purpose of my dissertation is to understand the structural and magnetic properties of the newly discovered FeAs-based superconductors and the interconnection between superconductivity, antiferromagnetism, and structure. X-ray and neutron scattering techniques are powerful tools to directly observe the structure and magnetism in this system. I used both x-ray and neutron scattering techniques on different transition substituted BaFe₂As₂ compounds in order to investigate the substitution dependence of structural and magnetic transitions and try to understand the connections between them.

Lattice dynamics of cubic Cs2NaLnX6 and CsNaLn1-xLn'xX6 elpasolites

International Nuclear Information System (INIS)

Acevedo, R.; Poblete, V.; Alzamora, R.; Venegas, R.; Navarro, G.; Henriquez, C.

1999-01-01

Crystal lattice dynamics of stoichiometric Cs 2 NaLnX 6 and nonstoichiometric CsNaLn 1-x Ln' x X 6 , 0.01 ≤ x ≤ 0.10, Ln and Ln' are trivalent positive lanthanide ions and X is chlorine or bromine, were studied.. Phonon dispersion relations were computed for similar compound, Cs 2 UBr 6 , and vibronic absorption spectra with reduced number of required input parameters are considered on the basis of proposed model. (author)

Synthesis and Characterization of Nanocrystalline Ni50Al50-xMox (X=0-5 Intermetallic Compound During Mechanical Alloying Process

Directory of Open Access Journals (Sweden)

A. Khajesarvi

2015-07-01

Full Text Available In the present study, nanocrystalline Ni50Al50-xMox (X = 0, 0.5, 1, 2.5, 5 intermetallic compound was produced through mechanical alloying of nickel, aluminum, and molybdenum powders. AlNi compounds with good and attractive properties such as high melting point, high strength to weight ratio and high corrosion resistance especially at high temperatures have attracted the attention of many researchers. Powders produced from milling were analyzed using scanning electron microscopy (SEM and X-ray diffractometry (XRD. The results showed that intermetallic compound of NiAl formed at different stage of milling operation. It was concluded that at first disordered solid solution of (Ni,Al was formed then it converted into ordered intermetallic compound of NiAl. With increasing the atomic percent of molybdenum, average grain size decreased from 3 to 0.5 μm. Parameter lattice and lattice strain increased with increasing the atomic percent of molybdenum, while the crystal structure became finer up to 10 nm. Also, maximum microhardness was obtained for NiAl49Mo1 alloy.

Magnetic properties of the LaCu5-xCox compounds

International Nuclear Information System (INIS)

Crisan, V.; Popescu, V.; Vernes, A.; Andreica, D.; Cristea, S.; Koepe, B.

1996-01-01

Magnetic moments and Curie temperatures of the intermetallic compounds LaCu 5-x Co x (x = 5) are calculated using a recursion method in the framework of the spin-fluctuation theory of Mohn and Wohlfarth. (orig.)

Polarized-x-ray-absorption studies of graphite intercalated-bromine compounds

International Nuclear Information System (INIS)

Feldman, J.L.; Elam, W.T.; Ehrlich, A.C.; Skelton, E.F.; Dominguez, D.D.; Chung, D.D.L.; Lytle, F.W.

1986-01-01

Details of both results and data analysis are given in the case of our polarized-x-ray-absorption experiments, using synchrotron radiation, on highly oriented pyrolytic graphite (HOPG)--based and graphite-fiber-based residual-bromine intercalation compounds. The effective angle which nearest-neighbor Br pairs make with crystallite graphite planes in some of these compounds, which was stated to be approx.20 0 in an earlier article, is shown to be 16X(de +- 4X(de: both Br-Br extended x-ray-absorption fine structure (EXAFS) and white-line features of the data are the basis of this result. We have also found that, whereas spherical averages of the areas under white-line spectra are independent of the choice of the material among all samples studied (including Br 2 vapor), differences in similarly spherically averaged Br-Br EXAFS amplitudes are evident, especially between Br 2 vapor and Br-graphite samples. We show that the latter differences which correspond to a coordination number less than one in Br-graphite are not due to either Gaussian or non-Gaussian (up to k 4 terms) Debye-Waller effects. In addition, we discuss the extraction of Br-C EXAFS and present results of model calculations of Br-C EXAFS, where several different structural models for the Br sites are considered. We also discuss thermal effects and their relation to known Br sublattice phase-transition behavior, based on our measurements at room temperature, 360 K, and 400 K

Study of X-ray L2 absorption edges of Gd, Dy, Ho and Er in metals and compounds

International Nuclear Information System (INIS)

Agarwal, B.K.; Agarwal, B.R.K.

1978-01-01

The positions and shapes of L2 X-ray absorption edges of Gd, Dy, Ho and Er have been studied in metals and in oxides and chlorides, using a forty centimetre bent mica crystal spectrograph. It has been found that the L2 edge shifts towards the high energy side in the compounds and that the chemical shift ΔE depends on the degree of covalency involved. The white line structure at the edge has been analysed in terms of transitions of L2 shell electron to optical nd (n >= 5) states. (author)

Electron spin resonance of Gd3+ in the intermetallic Gd1-xYxNi3Ga9 (0 ≤ x ≤ 0.90) compounds

Science.gov (United States)

Mendonça, E. C.; Silva, L. S.; Mercena, S. G.; Meneses, C. T.; Jesus, C. B. R.; Duque, J. G. S.; Souza, J. C.; Pagliuso, P. G.; Lora-Serrano, R.; Teixeira-Neto, A. A.

2017-10-01

In this work, experiments of X-ray diffraction, magnetic susceptibility, heat capacitance, and Electron Spin Resonance (ESR) carried out in the Gd1-xYxNi3Ga9 (0 ≤ x ≤ 0.90) compounds grown through a Ga self flux method are reported. The X-ray diffraction data indicate that these compounds crystallize in a trigonal crystal structure with a space group R32. This crystal structure is unaffected by Y-substitution, which produces a monotonic decrease of the lattice parameters. For the x = 0 compound, an antiferromagnetic phase transition is observed at TN = 19.2 K, which is continuously suppressed as a function of the Y-doping and extrapolates to zero at x ≈ 0.85. The ESR data, taken in the temperature range 15 ≤ T ≤ 300 K, show a single Dysonian Gd3+ line with nearly temperature independent g-values. The linewidth follows a Korringa-like behavior as a function of temperature for all samples. The Korringa rates (b = ΔH /ΔT ) are Y-concentration-dependent indicating a "bottleneck" regime. For the most diluted sample (x = 0.90), when it is believed that the "bottleneck" effect is minimized, we have calculated the q-dependent effective exchange interactions between Gd3+ local moments and the c-e of 〈Jf-ce 2(q ) 〉 1 /2 = 18(2) meV and Jf -c e(q =0 ) = 90(10) meV.

X-Ray Diffraction of Intermetallic Compounds: A Physical Chemistry Laboratory Experiment

Science.gov (United States)

Varberg, Thomas D.; Skakuj, Kacper

2015-01-01

Here we describe an experiment for the undergraduate physical chemistry laboratory in which students synthesize the intermetallic compounds AlNi and AlNi3 and study them by X-ray diffractometry. The compounds are synthesized in a simple one-step reaction occurring in the solid state. Powder X-ray diffractograms are recorded for the two compounds…

Resonant X-ray emission spectroscopy in Dy compounds

International Nuclear Information System (INIS)

Tanaka, Satoshi; Okada, Kozo; Kotani, Akio.

1994-01-01

The excitation spectrum of the L 3 -M 5 X-ray emission of Dy compounds in the pre-edge region of Dy L 3 X-ray absorption near edge structure (L 3 -XANES) is theoretically investigated based upon the coherent second order optical formula with multiplet coupling effects. The spectral broadening of the excitation spectrum is determined by the M 5 core hole lifetime, being free from the L 3 core hole lifetime. The fine pre-edge structure of the L 3 edge due to the 2p→4f quadrupole transition can be seen in the excitation spectrum, while this structure is invisible in the conventional XANES, in agreement with the recent experimental results. We clarify the conditions for the excitation spectrum to be regarded as the absorption spectrum with a smaller width. The resonant X-ray emission spectra for various incident photon energies around the L 3 edge are also calculated. (author)

Structural stability of (Pu{sub 1-x}Am{sub x})O{sub 2} (x=0.2;0.5;0.8) obtained by oxalate co-conversion

Energy Technology Data Exchange (ETDEWEB)

Jankowiak, A.; Donnet, L. [Commissariat a l' Energie Atomique, CEA/DEN/VRH/DTEC/SDTC/LEMA, 30207 Bagnols-sur-Ceze cedex (France); Maillard, C. [Commissariat a l' Energie Atomique, CEA/DEN/VRH/DRCP/SE2A/LEHA, 30207 Bagnols-sur-Ceze cedex (France)

2008-07-01

The EUROTRANS project investigates the transmutation of transuranium elements in dedicated reactors (ADS, FR). The study includes various subject areas: neutronics, physical properties, coolant type (sodium, lead, bismuth, helium), etc, and experimental work concerning the fabrication of minor actinide compounds for thermo-physical properties determination. For this program, the CEA was responsible for synthesizing three Pu{sub 1-x}Am{sub x}O{sub 2} compounds with various Am and Pu content (x = 0.2, 0.5, 0.8). The selected synthesis route for the mixed Am and Pu oxide powder consists in actinides oxalates co-conversion. The purpose of the study was to determine by XRD the crystal structure and the lattice parameters change as a function of the time for each co-converted mixed oxides. After one year of experiment, although the lattice parameters significantly expanded, the compounds remained monophasic. The observations showed that the initial expansion rate and the a{sub max} stage value vary according to the Pu and Am content. (authors)

A model for the “quasi” 60 K plateau in the YBa2Cu3O6+x high-Tc compound

International Nuclear Information System (INIS)

Matic, V.M.; Lazarov, N.Dj.; Milic, M.

2013-01-01

Highlights: ► A theoretical model for the chain-to-plane charge transfer process in YBCO has been expounded. ► Explained how the critical chain length parameter influences the behaviour of p(x) and T c (x) characteristics. ► The origin of the classic (horizontal) 60 K plateau in T c (x) is explained. ► The “quasi” 60 K plateau is explained in terms of increased orthorhombicity in recently produced YBCO samples. - Abstract: The 60 K plateau of the YBa 2 Cu 3 O 6+x high-T c superconducting compound has traditionally been known as a horizontal section in its T c (x) characteristics within which the critical temperature maintains at a constant level T c ≈ 60 K. However, recent experiments on a series of high quality single crystals samples of the YBa 2 Cu 3 O 6+x compound (produced by improved techniques of sample preparation) have shown the 60 K plateau does not manifest itself anymore as a horizontal section of the T c (x), but emerges as a section over which T c (x) keeps on continuously rising (the “quasi” 60 K plateau). Here we propose a theoretical model that explains how the classical (horizontal) 60 K plateau naturally evolves into the “quasi” 60 K plateau, due to the improved orthorhombicity in the high quality single crystal material accompanied by longer CuO chains. The model assumes that short CuO chains do not contribute to the hole transfer from chains to CuO 2 layers, but only chains whose length is greater than, or equal to, a certain threshold length l cr . Our calculations point to a conclusion that this minimal number of oxygen atoms in a CuO chain, that is required to trigger the hole transfer, is equal to four. The calculated values for T c (x) are in a very good correlation with the corresponding experimentally obtained results.

Electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) Heusler alloys: First-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Guezlane, M. [Department of Physics, Faculty of Science, University of Batna, 05000 Batna (Algeria); Baaziz, H., E-mail: baaziz_hakim@yahoo.fr [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); El Haj Hassan, F., E-mail: hassan.f@ul.edu.lb [Université Libanaise, Faculté des Sciences (I), Laboratoire de Physique et d’Electronique (LPE), Elhadath, Beirut (Lebanon); Charifi, Z. [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); Djaballah, Y. [Laboratoire d’étude Physico-Chimique des Matériaux, Département de Physique, Faculté des Sciences, Université de Batna, Rue Chahid Boukhlouf, 05000 Batna (Algeria)

2016-09-15

Density functional theory (DFT) based on the full-potential linearized augmented plane wave (FP-LAPW) method is used to investigate the structural, electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) full Heusler alloys, with L2{sub 1} structure. The structural properties and spin magnetic moments are investigated by the generalized gradient approximations (GGA) minimizing the total energy. For band structure calculations, GGA, the Engel–Vosko generalized gradient approximation (EVGGA) and modified Becke–Johnson (mBJ) schemes are used. Results of density of states (DOS) and band structures show that these alloys are half-metallic ferromagnets (HMFS). A regular-solution model has been used to investigate the thermodynamic stability of the compounds Co{sub 2}Cr{sub x}Fe{sub 1−x}X that indicates a phase miscibility gap. The thermal effects using the quasi-harmonic Debye model are investigated within the lattice vibrations. The temperature and pressure effects on the heat capacities, Debye temperatures and entropy are determined from the non-equilibrium Gibbs functions. - Highlights: • We present electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) Heusler alloys. • The calculated phase diagram indicates a significant phase miscibility gap. • The computed band structures of ternary compounds using GGA, EVGGA and mBJ schemes indicate an indirect band gap (Γ-X) for the ternary compounds Co{sub 2}FeAl, Co{sub 2}CrAl, Co{sub 2}FeSi and Co{sub 2}CrSi while both alloys have a direct band gap. • The quasi-harmonic Debye model is successfully applied to determine the thermal properties.

High Eu 4f low-energy oscillator strength in the isostructural rare-earth Zintl compounds EuIn2X2 (X = P,As)

KAUST Repository

Singh, Nirpendra

2012-04-11

The isostructral Zintl compounds EuIn2X2 (X = P,As) are investigated within density functional theory. We employ the local spin density approximation with onsite interaction (LSDA + U) for varying U from 0 eV to 7 eV to model the Coulomb repulsion of the Eu 4f electrons. The LSDA + U optical conductivity disagrees with the experimental spectrum, while the simple LSDA is successful. Contrary to the expectation, it is found that EuIn2X2 (X = P,As) has a large oscillator strength for the f → d transitions in the low-energy range (below 1.5 eV) in which effects of the joint density of states play a key role. The materials show a sizeable magneto-optical Kerr effect.

High Eu 4f low-energy oscillator strength in the isostructural rare-earth Zintl compounds EuIn2X2 (X = P,As)

KAUST Repository

Singh, Nirpendra; Schwingenschlö gl, Udo

2012-01-01

The isostructral Zintl compounds EuIn2X2 (X = P,As) are investigated within density functional theory. We employ the local spin density approximation with onsite interaction (LSDA + U) for varying U from 0 eV to 7 eV to model the Coulomb repulsion of the Eu 4f electrons. The LSDA + U optical conductivity disagrees with the experimental spectrum, while the simple LSDA is successful. Contrary to the expectation, it is found that EuIn2X2 (X = P,As) has a large oscillator strength for the f → d transitions in the low-energy range (below 1.5 eV) in which effects of the joint density of states play a key role. The materials show a sizeable magneto-optical Kerr effect.

Phase equilibria in M-X-X' and M-Al-X ternary systems (M-transition metal, X,X'-B,C,N,Si) and crystal chemistry of ternary compounds

International Nuclear Information System (INIS)

Gusev, A.I.

1996-01-01

The data on phase equilibria in the M-X-X' and M-Al-X ternary systems (M-transition metal of 3 to 8 groups, X-B,C, N, Si) have been considered and summarized. modern oxygen-free advanced ceramics is based on these ternary systems. Phase diagrams of the 130 ternary systems have been discussed, more than two hundred ternary phases forming in these systems have been systematized and described. The typical crystal structures of ternary compounds and phase have been considered, the common and distinctive features of these structures have been analysed. It has been shown that the ternary compounds with octahedral atomic groups XM 6 have a regions of homogeneity. Refs. 240

Thermal Expansion and Luminescent Properties of Triorthogermanates CaLa2- x Eu x Ge3O10 ( x = 0.0-0.6)

Science.gov (United States)

Lipina, O. A.; Surat, L. L.; Baklanova, Ya. V.; Berger, I. F.; Tyutyunnik, A. P.; Zubkov, V. G.

2018-02-01

Solid solutions CaLa2- x Eu x Ge3O10 ( x = 0.0-0.6, Δ x = 0.1) have been synthesized for the first time. The compounds are isostructural to CaLa2Ge3O10, they crystallize in the monoclinic system, space group P21/ c, Z = 4. The low-temperature X-ray diffraction studies have revealed the strain anisotropy of germanate CaLa2Ge3O10 crystal lattice in the temperature range 80-298 K, and the linear thermal expansion coefficients have been calculated. The optical properties of the activated phases have been studied, and the influence of the dopant concentration and the excitation wavelength on the luminescence characteristics of the synthesized compounds has been established.

Pyrid-2-yl and 2-CyanoPhenyl fused heterocyclic compounds as human P2X3 inhibitors: a combined approach based on homology modelling, docking and QSAR analysis.

Science.gov (United States)

Janardhan, Sridhara; Seth, Subhendu; Viswanadhan, Vellarkad N

2014-02-01

P2X receptors are hetero-oligomeric proteins that function as membrane ion channels and are gated by extracellular ATP. The hP2X[Formula: see text] subunit is a constituent of the channels on a subset of sensory neurons involved in pain signaling, where ATP released by damaged and inflamed tissue can initiate action potentials. Hence, the inhibition of ATP-activated P2X3 receptor is an exciting approach for the treatment of inflammatory and neuropathic pain. Recently, the crystal structures of zebrafish P2X4 (zP2X4) were obtained in closed, apo state (PDB ID: 3I5D) and ATP-bound, open state (PDB ID: 4DW1). These structures were used to develop a homology model of human P2X3 (hP2X3 in order to identify through docking studies, the binding modes of known P2X3 inhibitors and their key active site interactions, along with a pharmacophore-based 3D-QSAR model for a series of 136 Pyrid-2-yl and 2-CyanoPhenyl fused heterocyclic compounds. These 3D-QSAR models have been developed with different combinations of training and test set divisions obtained by random separation, Jarvis-Patrick clustering, K-means clustering and sphere exclusion methods. The best predictive 3D-QSAR model resulted in training set R2 of 0.75, internal test set Q2 of 0.74, Pearson-R value of 0.87 and root mean square error of 0.37. The information generated by the pharmacophore model and docking analyses using the homology model provides valuable clues to design novel potent hP2X3 inhibitors.

Dispersion of the linear and nonlinear optical susceptibilities of the CuAl(S1−xSex)2 mixed chaclcopyrite compounds

International Nuclear Information System (INIS)

Reshak, A. H.; Brik, M. G.; Auluck, S.

2014-01-01

Based on the electronic band structure, we have calculated the dispersion of the linear and nonlinear optical susceptibilities for the mixed CuAl(S 1−x Se x ) 2 chaclcopyrite compounds with x = 0.0, 0.25, 0.5, 0.75, and 1.0. Calculations are performed within the Perdew-Becke-Ernzerhof general gradient approximation. The investigated compounds possess a direct band gap of about 2.2 eV (CuAlS 2 ), 1.9 eV (CuAl(S 0.75 Se 0.25 ) 2 ), 1.7 eV (CuAl(S 0.5 Se 0.5 ) 2 ), 1.5 eV (CuAl(S 0.25 Se 0.75 ) 2 ), and 1.4 eV (CuAlSe 2 ) which tuned to make them optically active for the optoelectronics and photovoltaic applications. These results confirm that substituting S by Se causes significant band gaps' reduction. The optical function's dispersion ε 2 xx (ω) and ε 2 zz (ω)/ε 2 xx (ω), ε 2 yy (ω), and ε 2 zz (ω) was calculated and discussed in detail. To demonstrate the effect of substituting S by Se on the complex second-order nonlinear optical susceptibility tensors, we performed detailed calculations for the complex second-order nonlinear optical susceptibility tensors, which show that the neat parents compounds CuAlS 2 and CuAlSe 2 exhibit | χ 123 (2) (−2ω;ω;ω) | as the dominant component, while the mixed alloys exhibit | χ 111 (2) (−2ω;ω;ω) | as the dominant component. The features of | χ 123 (2) (−2ω;ω;ω) | and | χ 111 (2) (−2ω;ω;ω) | spectra were analyzed on the basis of the absorptive part of the corresponding dielectric function ε 2 (ω) as a function of both ω/2 and ω.

Antiferromagnetic ordering of Er2NiSi3 compound

International Nuclear Information System (INIS)

Pakhira, Santanu; Mazumdar, Chandan; Ranganathan, R.

2014-01-01

Ternary intermetallics of the stoichiometric composition R 2 TX 3 , where, R = rare earth element, T = d-electron transition metal and X= p-electron element, crystallizes in hexagonal A1B 2 type crystal structure with space group P6/mmm. We report here the synthesis and basic magnetic properties of the compound Er 2 NiSi 3 . Paramagnetic to antiferromagnetic phase change occurs below 5.4 K for this compound. (author)

Intensive structural investigation of R{sub 2}Fe{sub 17-x}M{sub x} intermetallic compounds using high resolution powder neutron diffractometer

Energy Technology Data Exchange (ETDEWEB)

Mujamilah,; Ridwan, [Materials Science Research Center, National Atomic Energy Agency of Indonesia, Jakarta (Indonesia)

1998-10-01

The crystallographic and magnetic structure of R{sub 2}Fe{sub 17-x}M{sub x} intermetallic compounds system were refined by Rietveld analyses of the high resolution neutron powder diffraction data. The analyses results show that the substituent atoms were not distributed randomly over the Fe sites, but preferentially occupied some Fe sites. More further, it was also found that the substituent atoms which atomic radius smaller than Fe tend to avoid the 6c site at low concentration while the larger substituent atom tend to replace the Fe atom at this 6c site corresponding to their concentration. From these crystallographic data, it was suggested that the change of magnetic ordering temperature Tc, is not mainly determined by the change of short bond distance between this `dumb-bell` atoms, but it was also influenced by the nearest coordinated atoms to this site. (author)

Plutonium oxychalcogenides Pu2O2X (X=O, S, Se, Te) crystal chemistry, magnetic and electrical properties. 5f electrons delocalization

International Nuclear Information System (INIS)

Costantini, Jean-Marc.

1980-05-01

We have studied the influence of the chalcogen X on the bonding and on the magnetic and electrical properties of the oxychalcogenides Pu 2 O 2 X. These compounds are isostructural with hexagonal La 2 O 3 for X=O, S, Se and with tetragonal La 2 O 2 Te for X=Te. Comparison of Nd 2 O 2 X and Pu 2 O 2 X cell volumes showed that plutonium crystal radius decreases from Pu 2 O 3 through Pu 2 O 2 Te with increasing 5f electrons delocalization and 5f-np overlap. Superexchange interactions through O 2- and X 2- were thought to be responsible for the observed antiferromagnetic ordering. Neel temperatures increase from Pu 2 O 3 through Pu 2 O 2 Te showing that these interactions and subsequent 5f-np covalency are strengthened as chalcogen electronegativity decreases. Hexagonal Pu 2 O 3 is an insulator while the other compounds are semi-conductors with energy gaps around 0.6 eV which were interpreted as the separation between the 6d-7s conduction band and the np valence band. The localized 5f states were located just below the np band, partially overlapping it [fr

Structural and magnetic properties of Gd1-xPrxMn2Si2 silicides

International Nuclear Information System (INIS)

Kilic, A.; Kervan, S.; Gencer, A.

2004-01-01

X-ray powder diffraction, AC susceptibility and differential scanning calorimetry (DSC) studies were performed on the polycrystalline Gd 1-x Pr x Mn 2 Si 2 (0≤x≤1) compounds. All compounds investigated crystallize in the body-centred tetragonal ThCr 2 Si 2 -type structure with the space group I4/mmm. Substitution of Pr for Gd leads to a linear increase of the lattice constants and the unit cell volume. The lattice constants and the unit cell volume obey Vegard's law. At the Curie temperature T C (Gd), the Gd sublattice orders and reconfigures the ordering in the Mn sublattice. This temperature becomes depressed and disappears with increasing Pr content x. The Neel temperature T N (Mn) determined by DSC technique decreases linearly with increasing Pr content x. The results are summarized in the x-T magnetic phase diagram

Structural study of U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 at high pressure

CERN Document Server

Sikolenko, V V; Pomjakushina, E V; Pomjakushin, V Y; Balagurov, A M; Keller, L; Glazkov, V P; Gribanov, A V; Goncharenko, I N; Savenko, B N

2003-01-01

The crystal structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with Fe content x = 0- 0.03 and the crystal and magnetic structure of U(Pd sub 0 sub . sub 9 sub 8 Fe sub 0 sub . sub 0 sub 2) sub 2 Ge sub 2 at high external pressures up to 4.5 GPa were studied by means of powder neutron diffraction in the temperature range 1.5-300 K. With increasing Fe content the values of the lattice parameters and interatomic distances change only slightly, but it is known from previous experiments that the magnetic structure changes drastically for x >= 0.015. In contrast to this, high external pressure modifies the crystal structure more significantly while the magnetic structure remains unchanged. The results obtained allow one to infer that drastic changes in the magnetic structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with increasing Fe content are a consequence of modification of the RKKY-type (RKKY standing for Ruderman, Kittel, Kasuya and Yosida) indirect exchange in...

Crystal Structure of the Sodium Cobaltate Deuterate Superconductor NaxCoO2o4xD2O (x=1/3)

OpenAIRE

Jorgensen, J. D.; Avdeev, M.; Hinks, D. G.; Burley, J. C.; Short, S.

2003-01-01

Neutron and x-ray powder diffraction have been used to investigate the crystal structures of a sample of the newly-discovered superconducting sodium cobaltate deuterate compound with composition Na0.31(3)CoO2o1.25(2)D2O and its anhydrous parent compound Na0.61(1)CoO2. The deuterate superconducting compound is formed by coordinating four D2O molecules (two above and two below) to each Na ion in a way that gives Na-O distances nearly equal to those in the parent compound. One deuteron of the D2...

Magnetism in ordered metallic perovskite compound GdPd{sub 3}B{sub x}C{sub 1-x}

Energy Technology Data Exchange (ETDEWEB)

Pandey, Abhishek [S.N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)], E-mail: abhishek.phy@gmail.com; Mazumdar, Chandan [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)], E-mail: chandan.mazumdar@saha.ac.in; Ranganathan, R. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Dattagupta, S. [Indian Institute of Science Education and Research, Block-HC, Sector-III, Salt Lake, Kolkata 700106 (India)

2009-08-15

We report results of dc-magnetization, ac-susceptibility and magnetoresistance measurements on crystalline metallic-perovskite compounds GdPd{sub 3}B{sub x}C{sub 1-x} (x=0.25, 0.50, 0.75 and 1.00) and the parent cubic compound GdPd{sub 3}. The interest in these materials stems from the observation of negative temperature coefficient of resistance and negative thermal expansion in some of the members of this series. In the present study, we show that by substitution of non-magnetic elements, boron and carbon, the nature of the magnetic interaction can be varied from dominating ferromagnetic to antiferromagnetic and finally to a canted magnetic structure without altering the crystal symmetry of the compounds. The variation of magnetic interaction by modifying the lattice parameter resembles Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillations.

Oxygen potential of Th1-yUyO2+x

International Nuclear Information System (INIS)

Schram, R.P.C.; Cordfunke, E.H.P.

1996-03-01

Oxygen potentials of UO 2 -ThO 2 solid solutions (Th 1-y U y O 2+x ) were retrieved from literature and stored in a database. For each datapoint the oxygen pressure p O 2 the nonstoichiometry x, the temperature T and the uranium concentration y was specified. The data were analyzed using a defect model, which includes electronic disorder, point defects and cluster formation. In addition, the thermochemical representation of Lindemer and Besmann for UO 2+x was extended for the analysis of the Th 1-y U y O 2+x data. The solid solution is regarded as an ideal ternary mixture of UO 2 , ThO 2 and a hypothetical compound U a O b . The thermodynamic properties of this compound U a O b were determined in two oxygen pressure ranges of the database. In both the defect model and thermochemical approach ThO 2 is treated as an inert compound that does not participate in any of the chemical equilibria describing the oxygen potential. (orig.)

Identification of minority compounds in natural ilmenites by X-ray absorption spectroscopy

International Nuclear Information System (INIS)

Klepka, M.T.; Lawniczak-Jablonska, K.; Wolska, A.; Jablonski, M.

2010-01-01

Research highlights: → White pigment TiO 2 production process. → The principal component analysis using XANES. → Ilmenite accompanying chemical compounds identification. → Chemical binding of Mg in ilmenite depends on the climatic and geological conditions. -- Abstract: Natural ilmenites are used all over the world as raw materials in white pigment (TiO 2 ) production. Besides the FeTiO 3 in the raw material many other compounds are present. The chemical compounds based on the minority elements influence quality of the final product and are difficult to identify. The knowledge about chemical bonding of the minor elements enables to properly adjust chemical reactions during production processes and to improve quality of the final product. In this paper the X-ray absorption spectroscopy (XAS) identification of the chemical compounds formed by Mg, Mn and Cr in natural ilmenites originating from different places is presented.

Measurement of spherical compound refractive X-ray lens at ANKA synchrotron radiation source

International Nuclear Information System (INIS)

Dudchik, Yu.I.; Simon, R.; Baumbach, T.

2007-01-01

Parameters of compound refractive X-ray lens were measured at ANKA synchrotron radiation source. The lens consists of 224 spherical concave epoxy microlenses formed inside glass capillary. The curvature radius of individual microlens is equal to 100 microns. Measured were: X-ray focal spot, lens focal length and gain in intensity. The energy of X-ray beam was equal to 12 keV and 14 keV. It is shown that when X-ray lens is used, the gain in intensity of the X-ray beam in some cases may exceed value of 100. Tested lens is suitable to focus X-rays into, at least, 2-microns in size spot. (authors)

X-ray magnetic circular dichroism in (Ge,Mn) compounds: Experiments and modeling

International Nuclear Information System (INIS)

Tardif, Samuel; Titov, Andrey; Arras, Emmanuel; Slipukhina, Ivetta; Hlil, El-Kébir; Cherifi, Salia; Joly, Yves; Jamet, Matthieu; Barski, André; Cibert, Joël; Kulatov, Erkin; Uspenskii, Yurii A.; Pochet, Pascal

2014-01-01

X-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) spectra at the L 2,3 edges of Mn in (Ge,Mn) compounds have been measured and are compared to the results of first principles calculation. Early ab initio studies show that the Density Functional Theory (DFT) can very well describe the valence band electronic properties but fails to reproduce a characteristic change of sign in the L 3 XMCD spectrum of Mn in Ge 3 Mn 5 , which is observed in experiments. In this work we demonstrate that this disagreement is partially related to an underestimation of the exchange splitting of Mn 2p core states within the local density approximation. It is shown that the change in sign experimentally observed is reproduced if the exchange splitting is accurately calculated within the Hartree–Fock approximation, while the final states can be still described by the DFT. This approach is further used to calculate the XMCD in different (Ge,Mn) compounds. It demonstrates that the agreement between experimental and theoretical spectra can be improved by combining state of the art calculations for the core and valence states respectively. - Highlights: • X-ray absorption and magnetic circular dichroism spectra are measured and compared to first principles calculations in (Ge,Mn) compounds. • Standard density functional theory fails in properly describing peculiar features observed in the experiment. • A new approach to calculate theoretical X-ray absorption and magnetic circular dichroism spectra is proposed. • Improved modeling of the core levels splitting using the Hartree–Fock approximation allows for a better matching with the experiment. • This new method could be generalized to any 3d metallic-like system

Evidence for dynamic behavior of O2 in oxy-heme model compounds

International Nuclear Information System (INIS)

Montiel-Montoya, R.; Bill, E.; Trautwein, A.X.; Winkler, H.

1986-01-01

The authors have performed Moessbauer studies on several oxy-heme model compounds, and for two of them they have also derived the three dimensional structure from X-ray studies. The X-ray structure analysis of these model compounds provides the information that O 2 occupies three different sites in one and only two sites in the other. (Auth.)

Magnetic and transport properties of the (Tb{sub 1-} {sub x} Y {sub x} )Mn{sub 2}Si{sub 2} and TbMn{sub 2}(Si{sub 1-} {sub y} Ge {sub y} ){sub 2} systems

Energy Technology Data Exchange (ETDEWEB)

Granovsky, S.A. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation) and TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany)]. E-mail: ser@plms.phys.msu.ru; Gaidukova, I.Yu. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation); Doerr, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Loewenhaupt, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Markosyan, A.S. [Department of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory GSP-2 119992 Moscow (Russian Federation)

2005-04-15

Magnetic and transport characteristics of pseudo-ternary compounds (Tb{sub 1-} {sub x} Y {sub x} )Mn{sub 2}Si{sub 2} and TbMn{sub 2}(Si{sub 1-} {sub y} Ge {sub y} ){sub 2} have been studied. The role of the 4f-3d exchange and Mn-Mn distances in the formation of the magnetic structure of these compounds is discussed.

Elimination of radical on the x-ray irradiated hydroxyapatite compounds

International Nuclear Information System (INIS)

Ohta, M.; Yasuda, M.; Miyazawa, C.; Okamura, H.; Suzuki, Y.

2002-01-01

We investigate the elimination of radical produced in a human tooth and synthetic calcium-deficient hydroxyapatite compounds after X-ray irradiation. Used samples were enamel and dentine of a human tooth and synthetic calcium-deficient hydroxyapatite (DAp), and stoichiometric hydroxyapatite (HAp). The ESR signal intensities at nearly g = 2 in the samples after X-ray irradiation were proportional to the absorbed dose in the range from 6 to 39 Gy. And these ESR signal intensities of the samples soaked in various ion containing fluids decreased with soaking time. Especially, the decrease in these ESR signal intensities was remarkably large in the samples soaked in Na 2 HPO 4 aqueous solution. This fact suggests that the surface layer of the samples easily dissolves in ion containing fluids

Magnetic properties and crystal field effects in TlLnX2 compounds (X=S, Se, Te)

International Nuclear Information System (INIS)

Duczmal, M.; Pawlak, L.

1997-01-01

Ternary thallium lanthanide chalcogenides TlLnX 2 (X=S, Se or Te) crystallize in the α-NaFeO 2 type of structure (R anti 3m). Each kind of the metal ions, surrounded by the distorted chalcogenide octahedra, forms separate layers. The TlX 6 octahedra are strongly elongated and the LnX 6 octahedra slightly shrunk along the threefold axis. The deformations of the coordination polyhedra and the cell volumes change regularly with the lanthanide ionic radii. The difference between the experimental and the calculated M-X distances increases on going from sulphides to tellurides, as a result of the growing covalent character of the bonds. The crystal field parameters were estimated from the high field magnetization (0-14 T) assuming trigonal distortion of the octahedral symmetry of LnX 6 polyhedra. The second-order crystal field parameters were found to correlate with the deformation of the lanthanide ions' environments. No magnetic transition was observed down to 4.2 K. (orig.)

Thermal, spectroscopic and magnetic properties of the Co xNi1-x(SeO3).2H2O (x = 0, 0.4, 1) phases

International Nuclear Information System (INIS)

Larranaga, A.; Mesa, J.L.; Pizarro, J.L.; Pena, A.; Chapman, J.P.; Arriortua, M.I.; Rojo, T.

2005-01-01

The Co x Ni 1-x (SeO 3 ).2H 2 O (x = 0, 0.4, 1) family of compounds has been hydrothermally synthesized under autogeneous pressure and characterized by elemental analysis, infrared and UV-vis spectroscopies and thermogravimetric and thermodiffractometric techniques. The crystal structure of Co 0.4 Ni 0.6 (SeO 3 ).2H 2 O has been solved from single-crystal X-ray diffraction data. This phase is isostructural with the M(SeO 3 ).2H 2 O (M = Co and Ni) minerals and crystallizes in the P2 1 /n space group, with a 6.4681(7), b = 8.7816(7), c = 7.5668(7) A, β = 98.927(9) deg and Z = 4. The crystal structure of this series of compounds consists of a three-dimensional framework formed by (SeO 3 ) 2- selenite oxoanions and edge-sharing M 2 O 10 dimeric octahedra in which the metallic cations are coordinated by the oxygens belonging to both the selenite groups and water molecules. The diffuse reflectance spectra show the essential characteristics of Co(II) and Ni(II) cations in slightly distorted octahedral environments. The calculated values of the Dq and Racah (B and C) parameters are those habitually found for the 3d 7 and 3d 8 cations in octahedral coordination. The magnetic measurements indicate the existence of antiferromagnetic interactions in all the compounds. The magnetic exchange pathways involve the metal orbitals from edge-sharing dimeric octahedra and the (SeO 3 ) 2- anions which are linked to the M 2 O 10 polyhedra in three dimensions

Impact of hydrogen absorption on crystal structure and magnetic properties of RE{sub 2}T{sub 2}X compounds

Energy Technology Data Exchange (ETDEWEB)

Mašková, S., E-mail: maskova@mag.mff.cuni.cz [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Kolomiets, A. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Department of Physics, Lviv Polytechnic National University, Lviv (Ukraine); Havela, L. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Andreev, A.V. [Institute of Physics, AVCR, Prague 8 (Czech Republic); Svoboda, P. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic)

2015-10-05

Highlights: • RE{sub 2}Pd{sub 2}In(Sn) compounds absorb, depending on RE, different amounts of hydrogen. • Compounds with the light rare earths become amorphous upon the hydrogenation. • Compounds with the heavy rare earths preserve the original tetragonal structure. • Magnetic ordering temperatures of RE{sub 2}Pd{sub 2}In compounds are reduced by the hydrogenation. - Abstract: RE{sub 2}Pd{sub 2}In, RE{sub 2}Pd{sub 2}Sn compounds (RE = rare earth) absorb, depending on the rare earth (RE) element, different amounts of hydrogen. The parent compounds RE{sub 2}Pd{sub 2}In show the linear decrease of both lattice parameters and the unit cell volume with the increasing atomic number of RE, attributed to the lanthanide contraction. All the compounds absorb at least 2 H/f.u.; the tetragonal structure is merely expanded. The expansion is anisotropic (Δc/c > Δa/a), and for RE = Tb, Dy, Ho, and Er the lattice even contracts along the a-axis (Δa/a < 0), whereas Δc/c still weakly increases. A higher H concentration can be achieved in the compounds with light rare earths (La, Nd, both for In and Sn), which then become amorphous. The magnetic ordering temperatures of all studied RE{sub 2}Pd{sub 2}In compounds are dramatically reduced by the hydrogenation, typically to the temperature range below 1.8 K.

Synthesis and Characterization of Tert-Butylgallium-Antimony Compounds; X-Ray Crystal Structures of t-Bu3Ga. Sb(SiMe3)3, T-Bu2GaSb(SiMe3)2, and t-Bu2GaSb(SiMe3)Ga(t-Bu)2Cl, The first Example of a Gallium-Antimony Mixed-Bridge Compound

National Research Council Canada - National Science Library

Wells, Richard

1997-01-01

...:1 equilibration of t-Bu2GaCl with 2. These new gallium-antimony compounds have been characterized through multinuclear solution NMR spectroscopy, partial elemental analysis, and single-crystal X-ray structural analysis...

Recent progress of soft X-ray photoelectron spectroscopy studies of uranium compounds

Energy Technology Data Exchange (ETDEWEB)

Fujimori, Shin-ichi; Takeda, Yukiharu; Okane, Tetsuo; Saitoh, Yuji [Condensed Matter Science Divisions, Japan Atomic Energy Agency, Sayo, Hyogo (Japan); Fujimori, Atsushi [Condensed Matter Science Divisions, Japan Atomic Energy Agency, Sayo, Hyogo (Japan); Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Yamagami, Hiroshi [Condensed Matter Science Divisions, Japan Atomic Energy Agency, Sayo, Hyogo (Japan); Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555 (Japan); Yamamoto, Etsuji; Haga, Yoshinori [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Ōnuki, Yoshichika [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213 (Japan)

2016-04-15

Recent progresses in the soft X-ray photoelectron spectroscopy (PES) studies (hν ≳ 100 eV) for uranium compounds are briefly reviewed. The soft X-ray PES has enhanced sensitivities for the bulk U 5f electronic structure, which is essential to understand the unique physical properties of uranium compounds. In particular, the recent remarkable improvement in energy resolutions from an order of 1 eV to 100 meV made it possible to observe fine structures in U 5f density of states. Furthermore, soft X-ray ARPES becomes available due to the increase of photon flux at beamlines in third generation synchrotron radiation facilities.The technique made it possible to observe bulk band structures and Fermi surfaces of uranium compounds and therefore, the results can be directly compared with theoretical models such as band-structure calculations. The core-level spectra of uranium compounds show a systematic behavior depending on their electronic structures, suggesting that they can be utilized to determine basic physical parameters such as the U 5f-ligand hybridizations or Comlomb interaction between U 5f electrons. It is shown that soft X-ray PES provides unique opportunities to understand the electronic structures of uranium compounds.

A study of shielding properties of x-ray and gamma in barium compounds

Energy Technology Data Exchange (ETDEWEB)

Seenappa, L.; Manjunatha, H. C. [Dept. of of Physics, Government College for women, Karnataka (India); Chandrika, B. M. [PC Extension, St. Annes School, Karnataka (India); Chikka, Hanumantharayappa [Vivekananda Degree College, Karnataka (India)

2017-03-15

Ionizing radiation is known to be harmful to human health. The shielding of ionizing radiation depends on the attenuation which can be achieved by three main rules, i.e. time, distance and absorbing material. The mass attenuation coefficient, linear attenuation coefficient, Half Value Layer (HVL) and Tenth Value Layer (TVL) of X-rays (32 keV, 74 keV) and gamma rays (662 keV) are measured in Barium compounds. The measured values agree well with the theory. The effective atomic numbers (Z{sub eff}) and electron density (Ne) of Barium compounds have been computed in the wide energy region 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program. The mass attenuation coefficient and linear attenuation coefficient for BaCO{sub 3} is higher than the BaCl{sub 2}, Ba(No{sub 3}){sub 2} and BaSO{sub 4}. HVL, TVL and mean free path are lower for BaCO{sub 3} than the BaCl{sub 2}, Ba(No{sub 3}){sub 2} and BaSO{sub 4}. Among the studied barium compounds, BaCO{sub 3} is best material for x-ray and gamma shielding.

Wet chemical passivation of YBa2Cu3O(7-x)

Science.gov (United States)

Vasquez, R. P.; Hunt, B. D.; Foote, M. C.

1990-01-01

Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, which result in the formation of native compounds known to have little or no reactivity to water. Suitable native compounds include CuI, BaSO4, CuS, Cu2S, YF3, and the oxalates. Formation of surface layers in which these nonreactive native compounds are major constituents is verified with X-ray photoelectron spectroscopy (XPS) measurements on YBa2Cu3O(7-x) films treated with dilute solutions of HI, H2SO4, Na2S, HF, or H2C2O4. No significant changes are observed in the XPS spectra when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide and fluoride films show evidence of reaction with water. X-ray diffraction measurements show that the superconducting phase is absent in the sulfide film, but is unaffected by the oxalate and sulfate treatments.

System Ba/sub 2/Gdsub(2/3)vacantsub(1/3)Usub(1-x)Wsub(x)O/sub 6/ and hexagonal perovskites of an 18-layer type

Energy Technology Data Exchange (ETDEWEB)

Wischert, W; Schittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

1978-04-01

In the system Ba/sub 2/Gdsub(2/3)vacantsub(1/3)Usub(1-x)Wsub(x)O/sub 6/ the formation of a continuous solid solution series is observed. With x <= 0.9 the mixed crystals have a cubic 1:1 ordered perovskite structure. With x >= 0.95 the compounds are polymorphic: besides an cubic 1:1 ordered perovskite type for x = 0.95; 0.99 and 1.00 one hexagonal layer structure exists. This lattice is in all cases rhombohedral (space group R3m) and represents an 18 L-type. Likewise the compounds Ba/sub 2/Bsub(2/3)sup(III)vacantsub(1/3)Wsup(VI)O/sub 6/ with Bsup(III) Tb-Lu and Y belong to the 18 L-type.

Crystal structure of U2+xCo2Ga1-x

International Nuclear Information System (INIS)

Zelinskii, A.V.; Fedorchuk, A.A.

1995-01-01

In studies of phase equilibria in the U-Co-Ga system at 600 degrees C, the authors found a ternary compound close in composition to U 2 Co 2 Ga. A sample of composition U 42 Co 40 Ga 18 was prepared by arc-melting a mixture of high-purity U (99.4%), Co (99.99%), and Ga (99.99%) in a purified argon atmosphere. The sample was homogenized at 600 degrees C for 720 h in an evacuated quartz tube and then quenched in cold water. In structure determination, the authors used a DRON-4-07 powder X-ray diffractometer (CuK α radiation, 0.02 degrees 2θ scan step) and the CSD software package. The X-ray diffraction pattern showed tetragonal symmetry, with lattice parameters obtained from least-squares refinements a = 0.707729(5) and c = 0.34707(4) nm

Lattice dynamics and electronic properties of superconducting Nbsub(x)Vsub(1-x)N compounds

International Nuclear Information System (INIS)

Geibel, C.; Rietschel, H.; Pelizzone, M.; Junod, A.; Muller, J.

1982-01-01

The Nbsub(x)Vsub(1-x)N-system presents a pronounced minimum in Tsub(c) at the composition Nbsub(0.5)Vsub(0.5)N. We investigated the structural, the electronic properties and the lattice dynamics of these compounds to study whether this minimum is induced by structural defects, a decrease of the electron-phonon-coupling or by spin fluctuations. (orig.)

X-Ray diffraction on rare earth-3d Laves phase compound ErCo2 in magnetic field

International Nuclear Information System (INIS)

Yagasaki, Katsuma; Notsu, Shiko; Takaesu, Yoshinao; Nakama, Takao; Sakai, Eijiro; Koyama, Keiichi; Watanabe, Kazuo; Burkov, Alexander T.

2006-01-01

X-Ray powder diffraction method is used to investigate the effect of magnetic ordering and external magnetic field on crystal structure of Laves phase intermetallic compound ErCo 2 . The diffraction patterns were recorded at temperatures from 300K down to 8.5K in magnetic field up to 5T. Distortion of the room-temperature cubic structure was found in magnetically ordered state below 32K. The symmetry at low temperature is rhombohedral in agreement with literature results, or lower symmetry than it. However the symmetry of the unit cell increases to cubic in external magnetic field of 5T

Structural stability of (Pu1-xAmx)O2 (x=0.2;0.5;0.8) obtained by oxalate co-conversion

International Nuclear Information System (INIS)

Jankowiak, A.; Donnet, L.; Maillard, C.

2008-01-01

The EUROTRANS project investigates the transmutation of transuranium elements in dedicated reactors (ADS, FR). The study includes various subject areas: neutronics, physical properties, coolant type (sodium, lead, bismuth, helium), etc, and experimental work concerning the fabrication of minor actinide compounds for thermo-physical properties determination. For this program, the CEA was responsible for synthesizing three Pu 1-x Am x O 2 compounds with various Am and Pu content (x = 0.2, 0.5, 0.8). The selected synthesis route for the mixed Am and Pu oxide powder consists in actinides oxalates co-conversion. The purpose of the study was to determine by XRD the crystal structure and the lattice parameters change as a function of the time for each co-converted mixed oxides. After one year of experiment, although the lattice parameters significantly expanded, the compounds remained monophasic. The observations showed that the initial expansion rate and the a max stage value vary according to the Pu and Am content. (authors)

Mixed nickel-gallium tellurides Ni{sub 3−x}GaTe{sub 2} as a matrix for incorporating magnetic cations: A Ni{sub 3−x}Fe{sub x}GaTe{sub 2} series

Energy Technology Data Exchange (ETDEWEB)

Kuznetsov, Alexey N., E-mail: alexei@inorg.chem.msu.ru [Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1-3, GSP-1, 119991 Moscow (Russian Federation); N.S. Kurnakov Institute of General and Inorganic Chemistry, RAS, Leninsky pr. 31, GSP-1, 119991 Moscow (Russian Federation); Stroganova, Ekaterina A.; Zakharova, Elena Yu; Solopchenko, Alexander V.; Sobolev, Alexey V.; Presniakov, Igor A. [Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1-3, GSP-1, 119991 Moscow (Russian Federation); Kirdyankin, Denis I.; Novotortsev, Vladimir M. [N.S. Kurnakov Institute of General and Inorganic Chemistry, RAS, Leninsky pr. 31, GSP-1, 119991 Moscow (Russian Federation)

2017-06-15

Using a high-temperature ampoule technique, a series of mixed nickel-iron-gallium metal-rich tellurides with layered structures, Ni{sub 3-x}Fe{sub x}GaTe{sub 2}, were prepared and characterized based on X-ray powder diffraction, energy-dispersive spectroscopy, and {sup 57}Fe Mössbauer spectroscopy data. These compounds may be regarded as a result of partial substitution of nickel by iron in the recently reported ternary Ni{sub 3-x}GaTe{sub 2} series, which are based on NiAs/Ni{sub 2}In type of structure. The compositional boundary for the substitution was found to be at x~1. According to the Mössbauer spectroscopy data, the substitution is not statistical, and iron atoms with the increase in x tend to preferentially occupy those nickel positions that are partially vacant in the initial ternary compound. Magnetic measurements data for the Ni{sub 3-x}Fe{sub x}GaTe{sub 2} series show dramatic change in behavior from temperature-independent paramagnetic properties of the initial matrix to a low-temperature (~75 K) ferromagnetic ordering in the Ni{sub 2}FeGaTe{sub 2}. - Graphical abstract: Ordered substitution of nickel by iron in the Ni{sub 3−x}GaTe{sub 2} series leading to ferromagnetic ordering. - Highlights: • A series of Ni{sub 3−x}Fe{sub x}GaTe{sub 2} compounds were synthesized. • They adopt the NiAs/Ni{sub 2}In type of structure with ordered iron distribution. • The distribution of iron was studied using {sup 57}Fe Mössbauer spectroscopy. • An increase in iron content leads to the strong ferromagnetic coupling.

Electronic structure of ZrX2 (X = Se, Te)

Science.gov (United States)

Shkvarin, A. S.; Merentsov, A. I.; Shkvarina, E. G.; Yarmoshenko, Yu. M.; Píš, I.; Nappini, S.; Titov, A. N.

2018-03-01

The electronic structure of the ZrX2 (X = Se, Te) compounds has been studied using photoelectron, resonant photoelectron and X-ray absorption spectroscopy, theoretical calculations of the X-ray absorption spectra, and density of electronic states. It was found that the absorption spectra and valence band spectra are influenced by the chalcogen type. The results of the multiplet calculation of the Zr4+ atom show that the change in the splitting in the crystal field, which is described by the 10Dq parameter, is due to the change in the ratio of covalent and ionic contributions to the chemical bond. The resonance band near the Fermi level in the valence band spectra is observed for ZrTe2 in the Zr 3p-4d resonant excitation mode. The extent of photon energy indicates the charge localization on the Zr atom. Similar resonance band for ZrSe2 is absent; it indicates the presence of a gap at the Fermi level.

Synthesis, magnetism and electronic structure of YbNi{sub 2-x}Fe{sub x}Al{sub 8} (x=0.91) isolated from Al flux

Energy Technology Data Exchange (ETDEWEB)

Xiuni, Wu [Department of Physical Sciences, Rhode Island College, Providence, RI 02908 (United States); Francisco, Melanie [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States); Rak, Zsolt [Department of Physics, Michigan State University, East Lansing, MI 48824 (United States); Bakas, T [Department of Physics, University of Ioannina, GR-45110 Ioannina (Greece); Mahanti, S D [Department of Physics, Michigan State University, East Lansing, MI 48824 (United States); Kanatzidis, Mercouri G. [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States)], E-mail: m-kanatzidis@northwestern.edu

2008-12-15

The combination of ytterbium, nickel, iron in liquid aluminum resulted in the formation of the new intermetallic compound YbNi{sub 2-x}Fe{sub x}Al{sub 8} (x=0.91) which adopts the CaCo{sub 2}Al{sub 8} structure type with a=14.458(3) A, b=12.455(3) A, c=3.9818(8) A and space group Pbam. Its resistivity drops with decreasing temperature, saturating to a constant value at lower temperatures. Above 50 K, the inverse magnetic susceptibility data follows Curie-Weiss Law, with a calculated {mu}{sub eff}=2.19 {mu}{sub B}. Although the observed reduced moment in magnetic susceptibility measurement suggests that the Yb ions in this compound are of mixed-valent nature, ab initio electronic structure calculations within density functional theory using LDA+U approximation give an f{sup 13} configuration in the ground state. - Graphical abstract: The reaction of ytterbium, nickel, iron in aluminum flux gives crystals of the intermetallic compound YbNi{sub 2-x}Fe{sub x}Al{sub 8} (x=0.96) which adopts the CaCo{sub 2}Al{sub 8} structure, ab initio electronic structure calculations within density functional theory using LDA+U approximation suggest an f{sup 13} configuration in the ground state.

Analysis of metals in organic compounds by energy dispersive X-ray fluorescence analysis

International Nuclear Information System (INIS)

Anjos, Marcelino J.; Lopes, Ricardo T.; Jesus, Edgar F.O. de

2000-01-01

Using energy dispersive X-ray fluorescence analysis with an X-ray tube filtered with Ti. It was possible to determine the concentration of the elements at ppm level of several elements: K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn As, Rb, Sr, Y, Zr, and Pb in two types of organic compound enough used in the agriculture: organic compound of urban garbage (Fertilurb) and aviary bed (birds manure). The experimental setup is composed of: x-ray tube (Oxford, 30 kV, 50 μA and W anode), an ORTEC Si-Li detector, with an energy resolution of about 180 eV at 5.9 keV and an ORTEC multichannel-analyser. The X-ray beam is quasi- monochromatic by using Ti filter. The samples were prepared in pellet form with superficial density in the range of 100 mg/cm 2 . The fundamental parameter method was used in order to verify the elemental concentration. The radiation transmission method was going used to the radiation absorption effects correction in the samples. (author)

The Soft X-Ray Spectra of Sulfur Compounds.

Science.gov (United States)

Zhou, Ling

1995-01-01

The sulfur compounds including CdS, ZnS, rm MoS_2, WS_2, NiS, FeS, GaS, SnS, MgS and Alloy rm ZnS_{x }Se_{1-x} were investigated by using photon/e-beam excited soft x-ray spectroscopy through SXA, SXE, SXF and inelastic Resonant Raman scattering and resonant elastic scattering processes. For valence bands, the PDOS of S L_{2,3}, Zn M_{2,3}, Se M _{4,5}, bands locations, band gaps Eg, core level spin splitting, the lifetime broadening of valence band t_{1/2}, branching ratio of rm L_2/L_3 and shallow d level and exciton state were measured in some of these materials respectively. The excitation mechanism or threshold effects were studied for CdS, ZnS, MoS_2, WS_2, FeS, NiS, and alloy. In photon excited S L_ {2,3}^ectra, local core levels with spin splitting were found to charge threshold effects. The threshold effects are also found to be influenced by resonant elastic and inelastic scattering process. A simple model and the second order perturbation theory are used to explain the observed inelastic Raman scattering of Zn M _{2,3} spectra near d threshold. The d participation in the chemical bonding and interactions was studied. Atomiclike d bands were found in FeS and NiS from strong d-d and d-p couplings. Two groups of d bands were observed in Transitional Metal Sulfides (TMS) and the no-bonding group with a few d bands was found to across whole valence bands in TMS. The direct connection between valence bands and conduction bands is built and some conduction bands were studied. A study of alloy was included briefly. These experiments provide a rich information about TMS, and prove that Soft X-ray Spectroscopy is a powerful, precise and reliable tool in the study of fine electronic band structure in solids.

Magnetic and magnetocaloric properties of itinerant-electron system Hf{sub 1−x}Ta{sub x}Fe{sub 2} (x = 0.125 and 0.175)

Energy Technology Data Exchange (ETDEWEB)

Diop, L.V.B. [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Kastil, J. [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Isnard, O. [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Arnold, Z.; Kamarad, J. [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic)

2015-04-05

Highlights: • First report of the direct measurement of ΔT{sub ad} in Hf{sub 1−x}Ta{sub x}Fe{sub 2} compounds. • ΔT{sub ad} reach values of 2.5 K under μ{sub 0}ΔH = 3 T for x = 0.175 compound. • A field induced metamagnetic phase transition has been observed. - Abstract: Intrinsic magnetic properties and magnetocaloric effect (MCE) have been investigated for Hf{sub 1−x}Ta{sub x}Fe{sub 2} (x = 0.125 and 0.175) itinerant-electron compounds which exhibit a temperature-induced transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) state. Upon increasing Ta concentration, the ferromagnetic ordering temperature strongly decreases with decreasing the lattice parameters and both the isothermal magnetic entropy change ΔS{sub M} and the adiabatic temperature change ΔT{sub ad} are enhanced. An adiabatic temperature change of ΔT{sub ad} = 2 and 2.5 K was observed in Hf{sub 0.875}Ta{sub 0.125}Fe{sub 2} and Hf{sub 0.825}Ta{sub 0.175}Fe{sub 2}, respectively, for a magnetic field change of 3 T. Therefore, the partial substitution of Ta for Hf is highly effective in the enhancement of the magnetocaloric effect in Hf{sub 1−x}Ta{sub x}Fe{sub 2} systems. In addition substitution can be used to tune both the transition temperature but also the magnetic transition from first toward second order type.

Photoluminescence studies on Cd(1-x)Zn(x)S:Mn2+ nanocrystals.

Science.gov (United States)

Sethi, Ruchi; Kumar, Lokendra; Pandey, A C

2009-09-01

Highly monodispersed, undoped and doped with Mn2+, binary and ternary (CdS, ZnS, Cd(1-x)Zn(x)S) compound semiconductor nanocrystals have been synthesized by co-precipitation method using citric acid as a stabilizer. As prepared sample are characterized by X-ray diffraction, Small angle X-ray scattering, Transmission electron microscope, Optical absorption and Photoluminescence spectroscopy, for their optical and structural properties. X-ray diffraction, Small angle X-ray scattering and Transmission electron microscope results confirm the preparation of monodispersed nanocrystals. Photoluminescence studies show a significant blue shift in the wavelength with an increasing concentration of Zn in alloy nanocrystals.

Superconductivity induced by doping Rh in CaFe2-xRhxAs2

International Nuclear Information System (INIS)

Qi Yanpeng; Wang Lei; Gao Zhaoshun; Wang Dongliang; Zhang Xianping; Wang Chunlei; Yao Chao; Ma Yanwei

2011-01-01

In this paper, we report the synthesis of iron-based superconductors CaFe 2-x Rh x As 2 using a one-step solid state reaction method that crystallizes in the ThCr 2 Si 2 -type structure with a space group I4/mmm. The systematic evolution of the lattice constants demonstrates that the Fe ions are successfully replaced by the Rh. By increasing the doping content of Rh, the spin-density-wave (SDW) transition in the parent compound is suppressed and superconductivity emerges. The maximum superconducting transition temperature is found at 18.5 K with a doping level of x=0.15. The temperature dependence of dc magnetization confirms superconducting transitions at around 15 K. The general phase diagram was obtained and found to be similar to the case of the Rh-doping Sr122 system. Our results explicitly demonstrate the feasibility of inducing superconductivity in Ca122 compounds by higher d-orbital electron doping; however, different Rh-doping effects between FeAs122 compounds and FeAs1111 systems still remains an open question.

Study by X-ray diffraction of structure modifications induced by pressure in different actinide compounds: AnO2 dioxides (An=Th, Pu, Am), AnCl4 tetrachlorides (An=Th, U), UBx borides (x=2,4,12) and the carbide UC2

International Nuclear Information System (INIS)

Dancausse, J.P.

1991-01-01

Structural transitions, induced by pressure, of actinide compounds are studied by X-ray diffraction, the determination of incompressibility is also studied at atmospheric pressure. The crystal structure of ThO 2 , PuO 2 and AmO 2 evolves, near 40 MPa from a fcc lattice to an orthorhombic lattice. Incompressibility values associated to UO 2 and NpO 2 incompressibility evidence an important discontinuity between UO 2 and NpO 2 and other dioxides due to their different electronic structure. Tetragonal ThCl 4 and UCl 4 undergo a structure transition respectively at 2 and 5 GPa. UCl 4 becomes monoclinic and its color changes. At higher pressure these compounds become progressively amorphous. The crystal structure of uranium borides is not changed up to 50 GPa. UC 2 presents a phase transition at 17.6 GPa from a tetragonal to a hexagonal lattice

NMR study of Gd2(Co1-xFex)14B compounds

International Nuclear Information System (INIS)

Hayashi, M.; Myojin, T.; Kasamatsu, Y.; Imaeda, Y.; Ushida, T.; Tsujimura, A.; Hihara, T.

1992-01-01

59 Co NMR measurements in Gd 2 (Co 1-x Fe x ) 14 B have been carried out at 4.2 K. The resonance line corresponding to each site of the Co atoms shifts gradually to a higher frequency region as the value of x increases, and when the value exceeds 0.3 the resonance line seems to be disturbed. (orig.)

Efficient UV-emitting X-ray phosphors: octahedral Zr(PO4)6 luminescence centers in potassium hafnium-zirconium phosphates K2Hf1-xZrx(PO4)2 and KHf2(1-x)Zr2x(PO4)3

International Nuclear Information System (INIS)

Torardi, C.C.; Miao, C.R.; Li, J.

2003-01-01

Potassium hafnium-zirconium phosphates, K 2 Hf 1-x Zr x (PO 4 ) 2 and KHf 2(1-x) Zr 2x (PO 4 ) 3 , are broad-band UV-emitting phosphors. At room temperature, they have emission peak maxima at approximately 322 and 305 nm, respectively, under 30 kV peak molybdenum X-ray excitation. Both phosphors demonstrate luminescence efficiencies that make them up to ∼60% as bright as commercially available CaWO 4 Hi-Plus. The solid-state and flux synthesis conditions, and X-ray excited UV luminescence of these two phosphors are discussed. Even though the two compounds have different atomic structures, they contain zirconium in the same active luminescence environment as that found in highly efficient UV-emitting BaHf 1-x Zr x (PO 4 ) 2 . All the three materials have hafnium and zirconium in octahedral coordination via oxygen-atom corner sharing with six separate PO 4 tetrahedra. This octahedral Zr(PO 4 ) 6 moiety appears to be an important structural element for efficient X-ray excited luminescence, as are the edge-sharing octahedral TaO 6 chains for tantalate emission

Routes for synthesis and characterization of the Lu{sub 1-x}Ca{sub x}Cu{sub 2}Si{sub 2} series

Energy Technology Data Exchange (ETDEWEB)

Radaelli, Matheus; Piva, Mario Moda; Christovam, Denise S.; Ribeiro, Ana L.A.; Pagliuso, Pascoal G., E-mail: goiba@ifi.unicamp.br [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

2016-07-01

Full text: New materials design always plays an important role in condensed matter physics. When CeCu{sub 2} Si{sub 2} was discovered,a new front in the field of superconductivity on strongly correlated materials started and led to the discovery of many classes of related materials. In such materials, the interplay between magnetism (affected by the hybridization strength between local f electrons and conduction electrons) and heavy-fermion superconductivity is still a matter of controversy and intense studies. Based on these materials, one can explore the structural and stoichiometric similarities among the several classes of related compounds to develop routes for new materials design of novel heavy fermion superconductors.The non-magnetic reference compound LuCu{sub 2}Si{sub 2} crystallizes in a ThCr{sub 2}Si{sub 2}-type structure (I4/mmm) and presents a metallic-like temperature dependent resistivity [2]. As such, it can be used as a based compound to search for 3d-based magnetic analogs of CeCu{sub 2}Si{sub 2}. In this work, we have performed Lu-site substitutions (Ba,Sr,Ca) in order to tune the orbital differentiation of the Cu 3d bands and potentially induce magnetism. We will discuss experiments of x-ray powder diffraction, elemental analysis (EDS, WDS), resistivity and DC magnetic susceptibility on single crystals Lu{sub 1-x}Ca{sub x}Cu{sub 2}Si{sub 2} (X{sub nominal} = 0, 0.3 and 0.5) grown from Tin-flux and evaluate the efficiency of different kinds of dopant to induce magnetism. (author)

Features of the structure of phospho- and arsenouranic acids of the composition of HPUO2x4H2O and HAsUO6x4H2O

International Nuclear Information System (INIS)

Chernorukov, N.G.; Karyakin, N.V.; Chernorukov, G.N.

1994-01-01

The structure of crystal phases of the composition HPUO 6 x4H 2 O and HAsUO 6 x4H 2 O has been studied using the methods of IR spectroscopy, thermography, X-ray phase analysis and calorimetry. The nature and binding energy of water within the compounds mentioned are determined. 10 refs., 2 figs

Structure and optical properties of [In{sub 1−2x}Sn{sub x}Zn{sub x}]GaO{sub 3}(ZnO){sub m}

Energy Technology Data Exchange (ETDEWEB)

Eichhorn, Simon; Mader, Werner, E-mail: mader@uni-bonn.de

2016-01-15

Compounds of [In{sub 1−2x}Sn{sub x}Zn{sub x}]GaO{sub 3}(ZnO){sub 1} (x≤0.22) and [In{sub 1−2x}Sn{sub x}Zn{sub x}]GaO{sub 3}(ZnO){sub 2} (x≤0.42) were prepared by solid state processing proving a substantial solid solution of Sn in the layered compounds InGaO{sub 3}(ZnO){sub m} (m=1, 2). Single crystal X-ray diffraction of the compounds reveals two In{sup 3+} ions to be substituted by one Sn{sup 4+} and one Zn{sup 2+} at the octahedral layer preserving the average charge of +3 at these sites. The substitution does not lead to an ordering of the ions but proves for the first time that the octahedral site can be occupied by different ions while all characteristics of the layered structures remain unchanged. Consequences of indium substitution are (i) decrease of the a axis compared to InGaO{sub 3}(ZnO){sub m} according to smaller ionic radii of Sn{sup 4+} and Zn{sup 2+} compared to In{sup 3+} and (ii) shift of the optical band gap to higher energies shown by UV–vis measurements. - Graphical abstract: Substitution limits of indium in InGaO{sub 3}(ZnO){sub m} (IGZO) by Sn and Zn are studied for m=1, 2 by single crystal X-ray diffraction and micro-chemical analysis. - Highlights: • New Oxides [In{sub 1−2x}Sn{sub x}Zn{sub x}]GaO{sub 3}(ZnO){sub m} (m=1, 2) with IGZO type structure. • Sn and Zn substitute for In at octahedral sites. • Crystal structures were characterized by single crystal X-ray diffraction. • Optical band gap energies were determined by UV–vis spectroscopy.

A study on magnetoelastic properties of Tb3 (Fe28-xCox) V1.0 (x=0, 3, 6) compounds

International Nuclear Information System (INIS)

Gholizadeh, A.; Tajabor, N.; Pourarian, F.

2012-01-01

In this work, The magnetoelastic properties of polycrystalline samples of Tb 3 (Fe 28-x Co x ) V 1.0 (x=0, 3, 6) intermetallic compounds are investigated by means of linear thermal expansion and magnetostriction measurements in the temperature range of 77-515 K under applied magnetic fields up to 1.5 T. The linear thermal expansion increases with the Co content. The well-defined anomalies observed in the linear thermal expansion coefficients for Tb 3 (Fe 28-x Co x ) V 1.0 (x=0, 3, 6) compounds are associated with the magnetic ordering temperature for x=0 and spin reorientation temperatures for x=3, 6. Below transition temperatures, the value of the longitudinal magnetostriction (λ Pa ) at 1.6 T increases with Co content.

Soft X-ray spectroscopy of transition metal compounds: a theoretical perspective

International Nuclear Information System (INIS)

Bokarev, S.I.; Hilal, R.; Aziz, S.G.; Kühn, O.

2017-01-01

To date, X-ray spectroscopy has become a routine tool that can reveal highly local and element-specific information on the electronic structure of atoms in complex environments. Here, we report on the development of an efficient and versatile theoretical methodology for the treatment of soft X-ray spectra of transition metal compounds based on the multi-configurational self-consistent field electronic structure theory. A special focus is put on the L-edge photon-in/photon-out and photon-in/electron-out processes, i.e. X-ray absorption, resonant inelastic scattering, partial fluorescence yield, and photoelectron spectroscopy, all treated on the same theoretical footing. The investigated systems range from small prototypical coordination compounds and catalysts to aggregates of biomolecules.

PHOTOELECTRON-SPECTROSCOPY STUDY OF THE ELECTRONIC-STRUCTURE OF THE INCOMMENSURATE INTERGROWTH COMPOUNDS (SBS)(1.15)(TIS2)(N) WITH N=1, 2

NARCIS (Netherlands)

REN, Y; HAAS, C; WIEGERS, GA

1995-01-01

The electronic structure of the inorganic misfit-layer compounds (SbS)(1.15)(TiS2)(n) (n = 1,2) has been investigated using x-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and x-ray absorption spectroscopy (XAS). These compounds are built of alternating modulated

Insight into π-hole interactions containing the inorganic heterocyclic compounds S2N2/SN2P2.

Science.gov (United States)

Lu, Bo; Zhang, Xueying; Meng, Lingpeng; Zeng, Yanli

2017-08-01

Similar to σ-hole interactions, the π-hole interaction has attracted much attention in recent years. According to the positive electrostatic potentials above and below the surface of inorganic heterocyclic compounds S 2 N 2 and three SN 2 P 2 isomers (heterocyclic compounds 1-4), and the negative electrostatic potential outside the X atom of XH 3 (X = N, P, As), S 2 N 2 /SN 2 P 2 ⋯XH 3 (X = N, P, As) complexes were constructed and optimized at the MP2/aug-cc-pVTZ level. The X atom of XH 3 (X = N, P, As) is almost perpendicular to the ring of the heterocyclic compounds. The π-hole interaction energy becomes greater as the trend goes from 1⋯XH 3 to 4⋯XH 3 . These π-hole interactions are weak and belong to "closed-shell" noncovalent interactions. According to the energy decomposition analysis, of the three attractive terms, the dispersion energy contributes more than the electrostatic energy. The polarization effect also plays an important role in the formation of π-hole complexes, with the contrasting phenomena of decreasing electronic density in the π-hole region and increasing electric density outside the X atom of XH 3 (X = N, P, As). Graphical abstract Computed density difference plots for the complexes 3⋯NH 3 (a 1 ), 3⋯PH 3 (b 1 ), 3⋯AsH 3 (c 1 ) and electron density shifts for the complexes 3⋯NH 3 (a 2 ), 3⋯PH 3 (b 2 ),3⋯AsH 3 (c 2 ) on the 0.001 a.u. contour.

Simulating and optimizing compound refractive lens-based X-ray microscopes

DEFF Research Database (Denmark)

Simons, Hugh; Ahl, Sonja Rosenlund; Poulsen, Henning Friis

2017-01-01

A comprehensive optical description of compound refractive lenses (CRLs) in condensing and full-field X-ray microscopy applications is presented. The formalism extends ray-transfer matrix analysis by accounting for X-ray attenuation by the lens material. Closed analytical expressions for critical......-lens limit. This limit may be satisfied by a range of CRL geometries, suggesting alternative approaches to improving the resolution and efficiency of CRLs and X-ray microscopes....

Degradation of organophosphorus compounds by X-ray irradiation

International Nuclear Information System (INIS)

Trebse, P.; Arcon, I.

2002-01-01

Complete text of publication follows. Our research presented in this contribution aims to elucidate the degradation mechanisms of organophosphate pesticides as organic pollutants by X-ray irradiation. Diazinon, one of the most widely used pesticides in Slovenia, has been chosen as a model compound for the study of radiation induced degradation of organophosphorus pesticides. Recent studies have shown that the degradation of the pesticide at normal conditions (room temperature, exposure to daylight) is strongly enhanced when the pesticide is exposed to UV light (Hg lamp, λ=254 nm, XeCl excimer laser, λ=308 nm). In our study we irradiated the pesticide in aqueous media with a white x-ray beam from a conventional x-ray source. Mo X-ray tube operating at the high voltage of 55 kV and a current of 45 mA was used. The flux of the continuous X-ray beam was stabilized within 1%. Saturated water solution of the pesticide (volume: 4mL, conc. of 40 mg L -1 ) was inserted in 1 cm long lucite cell with 1 mm thick lucite windows. The whole volume of the solution in the cell was exposed to the unfiltered X-ray beam. The dose rate on the sample was about 1 mGy/s. Different irradiation times between 30 min to 120 min were chosen to study the dependence of the pesticide decomposition with the absorbed dose. Solid phase extraction was employed for sample extraction from the solution, and gas chromatography was used for the identification and quantification of the compounds. The results show that the concentration of the pesticide in the solution decreases exponentially with the exposure time, i.e. with the absorbed dose. At irradiation conditions described above, the time constant of the exponential decrease was 74 min

The effect of hydrogen absorption on the structural, electronic and magnetic properties of the C15 Friauf-Laves phase compounds CeFe2, CeRu2 and LaRu2 : an x-ray absorption spectroscopy (XAS) study

International Nuclear Information System (INIS)

Chaboy, J.; Garcia, J.; Marcelli, A.

1995-08-01

An x-ray absorption spectroscopy (XAS) investigation of the structural changes occurred upon hydriding in the Friauf-Laves phase compounds CeFe 2 , CeRu 2 and LaRu 2 compounds is presented. The analysis of the extended x-ray absorption spectroscopy (EXAFS) spectra at the L-edges of the rare-earth and at the Fe K-edge indicates that the hydrogenation process leads to the suppression of the long-range crystalline order in all the hydride derivates investigated, as well as the different influence of H 2 in both the rare earth and transition metal sublattices. The correlation between the structural and magnetic changes induced by the hydrogen in the lost matrix is discussed in terms of the modification of the electronic properties, i.e., intermediate-valence of Ce, and of the hybridization between the transition metal and rare-earth

Influence of Al-atoms on the spin fluctuation scattering in R(Co,Al)2 compounds

International Nuclear Information System (INIS)

Duc, N.H.; Hung, D.T.; Kim-Ngan, N.H.; Sechovsky, V.

1992-01-01

The resistivity and magnetisation have been measured for the R(Co 1-x Al x ) 2 compounds with R=Nd, Gd, Tb, Dy, Ho, Er and Lu. For x=0.2 the resistivity enhancement is observed below T c , however, for the compounds with R=Lu-Tb only. The results are discussed in terms of the spin fluctuation scattering and indicate that the enhancement of the spin fluctuation scattering is strongly related to the lattice parameter. (orig.)

Medicinal chemistry of adenosine, P2Y and P2X receptors.

Science.gov (United States)

Jacobson, Kenneth A; Müller, Christa E

2016-05-01

Pharmacological tool compounds are now available to define action at the adenosine (ARs), P2Y and P2X receptors. We present a selection of the most commonly used agents to study purines in the nervous system. Some of these compounds, including A1 and A3 AR agonists, P2Y1R and P2Y12R antagonists, and P2X3, P2X4 and P2X7 antagonists, are potentially of clinical use in treatment of disorders of the nervous system, such as chronic pain, neurodegeneration and brain injury. Agonists of the A2AAR and P2Y2R are already used clinically, P2Y12R antagonists are widely used antithrombotics and an antagonist of the A2AAR is approved in Japan for treating Parkinson's disease. The selectivity defined for some of the previously introduced compounds has been revised with updated pharmacological characterization, for example, various AR agonists and antagonists were deemed A1AR or A3AR selective based on human data, but species differences indicated a reduction in selectivity ratios in other species. Also, many of the P2R ligands still lack bioavailability due to charged groups or hydrolytic (either enzymatic or chemical) instability. X-ray crystallographic structures of AR and P2YRs have shifted the mode of ligand discovery to structure-based approaches rather than previous empirical approaches. The X-ray structures can be utilized either for in silico screening of chemically diverse libraries for the discovery of novel ligands or for enhancement of the properties of known ligands by chemical modification. Although X-ray structures of the zebrafish P2X4R have been reported, there is scant structural information about ligand recognition in these trimeric ion channels. In summary, there are definitive, selective agonists and antagonists for all of the ARs and some of the P2YRs; while the pharmacochemistry of P2XRs is still in nascent stages. The therapeutic potential of selectively modulating these receptors is continuing to gain interest in such fields as cancer, inflammation, pain

Electrical resistivity and thermopower of Nd1-xTbxCo2 compounds

International Nuclear Information System (INIS)

Uchima, K; Takaesu, Y; Yonamine, S; Kinjyo, A; Hedo, M; Nakama, T; Yagasaki, K; Burkov, A T

2010-01-01

Electrical resistivity ρ and thermopower S of Nd 1-x Tb x Co 2 Laves phase quasibinary alloys (0 ≤ x ≤ 1) are investigated at temperatures from 2 K to 300 K. The magnetic transition temperature T C , determined from resistivity magnetic anomaly, increases linearly with increasing x. The low temperature thermopower changes its sign from negative to positive at the critical composition where the relative orientation of total magnetization and cobalt 3d moment is changed. We propose that this change is related to the dependence of s-d scattering rate on relative polarization of conduction electrons and cobalt 3d band.

Crystallographic characterization of divalent organosamarium compound (C5H5)2Sm(THF)2

International Nuclear Information System (INIS)

Jagannatha Swamy, S.

2002-01-01

The single pot reaction between SmX 2 (X = Cl - , I - ) and BuLi in THF at -40 degC, followed by the addition of C 5 H 5 - Na + results in a dark red solution. Leaving the concentrated reaction mixture at -25 degC for two days in a deep freezer results in the formation of the crystals of the compound, (C 5 H 5 ) 2 ; Sm(THF) 2 . The compound is insoluble in any solvent and it has been characterized by conventional methods. The crystals are monoclinic with space group C2/c, and a = 13.416(1), b = 9.644(1), c = 14.129(2) pm, β109.873(9) 0 and z = 4 for ρcalcd = 1.64 g cm -3 . Least squares refinement on the basis of 1804 observed reflections has led to a final R value of 0.037 and R w = 0.054. (author)

Effect of silver doping on infrared reflectance and Tc of superconducting GdBa2Cu(1 - x)3Ag3xO7

International Nuclear Information System (INIS)

Memon, A.; Khan, M.N.; Al-Dallal, S.; Tanner, D.B.; Porter, C.D.

1990-01-01

This paper reports on infrared reflectance of GdBa 2 Cu(1 - x) 3 Ag 3x O 7 ceramic superconductor with the composition of x = 0.025 and 0.05 performed in the frequency range of 100--5000 cm -1 . All the infrared active phonon modes allowed by the selection rules were observed in the reflection spectra of these compounds. The optical conductivity as calculated from K--K analysis further confirms the existence of these optical phonons. Besides the increase of the reflectivity in the silver doped samples, an extra phonon mode is observed, which is normally not seen at room temperature reflectance of GdBa 2 Cu 3 O 7 compounds. The four probe resistivity measurement show zero resistance at 88 K for x = 0, and 78 K for x = 0.025 in GdBa 2 Cu(1 - x) 3 Ag 3x O 7 compound

AC susceptibility, XRD and DSC studies of Sm1-xGdxMn2Si2 silicides

International Nuclear Information System (INIS)

Kervan, S.; Kilic, A.; Gencer, A.

2004-01-01

X-ray powder diffraction, AC susceptibility and differential scanning calorimetry (DSC) studies were performed on the polycrystalline Sm 1-x Gd x Mn 2 Si 2 (0≤x≤1) compounds. All compounds investigated crystallize in the body-centered tetragonal ThCr 2 Si 2 -type structure with the space group I4/mmm. Substitution of Gd for Sm leads to a linear decrease of the lattice constants and the unit cell volume. The lattice constants and the unit cell volume obey Vegard's law. At low temperatures, the rare earth sublattice orders and reconfigures the ordering in the Mn sublattice. The samples with x=0.6 and 0.8 exhibit spin reorientation phenomenon. The Neel temperature T N (Mn) determined by DSC technique and the Curie temperature T C (RE) increase linearly with increasing Gd content x. The results are summarized in the x-T magnetic phase diagram

X-ray and electron diffraction studies of the structures of pseudo-perovskite compounds Pb2(Sc,Ta)O6 and Pb2(Mg,W)O6

International Nuclear Information System (INIS)

Baba-Kishi, K.Z.; Cernik, R.J.

1992-01-01

Electron diffraction patterns, X-ray precession patterns and synchrotron Rietveld powder diffraction profiles were used to study the crystal structure of the pseudo-perovskite compound Pb 2 (Sc, Ta)O 6 (PST). The results of a Rietveld refinement and single-crystal X-ray precession studies showed that PST has a lower symmetry than the cubic Fm3m in the paraelectric state. The remarkable similarities between the crystal structures of the antiferroelectric Pb 2 (Mg, W)O 6 (PMW) and ferroelectric PST are studied in detail by electron diffraction and it is suggested that PST is a weak or frustrated antiferroelectric oxide. The influence of the degree of structural long-range order on the existence of an antiferroelectric phase transition in PST and PMW is discussed. (orig.)

Kinetic control of intralayer cobalt coordination in layered hydroxides: Co(1-0.5x)(oct) Co(x)(tet) (OH)2 (Cl)x (H2O)n.

Science.gov (United States)

Neilson, James R; Schwenzer, Birgit; Seshadri, Ram; Morse, Daniel E

2009-12-07

We report the synthesis and characterization of new structural variants of the isotypic compound with the generic chemical formula, Co(1-0.5x)(oct) Co(x)(tet) (OH)2 (Cl)x (H2O)n, all modifications of an alpha-Co(OH)2 lattice. We show that the occupancy of tetrahedrally coordinated cobalt sites and associated chloride ligands, x, is modulated by the rate of formation of the respective layered hydroxide salts from kinetically controlled aqueous hydrolysis at an air-water interface. This new level of structural control is uniquely enabled by the slow diffusion of a hydrolytic catalyst, a simple technique. Independent structural characterizations of the compounds separately describe various attributes of the materials on different length scales, revealing details hidden by the disordered average structures. The precise control over the population of distinct octahedrally and tetrahedrally coordinated cobalt ions in the lattice provides a gentle, generic method for modulating the coordination geometry of cobalt in the material without disturbing the lattice or using additional reagents. A mechanism is proposed to reconcile the observation of the kinetic control of the structure with competing interactions during the initial stages of hydrolysis and condensation.

Effect of X- and gamma-rays on phenolic compounds from Maytenus aquifolium Martius

International Nuclear Information System (INIS)

Campos, P.; Yariwake, J.H.; Lancas, F.M.

2005-01-01

The effect of irradiation using several doses of X- and γ-rays (10, 20, 40, 60, 80 and 100 kGy), upon total phenolic compounds contained in the leaves of Maytenus aquifolium Martius (Celastraceae) 'espinheira santa', was investigated. The content of phenolic compounds (measured by the Folin-Denis spectrophotometric method) was unaffected by X- or γ-ray irradiation, at any dose. (author)

Investigations in anhydrous liquid ammonia. Reaction of group 2, 4, 5, 11 metal and actinoids compounds

International Nuclear Information System (INIS)

Woidy, Patrick

2014-01-01

The solubility and reactivity of metal halides, transition metal halides, and actinoid halides in liquid ammonia can lead to new starting materials for the synthesis of fluorides in low oxidation states or for nitrides via a ''low-temperature route''. In this context the ability of metal and actinoid halides to act as an acceptor for or donor of fluoride ions is also of interest. Four different systems were investigated in this study. In the first section, the synthesis and characterization of new compounds were carried out in the system CuX/NH 3 (X = F, Cl, Br, I, and CN) and lead to a ligand stabilized monovalent copper fluoride as a main result. In the second section, the solubility of uranyl compounds and uranium halides in liquid ammonia was investigated and the products were characterized. In the third section, alkali metal thorates were synthesized. Their solubility in liquid ammonia and their behavior as an acceptor for fluoride ions was investigated. In the last section, the results on the solubility behavior of transition metal halides in liquid ammonia and their coordination behavior are presented. In the first system CuX/NH 3 several new compounds, such as [Cu(NH 3 ) 3 ]X (X = Br, I or CN) were synthesized and characterized. The reactions of this compounds with fluoride ion donors (NH 4 F or Me 4 NF) led unfortunately not to the monovalent copper fluoride CuF. The comproportionation reaction of Cu and CuF 2 in liquid ammonia lead to the compounds [Cu(NH 3 ) 3 ] 2 [Cu 2 (NH 3 ) 2 ] . 4 NH 3 and [Cu(NH 3 ) 2 ]F . NH 3 . For the preparation of binary CuF, various decomposition experiments were executed on the compound [Cu(NH 3 ) 2 ]F . NH 3 which resulted in different decomposition products. In additional studies various complexes of divalent copper was investigated and with the compound [Cu(NH 3 ) 5 ]F 2 . NH 3 the solubility of fluoride containing substances in liquid ammonia could be shown. Studies of six- and tetravalent uranium

Nuclear Magnetic Resonance Reveals Disordered Level-Crossing Physics in the Bose-Glass Regime of the Br-Doped Ni(Cl_{1-x}Br_{x})_{2}-4SC(NH_{2})_{2} Compound at a High Magnetic Field.

Science.gov (United States)

Orlova, Anna; Blinder, Rémi; Kermarrec, Edwin; Dupont, Maxime; Laflorencie, Nicolas; Capponi, Sylvain; Mayaffre, Hadrien; Berthier, Claude; Paduan-Filho, Armando; Horvatić, Mladen

2017-02-10

By measuring the nuclear magnetic resonance (NMR) T_{1}^{-1} relaxation rate in the Br (bond) doped DTN compound, Ni(Cl_{1-x}Br_{x})_{2}-4SC(NH_{2})_{2}(DTNX), we show that the low-energy spin dynamics of its high magnetic field "Bose-glass" regime is dominated by a strong peak of spin fluctuations found at the nearly doping-independent position H^{*}≅13.6  T. From its temperature and field dependence, we conclude that this corresponds to a level crossing of the energy levels related to the doping-induced impurity states. Observation of the local NMR signal from the spin adjacent to the doped Br allowed us to fully characterize this impurity state. We have thus quantified a microscopic theoretical model that paves the way to better understanding of the Bose-glass physics in DTNX, as revealed in the related theoretical study [M. Dupont, S. Capponi, and N. Laflorencie, Phys. Rev. Lett. 118, 067204 (2017).PRLTAO0031-900710.1103/PhysRevLett.118.067204].

Magnetisation and AC susceptibility studies of La1-xSrxFe0.8Cr0.2O3-δ (0.0<x<1.0) perovskites

International Nuclear Information System (INIS)

Ferreira, L.P.; Cruz, M.M.; Ramos, T.; Sa, M.A.; Carvalho, M.D.; Godinho, M.

2007-01-01

Magnetisation and AC magnetic susceptibility measurements have been performed in the perovskite-type compounds La 1-x Sr x Fe 0.8 Cr 0.2 O 3-δ (x=0.2, 0.4, 0.6 and 0.8). All compounds show an overall antiferromagnetic behaviour mainly attributed to predominant Fe 3+ -O-Fe 3+ interactions. For 0.2 ord . The coexistence of AFM and FM interactions leads to reentrant magnetic behaviour for the x=0.4 compound and to spin-glass like behaviour for x=0.8. Between x=0.6 and 0.8, the similar magnetic moments found in the paramagnetic region indicate that the Fe/Cr valences do not change significantly, pointing towards an increased role for oxygen vacancy formation in the charge compensation mechanism

X-ray diffraction and Moessbauer study of (Fe1-xNi x)4N (0.2 ≤ x ≤ 0.6) films

International Nuclear Information System (INIS)

El Khiraoui, S.; Sajieddine, M.; Vergnat, M.; Sahlaoui, M.; Bauer, Ph.; Mabrouki, M.

2007-01-01

Single phase (Fe 1-x Ni x ) 4 N compounds (0.2 ≤ x ≤ 0.6) have been synthesized by reactive evaporation and investigated by X-ray diffraction and Moessbauer spectrometry. The lattice parameters of the nitrides decrease from 3.796 to 3.774 A with increasing Ni concentration. The fitting results of Moessbauer spectra indicate that the average hyperfine field have the same changing tendency with lattice parameter and the nickel atoms have a tendency to be located at the corner site

Synthesis, structure and properties of layered iron-oxychalcogenides Nd2Fe2Se2−xSxO3

International Nuclear Information System (INIS)

Liu, Y.; Zhang, S.B.; Tan, S.G.; Yuan, B.; Kan, X.C.; Zu, L.; Sun, Y.P.

2015-01-01

A new series of sulfur-substituted iron-oxychalcogenides Nd 2 Fe 2 Se 2−x S x O 3 (0≤x≤0.4) was synthesized by solid state reaction method, and investigated by structure, transport, magnetic and specific heat measurements. The compounds crystallize in the layered tetragonal structure with I4/mmm space group, and show semiconducting behavior. The large discrepancy between the activation energies for conductivity, E ρ (152–202 meV), and thermopower, E S (15.6–39.8 meV), indicates the polaronic transport mechanism of the carrier. The parent compound Nd 2 Fe 2 Se 2 O 3 exhibits a frustrated antiferromagnetic (AFM) ground state, and the S-substitution induces an enhanced ferromagnetic (FM) component and possible increased degree of frustration. - Graphical abstract: The crystal structure of Nd 2 Nd 2 Fe 2 Se 2−x S x O 3 is built up by stacking fluorite-like Nd 2 O 2 layers and anti-CuO 2 -type Fe 2 O(Se/S) 2 layers with Fe 2+ cations coordinated by two in-plane O 2- and four Se 2- above and below the square Fe 2 O plane. - Highlights: • We have synthesized a new series of layered iron-oxychalcogenides Nd 2 Fe 2 Se 2−x S x O 3 . • They crystallize in layered tetragonal structure and show semiconducting behavior. • The transport analysis indicates the polaronic transport mechanism of the carrier. • The parent compound shows a frustrated antiferromagnetic (AFM) ground state. • The S-substitution induces an enhanced ferromagnetic (FM) component

Magnetic phase diagram of Co(Cr1-xA lx) 2O4 (x = 0.0-1.0)

Science.gov (United States)

Padam, R.; Sarkar, T.; Mathieu, R.; Thota, S.; Pal, D.

2017-08-01

We report the role of Al substitution in the magnetic properties of spinel CoCr2O4 by means of temperature dependent dc and ac magnetization and heat capacity measurements. Various compositions (0.0 ≤ x ≤ 1.0) of polycrystalline Co(Cr1-xAlx)2O4 samples have been prepared by sol-gel processing and their crystal structure was investigated by X-ray diffraction which was found to crystallize in the normal cubic spinel structure. For x ≤ 0.1, the system exhibits multiple magnetic orderings (long range ferrimagnetic ordering TC, spin-spiral ordering TS, and lock-in transition TL), similar to that of the parent compound, CoCr2O4. However, all the compositions between x = 0.1 and 0.5 exhibit long range ferrimagnetic ordering below TC and also a short range order at low temperature. Spin-glass like ordering was noticed between x = 0.6 and 0.8 due to the diluted B-site occupancy, whereas the end compound CoAl2O4 (x = 1.0) shows antiferromagnetic behavior. On the basis of these results, we propose a magnetic phase diagram for the Co(Cr1-xAlx)2O4 series as a function of the Al content (x) and measuring temperature (T).

Magnetism and transport studies in off-stoichiometric metallic perovskite compounds GdPd{sub 3}B{sub x} (x=0.25, 0.50 and 0.75)

Energy Technology Data Exchange (ETDEWEB)

Pandey, Abhishek, E-mail: abhishek.phy@gmail.co [S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Mazumdar, Chandan, E-mail: chandan.mazumdar@saha.ac.i [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Ranganathan, R. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)

2010-12-15

We report the magnetic and transport properties of the off-stoichiometric metallic perovskite like compounds GdPd{sub 3}B{sub x} (x=0.25, 0.50 and 0.75). Our results show that doping with boron in the lattice of parent binary-compound GdPd{sub 3} leads to lattice expansion. Which in turn manifests in contrasting magnetic and transport behaviors of the doped compounds in comparison with the undoped GdPd{sub 3}. An attempt has been made to compare and correlate the results of magnetic and transport measurements of GdPd{sub 3}B{sub x} with that of stoichiometric compositions GdPd{sub 3}B{sub x}C{sub 1-x}. The comparative study of GdPd{sub 3}B{sub x} and GdPd{sub 3}B{sub x}C{sub 1-x} confirms that there is a strong correlations between the structural, magnetic and transport properties of these compounds.

Magnetism in ordered metallic perovskite compound GdPd3BxC1-x

International Nuclear Information System (INIS)

Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Dattagupta, S.

2009-01-01

We report results of dc-magnetization, ac-susceptibility and magnetoresistance measurements on crystalline metallic-perovskite compounds GdPd 3 B x C 1-x (x=0.25, 0.50, 0.75 and 1.00) and the parent cubic compound GdPd 3 . The interest in these materials stems from the observation of negative temperature coefficient of resistance and negative thermal expansion in some of the members of this series. In the present study, we show that by substitution of non-magnetic elements, boron and carbon, the nature of the magnetic interaction can be varied from dominating ferromagnetic to antiferromagnetic and finally to a canted magnetic structure without altering the crystal symmetry of the compounds. The variation of magnetic interaction by modifying the lattice parameter resembles Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillations.

Chemical shift of U L3 edges in different uranium compounds obtained by X-ray absorption spectroscopy with synchrotron radiation

International Nuclear Information System (INIS)

Joseph, D.; Jha, S.N.; Nayak, C.; Bhattacharyya, D.; Babu, P. Venu

2014-01-01

Uranium L 3 X-ray absorption edge was measured in various compounds containing uranium in U 4+ , U 5+ and U 5+ oxidation states. The measurements have been carried out at the Energy Dispersive EXAFS beamline (BL-08) at INDUS-2 synchrotron radiation source at RRCAT, Indore. Energy shifts of ∼ 2-3 eV were observed for U L 3 edge in the U-compounds compared to their value in elemental U. The different chemical shifts observed for the compounds having the same oxidation state of the cation but different anions or ligands show the effect of different chemical environments surrounding the cations in determining their X-ray absorption edges in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on U cation in the above compounds. (author)

Competition of Kondo spin fluctuations and RKKY interactions in CeRh/sub 2/Si/sub 2-x/Ge/sub x/ and CeM/sub 2/X/sub 2/ compounds: a Kondo necklace problem

Energy Technology Data Exchange (ETDEWEB)

Godart, C; Gupta, L C; Tomy, C V; Vijayaraghavan, R; Thompson, J D

1989-02-15

We present the results of our measurements of the lattice constants and magnetic susceptibility of the pseudo-ternary system which crystallizes in the tetragonal ThCr/sub 2/Si/sub 2/ structure. Both of the cell constants a and c increase linearly with x. The magnetic ordering temperature T/sub N/ exhibits initially an enhancement with the increase in x and then decreases as x continues to increase further. These results, along with those on the pressure dependence of T/sub N/ in CeRh/sub 2/Si/sub 2/, can be understood on the basis of the Doniach's model of a Kondo necklace. We discuss also the applicability of this model to describe the strong correlation between the structural aspects and the ground-state properties of the whole series of Ce-based ternaries CeM/sub 2/X/sub 2/ (M = 3d, 4d and 5d elements; X = Si, Ge).

Static and dynamic magnetic properties of two synthetic francisites Cu3La(SeO3)2O2X (X = Br and Cl)

Science.gov (United States)

Markina, M. M.; Zakharov, K. V.; Zvereva, E. A.; Denisov, R. S.; Berdonosov, P. S.; Dolgikh, V. A.; Kuznetsova, E. S.; Olenev, A. V.; Vasiliev, A. N.

2017-04-01

The formation of long-range magnetic order at low temperatures was established in francisite—type compounds Cu3La(SeO3)2O2X (X = Br and Cl) through measurements of magnetic susceptibility, magnetization, specific heat and X-band electron spin resonance. The significantly enhanced critical index p = 1.0 ± 0.1 in Cu3La(SeO3)2Br and p = 0.8 ± 0.1 in Cu3La(SeO3)2Cl in the temperature dependence of the width of ESR signal evidence the reduced dimensionality of the kagome-type francisite's magnetic subsystem. Under action of external magnetic field, the presumably non-collinear six-sublattices antiferromagnetic structure of these compounds experiences the first-order metamagnetic transformation. The B- T magnetic phase diagrams were established from the positions of singularities in temperature and field dependences of thermodynamic properties. Contrary to pristine mineral Cu3Bi(SeO3)2Cl, no signature of structural phase transition was detected.

Electrical transport and magnetic studies of Nd1-xCaxSr2Cu2FeOδ compounds

International Nuclear Information System (INIS)

Walia, R.; Banerjee, R.; Grandjean, D.; Lanchester, P.C.; De Groot, P.A.J.; Weller, M.T.

1994-01-01

We have measured the temperature dependence of the DC electrical resistivity and susceptibility in the interval 4.2-300 K for Nd 1-x Ca x Sr 2 Cu 2 FeO δ (x=0.0, 0.1, 0.2 and 0.3). Analysis of the results showed the density of states to be a strong function of x, indicating the existence of short range fluctuations near the Fermi level E F . The magnetic susceptibility, however, shows the oxidation state of Fe remains at +3 for x≥0. ((orig.))

X-ray study of CuGa sub x In sub 1-x Se sub 2 solid solutions

Energy Technology Data Exchange (ETDEWEB)

Suri, D.K.; Nagpal, K.C. (National Physical Lab., New Delhi (India). Materials Characterization Div.); Chadha, G.K. (Delhi Univ. (India). Dept. of Physics and Astrophysics)

1989-12-01

The semiconducting compound CuGa{sub x}In{sub 1-x}Se{sub 2} crystallizes in the chalcopyrite structure (space group Ianti 42d, Z=4). The X-ray powder data for x=1, 0.75, 0.6, 0.5, 0.4, 0.25 and 0.0 have been collected and it is found that the lattice parameters a and c and their ratio c/a vary linearly with x. Thus the composition of any chalcopyrite in the pseudo-binary system CuGaSe{sub 2} and CuInSe{sub 2} can be obtained from the accurate lattice parameters. The crystallite size determined from the (112) plane is minimum for x=0.50 ({proportional to}1000 A) and away from x=0.50 it increases. A value of u=0.240 (5) has been established for fixing, the Se-atom positions in the CuGa{sub 0.5}In{sub 0.5}Se{sub 2} solid solution. The JCPDS Diffraction File No. for CuInSe{sub 2} is 40-1487 and for CuGa{sub 0.5}In{sub 0.5}Se{sub 2} is 40-1488. (orig.).

High magnetic ordering temperature in the perovskites Sr{sub 4-x}La{sub x}Fe{sub 3}ReO{sub 12} (x=0.0, 1.0, 2.0)

Energy Technology Data Exchange (ETDEWEB)

Retuerto, M.; Li, M.-R.; Go, Y.B. [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854 (United States); Ignatov, A.; Croft, M. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Ramanujachary, K.V. [Department of Chemistry and Physics, Rowan University, 210 Mullica Hill Road, Glassboro, NJ 08028 (United States); Herber, R.H.; Nowik, I. [Racah Institute of Physics, Hebrew University, Jerusalem, 91904 Israel (Israel); Hodges, J.P. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Dachraoui, W.; Hadermann, J. [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Greenblatt, M., E-mail: martha@rutchem.rutgers.edu [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854 (United States)

2012-10-15

A series of perovskites Sr{sub 4-x}La{sub x}Fe{sub 3}ReO{sub 12} (x=0.0, 1.0, 2.0) has been prepared by wet chemistry methods. The structure analyses by powder X-ray and neutron diffraction and electron microscopy show that these compounds adopt simple perovskite structures without cation ordering over the B sites: tetragonal (I4/mcm) for x=0.0 and 1.0 and orthorhombic (Pbmn) for x=2.0. The oxidation states of the cations in the compound with x=0.0 appear to be Fe{sup 3+/4+} and Re{sup 7+} and decrease for both with La substitution as evidenced by X-ray absorption spectroscopy. All the compounds are antiferromagnetically ordered above room temperature, as demonstrated by Moessbauer spectroscopy and the magnetic structures, which were determined by powder neutron diffraction. The substitution of Sr by La strongly affects the magnetic properties with an increase of T{sub N} up to {approx}750 K. - Graphical abstract: High resolution transmission electron microscopy image of Sr{sub 4-x}La{sub x}Fe{sub 3}ReO{sub 12} (x=2.0), showing twin domains. Fourier transforms are given of the areas indicated by the circles. Highlights: Black-Right-Pointing-Pointer Sr{sub 4-x}La{sub x}Fe{sub 3}ReO{sub 12} (x=0.0, 1.0, 2.0) perovskites prepared by wet chemistry. Black-Right-Pointing-Pointer PXD, PND, ED, indicate no cation ordering, I4/mcm) for x=0.0, 1.0, Pbmn for x=2. Black-Right-Pointing-Pointer XAS show oxidation states Fe{sup 3+/4+} and Re{sup 7+}; both decrease with increasing x. Black-Right-Pointing-Pointer All order antiferromagnetically above RT, with highest T{sub N} {approx}750 K.

Magnetic characterization of Nd0.8Sr0.2(Mn1-x Co x )O3 perovskites

International Nuclear Information System (INIS)

Vidal, Karmele; Lezama, Luis; Arriortua, Maria I.; Rojo, Teofilo; Gutierrez, Jon; Barandiaran, Jose M.

2005-01-01

We present a magnetic study of the family of perovskites Nd 0.8 Sr 0.2 (Mn 1- x Co x )O 3 (x=0.1, 0.2 and 0.3). These compositions have been prepared by using both the sol-gel method and the freeze-drying technique. As a result, we have obtained polycrystalline powder-like samples. We have obtained pure compounds that have been indexed in the Pnma space group. The study of their magnetic properties shows a decrease of the measured low-temperature magnetic moment as the content of Co increases in the composition. However, a similar magnetic ordering temperature of about 130 K has been determined for all samples. All the studied compounds show insulating behaviour of the electrical resistivity

Phase relations, crystal structure, and phase transformation of In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) in In_2O_3–Nb_2O_5–TiO_2 system

International Nuclear Information System (INIS)

Su, Liumei; Fan, Xing; Cai, Gemei; Liu, Huashan; Jin, Zhanpeng

2015-01-01

Phase relations, crystal structures, and phase transformation of In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) in In_2O_3–Nb_2O_5–TiO_2 ternary system were investigated for the first time. A number of samples with different compositions were prepared by a solid-state reaction method, and phase assembles were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe micro-analysis (EPMA). Five three-phase regions, ten two-phase regions, and six single-phase solid solutions were determined in this system. The solid solution of In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) is composed of both ordered monoclinic wolframite-type structure (0 ≤ x < 0.35) and disordered orthorhombic α-PbO_2 type structure (0.35 < x < 0.45). Driving force for composition-driven phase transformation in In_1_−_xNb_1_−_xTi_2_xO_4 (0 ≤ x < 0.45) stems from the ordering of cations. The ever reported compound InNbTiO_6 with an orthorhombic α-PbO_2 type structure was amended to be a monoclinic wolframite-type structure. Present investigations will be useful for the whole ceramic community working with In_2O_3–Nb_2O_5–TiO_2 ternary system as well as for the development of functional materials. - Highlights: • Phase relations of In_2O_3–Nb_2O_5–TiO_2 ternary system were constructed. • Crystal structures of a novel solid solution In_1_−_xNb_1_−_xTi_2_xO_4 were determined. • Crystal structure of InNbTiO_6 was amended to be a wolframite-type structure. • Composition-driven phase transformation of In_1_−_xNb_1_−_xTi_2_xO_4 was investigated.

Moessbauer Investigation of Spin Arrangements in Er2-xCexFe14B

International Nuclear Information System (INIS)

Bogacz, B.F.; Pedziwiatr, A.T.

2008-01-01

It was theoretically postulated earlier that in compounds Er 2-x Ce x Fe 14 B it may be possible to observe not only axial and planar spin arrangements but also a conical one. In order to experimentally verify this hypothesis, 57 Fe Moessbauer spectroscopy analysis was used to study the polycrystalline compounds Er 2-x Ce x Fe 14 B in the postulated composition region (x = 1.0, 1.1, 1.2, 1.3) in the wide range of temperatures. The obtained experimental data do not clearly support the suggestion of conical arrangement occurrence in the postulated compositions. They indicate that such phenomenon may be shifted towards higher Ce content. (authors)

Structural, thermal, spectroscopic and magnetic studies of the (C2N2H10)0.5[Fe xV1-x(HPO3)2] (x = 0.26, 0.52, 0.74) solid solution

International Nuclear Information System (INIS)

Cisneros, Jose L.; Fernandez-Armas, Sergio; Mesa, Jose L.; Pizarro, Jose L.; Arriortua, Maria I.; Rojo, Teofilo

2006-01-01

The (C 2 N 2 H 10 ) 0.5 [Fe x V 1-x (HPO 3 ) 2 ] (x = 0.26, 0.52 0.74) compounds have been obtained by mild solvothermal conditions in the form of micro-crystalline powder with brown color. The crystal structures were refined by X-ray powder diffraction data using the Rietveld method. The compounds crystallize in the monoclinic system, space group P2/c with the unit-cell parameters, a = 9.262(5) A, b = 8.823(5) A, c = 9.714(6) A, β = 120.84(3) o ; a = 9.245(1) A, b = 8.823(1) A, c = 9.698(1)A, β = 120.80(1) o and, a = 9.254(4)A, b = 8.822(4)A, c = 9.702(4)A, β = 120.73(3) o for (C 2 N 2 H 10 ) 0.5 [Fe 0.26 V 0.74 (HPO 3 ) 2 ] (1) (C 2 N 2 H 10 ) 0.5 [Fe 0.52 V 0.48 (HPO 3 ) 2 ] (2), and (C 2 N 2 H 10 ) 0.5 [Fe 0.74 V 0.26 (HPO 3 ) 2 ] (3). The compounds show an open crystalline structure with three-dimensional character, whose formula for the anionic inorganic skeleton is [M(HPO 3 ) 2 ] 2- . The inorganic framework is formed by [MO 6 ] octahedra inter-connected by phosphite groups. The structure of the compounds exhibits channels extended along the [1 0 0] and [0 0 1] directions and the ethylendiammonium cations are located inside these channels, linked through hydrogen bonds and ionic interactions. The infrared spectra show the bands corresponding to the stretching (P-H) vibration of the phosphite group and the band corresponding to the deformation mode of the ethylendiammonium cation, δ(NH 3 + ). The thermal and thermodiffractometric behavior show that the compounds are stable up to approximately 300 deg. C, at higher temperatures the decomposition of the crystal structure by calcination of the organic cation starts. The diffuse reflectance spectra show bands of the V 3+ ion (d 2 ), and a band of the Fe 3+ ion (d 5 ), in a slightly distorted octahedral symmetry. The values of the Dq and Racah parameters (B and C) have been calculated for the V(III) cation. Magnetic measurements were performed on a powdered sample from 5 to 300 K at magnetic fields 1000, 500

(C2N2H10)[Fe xV1-x(HPO3)F3] (x = 0.44, 0.72): Two new organically templated phosphites

International Nuclear Information System (INIS)

Cisneros, Jose L.; Fernandez-Armas, Sergio; Mesa, Jose L.; Pizarro, Jose L.; Arriortua, Maria I.; Rojo, Teofilo

2006-01-01

(C 2 N 2 H 10 )[Fe x V 1-x (HPO 3 )F 3 ] (x = 0.44, 0.72) have been synthesized using mild solvothermal conditions under autogenous pressure and the ethylenediamine molecule as templating agent. The crystal structures have been determined from X-ray single-crystal diffraction data. The compounds crystallize in the orthorhombic P2 1 2 1 2 1 space group with Z = 4 and unit-cell parameters a = 12.8494(9), b = 9.5430(6), c = 6.4372(5) A, and a = 12.8578(1), b = 9.5342(1), c = 6.4370(7) A for (C 2 N 2 H 10 )[Fe 0.44 V 0.56 (HPO 3 )F 3 ] and (C 2 N 2 H 10 )[Fe 0.72 V 0.28 (HPO 3 )F 3 ] (1) and (2), respectively. These isostructural compounds exhibit a monodimensional crystal structure formed by pillared double anionic chains with the formula [M(HPO 3 )F 3 ] 2- , extended along the [0 0 1] direction. These doubled ionic chains are the result of the linking of two simple chains in which there are alternating octahedral [MO 3 F 3 ] and tetrahedral groups [HPO 3 ]. The ethylendiammonium cations are placed in the space delimited by three different chains. The metallic ions are interconnected by the pseudo-pyramidal (HPO 3 ) 2- phosphite oxoanions, adopting a slightly distorted octahedral geometry. The IR spectra show bands corresponding to the phosphite oxoanion and the ethylendiamonium cation at 2400 and 1600 cm -1 , respectively. The thermogravimetric analyses show that these phases are stable up to ca. 280 deg. C, at higher temperatures, the decomposition of the crystal structure begins by calcination of the organic cation and the elimination of the fluoride anions. The diffuse reflectance spectra show bands of the V 3+ ion (d 2 ) in octahedral symmetry. The values of the Dq (1540, 1540 cm -1 ), and Racah parameters, B (560, 535 cm -1 ) and C (3055, 3140 cm -1 ) for (1) and (2), respectively, correspond with those usually found for octahedrically coordinated V(III) compounds. Magnetic measurements, performed on a powered sample from 5.0 to 300 K at 1000 G, in the ZFC and

Orientation distribution in Bi2Te3-based compound prepared by spark plasma sintering

International Nuclear Information System (INIS)

Kim, K.T.; Kim, Y.H.; Lim, C.H.; Cho, D.C.; Lee, Y.S.; Lee, C.H.

2005-01-01

P-type Bi 0.5 Sb 1.5 Te 3 compounds doped with 3wt.% Te were fabricated by spark plasma sintering after mixing large powders(P L ) and small powders(P S ). We could obtained the highest figure of merit(Z C ) of 2.89 x 10 -3 /K in sintered compound mixed to P L :P S =80:20. This resulted from the increase of orientation by large powders(P S ) and the reduce of pores by small powders. The figure of merit(Z C ) of the sintered compound using only small powders(P S ) showed lower value of 2.67 x 10 -3 /K compared with that of sintered compound mixed to P L :P S =80:20 due to the increase of electrical resistivity. (orig.)

Charge transfer from TiO2 into adsorbed benzene diazonium compounds

Science.gov (United States)

Merson, A.; Dittrich, Th.; Zidon, Y.; Rappich, J.; Shapira, Yoram

2004-08-01

Electron transfer from sol-gel-prepared TiO2 into adsorbed benzene diazonium compounds has been investigated using cyclic voltammetry, x-ray photoelectron spectroscopy, contact potential difference, and surface photovoltage spectroscopy. The results show that the potential of maximum electron transfer depends strongly on the dipole moment of the benzene compound. Two reactive surface sites at which electron transfer occurs have been identified.

Synthesis, electrical and thermal properties of Bi{sub 4}V{sub 2-x}Zr{sub x}O{sub 11} (x=0.0 and 0.02) ceramics

Energy Technology Data Exchange (ETDEWEB)

Sahu, S.; Jangid, S.; Roy, M. [Department of Physics, M. L. Sukhadia University, Udaipur-313002 (Rajasthan) (India); Barbar, S. K. [Center for Condensed Matter Sciences, National Taiwan University, Taipei-10617, Taiwan (China)

2013-02-05

Polycrystalline ceramic samples of Bi{sub 4}V{sub 2-x}Zr{sub x}O{sub 11} (x=0.0 and 0.02) have been synthesized by standard solid state reaction method. The formation of the compounds has been verified by room temperature (RT) X-ray diffraction. The frequency and temperature dependent dielectric constant of both the compounds have been measured. The dielectric studies indicate that the materials are highly lossy. The dc conductivity of the materials has been measured as a function of temperature from RT to 653K and their activation energies were calculated using Arrhenius relation {sigma} = {sigma}{sub Masculine-Ordinal-Indicator }exp)-Ea/kT). The heat capacity and heat flow of both the compounds were determined as a function of temperature using Modulated Differential Scanning Calorimetry (MDSC).

Magnetic frustration and instability in Dy{sub 1-x}La{sub x}Mn{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Ouladdiaf, B. [Institut Laue-Langevin, BP 156, 38042, Grenoble Cedex 9 (France); Ballou, R. [Laboratoire de Magnetisme Louis Neel , CNRS, BP 166, 38042, Grenoble Cedex 9 (France); Deportes, J. [Laboratoire de Magnetisme Louis Neel , CNRS, BP 166, 38042, Grenoble Cedex 9 (France); Lelievre-Berna, E. [Laboratoire de Magnetisme Louis Neel , CNRS, BP 166, 38042, Grenoble Cedex 9 (France)

1995-02-09

A structural dimorphism exists in the Dy{sub 1-x}La{sub x}Mn{sub 2} (0.05{<=}x{<=}0.25) compounds. When the C15 Laves phase is stabilized, no evidence for a long range order is found although the magnetovolume effect is observed at 34 K. When the C14 Laves phase is stabilized, an antiferromagnetic order sets in below 38 K without any magnetovolume effect. ((orig.)).

Ion irradiation induced order-to-disorder transformations in δ-phase Sc4-xZr3+xO12+x/2

International Nuclear Information System (INIS)

Zhang, J.; Wang, Y.Q.; Tang, M.; Valdez, J.A.; Sickafus, K.E.

2010-01-01

The purpose of this study is to investigate the role of stoichiometry on crystal structure transformations in derivative fluorite compounds known as delta (δ) phase. In this study, polycrystalline δ-phase ceramic pellets were prepared with stoichiometries given by Sc 4-x Zr 3+x O 12+x/2 (x = 0, 0.77 and 1.20) . The pressed and polished pellets were then irradiated under cryogenic conditions with 200 keV Ne + ions to fluences ranging from 1-5 x 10 14 Ne/cm 2 . An order-to-disorder (O-D) transformation was observed for all compositions, as determined using grazing incidence X-ray diffraction (GIXRD). However, the transformation threshold dose was found to systematically decrease with increasing ZrO 2 content: ∼0.2, ∼0.16, and ∼0.08 dpa for Sc 4-x Zr 3+x O 12+x/2 with x = 0, 0.77, and 1.20, respectively. These irradiation-induced phase transformation results are discussed in terms of the crystal structure of the δ-phase.

Magnetic properties of nearly stoichiometric CeAuBi2 heavy fermion compound

International Nuclear Information System (INIS)

Adriano, C.; Jesus, C. B. R.; Pagliuso, P. G.; Rosa, P. F. S.; Grant, T.; Fisk, Z.; Garcia, D. J.

2015-01-01

Motivated by the interesting magnetic anisotropy found in the heavy fermion family CeTX 2 (T = transition metal and X = pnictogen), here, we study the novel parent compound CeAu 1−x Bi 2−y by combining magnetization, pressure dependent electrical resistivity, and heat-capacity measurements. The magnetic properties of our nearly stoichiometric single crystal sample of CeAu 1−x Bi 2−y (x = 0.92 and y = 1.6) revealed an antiferromagnetic ordering at T N  = 12 K with an easy axis along the c-direction. The field dependent magnetization data at low temperatures reveal the existence of a spin-flop transition when the field is applied along the c-axis (H c  ∼ 7.5 T and T = 5 K). The heat capacity and pressure dependent resistivity data suggest that CeAu 0.92 Bi 1.6 exhibits a weak heavy fermion behavior with strongly localized Ce 3+ 4f electrons. Furthermore, the systematic analysis using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian allows us to extract a CEF scheme and two different values for the anisotropic J RKKY exchange parameters between the Ce 3+ ions in this compound. Thus, we discuss a scenario, considering both the anisotropic magnetic interactions and the tetragonal CEF effects, in the CeAu 1−x Bi 2−y compounds, and we compare our results with the isostructural compound CeCuBi 2

Magnetic phenomena in UNi1-xRhxAl compounds

International Nuclear Information System (INIS)

Andreev, A.V.; Dremov, R.V.; Uwatoko, Y.; Mushnikov, N.V.; Goto, T.; Shiokawa, Y.; Homma, Y.; Hagmusa, I.H.; Klaasse, J.C.P.

1999-01-01

We report on structure investigation and magnetization study of UNi 1-x Rh x Al solid solutions between an antiferromagnet UNiAl and a ferromagnet URhAl. The ZrNiAl-type hexagonal crystal structure of the parent compounds is preserved in the whole concentration range. Magnetization was measured as a function of magnetic field, temperature and external hydrostatic pressure. The observed complex evolution of magnetic phenomena with Rh substitution for Ni is discussed in terms of effects of the varying 5f-ligand hybridization. A tentative magnetic phase diagram is proposed. (orig.)

Direct labelling of the human P2X7 receptor and identification of positive and negative cooperativity of binding.

Science.gov (United States)

Michel, A D; Chambers, L J; Clay, W C; Condreay, J P; Walter, D S; Chessell, I P

2007-05-01

The P2X(7) receptor exhibits complex pharmacological properties. In this study, binding of a [(3)H]-labelled P2X(7) receptor antagonist to human P2X(7) receptors has been examined to further understand ligand interactions with this receptor. The P2X(7) receptor antagonist, N-[2-({2-[(2-hydroxyethyl)amino]ethyl}amino)-5-quinolinyl]-2-tricyclo[3.3.1.1(3,7)]dec-1-ylacetamide (compound-17), was radiolabelled with tritium and binding studies were performed using membranes prepared from U-2 OS or HEK293 cells expressing human recombinant P2X(7) receptors. Binding of [(3)H]-compound-17 was higher in membranes prepared from cells expressing P2X(7) receptors than from control cells and was inhibited by ATP suggesting labelled sites represented human P2X(7) receptors. Binding was reversible, saturable and modulated by P2X(7) receptor ligands (Brilliant Blue G, KN62, ATP, decavanadate). Furthermore, ATP potency was reduced in the presence of divalent cations or NaCl. Radioligand binding exhibited both positive and negative cooperativity. Positive cooperativity was evident from bell shaped Scatchard plots, reduction in radioligand dissociation rate by unlabelled compound-17 and enhancement of radioligand binding by KN62 and unlabelled compound-17. ATP and decavanadate inhibited binding in a negative cooperative manner as they enhanced radioligand dissociation. These data demonstrate that human P2X(7) receptors can be directly labelled and provide novel insights into receptor function. The positive cooperativity observed suggests that binding of compound-17 to one subunit in the P2X(7) receptor complex enhances subsequent binding to other P2X(7) subunits in the same complex. The negative cooperative effects of ATP suggest that ATP and compound-17 bind at separate, interacting, sites on the P2X(7) receptor.

Supraconductivity of TR-Ru3Si2 compounds (TR = La, Ce)

International Nuclear Information System (INIS)

Godart, C.; Gupta, L.C.; Parks, R.D.; Rauschwalbe, U.; Alheim, U.; Gottwick, U.; Lieke, W.; Steglich, F.

1984-01-01

A new family of superconducting ternary silicides MRu 3 Si 2 with M = La (Tsub(s) approximately 7 K), Y and Th was discovered by Barz and Vandenberg. Same compounds with M from Nd to Tm are magnetic and not superconductors. We studied superconductivity in the solid solution Cesub(1-x)Lasub(x)Ru 3 Si 2 of hexagonal structure from x = 0 to 1. CeRu 3 Si 2 is type II superconductor (Tsub(s) approximately 1 K), like LaRu 3 Si 2 , and is mixed valent (M.V.). Spin fluctuations temperature (Tsub(sf) approximately 440 K) is between these of non superconducting M.V. like CeSn 3 (Tsub(sf) approximately 270) and these of superconducting M.V. like CeRu 2 (Tsub(sf) approximately 770 K). Cesub(1-x)Lasub(x)Ru 3 Si 2 is the first M.V. system of Ce which is superconductor from x = 0 to 1 [fr

Doping-induced quantum crossover in Er2Ti2 -xSnxO7

Science.gov (United States)

Shirai, M.; Freitas, R. S.; Lago, J.; Bramwell, S. T.; Ritter, C.; Živković, I.

2017-11-01

We present the results of the investigation of magnetic properties of the Er2Ti2 -xSnxO7 series. For small doping values, the ordering temperature decreases linearly with x , while the moment configuration remains the same as in the x =0 parent compound. Around x =1.7 doping level, we observe a change in the behavior, where the ordering temperature starts to increase and new magnetic Bragg peaks appear. For the first time, we present evidence of a long-range order (LRO) in Er2Sn2O7 (x =2.0 ) below TN=130 mK. It is revealed that the moment configuration corresponds to a Palmer-Chalker type with a value of the magnetic moment significantly renormalized compared to x =0 . We discuss our results in the framework of a possible quantum phase transition occurring close to x =1.7 .

Cu{sub x}Y compounds as thin films: crystallographic and compositional analyses of yttrium rich phases

Energy Technology Data Exchange (ETDEWEB)

Engels, J.M.; Blaise, G. [Paris-11 Univ., 91 - Orsay (France). Lab. de Physique des Solides; Gasgnier, M. [Laboratoire des Ractions Slectives sur Support, Bt. 410, Universit Paris-Sud, 91405, Orsay CEDEX (France)

1998-03-06

The interdiffusion of Y films deposited onto Cu substrate by flash evaporation and sputtering was studied (concentration profiles, X-ray and electron diffraction patterns) in the temperature range 373-553 K. In samples deposited by flash evaporation the first phase to be detected is CuY at 393 K. At higher temperatures an intermediate phase, close to the Cu{sub 3}Y{sub 2} compound, is formed before the Cu{sub 2}Y stoichiometric phase is produced at 513 K. Crystallographic data confirm the formation of this intermediate Cu{sub 3}Y{sub 2} phase (orthorhombic unit-cell) as resulting from the reaction CuY+Cu{sub 2}Y{yields}Cu{sub 3}Y{sub 2}. The results are identical for sputtered Y films deposited under a cryogenic vacuum (2-5 x 10{sup -7} Pa). When Y is deposited under a standard vacuum (2-5 x 10{sup -6} Pa), the influence of a diffusion barrier at the Cu-Y interface is noticed. This influence is characterized in the concentration profiles by an Y concentration hump at the Cu-Y interface and a depletion of Y at the front of the profile. Three main phases are observed. They correspond to the Cu{sub 5}Y{sub 2}, Cu{sub 2}Y and Cu{sub 3}Y{sub 2} compounds. (orig.) 24 refs.

Complementary methods of study for Zr1-xCexO2 compounds for applications in medical prosthesis

Science.gov (United States)

Savin, Adriana; Craus, Mihail-Liviu; Turchenko, Vitalii; Bruma, Alina; Dubos, Pierre-Antoine; Malo, Sylvie; Konstantinova, Tatiana E.; Burkhovetsky, Valerii V.

2017-08-01

Zirconia (ZrO2)-based ceramics are preferred due to their advanced mechanical properties such as high-fracture toughness and bulk modulus, corrosion resistance, high dielectric constant, chemical inertness, low chemical conductivity and biocompatibility. The medical prosthesis components made from ZrO2 oxides present a very good biocompatibility as well as especially mechanical properties. In order to ensure implant safety of these prostheses, wide ranges of examinations based on nondestructive testing are imperative for these medical implants. In this study, we aim to emphasize the improvement of Zr-based ceramics properties as a function of addition of Ce ions in the structure of the original ceramics. The substitution of the Zr with Ce in the Zr1-xCexO2 compounds, where x = 0.0-0.17, leads to a change of the phase composition, a gradual transition from the monoclinic to tetragonal structure, at room temperature. The structural investigations proposed in this paper are based on X-ray and neutron diffraction in order to establish a first indication of the variation of the phase composition and the structural parameters, as well as micro-hardness measurements and nondestructive evaluations in order to establish a correlation between the structural parameters and mechanical properties of the samples. These ranges of tests are imperative in order to ensure the safety and reliability of these composite materials, which are widely used as hip-implants or dental implants/coatings. In combination of Resonant Ultrasound Spectroscopy, which makes use of the resonance frequencies corresponding to the normal vibrational modes of a solid in order to evaluate the elastic constants of the materials, we emphasize a unique approach on evaluating the physical properties of these ceramics, which could help in advancing the understanding of properties and applications in medical fields.

Assessment of off-stoichiometric Zr33-xFe52+xSi15 C14 Laves phase compounds as permanent magnet materials

Science.gov (United States)

Gabay, A. M.; Hadjipanayis, G. C.

2018-05-01

Recently, Fe-based rare-earth-free compounds with non-cubic crystal structures were proposed as a base for permanent magnets which would not rely on critical elements. In this work, two series of alloys, Zr27Fe73-wSiw (0 ≤ w ≤ 15) and Zr33-xFe52+xSi15 (0 ≤ x ≤ 11), were prepared and characterized after annealing at 1538 K in order to determine the fundamental magnetic properties of the C36 and C14 hexagonal Laves phase compounds. A mixture of the cubic C15 and Zr6Fe23 structures was observed instead of the expected C36 structure. The hexagonal C14 was found in all Zr33-xFe52+xSi15 alloys with its lattice parameters linearly decreasing as the Fe(Si) atoms occupy the Zr sites in the Laves phase crystal structure. The solubility limit of Fe in the C14 structure at 1538 K corresponds to x = 9.5. The Curie temperature of the C14 compounds increases with deviation from the Laves phase stoichiometry from 290 K to 530 K. The room-temperature spontaneous magnetization also increases reaching, after correcting for the non-magnetic impurities, a value of 6.7 kG. The magnetocrystalline anisotropy of the off-stoichiometric C14 Laves phase was found to be uniaxial with the easy magnetization direction parallel to the hexagonal axis. Unfortunately, the anisotropy field, which does not exceed 10 kOe, is not sufficiently high to make the compounds interesting as permanent magnet materials.

Preparation and Crystal Structures of Some AIVB2IIO4 Compounds: Powder X-Ray Diffraction and Rietveld Analysis

Directory of Open Access Journals (Sweden)

K. Jeyadheepan

2014-01-01

Full Text Available The AIVB2IIO4 compounds such as cadmium tin oxide (Cd2SnO4 or CTO and zinc tin oxide (Zn2SnO4 or ZTO are synthesized by solid state reaction of the subsequent binary oxides. The synthesized powders were analyzed through the powder X-ray diffraction (PXRD. Cell search done on the PXRD patterns shows that the Cd2SnO4 crystallizes in orthorhombic structure with space group Pbam and the cell parameters as a=5.568(2 Å, b=9.894(3 Å, and c=3.193(1 Å and the Zn2SnO4 crystallizes as cubic with the space group Fd3 -m and with the cell parameter a=8.660(2 Å. Rietveld refinement was done on the PXRD patterns to get the crystal structure of the Cd2SnO4 and Zn2SnO4 and to define the site deficiency of atoms which causes the electrical properties of the materials.

Insight into the optoelectronic and thermoelectric properties of Ca-based Zintl phase CaCd2X2 (X = P, As) from first principles calculation

Science.gov (United States)

Belfarh, T.; Batouche, M.; Seddik, T.; Uğur, G.; Omran, S. Bin; Bouhemadou, A.; Sandeep; Wang, Xiaotian; Sun, Xiao-Wei; Khenata, R.

2018-06-01

We have studied the structural, optical, electronic and thermoelectric properties of the CaCd2X2 (X = P, As) compounds by using the full-potential augmented plane wave plus local orbitals method (FP-APW + lo). The exchange-correlation potential was treated using both the gradient generalized approximation (WC-GGA) and local density approximation (LDA). The estimated structural parameters, including the lattice parameters and internal coordinates agree well with the available experimental data. Our computed band structure shows that both studied compounds are semiconductors, with direct band gaps (Γ-Γ) of approximately 1.78 eV and 1.2 eV for CaCd2P2 and CaCd2As2, respectively, using GGA-TB-mBJ approach. The calculated optical spectra reveal a strong response of these materials in the energy range between the visible light and extreme UV regions, making them a good candidate for optoelectronic devices. Thermoelectric parameters, such as thermal conductivity, electrical conductivity, Seebeck coefficient, power factor and figure of merit were calculated. We note that both the CaCd2P2 and CaCd2As2 compounds show promising thermoelectric properties.

[Study of selegiline and related compounds with x-ray diffraction].

Science.gov (United States)

Simon, K; Böcskei, Z; Török, Z

1992-09-01

Selegiline and its parent compounds were studied by X-ray diffraction. It was established that the racemates of primary and secondary amines (p-fluoro-amphetamine, methamphetamine, p-fluoro-methamphetamine) hydrochloride do not form racemic compounds but crystalline as conglomerates, at the same time tertiary amines like selegiline and p-fluoro-selegiline hydrochlorides do. The crystalline structure of five enantiomeric hydrochlorides were determined, the CPhe-C-C-N torsion angle is anti-periplanar in all cases but in p-fluoro-amphetamine where it is gauche.

Syntheses and crystal structure determination by X-ray powder diffraction of new compounds of Benzovesamicol

International Nuclear Information System (INIS)

Rukiah, M.; Assaad, Th.

2012-06-01

The compound 2,2,2-Trifluoro-N-(1a,2,7,7 a-tetra-hydronaphtho[2,3-b]oxiren-3-yl)- acetamide, C 1 2H 1 0F 3 NO 2 , an important precursor in the preparation of benzovesamicol analogues for the diagnosis of Alzheimers disease, was prepared by the epoxidation of 5,8-dihydronaphthalene-1-amine using 3-chloroperoxybenzoic acid. The structure was determined by X-ray powder diffraction, multinuclear NMR spectroscopy and FT-IR spectroscopy. A pair of molecules form intermolecular N- H...O hydrogen bonds, involving the amino and oxirene groups, to produce a dimer.The two racemic compounds (2RS,3RS)-5-amino-3-(4-phenylpiperazin-1-yl)-1,2,3,4 tetrahydronaphthalene-2-ol, C 2 0H 2 5N 3 O, (I) and (2RS,3RS)-5-amino-3-[4-(3- methoxyphenyl)piperazin-1-yl]-1,2,3,4-tetrahydronaphthalene-2-ol, C 2 1H 2 7N 3 O 2 , (II) important benzovesamicol analogues for the diagnosis of Alzheimer's disease, have been synthesized and characterized by FT-IR, and 1 H and 13 C NMR spectroscopic analyses. The crystal structures were analyses using powder diffraction as no suitable single crystal were obtained. The two compounds are racemic mixtures of enantiomers which crystallize in the monoclinic system in a centrosymmetric space group (P21/c). Crystallography, in particular powder X-ray diffraction, was pivotal in revealing that the enantio-resolution did not succeed. In two compounds, the piperazine ring has a chair conformation, while the cyclohexene ring assumes a half-chair conformation. In (I) the crystal packing is mediated by weak contacts, principally by complementary intermolecular N--H...O hydrogen bonds that connect successive molecules into a chain. Further stabilization is provided by weak C--H...N contacts and by a weak intermolecular C--H...π interaction. While in (II), the crystal packing is dominated by intermolecular O--H...N hydrogen bonding which links molecules along the c direction. (authors)

X-ray photoelectron spectra structure of actinide compounds stipulated by electrons of the inner valence molecular orbitals (IVMO)

International Nuclear Information System (INIS)

Teterin, Yu. A.; Ivanov, K. E.

1997-01-01

Development of precise X-ray photoelectron spectroscopy using X-ray radiation hν< 1.5 KeV allowed to carry out immediate investigations of fine spectra structure of both weakly bond and deep electrons. Based on the experiments and the obtained results it may be concluded: 1. Under favourable conditions the inner valence molecular orbitals (IVMO) may form in all actinide compounds. 2. The XPS spectra fine structure stipulated by IVMO electrons allows to judge upon the degree of participation of the filled AO electrons in the chemical bond, on the structure o considered atom close environment and the bond lengths in compounds. For amorphous compounds the obtaining of such data based on X-ray structure analysis is restricted. 3. The summary contribution of IVMO electrons to the absolute value of the chemical bonding is comparable with the corresponding value of OMO electrons contribution to the atomic bonding. This fact is very important and new in chemistry. (author)

Improving the Carprofen Solubility: Synthesis of the Zn2Al-LDH Hybrid Compound.

Science.gov (United States)

Capsoni, Doretta; Quinzeni, Irene; Bruni, Giovanna; Friuli, Valeria; Maggi, Lauretta; Bini, Marcella

2018-01-01

The development of efficient strategies for drug delivery is considerably desired. Indeed, often several issues such as the drug solubility, the control of the drug release rate, the targeted delivery of drugs, the drug bioavailability, and the minimization of secondary effects still present great obstacles. Different methodologies have been proposed, but the use of nano-hybrids compounds that combine organic and inorganic substances seems particularly promising. An interesting inorganic host is the layered double hydroxide (LDH) with a sheets structure and formula [M 2+ 1-x M 3+ x (OH) 2 ](A n- ) x/n yH 2 O (M 2+  = Zn, Mg; M 3+  = Al; A n-  = nitrates, carbonates, chlorides). The possibility to exchange these counterions with drug molecules makes these systems ideal candidates for the drug delivery. In this article, we synthesize by co-precipitation method the hybrid compound Carprofen-Zn 2 Al-LDH. Carprofen, a poorly soluble anti-inflammatory drug, could also benefit of the association with a natural antacid such as LDH, to reduce the gastric irritation after its administration. Through X-ray diffraction and Fourier-transformed infrared spectroscopy (FT-IR), we could verify the effective drug intercalation into LDH. The dissolution tests clearly demonstrate a significant improvement of the drug release rate when carprofen is in the form of hybrid compound. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

SÍNTESIS, CARACTERIZACIÓN ESTRUCTURAL Y PROPIEDADES MAGNÉTICAS DE COMPUESTOS SEMICONDUCTORES DEL TIPO Dy (x In (1-x Sb ISYNTHESIS, STRUCTURAL CHARACTERIZATION AND MAGNETIC PROPERTIES OF SEMICONDUCTOR COMPOUNDS OF TYPE Dy x In (1-x S

Directory of Open Access Journals (Sweden)

Euclides J. Velazco Rivero

2018-04-01

Full Text Available Semiconductor compounds of molecular formula of type DyxIn (1-x Sb (x = 0,02; 0,03; 0,04; 0,05; 0,06 y 0,07 were synthesized by means of direct interaction of the elements under heat treatment to 550°C during 11 days in vacuum sealed quartz ampoules. The analyses by X-rays diffraction showed that the compounds with x = 0,02; 0,03 y 0,04 presented pure phases of InSb doped with Dy without presence of alternate phases of DySb. These compounds, analyzed by scanning electronic microscopy – SEM, showed particles with a variety of shapes and sizes each one. Whereas the magnetic susceptibility measurements showed that those doped compounds, in spite of their paramagnetic behavior, the predominant magnetic interaction is ferromagnetic due to their positive Curie temperature (θ

Synthesis of Li(x)Na(2-x)Mn2S3 and LiNaMnS2 through redox-induced ion exchange reactions

International Nuclear Information System (INIS)

Luthy, Joshua A.; Goodman, Phillip L.; Martin, Benjamin R.

2009-01-01

Na 2 Mn 2 S 3 was oxidatively deintercalated using iodine in acetonitrile to yield Na 1.3 Mn 2 S 3 , with lattice constants nearly identical to that of the reactant. Lithium was then reductively intercalated into the oxidized product to yield Li 0.7 Na 1.3 Mn 2 S 3 . When heated, this metastable compound decomposed to form a new crystalline compound, LiNaMnS 2 , along with MnS and residual Na 2 Mn 2 S 3 . Single crystal X-ray diffraction structural analysis of LiNaMnS 2 revealed that this compound crystallizes in P-3m1 with cell parameters a=4.0479(6) A, c=6.7759(14) A, V=96.15(3) A 3 (Z=1, wR2=0.0367) in the NaLiCdS 2 structure-type. - Graphical abstract: Structure of LiNaMnS 2 . Li and Mn are statistically distributed in edge-shared tetrahedral environments linked into infinite planes. Sodium ions occupy interlayer sites

Hexagonal perovskites with cationic vacancies. 25. Hexagonal 5 L stacking polytypes in the systems Ba/sub 5/BaWsub(3-x)sup(VI)Msub(x)sup(V)vacantOsub(15-x/2)vacantsub(x/2) with Msup(V) = Nb, Ta

Energy Technology Data Exchange (ETDEWEB)

Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

1980-12-01

In the systems BaO-M/sub 2/sup(V)O/sub 5/-WO/sub 3/ (Msup(V) = Nb, Ta) a new phase Ba/sub 5/BaWsub(3-x)Msub(x)sup(V)vacantOsub(15-x/2)vacantsub(x/2) with hexagonal 5 L structure (sequence hhccc; space group P-3m1) could be prepared. The range of existence is restricted to Msup(V) containing compounds. With Msup(V) = Nb the lower phase boundary is x = 3. In the Ta system it is reached between x = 2 and 3; the pure Ta pervoskite (Ba:Ta:O = 6:3:13 1/2 = 4:2:9) represents the final member of the series Ba/sub 3/Srsub(1-y)Basub(y)Ta/sub 2/O/sub 9/ with y = 1.

Ammonothermal synthesis of alkali-alkaline earth metal and alkali-rare earth metal carbodiimides. K{sub 5-x}M{sub x}(CN{sub 2}){sub 2+x}(HCN{sub 2}){sub 1-x} (M = Sr, Eu) and Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}

Energy Technology Data Exchange (ETDEWEB)

Mallmann, Mathias; Haeusler, Jonas; Cordes, Niklas; Schnick, Wolfgang [Department of Chemistry, University of Munich (LMU) (Germany)

2017-12-13

Alkali-alkaline earth metal and alkali-rare earth metal carbodiimides, namely K{sub 5-x}M{sub x}(CN{sub 2}){sub 2+x}(HCN{sub 2}){sub 1-x} (x = 0 - 1) (M = Sr, Eu) and Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}, were synthesized under ammonothermal conditions in high-pressure autoclaves. The structures of the three compounds can be derived from homeotypic K{sub 5}H(CN{sub 2}){sub 3} and Na{sub 5}H(CN{sub 2}){sub 3} by partial substitution of K{sup +} or Na{sup +}by Sr{sup 2+} or Eu{sup 2+}. The reactions were carried out in two step syntheses (T{sub 1} = 673 K, T{sub 2} = 823 K) starting from sodium or potassium azide, dicyandiamide and strontium or Eu(NH{sub 2}){sub 2}, respectively. The crystal structures were solved and refined from single-crystal X-ray diffraction data [K{sub 4.16}Sr{sub 0.84}(CN{sub 2}){sub 2.84}(HCN{sub 2}){sub 0.16}: space group Im3m (no. 229), a = 7.8304(5) Aa, Z = 2, R{sub 1} = 0.024, wR{sub 2} = 0.052; K{sub 4.40}Eu{sub 0.60}(CN{sub 2}){sub 2.60}(HCN{sub 2}){sub 0.40}: space group Im anti 3m (no. 229), a = 7.8502(6) Aa, Z = 2, R{sub 1} = 0.022, wR{sub 2} = 0.049]. In contrast to the potassium carbodiimides, the sodium-strontium carbodiimide was only synthesized as microcrystalline powder. The crystal structure was determined by powder X-ray diffraction and refined by the Rietveld method [Na{sub 4.32}Sr{sub 0.68}(CN{sub 2}){sub 2.68}(HCN{sub 2}){sub 0.32}: space group Im3m (no. 229), a = 7.2412(1) Aa, Z = 2, R{sub wp} = 0.050]. The presence of hydrogencyanamide units ([HNCN]{sup -}) next to carbodiimide units ([CN{sub 2}]{sup 2-}) in all compounds was confirmed by FT-IR spectroscopy. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Sub-25-nm laboratory x-ray microscopy using a compound Fresnel zone plate.

Science.gov (United States)

von Hofsten, Olov; Bertilson, Michael; Reinspach, Julia; Holmberg, Anders; Hertz, Hans M; Vogt, Ulrich

2009-09-01

Improving the resolution in x-ray microscopes is of high priority to enable future applications in nanoscience. However, high-resolution zone-plate optics often have low efficiency, which makes implementation in laboratory microscopes difficult. We present a laboratory x-ray microscope based on a compound zone plate. The compound zone plate utilizes multiple diffraction orders to achieve high resolution while maintaining reasonable efficiency. We analyze the illumination conditions necessary for this type of optics in order to suppress stray light and demonstrate microscopic imaging resolving 25 nm features.

Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Ward, Jesse D.; Bowden, Mark; Tom Resch, C.; Eiden, Gregory C.; Pemmaraju, C. D.; Prendergast, David; Duffin, Andrew M.

2017-01-01

Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Non-destructive chemical analyses of these compounds is important for process and environmental monitoring and X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride, and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. These compounds have unique spectral signatures that can be used to identify unknown samples.

Microstructure study of the rare-earth intermetallic compounds R₅(Si_xGe_1-x)₄ and R₅(Si_xGe_1-x)₃

Energy Technology Data Exchange (ETDEWEB)

Cao, Qing [Iowa State Univ., Ames, IA (United States)

2012-01-01

The unique combination of magnetic properties and structural transitions exhibited by many members of the R₅(Si_xGe_1-x)₄ family (R = rare earths, 0 ≤ x ≤ 1) presents numerous opportunities for these materials in advanced energy transformation applications. Past research has proven that the crystal structure and magnetic ordering of the R₅(Si_xGe_1-x)₄ compounds can be altered by temperature, magnetic field, pressure and the Si/Ge ratio. Results of this thesis study on the crystal structure of the Er₅Si₄ compound have for the first time shown that the application of mechanical forces (i.e. shear stress introduced during the mechanical grinding) can also result in a structural transition from Gd₅Si₄-type orthorhombic to Gd₅Si₂Ge₂-type monoclinic. This structural transition is reversible, moving in the opposite direction when the material is subjected to low-temperature annealing at 500 °C.

Coordination compounds of thorium(4) containing tris(dimethylamino)-phosphinoxide

International Nuclear Information System (INIS)

Skopenko, V.V.; Klunnik, L.A.

1983-01-01

Compounds including tris(dimethylamino)-phosphinoxide of the following composition: [ThX 4 (HMPA) 4 ] and [ThX 2 (HMPA) 4 ](BPh 4 ) 2 , where X=NCSe, N(CN) 2 =, C(CN) 3 , ONC(CN) 2 -, [C(CN) 2 C(O)NH 2 ], BPh 4 =[B(C 6 H 5 ) 4 ] - , and HMPA=OP[N(CN 3 ) 2 ] 3 are prepared by interactions of thoriUm chloride with different pseudohalogenides and sodium tetraphenylborate. Some properties of the above compoUnds are studied. Using the IR spectroscopy, the way of coordinating these compounds is determined; the X-ray crystal analysis has determined isostrUcture of compounds: [Th(NCX) 4 (HMPA) 4 ] and [ThX 2 (HMPA) 4 ](BPh 4 ) 2 , where X is Se, S

Crystallographic and Mössbauer investigations on Np1- xPuxB2

Science.gov (United States)

Chipaux, R.; Bonnisseau, D.; Bogé, M.; Larroque, J.

1988-08-01

The diborides of neptunium and plutonium and their solid solutions Np 1- xPu xB 2 have been synthesized by direct reaction with a good purity. The lattice parameters follow Vegard's law. The magnetic properties of the samples containing neptunium have been investigated by Mössbauer spectrometry. The isomer shift is almost constant in all compounds (-14.5 (0.2) mm/s resp. to NpAl 2), suggesting tetravalent Np ions. At high temperatures, a large quadrupolar interaction, clearly connected to the crystal structure, is observed in all compounds, decreasing slowly with the neptunium concentration. At low temperature, magnetic patterns appear for x ⩽ 0.5. The magnetic moments are ordered perpendicular to the c-axis and equal to 0.57μ B for x = 0. In Np 0.5Pu 0.5B 2 and, in less degree in Np 0.7Pu 0.3B 2 and Np 0.33Pu 0.67B 2, magnetic fluctuations are detec ted.

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.

Structure and thermoelectric property of Te doped paracostibite CoSb1-xTexS compounds

Science.gov (United States)

You, Yonghui; Su, Xianli; Liu, Wei; Yan, Yonggao; Fu, Jiefei; Cheng, Xin; Zhang, Cheng; Tang, Xinfeng

2018-06-01

Paracostibite (CoSbS), a newly developed thermoelectric material, has aroused lots of interest due to its highly earth abundant and inexpensive constituent elements and potential application for thermoelectric power generation in the intermediate temperature range. Herein, a series of CoSb1-xTexS (x = 0-0.09) compounds were prepared by vacuum melting and annealing followed by SPS processing, and the effects of Te doping on the structure and thermoelectric properties were systematically investigated. Doping Te on the Sb site increases the carrier concentration up to 7.24 × 1020 cm-3 for CoSb0.93Te0.07S compound which is several orders of magnitude higher than that of un-doped CoSbS, and enhances the power factor. The maximum power factor of 14.07 μW cm-1 K-2 is attained at 900 K. Concomitantly, doping with Te on the Sb site leads to effective scattering of heat carrying phonon, accompanying with a strong suppression of the thermal conductivity with the increase of Te content, resulting in an increase of the ZT. A maximum ZT of 0.43 at 900 K is attained for CoSb0.93Te0.07S compound, which is 139% higher than that of un-doped CoSbS compound.

Forecasting of chalcogenide spinels of the general formula AB2X4 using the method of training of an electronic computer

International Nuclear Information System (INIS)

Kiseleva, N.N.; Savitskij, E.M.

1979-01-01

Experimental evidence on the existence of AB 2 X 4 compounds in A-B-X systems (A and B are any elements of the periodic system, in particular, rare earth elements, X is S or Se) and the data on the properties of elements and simple sulphides (selenides) were used for an attempt to find the probability of formation of AB 2 X 4 compounds as a function of the component properties. The experimental evidence was analyzed by a computer employing algorithms of concept formation training. The results were used to predict new AB 2 X 4 compounds. The computer training method proved an efficient means of revealing the connection between probability of spinel type compounds existence with the component properties. Certain compounds of general formula AB 2 X 4 were predicted and the probability that they possess spinel structure was evaluated

Large magnetocaloric effect of GdNiAl2 compound

International Nuclear Information System (INIS)

Dembele, S.N.; Ma, Z.; Shang, Y.F.; Fu, H.; Balfour, E.A.; Hadimani, R.L.; Jiles, D.C.; Teng, B.H.; Luo, Y.

2015-01-01

This paper presents the structure, magnetic properties, and magnetocaloric effect of the polycrystalline compound GdNiAl 2 . Powder X-ray diffraction (XRD) measurement and Rietveld refinement revealed that GdNiAl 2 alloy is CuMgAl 2 -type phase structure with about 1 wt% GdNi 2 Al 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 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 2 compound. • The ΔS 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 2 comparing with other candidates

Modulation-free bismuth-lead cuprate superconductors: BiPbSr1+xL1-xCuO6 and BiPbSr2Y1-xCaxCu2O8

International Nuclear Information System (INIS)

Manivannan, V.; Gopalakrishnan, J.; Rao, C.N.R.

1991-01-01

Modulation-free BiPbSrLCuO 6 (L=La, Pr, Nd) and BiPbSr 2 YCu 2 O 8 , which are isotypic with the n=1 and 2 members of the Bi 2 Sr 2 Ca n-1 Cu n O 2n+4 family, have been prepared and characterized. These parent compounds are nonsuperconducting, but when doped with holes by substitution chemistry give modulation-free superconducting cuprates of the general formulas BiPbSr 1+xL1-x CuO 6 and BiPbSr 2 Y 1-x Ca x Cu 2 O 8 , exhibiting maximum T c 's of 24 and 85 K, respectively. Significantly, the hole concentration at the maximum T c is 0.12 in the cuprate family with a single Cu-O layer and 0.22 in that with two Cu-O layers

Microwave assistant synthesis, crystal structure and biological activity of a 1,2,4-triazole compound

International Nuclear Information System (INIS)

Ke, W.; Sun, N.B.

2013-01-01

The title compound (C/sub 17/H/sub 14/F/sub 2/N/sub 4/SO) were synthesized and recrystallized from CH/sub 3/CN. The compound was characterized by 1h-nmr, ftir, ms, hrms and x-ray diffraction. the compound crystallized in the monoclinic space group c2/c with a = 27.532(6), b 8.9596(18), c 14.609(3) alpha = 90, beta = 112.59(3), lambda =90 degree, gamma = 3327.1(12) alpha 3, z = 8 and r = 0.0327 for 2596 observed reflections with 1 > 2 (i). x-ray analysis reveals that not only intermolecular N-H-N interactions, but also C-H Pie stacking interactions exist in the adjacent molecules. The biological activities results showed that it exhibited significant herbicidal activity towards brassica napus. (author)

The crystallographic phases and magnetic properties of Fe2MnSi1-xGex

International Nuclear Information System (INIS)

Zhang, L.; Brueck, E.; Tegus, O.; Buschow, K.H.J.; Boer, F.R. de

2003-01-01

Fe 2 MnSi 1-x Ge x (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) compounds were prepared by a mechanically activated solid-state diffusion method. Both X-ray diffraction and differential scanning calorimetry evidenced the presence of an amorphous phase after 10 h of milling. The X-ray data reveal that in the high-temperature annealing the single D0 3 -type phase can be retained up to 50% substitution of Ge for Si in Fe 2 MnSi. A metastable D0 3 phase is obtained after crystallization of the as-milled amorphous compounds with x>0.5. High-temperature annealing transforms the low-temperature D0 3 phase into a single D0 19 phase (x=1) or a mixture of D0 3 and D0 19 phase (x=0.6 and 0.8). Low-field thermomagnetic measurements show a moderately sharp ferromagnetic-paramagnetic transition, which becomes enormously broad in higher magnetic fields. The Curie temperature is significantly enhanced when going from the D0 3 phase to the D0 19 phase. Neither a magnetic-field-induced transition nor a reversible structural transition is observed throughout this compound series. The magnetocaloric effect associated with the magnetic transition is small

Muon Spin Relaxation Studies of RFeAsO and MFe2As2 Based Compounds

Science.gov (United States)

Luke, Graeme

2010-03-01

Muon spin relaxation measurements of a variety of iron pnictide systems have revealed commensurate long range magnetic order in the parent compounds which can change to incommensurate order with carrier doping. Magnetic order gives way to superconductivity with increased doping; however there are regions of the phase diagrams where the two phenomena co-exist. In the case of Ba1-xKxFe2As2 there is phase separation into superconducting and magnetic domains, whereas in Ba(Fe1-xCox)2As2 the coexistence is apparently microscopic for x=0.035->0.048. Transverse field muon spin rotation measurements of single crystal Ba(Fe1-xCox)2 and Sr(Fe1-xCox)2 exhibit an Abrikosov vortex lattice from which we are able to determine the magnetic field penetration depth and Ginzburg-Landau parameter. The temperature variation of the superfluid density is well described by a two-gap model. In Ba(Fe1-xCox)2As2, both the superconducting TC and the superfluid density decrease with increasing doping above x=0.06; in all of the pnictides we find that the superfluid density obeys the same nearly linear scaling with TC as found in the cuprates.

Moessbauer and muon spin relaxation investigation of magnetic and superconducting properties of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Materne, Philipp; Bubel, Sirko; Maeter, Hemke; Sarkar, Rajib; Klauss, Hans-Henning [Institut fuer Festkoerperphysik, Technische Universitaet Dresden, 01062 Dresden (Germany); Harnagea, Luminita; Wurmehl, Sabine; Buechner, Bernd [IFW Dresden, Postfach 270016, 01171 Dresden (Germany); Luetkens, Hubertus [Paul-Scherrer-Institut, 5232 Villigen (Switzerland)

2013-07-01

The antiferromagnetic parent compound, CaFe{sub 2}As{sub 2}, shows a supression of the spin density wave and a subsequent superconducting state upon partial substitution of Ca by Na. Along the substitution series, superconducting transition temperatures up to ∼35 K were found. We studied the electronic phase diagram of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} using Moessbauer spectroscopy and muon spin relaxation experiments. We have analyzed the data in terms of magnetic and superconducting properties and possible coexistence of superconductivity and spin density wave order. We compared our results with recently published data of Ba{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2}.

X-ray diffraction studies of NbTe2 single crystal

Indian Academy of Sciences (India)

Unknown

X-ray (EDAX) and remaining structural characterization was also accomplished by X-ray diffraction (XRD) studies. Lattice parameters, volume and ... The layered structure compound, NbTe2, is one of the typical materials which lead to charge .... financial assistance to carry out this work. References. Brown B E 1966 Acta ...

Polymorphism of Bi1-xLnxO1.5 phases (04Ln2O9 (x=0.33; Ln=La, Pr, Nd)

International Nuclear Information System (INIS)

Drache, Michel; Huve, Marielle; Roussel, Pascal; Conflant, Pierre

2003-01-01

The Bi 1-x Ln x O 1.5 solid solutions (Ln=La, Pr, Nd), of the β 2 /β 1 /ε (Bi-Sr-O) structural type, have been investigated in their Ln-rich domains. For Ln=La, Pr, and Nd, the upper limits are 0.35, 0.35 and 0.33, respectively. The Bi 4 Ln 2 O 9 ε phase (x=0.33) appears to be the single definite compound. For Bi 4 La 2 O 9 , Bi 4 Pr 2 O 9 and Bi 4 Nd 2 O 9 , the ε-type cells are respectively: a=9.484(4) A, b=3.982(2) A, c=7.030(3) A, β=104.75(3) deg.; a=9.470(5) A, b=3.945(2) A, c=6.968(4) A, β=104.73(3) deg. and a=9.439(3) A, b=3.944(2) A, c=6.923(2) A, β=105.03(3) deg. . Upon heating, each monoclinic (ε) compound transforms successively into rhombohedral phases (β 2 /β 1 ) and finally into a cubic fluorite-type phase. For La- and Pr-based compounds, all transitions are reversible; for Nd, depending on the thermal treatment, the reversibility of ε→β 2 can be incomplete. These transformations are characterized using X-ray thermodiffractometry, differential thermal analysis, dilatometry and impedance spectroscopy versus temperature. Examination of Bi 4 (Ln, Ln') 2 O 9 samples allows to correlate the evolution of the thermal behavior and of the unit cell parameters, to the lanthanide size. A partial plot of the (Bi 2 O 3 ) 1-x -(La 2 O 3 ) x phase diagram (0≤x≤0.40) is proposed

Synthesis, characterization and sorption properties of functionalized Cr-MIL-101-X (X=–F, –Cl, –Br, –CH3, –C6H4, –F2, –(CH3)2) materials

International Nuclear Information System (INIS)

Buragohain, Amlan; Couck, Sarah; Van Der Voort, Pascal; Denayer, Joeri F.M.; Biswas, Shyam

2016-01-01

Four existing and three new functionalized chromium terephthalates having MIL-101 topology and denoted as Cr-MIL-101-X (existing ones with X=–F, 1-F; –Cl, 2-Cl; –Br, 3-Br; –CH 3 , 4-CH 3 ; new ones with X=–C 6 H 4 , 5-C 6 H 4 ; –F 2 , 6-F 2 , –(CH 3 ) 2 , 7-(CH 3 ) 2 ) were synthesized under hydrothermal conditions. All the materials except 5-C 6 H 4 could be prepared by a general synthetic route, in which the mixtures of CrO 3 , H 2 BDC-X (BDC=1,4-benzenedicarboxylate) linkers, conc. HCl and water with a molar ratio of 1:1:3.9:222.2 were reacted at 180 °C for 144 h. Compared to the 144 h of synthesis time, three of the compounds, namely 1-Cl, 2-Br and 5-C 6 H 4 , could be prepared in much shorter reaction times (12–18 h at 180–210 °C). The materials possess high thermal stability up to 270–300 °C in an air atmosphere. The activated compounds exhibit significant porosity (S BET range: 1273–2135 m 2 g −1 ). At 0 °C and 1 bar, the CO 2 adsorption capacities of the compounds fall in the 1.7–2.9 mmol g −1 range. Compounds 1-F and 6-F 2 showed enhanced CO 2 uptake values compared to parent Cr-MIL-101. The benzene adsorption capacities of the compounds lie in the range of 66.2–139.5 molecules per unit cell at 50 °C and p/p 0 =0.35. The increased benzene uptake value of 1-F compared to un-functionalized Cr-MIL-101 and 4-CH 3 suggests that the fluorination has induced more hydrophobicity in Cr-MIL-101 as compared to the methylation. - Graphical abstract: Benzene adsorption by seven functionalized Cr-MIL-101-X metal-organic framework (MOF) materials Display Omitted - Highlights: • Seven functionalized Cr-MIL-101-X materials were synthesized solvothermally. • All Cr-MIL-101-X materials exhibited high thermal stability up to 270–300 °C in air. • All Cr-MIL-101-X compounds displayed considerable porosity towards N 2 , CO 2 and benzene. • Mono- and di-fluorinated Cr-MIL-101 materials showed enhanced CO 2 adsorption capacities. �

Studies on the Ln/sub 2/O/sub 3/ (Ln: rare-earth elements)-SrO-V/sub 2/O/sub 3/ system, 2. Some physical properties for Ln sub(1-x)Sr sub(x)VO sub(3-0. 1x) and SrO. Ln sub(1-x)Sr sub(x)VO sub(3-0. 1x) (Ln: Nd or Eu)

Energy Technology Data Exchange (ETDEWEB)

Shin-ike, T [Osaka Dental Coll., Hirakata (Japan); Adachi, G; Shiokawa, J

1981-01-01

Electrical and magnetic properties of the perovskite type solid solutions, Ln sub(1-x)Sr sub(x)VO sub(3-0.1x) (Ln: Nd or Eu), and the K/sub 2/NiF/sub 4/ type solid solutions, SrO.Ln sub(1-x)Sr sub(x)VO sub(3-0.1x) (Ln: Nd or Eu), were studied in the temperature range 77 - 300 K. The electrical conductivity increased with x for the perovskite type solid solutions and the reverse behavior was observed for the K/sub 2/NiF/sub 4/ type compounds. All the solid solutions examined exhibited a metal-insulator transition at some values of x. Both Nd sub(1-x)Sr sub(x)VO sub(3-0.1x) and Eu sub(1-x)Sr sub(x)VO sub(3-0.1x) were antiferromagnets having a weak ferromagnetism at a low value of x at a low temperature. The K/sub 2/NiF/sub 4/ type solid solutions revealed a weak ferromagnetism at a high value of x at a low temperature.

The crystal structure of a new ternary antimonide: TmCu4-xSb2 (x 1.065)

International Nuclear Information System (INIS)

Fedyna, L.O.; Bodak, O.I.; Fedorchuk, A.O.; Tokaychuk, Ya.O.

2005-01-01

The crystal structure of the new ternary compound TmCu 4-x Sb 2 (x 1.065) was determined by direct methods from X-ray powder data (diffractometer DRON-3M, Cu Kα-radiation). It crystallizes with the orthorhombic structure type ErFe 4 Ge 2 (low-temperature modification) and is the first representative of this structure type among known antimonides: space group Pnnm, Pearson code oP14-2.13, a = 7.00565(6) A, b = 7.83582(6) A, c = 4.25051(3) A, Z = 2. Investigated structure is an orthorhombically deformed derivative of the ZrFe 4 Si 2 structure type

Magnetic and superconducting order in some random pseudobinary compounds

International Nuclear Information System (INIS)

Dongen, J.C.M. van.

1982-01-01

This thesis presents the results of a study on the magnetic and superconducting ordering phenomena in some random pseudobinary compounds. In the investigations ternary systems are utilised in which two of the elements form a binary intermetallic compound, e.g. PdH, GdCu and YCo 2 . A third element is then randomly substituted into one of the sublattices without changing the basic intermetallic compound structure. In chapter II a study is presented on the Kondo effect and spin-glass freezing of the magnetic impurities Cr, Mn, and Fe in superconducting palladium hydride. Chapter III contains a study on crystal structure transformations and magnetic ordering phenomena in GdCusub(1-x)Gasub(x) and related pseudobinary compounds. In Chapter IV experiments on the magnetic properties and the electrical resistivity of the transition metal Laves phase compounds Y(Cosub(1-x)Fesub(x)) 2 , Y(Irsub(1-x)Fesub(x)) 2 and Hf(Cosub(1-x)Fesub(x)) 2 are described. (Auth.)

Type conversion by high-energy particles in Hg1-xCdxTe compounds

International Nuclear Information System (INIS)

Blanchard, C.; Favre, J.; Barbot, J.F.; Desoyer, J.C.; Toulemonde, M.; Konczykowski, M.; Le Scoul, D.; Dessus, J.L.

1990-01-01

p-type crystals of the ternary compounds Hg 1-x Cd x Te have been irradiated with high-energy ions and electrons. Electron-beam-induced current signals on xenon- and krypton-irradiated Hg 1-x Cd x Te show that n-type conversion, occurring all along the ion path, is related to the presence of mercury atoms. Resistivity and Hall measurements on carbon-, oxygen-, xenon- and electron-irradiated Hg 0.8 Cd 0.2 Te crystals allow us to determine the effective cross section for atomic displacement. We observe, for electron-irradiated samples, a saturation in carrier concentration interpreted as the pinning of the Fermi level at a resonant donor state 370 meV above the bottom of the conduction band. Comparison between ion and electron irradiations shows that electrically active produced defects are mainly due to atomic collisions. Additional reduction of defect production efficiency for xenon ions may be the onset of some energy transfer from electronic loss to target atoms

Structural and magnetic properties of the (Ca1-xNax)(Fe2-xTix)O4 solid solution (0 ≤ x ≤ 1)

International Nuclear Information System (INIS)

Zouari, S.; Ranno, L.; Cheikh-Rouhou, A.; Isnard, O.; Wolfers, P.; Bordet, P.; Strobel, P.

2008-01-01

New compounds corresponding to the (Ca 1-x Na x )(Fe 2-x Ti x )O 4 formula with 0 ≤ x ≤ 1 were prepared by solid state reactions at 1100 deg. C in air. A continuous solid solution was found between end members CaFe 2 O 4 and NaFeTiO 4 . The evolution of structural parameters and bonding geometry with composition is discussed in detail. Magnetic measurements show that the antiferromagnetic ordering known in CaFe 2 O 4 is suppressed for all x values investigated (x ≥ 0.2). The absence of crystallographic transition at low temperature was checked by X-ray diffraction down to 10 K. The magnetic structure of CaFe 2 O 4 was redetermined from powder neutron diffraction. Spins on the two iron sites order antiparallel (F z F z spin arrangement), as described previously. The difference in magnetic moments on Fe 1 and Fe 2 sites result in a ferrimagnetic configuration with net moment 2.72μ B at 2 K

Thin film Heusler compounds manganese nickel gallium

Science.gov (United States)

Jenkins, Catherine Ann

Multiferroic Heusler compounds Mn3--xNi xGa (x=0,1,2) have a tetragonal unit cell that can variously be used for magneto-mechanically coupled shape memory ( x=1,2) and spin-mechanical applications (x=0). The first fabrication of fully epitaxial thin films of these and electronically related compounds by sputtering is discussed. Traditional and custom lab characterization of the magnetic and temperature driven multiferroic behavior is augmented by more detailed synchrotron-based high energy photoemission spectroscopic techniques to describe the atomic and electronic structure. Integration of the MnNi2Ga magnetic shape memory compound in microwave patch antennas and active free-standing structures represents a fraction of the available and promising applications for these compounds. Prototype magnetic tunnel junctions are demonstrated by Mn3Ga electrodes with perpendicular anisotropy for spin torque transfer memory structures. The main body of the work concentrates on the definition and exploration of the material series Mn3--xNi xGa (x=0,1,2) and the relevant multiferroic phenomena exhibited as a function of preparation and external stimuli. Engineering results on each x=0,1,2 are presented with device prototypes where relevant. In the appendices the process of the materials design undertaken with the goal of developing new ternary intermetallics with enhanced properties is presented with a full exploration of the road from band structure calculations to device implementation. Cobalt based compounds in single crystal and nanoparticle form are fabricated with an eye to developing the production methods for new cobalt- and iron-based magnetic shape memory compounds for device applications in different forms. Mn2CoSn, a compound isolectronic and with similar atomic ordering to Mn2NiGa is experimentally determined to be a nearly half-metallic ferromagnet in contrast to the metallic ferrimagnetism in the parent compound. High energy photoemission spectroscopy is shown to

Magnetic properties and superconducting-fluctuation diamagnetism above Tc in Bi2-xPbxSr2CaCu2O8+δ (x=0.0, 0.1, 0.2, 0.3, 0.5) and

International Nuclear Information System (INIS)

Lee, W.C.; Cho, J.H.; Johnston, D.C.

1991-01-01

The magnetic susceptibilities χ(T) of the title compounds above and below T c are reported. For the Bi 2-x Pb x Sr 2 CaCu 2 O 8+δ (Bi 2:2:1:2) system, optimization of the phase purity and superconducting properties is found between x=0.2 and 0.3. The χ(T) data for these Bi 2:2:1:2 and for the two Bi 2:2:2:3 samples increase monotonically with temperature from T c up to at least 400 K, exhibiting strong negative curvature below ∼200 K. From theoretical fits to the data in the two-dimensional regime above T c using the static Lawrence-Doniach model as modified by Klemm, we conclude that the negative curvature in χ(T) for each sample arises from superconducting-fluctuation diamagnetism (SFD). The data are thus consistent with a superconducting order parameter of s-wave symmetry. From the fits to the data, the Ginzburg-Landau coherence lengths in the CuO 2 planes were obtained and found to be ξ ab (0)=20.4(2) A for Bi 2:2:1:2 and 11.8(4) A for Bi 2:2:2:3. The value for Bi 2:2:1:2 is comparable to those calculated from upper critical magnetic-field data for this compound (23.5--27.1 A). Our ξ ab (0) values for Bi 2:2:1:2 and Bi 2:2:2:3 are also comparable with that (13.6 A) found from our previous similar analysis of the SFD in YBa 2 Cu 3 O 7 . The possible role of the bridging oxygens out of the CuO 2 plane in Bi 2:2:2:3 and the influence of the dynamics in the fits to the SFD in the Bi-based compounds remain to be addressed

Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}

Energy Technology Data Exchange (ETDEWEB)

Corredor, L.T. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Programa de Pós-Graduação em Ciências de Materiais-CCEN, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia); Albino Aguiar, J. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Programa de Pós-Graduação em Ciências de Materiais-CCEN, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Landínez Téllez, D.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia); Pureur, P.; Mesquita, F. [Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Roa-Rojas, J. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia)

2015-06-15

Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr{sub 2}GdCu{sub 2}O{sub 8}. • We synthesized the doped compound Rui{sub x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}, for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y} ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr{sub 2}GdRu{sub 1−x}Re{sub x}O{sub y}, which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO{sub 2} (magnetic) and CuO{sub 2} (superconductor) sub-lattices can clearly be observed.

Synthesis, Characterization, and Gas-Sensing Properties of Mesoporous Nanocrystalline Sn(x)Ti(1-x)O2.

Science.gov (United States)

Zhong, Cheng; Lin, Zhidong; Guo, Fei; Wang, Xuehua

2015-06-01

A nanocomposite mesoporous material composed by SnO2 and TiO2 with the size of -5-9 nm were prepared via a facile wet-chemical approach combining with an annealing process. The microstructure of obtained Sn(x)Ti(1-x)O2 powders were characterized by X-ray diffraction, X-ray Photo-electronic Spectroscopy, scanning electron microscope, transmission electron microscope and nitrogen adsorption-desorption experiment. The gas sensing performances to several gases of the mesoporous material were studied. The sensors of Sn(x)Ti(1-x)O2 (ST10, with 9.1% Ti) exhibited very high responses to volatile organic compounds at 160 degrees C. The order of the responses to volatile gases based on ST10 was ethanol > formaldehyde > acetone > toluene > benzene > methane. Sensor based on ST10 displays a highest sensitivity to hydrogen at 200 degrees C. Sensor responses to H2 at 200 degrees C have been measured and analyzed in a wide concentration range from 5 to 2000 ppm. The solid solution Sn(x)Ti(1-x)O2 can be served as a potential gas-sensing material for a broad range of future sensor applications.

Structural studies of type N superconductive compounds: R2-xCexCuO4±δ (R = Gd, Eu, Sm, Nd, Pr); influences of chemical treatments on physical properties

International Nuclear Information System (INIS)

Vigoureux, P.

1995-06-01

Different chemical treatments of R 2-x Ce x CuO 4±δ compounds monocrystals (gadolinium, europium, samarium, neodymium and praseodymium cuprates) modify their physical properties especially their superconductive properties. The presented chemical treatments are: the substitution of the trivalent rare earth element R by an other trivalent lanthanide, its substitution by tetravalent cerium, and heat treatment under low oxygen pressure. After these chemical treatments, structural modifications are observed by neutrons and X-rays diffraction, and allow to precise their actions: size effect of the rare earth element on the deformation of the CuO 2 planes, links between deformation and superconductivity and magnetic properties. (A.B.)

Thermal Expansion Anomaly and Spontaneous Magnetostriction of Y2Fe14Al3 Compound

International Nuclear Information System (INIS)

Yan-Ming, Hao; Xin-Yuan, Jiang; Chun-Jing, Gao; Yan-Zhao, Wu; Yan-Yan, Zhang

2009-01-01

The structure and magnetic properties of Y 2 Fe 14 Al 3 compound are investigated by means of x-ray diffraction and magnetization measurements. The Y 2 Fe 14 Al 3 compound has a hexagonal Th 2 Ni 17 -type structure. Negative thermal expansion is found in Y 2 Fe 14 Al 3 compound in the temperature range from 403 to 491K by x-ray dilatometry. The coefficient of the average thermal expansion is α-bar = –2.54 × 10 −5 K −1 . The spontaneous magnetostrictive deformations from 283 to 470K are calculated by means of the differences between the experimental values of the lattice parameters and the corresponding values extrapolated from the paramagnetic range. The result shows that the spontaneous volume magnetostrictive deformation ω S decreases from 5.74 × 10 −3 to nearly zero with temperature increasing from 283 to 470 K, the spontaneous linear magnetostrictive deformation λ c along the c-axis is larger than the spontaneous linear magnetostrictive deformation λ a in basal-plane in the same temperature below 350 K

Neutron scattering study of MnX2 (X = Br, I)

International Nuclear Information System (INIS)

Sato, Taku; Kadowaki, Hiroaki.

1993-01-01

Successive magnetic phase transitions in MnX 2 (X = Br, I), found by bulk measurements, are studied by neutron scattering experiments. There occur two (T N1 = 2.32K, T N2 = 2.17K) and three (T N1 = 3.95K, T N2 = 3.8K, T N3 = 3.45K) phase transitions in MnBr 2 and MnI 2 , respectively. We have found that magnetic structures of the both compounds in the intermediate temperature phases (MnBr 2 : T N1 > T > T N2 ; MnI 2 : T N1 > T > T N3 ) are transverse sinusoidally-modulated structures with incommensurate wave-vectors which vary as a function of temperature. As the temperature is lowered into the lowest temperature phases, the magnetic structures change via first order transition into ↑↑↓↓ and a helical structure for MnBr 2 and MnI 2 , respectively, which were determined by previous experiments. The successive phase transitions in MnBr 2 are accounted for quantitatively using a mean field approximation of a Hamiltonian consisting of exchange interactions up to third inter- and third intra-layer neighbor sites and the dipolar interaction. (author)

Thermodynamics, dielectric permittivity and phase diagrams of the Rb1-x(NH4xH2PO4 type proton glasses

Directory of Open Access Journals (Sweden)

S.I. Sorokov

2010-01-01

Full Text Available The cluster pseudospin model of proton glasses, which takes into account the energy levels of protons around the PO4 group, the long-range interactions between the hydrogen bonds, and an internal random deformational field is used to investigate thermodynamical characteristics, longitudinal and transverse dielectric permittivities of Rb1-x(ND4xD2PO4 and Rb1-x(NH4xH2AsO4 compounds. A review of experimental and theoretical works on the Rb1-x(NH4xH2PO4 type crystals is presented.

Novel compound heterozygous mutations in SERPINH1 cause rare autosomal recessive osteogenesis imperfecta type X.

Science.gov (United States)

Song, Y; Zhao, D; Xu, X; Lv, F; Li, L; Jiang, Y; Wang, O; Xia, W; Xing, X; Li, M

2018-03-09

We identified novel compound heterozygous mutations in SERPINH1 in a Chinese boy suffering from recurrent fractures, femoral deformities, and growth retardation, which resulted in extremely rare autosomal recessive OI type X. Long-term treatment of BPs was effective in increasing BMD Z-score, reducing fracture incidence and reshaping vertebrae compression. Osteogenesis imperfecta (OI) is a heritable bone disorder characterized by low bone mineral density, recurrent fractures, and progressive bone deformities. Mutation in serpin peptidase inhibitor clade H, member 1 (SERPINH1), which encodes heat shock protein 47 (HSP47), leads to rare autosomal recessive OI type X. We aimed to detect the phenotype and the pathogenic mutation of OI type X in a boy from a non-consanguineous Chinese family. We investigated the pathogenic mutations and analyzed their relationship with the phenotype in the patient using next-generation sequencing (NGS) and Sanger sequencing. Moreover, the efficacy of long-term bisphosphonate treatment in this patient was evaluated. The patient suffered from multiple fractures, low bone mass, and bone deformities in the femur, without dentinogenesis imperfecta or hearing loss. Compound heterozygous variants were found in SERPINH1 as follows: c.149 T>G in exon 2 and c.1214G>A in exon 5. His parents were heterozygous carriers of each of these mutations, respectively. Bisphosphonates could be helpful in increasing BMD Z-score, reducing bone fracture risk and reshaping the compressed vertebral bodies of this patient. We reported novel compound heterozygous mutations in SERPINH1 in a Chinese OI patient for the first time, which expanded the spectrum of phenotype and genotype of extremely rare OI type X.

Bacillus pumilus KatX2 confers enhanced hydrogen peroxide resistance to a Bacillus subtilis PkatA::katX2 mutant strain.

Science.gov (United States)

Handtke, Stefan; Albrecht, Dirk; Zühlke, Daniela; Otto, Andreas; Becher, Dörte; Schweder, Thomas; Riedel, Kathrin; Hecker, Michael; Voigt, Birgit

2017-04-26

Bacillus pumilus cells exhibit a significantly higher resistance to hydrogen peroxide compared to closely related Bacilli like Bacillus subtilis. In this study we analyzed features of the catalase KatX2 of B. pumilus as one of the most important parts of the cellular response to hydrogen peroxide. KatX2, the vegetative catalase expressed in B. pumilus, was compared to the vegetative catalase KatA of B. subtilis. Data of our study demonstrate that B. pumilus can degrade toxic concentrations of hydrogen peroxide faster than B. subtilis. By replacing B. subtilis katA gene by katX2 we could significantly enhance its resistance to H 2 O 2 and its potential to eliminate this toxic compound. Mutant cells showed a 1.5- to 2-fold higher survival to toxic concentrations of hydrogen peroxide compared to wild type cells. Furthermore, we found reversible but also irreversible oxidations of the KatX2 protein which, in contrast to KatA, contains several cysteine residues. Our study indicates that the catalase KatX2 plays a major role in the increased resistance of B. pumilus to oxidative stress caused by hydrogen peroxide. Resistance to hydrogen peroxide of other Bacilli can be enhanced by exchanging the native catalase in the cells with katX2.

Thermoanalytical investigation of the hydrogen absorption behaviour of Sm{sub 2}Fe{sub 17-x}Ga{sub x} at high hydrogen pressures

Energy Technology Data Exchange (ETDEWEB)

Handstein, A.; Kubis, M.; Gebel, B.; Mueller, K.-H.; Schultz, L. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe; Gutfleisch, O.; Harris, I.R. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe]|[Birmingham Univ. (United Kingdom). School of Metallurgy and Materials

1998-07-01

The complete disproportionation of Sm{sub 2}Fe{sub 17-x}Ga{sub x} during annealing in hydrogen is hindered due to an increased stability of the compounds with a higher Ga content (x {>=} 1). Therefore the HD process as the first step of HDDR (hydrogenation-disproportionation-desorption-recombination) has to be carried out at a high hydrogen pressure for x {>=} 1. The hydrogen absorption behaviour of Sm{sub 2}Fe{sub 17-x}Ga{sub x} (x = 0, 0.5, 1 and 2) was investigated by means of hydrogen differential thermal analysis (HDTA) and high pressure differential scanning calorimetry (HPDSC) at hydrogen pressures up to 70 bar. A dependency of hydrogenation and disproportionation temperatures on hydrogen pressure and Ga content was found. The comparison with other substituents (M = Al and Si) instead of M = Ga showed an increased stability of Sm{sub 2}Fe{sub 17-x}M{sub x} compounds against disproportionation by hydrogen in the sequence Al, Ga and Si. The Curie temperatures of the interstitially hydrogenated Th{sub 2}Zn{sub 17}-type materials increase with the hydrogen pressure. In order to produce coercive and thermally stable Sm{sub 2}Fe{sub 15}Ga{sub 2}C{sub y} powder by means of the HDDR process, we recombined material disproportionated at different hydrogen pressures. Preliminary results of magnetic properties of this HDDR treated and gas-carburized Sm{sub 2}Fe{sub 15}Ga{sub 2}C{sub y} are discussed. (orig.)

CuIn{sub x}Ga{sub 1-x}Se{sub 2} thin films prepared by electron beam evaporation

Energy Technology Data Exchange (ETDEWEB)

Venkatachalam, M.; Kannan, M.D.; Jayakumar, S.; Balasundaraprabhu, R.; Nandakumar, A.K. [Thin Film Center, Department of Physics, PSG College of Technology (India); Muthukumarasamy, N. [Department of Physics, Coimbatore Institute of Technology (India)

2008-05-15

CuIn{sub x}Ga{sub 1-x}Se{sub 2} bulk compound of three different compositions x=0.75, 0.80 and 0.85 have been prepared using individual elements of copper, indium, gallium and selenium. Thin films of CuIn{sub x}Ga{sub 1-x}Se{sub 2} have been deposited using the prepared bulk by electron beam evaporation method. The structural studies carried on the deposited films revealed that films annealed at 400 C are crystalline in nature exhibiting chalcopyrite phase. The position of the (1 1 2) peak in the X-ray diffractogram corresponding to the chalcopyrite phase has been found to be dependent on the percentage of gallium in the films. The composition of the prepared bulk and thin films has been identified using energy dispersive X-ray analysis. The photoluminescence spectra of the CuIn{sub x}Ga{sub 1-x}Se{sub 2} films exhibited sharp luminescence peaks corresponding to the band gap of the material. (author)

Magnetostructural correlations in the antiferromagnetic Co2-x Cux(OH)AsO4 (x=0 and 0.3) phases

International Nuclear Information System (INIS)

Pedro, I. de; Rojo, J.M.; Pizarro, J.L.; Rodriguez Fernandez, J.; Arriortua, M.I.; Rojo, T.

2011-01-01

The Co 2-x Cu x (OH)AsO 4 (x=0 and 0.3) compounds have been synthesized under mild hydrothermal conditions and characterized by X-ray single-crystal diffraction and spectroscopic data. The hydroxi-arsenate phases crystallize in the Pnnm orthorhombic space group with Z=4 and the unit-cell parameters are a=8.277(2) A, b=8.559(2) A, c=6.039(1) A and a=8.316(1) A, b=8.523(2) A, c=6.047(1) A for x=0 and 0.3, respectively. The crystal structure consists of a three-dimensional framework in which M(1)O 5 -trigonal bipyramid dimers and M(2)O 6 -octahedral chains (M=Co and Cu) are present. Co 2 (OH)AsO 4 shows an anomalous three-dimensional antiferromagnetic ordering influenced by the magnetic field below 21 K within the presence of a ferromagnetic component below the ordering temperature. When Co 2+ is partially substituted by Cu 2+ ions, Co 1.7 Cu 0.3 (OH)AsO 4 , the ferromagnetic component observed in Co 2 (OH)AsO 4 disappears and the antiferromagnetic order is maintained in the entire temperature range. Heat capacity measurements show an unusual magnetic field dependence of the antiferromagnetic transitions. This λ-type anomaly associated to the three-dimensional antiferromagnetic ordering grows with the magnetic field and becomes better defined as observed in the non-substituted phase. These results are attributed to the presence of the unpaired electron in the dx 2 -y 2 orbital and the absence of overlap between neighbour ions. - Graphical abstract: Schematic drawing of the Co 2-x Cu x (OH)AsO 4 (x=0 and 0.3) crystal structure view along the |0 1 0| direction. Polyhedra are occupied by the M(II) ions (M=Co and Cu) and the AsO 4 groups are represented by tetrahedra. Open circles correspond to the oxygen atoms, and small circles show the hydrogen atoms. Highlights: → Synthesis of a new adamite-type compound, Co 1.7 Cu 0.3 (OH)AsO 4 . → Single crystal structure, spectroscopic characterization and magnetic properties. → Unusual dependence on the magnetic field for

Sterically crowded monomeric neutral bis(benzamidinato) compounds of aluminium, [PhC(NSiMe(3))(2)](2)AlX (X=Cl, H); X-ray crystal structure of [PhC(NSiMe(3))(2)]2AlH

NARCIS (Netherlands)

Duchateau, R; Meetsma, A; Teuben, JH

1996-01-01

AlCl3 reacts with [PhC(NSiMe(3))(2)]Li(OEt(2)) to afford the bis(N,N'-bis(trimethylsilyl)benzamidinato)aluminium chloro compound which, on treatment with KBEt(3)H, yields the structurally characterized monomeric hydride derivative, [PhC(NSiMe(3))(2)]2AlH, whose reactivity towards unsaturated

Study of the mixed ferrite Basub(x)Tisub(4-2x)Fesub(2x)Osub(8) (x=0.65) with hollandite structure by electrical, magnetic and Moessbauer effect measurements

International Nuclear Information System (INIS)

Abbas, Y.; Ahmed, M.A.

1982-01-01

Mixed ferrite Basub(x)Tisub(4-2x)Fesub(2x)Osub(8) with hollandite structure has been studies by electrical, magnetic and Moessbauer effect measurements. Electrical measurements show a semiconducting behaviour and a triclinic phase transition at about 455 K. Susceptibility data show that the compound is paramagnetic in the range 80-300 K and can be interpreted in terms of Curie-Weiss behaviour above about 200 K yielding the parameters usub(eff)5.95B.M. and Osub(p)-320 K. The susceptibility curve shows eveidence for an important ferromagnetic component due to the short range interactions preceeding the antiferromagnetic ordering and leads to the conclusion of the existance of spin canting magnetic ordering at Tsub(N)80 K. The values of the chemical shift 0.43mm/sec and quadrupole splitting 0.44mm/sec are typical of high spin Fesup(Fe 3+ ) in distorted octahedral coordination

ThSi_2 type ytterbium disilicide and its analogues YbT_xSi_2_-_x (T = Cr, Fe, Co)

International Nuclear Information System (INIS)

Peter, Sebastian C.; Kanatzidis, Mercouri G.

2012-01-01

YbSi_2 and the derivatives YbT_xSi_2_-_x (T = Cr, Fe, Co) crystallizing in the α-ThSi_2 structure type were obtained as single crystals from reactions run in liquid indium. All silicides were investigated by single-crystal X-ray diffraction, I4_1/amd space group and the lattice constants are: a = 3.9868(6) Aa and c = 13.541(3) Aa for YbSi_2, a = 4.0123(6) Aa and c = 13.542(3) Aa for YbCr_0_._2_7Si_1_._7_3, a = 4.0142(6) Aa and c = 13.830(3) Aa for YbCr_0_._7_1Si_1_._2_9, a = 4.0080(6) Aa and c = 13.751(3) Aa for YbFe_0_._3_4Si_1_._6_6, and a = 4.0036(6) Aa, c = 13.707(3) Aa for YbCo_0_._2_1Si_1_._7_9. YbSi_2 and YbT_xSi_2_-_x compounds are polar intermetallics with three-dimensional Si and M (T+Si) polyanion sub-networks, respectively, filled with ytterbium atoms. The degree of substitution of transition metal at the silicon site is signficant and leads to changes in the average bond lengths and bond angles substantially. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Hyperfine properties of La(V{sub 1−x}Fe{sub x})O{sub 3} compounds

Energy Technology Data Exchange (ETDEWEB)

Tupan, L. F. S.; Ivashita, F. F.; Barco, R. [Universidade Estadual de Maringá (Brazil); Hallouche, B. [Universidade de Santa Cruz do Sul (Brazil); Paesano, A., E-mail: paesano@wnet.com.br [Universidade Estadual de Maringá (Brazil)

2017-11-15

LaV{sub 1−x}Fe{sub x}O{sub 3} perovskites were synthesized in the vanadium-rich concentration range (i.e., x < 0.5) and characterized structurally and for the hyperfine properties of the iron nuclear probe. The aim of this investigation was to better understand the physical transformations that take place in the undoped compound (LaVO{sub 3}) at low temperatures. For that, X-ray diffraction analysis and, more extensively, {sup 57}Fe Mössbauer spectroscopy were applied. The results revealed that the LaV{sub 1}-xFexO{sub 3} vanadium-rich perovskites are orthorhombic at RT, and their lattice parameters decrease with increasing vanadium concentration. Lowering the temperature, the system becomes magnetic, with the iron moment freezing progressively. The presence of two magnetic subspectral components obtained at the lowest measurement temperatures suggests that the vanadium-rich samples, including LaVO{sub 3}, undergo a phase transition from an orthorhombic to a monoclinic structure at low temperatures.

X1X1X2X2/X1X2Y sex chromosome systems in the Neotropical Gymnotiformes electric fish of the genus Brachyhypopomus

Directory of Open Access Journals (Sweden)

Adauto Lima Cardoso

2015-06-01

Full Text Available Several types of sex chromosome systems have been recorded among Gymnotiformes, including male and female heterogamety, simple and multiple sex chromosomes, and different mechanisms of origin and evolution. The X1X1X2X2/X1X2Y systems identified in three species of this order are considered homoplasic for the group. In the genus Brachyhypopomus, only B. gauderio presented this type of system. Herein we describe the karyotypes of Brachyhypopomus pinnicaudatus and B. n. sp. FLAV, which have an X1X1X2X2/X1X2Y sex chromosome system that evolved via fusion between an autosome and the Y chromosome. The morphology of the chromosomes and the meiotic pairing suggest that the sex chromosomes of B. gauderio and B. pinnicaudatus have a common origin, whereas in B . n. sp. FLAV the sex chromosome system evolved independently. However, we cannot discard the possibility of common origin followed by distinct processes of differentiation. The identification of two new karyotypes with an X1X1X2X2/X1X2Y sex chromosome system in Gymnotiformes makes it the most common among the karyotyped species of the group. Comparisons of these karyotypes and the evolutionary history of the taxa indicate independent origins for their sex chromosomes systems. The recurrent emergence of the X1X1X2X2/X1X2Y system may represent sex chromosomes turnover events in Gymnotiformes.