WorldWideScience

Sample records for isee-3 magnetic field

  1. On Ising - Onsager problem in external magnetic field

    International Nuclear Information System (INIS)

    Kochmanski, M.S.

    1997-01-01

    In this paper a new approach to solving the Ising - Onsager problem in external magnetic field is investigated. The expression for free energy on one Ising spin in external field both for the two dimensional and three dimensional Ising model with interaction of the nearest neighbors are derived. The representations of free energy being expressed by multidimensional integrals of Gauss type with the appropriate dimensionality are shown. Possibility of calculating the integrals and the critical indices on the base of the derived representations for free energy is investigated

  2. Interplanetary magnetic field orientations associated with bidirectional electron heat fluxes detected at ISEE 3

    International Nuclear Information System (INIS)

    Stansberry, J.A.; Gosling, J.T.; Thomsen, M.F.; Bame, S.J.; Smith, E.J.

    1988-01-01

    A statistical survey of interplanetary magnetic field orientations associated with bidirectional electron heat fluxes observed at ISEE 3 in orbit about the Sunward Lagrange point indicates that magnetic connection of the spacecraft to the Earth's bow shock was frequently the source of the bidirectionality. When the interplanetary magnetic field was oriented within 5 0 of the Earth-spacecraft line, backstreaming electrons from the bow shock were clearly observed approximately 18% of the time, and connections apparently occurred for angles as large as ∼30 0 --35 0 . copyright American Geophysical Union 1988

  3. Factors controlling degree of correlation between ISEE 1 and ISEE 3 interplanetary magnetic field measurements

    International Nuclear Information System (INIS)

    Crooker, N.U.; Siscoe, G.L.; Russell, C.T.; Smith, E.J.

    1982-01-01

    The degree of correlation between ISEE 1 and ISEE 3 IMF measurements is highly variable. Approximately 200 two-hour periods when the correlation was good and 200 more when the correlation was poor are used to determine the relative control of several factors over the degree of correlation. Both IMF variance and spacecraft separation distance in the plane perpendicular to the earth-sun line exert substantial control. Good correlations are associated with high variance and distances less than 90 R/sub E/. During periods of highest variance, good correlations occur at distances beyond 90 R/sub E/ up to 120 R/sub E/, the maximum range of ISEE 1-ISEE 3 separation. Thus it appears that the scale size of magnetic features is larger when the variance is high. Abrupt changes in the correlation coefficient from poor to good or good to poor in adjacent two-hour intervals appear to be governed by the sense of change of IMF variance: changes in correlation from poor to good correspond to increasing variance and vice versa. The IMF orientation also exerts control over the degree of correlation. During periods of low variance, good correlations are most likely to occur when the distance between ISEE 1 and ISEE 3 perpendicular to the IMF is less than 20 R/sub E/. This scale size expands to approx.50 R/sub E/ during periods of high variance. Solar wind speed shows little control over the degree of correlation in the speed range 300--500 km/s

  4. Dynamic compensation temperatures in a mixed spin-1 and spin-3/2 Ising system under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, Mustafa, E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Kantar, Ersin [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)

    2010-09-15

    We study the existence of dynamic compensation temperatures in the mixed spin-1 and spin-3/2 Ising ferrimagnetic system Hamiltonian with bilinear and crystal-field interactions in the presence of a time-dependent oscillating external magnetic field on a hexagonal lattice. We employ the Glauber transitions rates to construct the mean-field dynamic equations. We investigate the time dependence of an average sublattice magnetizations, the thermal behavior of the dynamic sublattice magnetizations and the total magnetization. From these studies, we find the phases in the system, and characterize the nature (continuous or discontinuous) of transitions as well as obtain the dynamic phase transition (DPT) points and the dynamic compensation temperatures. We also present dynamic phase diagrams, including the compensation temperatures, in the five different planes. A comparison is made with the results of the available mixed spin Ising systems.

  5. Dynamic compensation temperatures in a mixed spin-1 and spin-3/2 Ising system under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Kantar, Ersin

    2010-01-01

    We study the existence of dynamic compensation temperatures in the mixed spin-1 and spin-3/2 Ising ferrimagnetic system Hamiltonian with bilinear and crystal-field interactions in the presence of a time-dependent oscillating external magnetic field on a hexagonal lattice. We employ the Glauber transitions rates to construct the mean-field dynamic equations. We investigate the time dependence of an average sublattice magnetizations, the thermal behavior of the dynamic sublattice magnetizations and the total magnetization. From these studies, we find the phases in the system, and characterize the nature (continuous or discontinuous) of transitions as well as obtain the dynamic phase transition (DPT) points and the dynamic compensation temperatures. We also present dynamic phase diagrams, including the compensation temperatures, in the five different planes. A comparison is made with the results of the available mixed spin Ising systems.

  6. Magnetic properties of a mixed spin-3/2 and spin-2 Ising ferrimagnetic system within the effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Kantar, Ersin; Keskin, Mustafa

    2010-01-01

    The magnetic properties of the ferrimagnetic mixed spin-3/2 and spin-2 Ising model with a crystal field in a longitudinal magnetic field on a honeycomb (δ = 3) and a square lattice (δ = 4) are studied by using the effective-field theory with correlations. The ground-state phase diagram of the model is obtained in a longitudinal magnetic field (h) for a single-ion potential or a crystal-field interaction (Δ) plane. We also investigate the thermal variations of the sublattice magnetization, and present the phase diagrams in the (Δ/|J|, k B T/|J|) plane. The susceptibility, internal energy, and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the applied longitudinal magnetic field. Moreover, the system undergoes first- and second-order phase transitions; hence, the system has a tricritical point. The system also exhibits reentrant behaviors.

  7. Magnetic properties of a mixed spin-3/2 and spin-2 Ising ferrimagnetic system within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Nevsehir University, Nevsehir (Turkmenistan); Kantar, Ersin; Keskin, Mustafa [Erciyes University, Kayseri (Turkmenistan)

    2010-06-15

    The magnetic properties of the ferrimagnetic mixed spin-3/2 and spin-2 Ising model with a crystal field in a longitudinal magnetic field on a honeycomb ({delta} = 3) and a square lattice ({delta} = 4) are studied by using the effective-field theory with correlations. The ground-state phase diagram of the model is obtained in a longitudinal magnetic field (h) for a single-ion potential or a crystal-field interaction ({Delta}) plane. We also investigate the thermal variations of the sublattice magnetization, and present the phase diagrams in the ({Delta}/|J|, k{sub B}T/|J|) plane. The susceptibility, internal energy, and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the applied longitudinal magnetic field. Moreover, the system undergoes first- and second-order phase transitions; hence, the system has a tricritical point. The system also exhibits reentrant behaviors.

  8. Average configuration of the distant (less than 220-earth-radii) magnetotail - Initial ISEE-3 magnetic field results

    Science.gov (United States)

    Slavin, J. A.; Tsurutani, B. T.; Smith, E. J.; Jones, D. E.; Sibeck, D. G.

    1983-01-01

    Magnetic field measurements from the first two passes of the ISEE-3 GEOTAIL Mission have been used to study the structure of the trans-lunar tail. Good agreement was found between the ISEE-3 magnetopause crossings and the Explorer 33, 35 model of Howe and Binsack (1972). Neutral sheet location was well ordered by the hinged current sheet models based upon near earth measurements. Between X = -20 and -120 earth radii the radius of the tail increases by about 30 percent while the lobe field strength decreases by approximately 60 percent. Beyond X = -100 to -1200 earth radii the tail diameter and lobe field magnitude become nearly constant at terminal values of approximately 60 earth radii and 9 nT, respectively. The distance at which the tail was observed to cease flaring, 100-120 earth radii, is in close agreement with the predictions of the analytic tail model of Coroniti and Kennel (1972). Overall, the findings of this study suggest that the magnetotail retains much of its near earth structure out to X = -220 earth radii.

  9. Quantum Ising chains with boundary fields

    International Nuclear Information System (INIS)

    Campostrini, Massimo; Vicari, Ettore; Pelissetto, Andrea

    2015-01-01

    We present a detailed study of the finite one-dimensional quantum Ising chain in a transverse field in the presence of boundary magnetic fields coupled with the order-parameter spin operator. We consider two magnetic fields located at the boundaries of the chain that have the same strength and that are aligned in the same or in the opposite direction. We derive analytic expressions for the gap in all phases for large values of the chain length L, as a function of the boundary field strength. We also investigate the behaviour of the chain in the quantum ferromagnetic phase for oppositely aligned fields, focusing on the magnet-to-kink transition that occurs at a finite value of the magnetic field strength. At this transition we compute analytically the finite-size crossover functions for the gap, the magnetisation profile, the two-point correlation function, and the density of fermionic modes. As the magnet-to-kink transition is equivalent to the wetting transition in two-dimensional classical Ising models, our results provide new analytic predictions for the finite-size behaviour of Ising systems in a strip geometry at this transition. (paper)

  10. Quantum Criticality of an Ising-like Spin-1 /2 Antiferromagnetic Chain in a Transverse Magnetic Field

    Science.gov (United States)

    Wang, Zhe; Lorenz, T.; Gorbunov, D. I.; Cong, P. T.; Kohama, Y.; Niesen, S.; Breunig, O.; Engelmayer, J.; Herman, A.; Wu, Jianda; Kindo, K.; Wosnitza, J.; Zherlitsyn, S.; Loidl, A.

    2018-05-01

    We report on magnetization, sound-velocity, and magnetocaloric-effect measurements of the Ising-like spin-1 /2 antiferromagnetic chain system BaCo2V2O8 as a function of temperature down to 1.3 K and an applied transverse magnetic field up to 60 T. While across the Néel temperature of TN˜5 K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature the field-dependent measurements reveal a sharp softening of sound velocity v (B ) and a clear minimum of temperature T (B ) at B⊥c,3 D=21.4 T , indicating the suppression of the antiferromagnetic order. At higher fields, the T (B ) curve shows a broad minimum at B⊥c=40 T , accompanied by a broad minimum in the sound velocity and a saturationlike magnetization. These features signal a quantum phase transition, which is further characterized by the divergent behavior of the Grüneisen parameter ΓB∝(B -B⊥c)-1. By contrast, around the critical field, the Grüneisen parameter converges as temperature decreases, pointing to a quantum critical point of the one-dimensional transverse-field Ising model.

  11. Nonequilibrium dynamics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic system with a time dependent oscillating magnetic field source

    Energy Technology Data Exchange (ETDEWEB)

    Vatansever, Erol [Dokuz Eylül University, Graduate School of Natural and Applied Sciences, TR-35160 Izmir (Turkey); Polat, Hamza, E-mail: hamza.polat@deu.edu.tr [Department of Physics, Dokuz Eylül University, TR-35160 Izmir (Turkey)

    2015-10-15

    Nonequilibrium phase transition properties of a mixed Ising ferrimagnetic model consisting of spin-1/2 and spin-3/2 on a square lattice under the existence of a time dependent oscillating magnetic field have been investigated by making use of Monte Carlo simulations with a single-spin flip Metropolis algorithm. A complete picture of dynamic phase boundary and magnetization profiles have been illustrated and the conditions of a dynamic compensation behavior have been discussed in detail. According to our simulation results, the considered system does not point out a dynamic compensation behavior, when it only includes the nearest-neighbor interaction, single-ion anisotropy and an oscillating magnetic field source. As the next-nearest-neighbor interaction between the spins-1/2 takes into account and exceeds a characteristic value which sensitively depends upon values of single-ion anisotropy and only of amplitude of external magnetic field, a dynamic compensation behavior occurs in the system. Finally, it is reported that it has not been found any evidence of dynamically first-order phase transition between dynamically ordered and disordered phases, which conflicts with the recently published molecular field investigation, for a wide range of selected system parameters. - Highlights: • Spin-1/2 and spin-3/2 Ising ferrimagnetic model is examined. • The system is exposed to time-dependent magnetic field. • Kinetic Monte Carlo simulation technique is used. • Any evidence of first-order phase transition has not been found.

  12. A mean field approach to the Ising chain in a transverse magnetic field

    Science.gov (United States)

    Osácar, C.; Pacheco, A. F.

    2017-07-01

    We evaluate a mean field method to describe the properties of the ground state of the Ising chain in a transverse magnetic field. Specifically, a method of the Bethe-Peierls type is used by solving spin blocks with a self-consistency condition at the borders. The computations include the critical point for the phase transition, exponent of magnetisation and energy density. All results are obtained using basic quantum mechanics at an undergraduate level. The advantages and the limitations of the approach are emphasised.

  13. Properties of a random bond Ising chain in a magnetic field

    International Nuclear Information System (INIS)

    Landau, D.P.; Blume, M.

    1976-01-01

    The Ising chain with random bonds in a magnetic field H = -Σ/sub i/J/sub i/sigma/sub i/sigma/sub i + l/ - hΣ/sub i/sigma/sub i/, where J/sub i/ = +- 1 at random, and Σ/sub i/J/sub i/ = 0, represents a model of a magnetic glass, or of heteropolymer melting. Calculations of the thermodynamic properties of the chain as a function of field strength and temperature have been performed by Monte Carlo techniques. These results are compared with perturbation calculations for small and large values of h/T. The Monte Carlo results show, in agreement with the perturbation calculations, that the field-induced magnetization is generally smaller for the random bond model than for a chain of noninteracting spins. As T → 0 the magnetization approaches the result for noninteracting spins

  14. Effects of the randomly distributed magnetic field on the phase diagrams of the Ising Nanowire II: Continuous distributions

    International Nuclear Information System (INIS)

    Akıncı, Ümit

    2012-01-01

    The effect of the random magnetic field distribution on the phase diagrams and ground state magnetizations of the Ising nanowire has been investigated with effective field theory with correlations. Gaussian distribution has been chosen as a random magnetic field distribution. The variation of the phase diagrams with that distribution parameters has been obtained and some interesting results have been found such as disappearance of the reentrant behavior and first order transitions which appear in the case of discrete distributions. Also for single and double Gaussian distributions, ground state magnetizations for different distribution parameters have been determined which can be regarded as separate partially ordered phases of the system. - Highlights: ► We give the phase diagrams of the Ising nanowire under the continuous randomly distributed magnetic field. ► Ground state magnetization values obtained. ► Different partially ordered phases observed.

  15. Analytical and computational study of magnetization switching in kinetic Ising systems with demagnetizing fields

    DEFF Research Database (Denmark)

    Richards, H.L.; Rikvold, P.A.

    1996-01-01

    particularly promising as materials for high-density magnetic recording media. In this paper we use analytic arguments and Monte Carlo simulations to quantitatively study the effects of the demagnetizing field on the dynamics of magnetization switching in two-dimensional, single-domain, kinetic Ising systems....... For systems in the weak-field ''stochastic region,'' where magnetization switching is on average effected by the nucleation and growth of a single droplet, the simulation results can be explained by a simple model in which the free energy is a function only of magnetization. In the intermediate......-field ''multidroplet region,'' a generalization of Avrami's law involving a magnetization-dependent effective magnetic field gives good agreement with the simulations. The effects of the demagnetizing field do not qualitatively change the droplet-theoretical picture of magnetization switching in highly anisotropic...

  16. Magnetic properties of mixed spin (1, 3/2) Ising nanoparticles with core–shell structure

    International Nuclear Information System (INIS)

    Deviren, Bayram; Şener, Yunus

    2015-01-01

    The magnetic properties of mixed spin-1 and spin-3/2 Ising nanoparticles with core/shell structure are studied by using the effective-field theory with correlations. We investigate the thermal variations of the core, shell and total magnetizations and the Q-, R-, P-, S-, N- and L-types of compensation behavior in Néel classification nomenclature exists in the system. The effects of the crystal-field, core and shell interactions and interface coupling, on the phase diagrams are investigated in detail and the obtained phase diagrams are presented in three different planes. The system exhibits both second- and first-order phase transitions besides tricritical point, double critical end point, triple point and critical end point depending on the appropriate values of the interaction parameters. The system strongly affected by the surface situations and some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. - Highlights: • Magnetic properties of mixed spin (1, 3/2) Ising nanoparticles are investigated. • The system exhibits tricritical, double critical end, triple, critical end points. • Q-, R-, P-, S-, N- and L-types of compensation behavior are found. • Some characteristic phenomena are found depending on the interaction parameters. • Effects of crystal-field and bilinear interactions on the system are examined

  17. Magnetic properties of mixed spin (1, 3/2) Ising nanoparticles with core–shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir Hacı Bektaş Veli University, 50300 Nevşehir (Turkey); Şener, Yunus [Institute of Science, Department of Physics, Nevsehir Hacı Bektaş Veli University, 50300 Nevşehir (Turkey)

    2015-07-15

    The magnetic properties of mixed spin-1 and spin-3/2 Ising nanoparticles with core/shell structure are studied by using the effective-field theory with correlations. We investigate the thermal variations of the core, shell and total magnetizations and the Q-, R-, P-, S-, N- and L-types of compensation behavior in Néel classification nomenclature exists in the system. The effects of the crystal-field, core and shell interactions and interface coupling, on the phase diagrams are investigated in detail and the obtained phase diagrams are presented in three different planes. The system exhibits both second- and first-order phase transitions besides tricritical point, double critical end point, triple point and critical end point depending on the appropriate values of the interaction parameters. The system strongly affected by the surface situations and some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. - Highlights: • Magnetic properties of mixed spin (1, 3/2) Ising nanoparticles are investigated. • The system exhibits tricritical, double critical end, triple, critical end points. • Q-, R-, P-, S-, N- and L-types of compensation behavior are found. • Some characteristic phenomena are found depending on the interaction parameters. • Effects of crystal-field and bilinear interactions on the system are examined.

  18. Effective field study of ising model on a double perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Ngantso, G. Dimitri; El Amraoui, Y. [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Benyoussef, A. [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Center of Materials and Nanomaterials, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); El Kenz, A., E-mail: elkenz@fsr.ac.ma [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco)

    2017-02-01

    By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one. - Highlights: • Magnetic properties of double perovskite Structure have been studied. • Compensation temperature has been observed below the critical temperature. • Hysteresis behaviors have been studied.

  19. Effective field study of ising model on a double perovskite structure

    International Nuclear Information System (INIS)

    Ngantso, G. Dimitri; El Amraoui, Y.; Benyoussef, A.; El Kenz, A.

    2017-01-01

    By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one. - Highlights: • Magnetic properties of double perovskite Structure have been studied. • Compensation temperature has been observed below the critical temperature. • Hysteresis behaviors have been studied.

  20. Emergent Ising degrees of freedom above a double-stripe magnetic ground state

    Science.gov (United States)

    Zhang, Guanghua; Flint, Rebecca

    2017-12-01

    Double-stripe magnetism [Q =(π /2 ,π /2 )] has been proposed as the magnetic ground state for both the iron-telluride and BaTi2Sb2O families of superconductors. Double-stripe order is captured within a J1-J2-J3 Heisenberg model in the regime J3≫J2≫J1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector (π ,π ) . Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one.

  1. Mean-Field Studies of a Mixed Spin-3/2 and Spin-2 and a Mixed Spin-3/2 and Spin-5/2 Ising System with Different Anisotropies

    International Nuclear Information System (INIS)

    Wei Guozhu; Miao Hailing

    2009-01-01

    The magnetic properties of a mixed spin-3/2 and spin-2 and a mixed spin-3/2 and spin-5/2 Ising ferromagnetic system with different anisotropies are studied by means of mean-field theory (MFT). The dependence of the phase diagram on single-ion anisotropy strengths is studied too. In the mixed spin-3/2 and spin-2 Ising model, besides the second-order phase transition, the first order-disorder phase transition and the tricritical line are found. In the mixed spin-3/2 and spin-5/2 Ising model, there is no first-order transition and tricritical line. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  2. Thermal and magnetic properties of ternary mixed Ising nanoparticles with core–shell structure: Effective-field theory approach

    International Nuclear Information System (INIS)

    Kantar, Ersin; Keskin, Mustafa

    2014-01-01

    We propose a ternary Ising spins (1/2, 1, 3/2) model to investigate the thermal and magnetic properties of magnetic nanoparticles with core–shell structure within the framework of the effective-field theory with correlations. The center site of the core is occupied by σ=±1/2 spin, while those surrounding the center site are occupied by S=±1, 0 spins and the shell sites are occupied by m=±1/2,±3/2 spins. Thermal behaviors of the core and shell magnetizations, susceptibilities and internal energies as well as total magnetization are examined. In order to confirm the stability of the solutions we also investigate the free energy of the system. According to the values of Hamiltonian parameters, the system undergoes first- and second-order phase transitions. Phase diagrams are calculated and discussed in detail. We find that the system exhibits a tricritical point, reentrant and five different type (Q, P, R, S and W) of compensation behaviors that strongly depend on interaction parameters. The results are in good agreement with some experimental and theoretical results. - Highlights: • Thermal and magnetic properties of ternary Ising nanoparticles are studied. • Phase diagrams within the EFT with correlations are calculated and discussed. • The effects of the exchange interactions and crystal field have been studied. • Reentrant phenomena and compensation behaviors have been found

  3. Thermal and magnetic properties of ternary mixed Ising nanoparticles with core–shell structure: Effective-field theory approach

    Energy Technology Data Exchange (ETDEWEB)

    Kantar, Ersin [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2014-01-15

    We propose a ternary Ising spins (1/2, 1, 3/2) model to investigate the thermal and magnetic properties of magnetic nanoparticles with core–shell structure within the framework of the effective-field theory with correlations. The center site of the core is occupied by σ=±1/2 spin, while those surrounding the center site are occupied by S=±1, 0 spins and the shell sites are occupied by m=±1/2,±3/2 spins. Thermal behaviors of the core and shell magnetizations, susceptibilities and internal energies as well as total magnetization are examined. In order to confirm the stability of the solutions we also investigate the free energy of the system. According to the values of Hamiltonian parameters, the system undergoes first- and second-order phase transitions. Phase diagrams are calculated and discussed in detail. We find that the system exhibits a tricritical point, reentrant and five different type (Q, P, R, S and W) of compensation behaviors that strongly depend on interaction parameters. The results are in good agreement with some experimental and theoretical results. - Highlights: • Thermal and magnetic properties of ternary Ising nanoparticles are studied. • Phase diagrams within the EFT with correlations are calculated and discussed. • The effects of the exchange interactions and crystal field have been studied. • Reentrant phenomena and compensation behaviors have been found.

  4. Electric fields in the magnetosphere - the evidence from ISEE, S3-3, GEOS and Viking

    International Nuclear Information System (INIS)

    Faelthammar, C.G.

    1988-08-01

    Electric field measurements on the satellites S3-3, GEOS-1, GEOS-2, ISEE-1 and Viking have extended the empirical knowledge of electric fields in space so as to include the outer regions of the magnetosphere. While the measurements confirm some of the theoretically expected properties of the electric fields, they also reveal unexpected features and a high degree of complexity and variability. The existence of a magnetospheric dawn-to-dusk electric field, as expected on the basis of extrapolation from low altitude measurements, is confirmed in an average sense. However, the actual field exhibits large spatial and temporal variations, including strong fields of inductive origin. At the magnetopause the average (dawn to dusk directed) tangential electric field component is typically obscured by irregular fluctuations of large amplitude. The magnetic-field aligned component of the electric field, which is of particular importance for ionosphere-magnetosphere coupling and for auroral acceleration is even now very difficult to measure directly. However, the data from electric field measurements provide further support for the conclusion, based on a variety of evidence, that a non-vanishing magnetic-field aligned electric field exists in the auroral acceleration region. (93 refs.) (author)

  5. Comparable studies of magnetic properties of Ising spins-5/2 and 3/2 systems on decorated square and triangular lattices

    International Nuclear Information System (INIS)

    Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.

    2016-01-01

    In this work, we have studied and compared the magnetic properties of Ising spins-5/2 and 3/2 systems on decorated square and triangular lattices using the Monte Carlo simulations. The transition temperature of the two-dimensional decorated square and triangular lattices has been obtained. The effect of the exchange interactions and crystal field on the magnetization is investigated. The magnetic coercive field and saturation magnetization of the two-dimensional decorated square and triangular lattices have been obtained.

  6. Comparable studies of magnetic properties of Ising spins-5/2 and 3/2 systems on decorated square and triangular lattices

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); Jabar, A. [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); Benyoussef, A. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2016-07-15

    In this work, we have studied and compared the magnetic properties of Ising spins-5/2 and 3/2 systems on decorated square and triangular lattices using the Monte Carlo simulations. The transition temperature of the two-dimensional decorated square and triangular lattices has been obtained. The effect of the exchange interactions and crystal field on the magnetization is investigated. The magnetic coercive field and saturation magnetization of the two-dimensional decorated square and triangular lattices have been obtained.

  7. Dynamic phase transitions in a cylindrical Ising nanowire under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Deviren, Bayram; Kantar, Ersin; Keskin, Mustafa

    2012-01-01

    The dynamic phase transitions in a cylindrical Ising nanowire system under a time-dependent oscillating external magnetic field for both ferromagnetic and antiferromagnetic interactions are investigated within the effective-field theory with correlations and the Glauber-type stochastic dynamics approach. The effective-field dynamic equations for the average longitudinal magnetizations on the surface shell and core are derived by employing the Glauber transition rates. Temperature dependence of the dynamic magnetizations, the dynamic total magnetization, the hysteresis loop areas and the dynamic correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, five different types of compensation behaviors in the Néel classification nomenclature exist in the system. The system also exhibits a reentrant behavior. - Highlights: ► The dynamic aspects of a cylindrical Ising nanowire are investigated in detail. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► We studied both the FM and AFM interactions within the EFT with correlations. ► Some characteristic phenomena are found depending on the interaction parameters. ► We obtained five different types of compensation behaviors and reentrant behavior.

  8. Dynamic phase transitions in a cylindrical Ising nanowire under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Kantar, Ersin [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-07-15

    The dynamic phase transitions in a cylindrical Ising nanowire system under a time-dependent oscillating external magnetic field for both ferromagnetic and antiferromagnetic interactions are investigated within the effective-field theory with correlations and the Glauber-type stochastic dynamics approach. The effective-field dynamic equations for the average longitudinal magnetizations on the surface shell and core are derived by employing the Glauber transition rates. Temperature dependence of the dynamic magnetizations, the dynamic total magnetization, the hysteresis loop areas and the dynamic correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, five different types of compensation behaviors in the Neel classification nomenclature exist in the system. The system also exhibits a reentrant behavior. - Highlights: Black-Right-Pointing-Pointer The dynamic aspects of a cylindrical Ising nanowire are investigated in detail. Black-Right-Pointing-Pointer The dynamic magnetizations, hysteresis loop areas and correlations are calculated. Black-Right-Pointing-Pointer We studied both the FM and AFM interactions within the EFT with correlations. Black-Right-Pointing-Pointer Some characteristic phenomena are found depending on the interaction parameters. Black-Right-Pointing-Pointer We obtained five different types of compensation behaviors and reentrant behavior.

  9. Dynamic hysteresis behaviors for the two-dimensional mixed spin (2, 5/2) ferrimagnetic Ising model in an oscillating magnetic field

    Science.gov (United States)

    Ertaş, Mehmet

    2015-09-01

    Keskin and Ertaş (2009) presented a study of the magnetic properties of a mixed spin (2, 5/2) ferrimagnetic Ising model within an oscillating magnetic field. They employed dynamic mean-field calculations to find the dynamic phase transition temperatures, the dynamic compensation points of the model and to present the dynamic phase diagrams. In this work, we extend the study and investigate the dynamic hysteresis behaviors for the two-dimensional (2D) mixed spin (2, 5/2) ferrimagnetic Ising model on a hexagonal lattice in an oscillating magnetic field within the framework of dynamic mean-field calculations. The dynamic hysteresis curves are obtained for both the ferromagnetic and antiferromagnetic interactions and the effects of the Hamiltonian parameters on the dynamic hysteresis behaviors are discussed in detail. The thermal behaviors of the coercivity and remanent magnetizations are also investigated. The results are compared with some theoretical and experimental works and a qualitatively good agreement is found. Finally, the dynamic phase diagrams depending on the frequency of an oscillating magnetic field in the plane of the reduced temperature versus magnetic field amplitude is examined and it is found that the dynamic phase diagrams display richer dynamic critical behavior for higher values of frequency than for lower values.

  10. Magnetic and thermodynamic properties of Ising model with borophene structure in a longitudinal magnetic field

    Science.gov (United States)

    Shi, Kaile; Jiang, Wei; Guo, Anbang; Wang, Kai; Wu, Chuang

    2018-06-01

    The magnetic and thermodynamic properties of borophene structure have been studied for the first time by Monte Carlo simulation. Two-dimensional borophene structure consisting of seven hexagonal B36 units is described by Ising model. Each B36 basic unit includes three benzene-like with spin-3/2. The general formula for the borophene structure is given. The numerical results of the magnetization, the magnetic susceptibility, the internal energy and the specific heat are studied with various parameters. The possibility to test the predicted magnetism in experiment are illustrated, for instance, the maximum on the magnetization curve. The multiple hysteresis loops and the magnetization plateaus are sensitive to the ferromagnetic or ferrimagnetic exchange coupling in borophene structure. The results show the borophene structure could have applications in spintronics, which deserves further studies in experiments.

  11. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2010-07-12

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  12. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Keskin, Mustafa

    2010-01-01

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  13. Thermal behavior of dynamic magnetizations, hysteresis loop areas and correlations of a cylindrical Ising nanotube in an oscillating magnetic field within the effective-field theory and the Glauber-type stochastic dynamics approach

    International Nuclear Information System (INIS)

    Deviren, Bayram; Keskin, Mustafa

    2012-01-01

    The dynamical aspects of a cylindrical Ising nanotube in the presence of a time-varying magnetic field are investigated within the effective-field theory with correlations and Glauber-type stochastic approach. Temperature dependence of the dynamic magnetizations, dynamic total magnetization, hysteresis loop areas and correlations are investigated in order to characterize the nature of dynamic transitions as well as to obtain the dynamic phase transition temperatures and compensation behaviors. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and core, i.e., five different types of compensation behaviors in the Néel classification nomenclature exist in the system. -- Highlights: ► Kinetic cylindrical Ising nanotube is investigated using the effective-field theory. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► The effects of the exchange interactions have been studied in detail. ► Five different types of compensation behaviors have been found. ► Some characteristic phenomena are found depending on ratio of physical parameters.

  14. Thermal behavior of dynamic magnetizations, hysteresis loop areas and correlations of a cylindrical Ising nanotube in an oscillating magnetic field within the effective-field theory and the Glauber-type stochastic dynamics approach

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-02-20

    The dynamical aspects of a cylindrical Ising nanotube in the presence of a time-varying magnetic field are investigated within the effective-field theory with correlations and Glauber-type stochastic approach. Temperature dependence of the dynamic magnetizations, dynamic total magnetization, hysteresis loop areas and correlations are investigated in order to characterize the nature of dynamic transitions as well as to obtain the dynamic phase transition temperatures and compensation behaviors. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and core, i.e., five different types of compensation behaviors in the Néel classification nomenclature exist in the system. -- Highlights: ► Kinetic cylindrical Ising nanotube is investigated using the effective-field theory. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► The effects of the exchange interactions have been studied in detail. ► Five different types of compensation behaviors have been found. ► Some characteristic phenomena are found depending on ratio of physical parameters.

  15. Inverse freezing in the Hopfield fermionic Ising spin glass with a transverse magnetic field

    International Nuclear Information System (INIS)

    Morais, C.V.; Zimmer, F.M.; Magalhaes, S.G.

    2011-01-01

    The Hopfield fermionic Ising spin glass (HFISG) model in the presence of a magnetic transverse field Γ is used to study the inverse freezing transition. The mean field solution of this model allows introducing a parameter a that controls the frustration level. Particularly, in the present fermionic formalism, the chemical potential μ and the Γ provide a magnetic dilution and quantum spin flip mechanism, respectively. Within the one step replica symmetry solution and the static approximation, the results show that the reentrant transition between the spin glass and the paramagnetic phases, which is related to the inverse freezing for a certain range of μ, is gradually suppressed when the level of frustration a is decreased. Nevertheless, the quantum fluctuations caused by Γ can destroy this inverse freezing for any value of a.

  16. Dynamic phase transition properties for the mixed spin-(1/2, 1) Ising model in an oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ertaş, Mehmet, E-mail: mehmetertas@erciyes.edu.tr; Keskin, Mustafa

    2015-08-15

    Herein we study the dynamic phase transition properties for the mixed spin-(1/2, 1) Ising model on a square lattice under a time-dependent magnetic field by means of the effective-field theory (EFT) with correlations based on Glauber dynamics. We present the dynamic phase diagrams in the reduced magnetic field amplitude and reduced temperature plane and find that the phase diagrams exhibit dynamic tricitical behavior, multicritical and zero-temperature critical points as well as reentrant behavior. We also investigate the influence of frequency (ω) and observe that for small values of ω the mixed phase disappears, but for high values it appears and the system displays reentrant behavior as well as a critical end point. - Highlights: • Dynamic behaviors of a ferrimagnetic mixed spin (1/2, 1) Ising system are studied. • We examined the effects of the Hamiltonian parameters on the dynamic behaviors. • The phase diagrams are obtained in (T-h) plane. • The dynamic phase diagrams exhibit the dynamic tricritical and reentrant behaviors.

  17. Dynamic phase transition properties for the mixed spin-(1/2, 1) Ising model in an oscillating magnetic field

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Keskin, Mustafa

    2015-01-01

    Herein we study the dynamic phase transition properties for the mixed spin-(1/2, 1) Ising model on a square lattice under a time-dependent magnetic field by means of the effective-field theory (EFT) with correlations based on Glauber dynamics. We present the dynamic phase diagrams in the reduced magnetic field amplitude and reduced temperature plane and find that the phase diagrams exhibit dynamic tricitical behavior, multicritical and zero-temperature critical points as well as reentrant behavior. We also investigate the influence of frequency (ω) and observe that for small values of ω the mixed phase disappears, but for high values it appears and the system displays reentrant behavior as well as a critical end point. - Highlights: • Dynamic behaviors of a ferrimagnetic mixed spin (1/2, 1) Ising system are studied. • We examined the effects of the Hamiltonian parameters on the dynamic behaviors. • The phase diagrams are obtained in (T-h) plane. • The dynamic phase diagrams exhibit the dynamic tricritical and reentrant behaviors

  18. Effective-field treatment of an anisotropic Ising ferromagnet: thermodynamical properties

    International Nuclear Information System (INIS)

    Sarmento, E.F.; Honmura, R.; Tsallis, C.

    1982-01-01

    The anisotropic square lattice spin -1/2 Ising ferromagnet is discussed. Through this system it is illustrated how all relevant thermodynamical quantities (phase diagram, magnetization, short range order parameter, specific heat and susceptibility) can be approximatively calculated within an effective-field unified procedure (which substantially improves the Mean Field Approximation). Two slightly different approximations for the susceptibility (whose exact computation is still lacking) are presented. The (square lattice) - (linear chain) crossover is exhibited. The present (mathematically simple) procedures could be useful in the study of complex Ising problems. (Author) [pt

  19. Dynamic Phase Transitions In The Spin-2 Ising System Under An Oscillating Magnetic Field Within The Effective-Field Theory

    International Nuclear Information System (INIS)

    Ertas, Mehmet; Keskin, Mustafa; Deviren, Bayram

    2010-01-01

    The dynamic phase transitions are studied in the spin-2 Ising model under a time-dependent oscillating magnetic field by using the effective-field theory with correlations. The effective-field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.

  20. Coupling between Spin and Charge Order Driven by Magnetic Field in Triangular Ising System LuFe2O4+δ

    Directory of Open Access Journals (Sweden)

    Lei Ding

    2018-02-01

    Full Text Available We present a study of the magnetic-field effect on spin correlations in the charge ordered triangular Ising system LuFe2O4+δ through single crystal neutron diffraction. In the absence of a magnetic field, the strong diffuse neutron scattering observed below the Neel temperature (TN = 240 K indicates that LuFe2O4+δ shows short-range, two-dimensional (2D correlations in the FeO5 triangular layers, characterized by the development of a magnetic scattering rod along the 1/3 1/3 L direction, persisting down to 5 K. We also found that on top of the 2D correlations, a long range ferromagnetic component associated with the propagation vector k1 = 0 sets in at around 240 K. On the other hand, an external magnetic field applied along the c-axis effectively favours a three-dimensional (3D spin correlation between the FeO5 bilayers evidenced by the increase of the intensity of satellite reflections with propagation vector k2 = (1/3, 1/3, 3/2. This magnetic modulation is identical to the charge ordered superstructure, highlighting the field-promoted coupling between the spin and charge degrees of freedom. Formation of the 3D spin correlations suppresses both the rod-type diffuse scattering and the k1 component. Simple symmetry-based arguments provide a natural explanation of the observed phenomenon and put forward a possible charge redistribution in the applied magnetic field.

  1. The anisotropic Ising superantiferromagnet on a simple cubic lattice in the presence of a magnetic field: Effective-field theory analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ricardo de Sousa, J. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Neto, Minos A., E-mail: minos@pq.cnpq.br [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Padilha, Igor T.; Salmon, Octavio D.R.; Viana, J. Roberto [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil)

    2013-12-15

    We have studied the anisotropic three-dimensional nearest-neighbor Ising model with competitive interactions in an uniform longitudinal magnetic field H. The model consists of ferromagnetic interactions J{sub z}=λ{sub 2}J{sub x} in the x(z) direction and antiferromagnetic interactions J{sub y}=λ{sub 1}J{sub x} in the y direction (Ising superantiferromagnet). For the particular case λ{sub 1}=λ{sub 2}=1 we obtain the phase diagram in the H−T plane, using the framework of the differential operator technique in the effective-field theory with finite cluster of N=4 spins (EFT-4). It was observed first- and second-order transitions in the low and high temperature limits, respectively, with the presence of a tricritical point and a reentrant behavior is observed at low temperature. The critical curve in the classical approach is also obtained and the results are compared.

  2. Magnetic structure and dispersion relation of the S =1/2 quasi-one-dimensional Ising-like antiferromagnet BaCo2V2O8 in a transverse magnetic field

    Science.gov (United States)

    Matsuda, M.; Onishi, H.; Okutani, A.; Ma, J.; Agrawal, H.; Hong, T.; Pajerowski, D. M.; Copley, J. R. D.; Okunishi, K.; Mori, M.; Kimura, S.; Hagiwara, M.

    2017-07-01

    BaCo2V2O8 consists of Co chains in which a Co2 + ion carries a fictitious spin 1/2 with Ising anisotropy. We performed elastic and inelastic neutron scattering experiments in BaCo2V2O8 in a magnetic field perpendicular to the c axis which is the chain direction. With applying magnetic field along the a axis at 3.5 K, the antiferromagnetic order with the easy axis along the c axis, observed in zero magnetic field, is completely suppressed at 8 T, while the magnetic field gradually induces an antiferromagnetic order with the spin component along the b axis. We also studied magnetic excitations as a function of transverse magnetic field. The lower boundary of the spinon excitations splits gradually with increasing magnetic field. The overall feature of the magnetic excitation spectra in the magnetic field is reproduced by the theoretical calculation based on the spin 1/2 X X Z antiferromagnetic chain model, which predicts that the dynamic magnetic structure factor of the spin component along the chain direction is enhanced and that along the field direction has clear incommensurate correlations.

  3. Dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field

    International Nuclear Information System (INIS)

    Kantar, Ersin; Ertaş, Mehmet; Keskin, Mustafa

    2014-01-01

    The dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field are obtained by using the effective-field theory with correlations based on the Glauber-type stochastic dynamics. According to the values of interaction parameters, a number of interesting properties have been found in the dynamic phase diagrams, such as many dynamic critical points (tricritical point, double critical end point, critical end point, zero temperature critical point, multicritical point, tetracritical point, and triple point) as well as reentrant phenomena. - Highlights: • The cylindrical Ising nanowire is investigated within the Glauber dynamics based on EFT. • The time variations of average order parameters to find phases are studied. • The dynamic phase diagrams are found for the different interaction parameters. • The system displays the critical points as well as a reentrant behavior

  4. Dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kantar, Ersin; Ertaş, Mehmet, E-mail: mehmetertas@erciyes.edu.tr; Keskin, Mustafa

    2014-06-01

    The dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field are obtained by using the effective-field theory with correlations based on the Glauber-type stochastic dynamics. According to the values of interaction parameters, a number of interesting properties have been found in the dynamic phase diagrams, such as many dynamic critical points (tricritical point, double critical end point, critical end point, zero temperature critical point, multicritical point, tetracritical point, and triple point) as well as reentrant phenomena. - Highlights: • The cylindrical Ising nanowire is investigated within the Glauber dynamics based on EFT. • The time variations of average order parameters to find phases are studied. • The dynamic phase diagrams are found for the different interaction parameters. • The system displays the critical points as well as a reentrant behavior.

  5. Plasma electron signature of magnetic connection to the earth's bow shock: ISEE 3

    International Nuclear Information System (INIS)

    Feldman, W.C.; Anderson, R.C.; Asbridge, J.R.; Bame, S.J.; Gosling, J.T.; Zwickl, R.D.

    1982-01-01

    Enhanced fluxes of low-energy electrons backstreaming from the earth's bow shock have been identified at ISEE 3. When present, these fluxes modify ambient solar wind electron velocity distributions f(v) in characteristic ways that depends on whether ISEE 3 is near the edge, or within the interior of the earth's electron foreshock. Near the edge, energy peaks in f(v) are observed. Such distributions should be locally unstable to electron plasma oscillations. Well within the interior of the foreshock, enhanced fluxes of electrons with energies up to the maximum detected by the Los Alamos electron analyzer (approx.1 keV) are observed over the full backward hemisphere. These electrons can be modelled with an asymptotic power law distribution having index in the range 4< or approx. =p/sub b/s< or approx. =6. At intermediate energies (approx.20--50 eV), twin angular peaks are observed centered on the magnetic field direction B. Also observed at these times are depressions in f(v) at energies less than approx.20 eV that are centered on B. Such distributions having a perpendicular temperature greater than their parallel temperature may be locally unstable to the generation of whistler waves. Analysis of a particularly clean example of connection to the bow shock is consistent with the possiblility that the observed electron fluxes emerge from the forward foot of the electron heating region within bow shock where the electron density and temperature are larger than that of the uperturbed upstream solar wind by a factor of approx.1.2. This analysis also indicates that the electrostatic potential within the forward foot of the shock is between approx.5 and 50 V more positive than that within plasma far upstream at ISEE 3. However, these interpretations depend on the assumption of nearly scatter-free propagation, which may not hold

  6. Reentrant behavior in the nearest-neighbor Ising antiferromagnet in a magnetic field

    Science.gov (United States)

    Neto, Minos A.; de Sousa, J. Ricardo

    2004-12-01

    Motived by the H-T phase diagram in the bcc Ising antiferromagnetic with nearest-neighbor interactions obtained by Monte Carlo simulation [Landau, Phys. Rev. B 16, 4164 (1977)] that shows a reentrant behavior at low temperature, with two critical temperatures in magnetic field about 2% greater than the critical value Hc=8J , we apply the effective field renormalization group (EFRG) approach in this model on three-dimensional lattices (simple cubic-sc and body centered cubic-bcc). We find that the critical curve TN(H) exhibits a maximum point around of H≃Hc only in the bcc lattice case. We also discuss the critical behavior by the effective field theory in clusters with one (EFT-1) and two (EFT-2) spins, and a reentrant behavior is observed for the sc and bcc lattices. We have compared our results of EFRG in the bcc lattice with Monte Carlo and series expansion, and we observe a good accordance between the methods.

  7. Selection rules for single-chain-magnet behaviour in non-collinear Ising systems

    International Nuclear Information System (INIS)

    Vindigni, Alessandro; Pini, Maria Gloria

    2009-01-01

    The magnetic behaviour of molecular single-chain magnets is investigated in the framework of a one-dimensional Ising model with single spin-flip Glauber dynamics. Opportune modifications to the original theory are required in order to account for non-collinearity of local anisotropy axes between themselves and with respect to the crystallographic (laboratory) frame. The extension of Glauber's theory to the case of a collinear Ising ferrimagnetic chain is also discussed. Within this formalism, both the dynamics of magnetization reversal in zero field and the response of the system to a weak magnetic field, oscillating in time, are studied. Depending on the experimental geometry, selection rules are found for the occurrence of slow relaxation of the magnetization at low temperatures, as well as for resonant behaviour of the a.c. susceptibility as a function of temperature at low frequencies. The present theory applies successfully to some real systems, namely Mn-, Dy- and Co-based molecular magnetic chains, showing that single-chain-magnet behaviour is not only a feature of collinear ferro- and ferrimagnetic, but also of canted antiferromagnetic chains.

  8. Selection rules for single-chain-magnet behaviour in non-collinear Ising systems

    Energy Technology Data Exchange (ETDEWEB)

    Vindigni, Alessandro [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zuerich (Switzerland); Pini, Maria Gloria [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy)], E-mail: vindigni@phys.ethz.ch

    2009-06-10

    The magnetic behaviour of molecular single-chain magnets is investigated in the framework of a one-dimensional Ising model with single spin-flip Glauber dynamics. Opportune modifications to the original theory are required in order to account for non-collinearity of local anisotropy axes between themselves and with respect to the crystallographic (laboratory) frame. The extension of Glauber's theory to the case of a collinear Ising ferrimagnetic chain is also discussed. Within this formalism, both the dynamics of magnetization reversal in zero field and the response of the system to a weak magnetic field, oscillating in time, are studied. Depending on the experimental geometry, selection rules are found for the occurrence of slow relaxation of the magnetization at low temperatures, as well as for resonant behaviour of the a.c. susceptibility as a function of temperature at low frequencies. The present theory applies successfully to some real systems, namely Mn-, Dy- and Co-based molecular magnetic chains, showing that single-chain-magnet behaviour is not only a feature of collinear ferro- and ferrimagnetic, but also of canted antiferromagnetic chains.

  9. Magnetic and magnetocaloric properties of the exactly solvable mixed-spin Ising model on a decorated triangular lattice in a magnetic field

    Science.gov (United States)

    Gálisová, Lucia; Strečka, Jozef

    2018-05-01

    The ground state, zero-temperature magnetization process, critical behaviour and isothermal entropy change of the mixed-spin Ising model on a decorated triangular lattice in a magnetic field are exactly studied after performing the generalized decoration-iteration mapping transformation. It is shown that both the inverse and conventional magnetocaloric effect can be found near the absolute zero temperature. The former phenomenon can be found in a vicinity of the discontinuous phase transitions and their crossing points, while the latter one occurs in some paramagnetic phases due to a spin frustration to be present at zero magnetic field. The inverse magnetocaloric effect can also be detected slightly above continuous phase transitions following the power-law dependence | - ΔSisomin | ∝hn, where n depends basically on the ground-state spin ordering.

  10. Frustrated lattices of Ising chains

    International Nuclear Information System (INIS)

    Kudasov, Yurii B; Korshunov, Aleksei S; Pavlov, V N; Maslov, Dmitrii A

    2012-01-01

    The magnetic structure and magnetization dynamics of systems of plane frustrated Ising chain lattices are reviewed for three groups of compounds: Ca 3 Co 2 O 6 , CsCoCl 3 , and Sr 5 Rh 4 O 12 . The available experimental data are analyzed and compared in detail. It is shown that a high-temperature magnetic phase on a triangle lattice is normally and universally a partially disordered antiferromagnetic (PDA) structure. The diversity of low-temperature phases results from weak interactions that lift the degeneracy of a 2D antiferromagnetic Ising model on the triangle lattice. Mean-field models, Monte Carlo simulation results on the static magnetization curve, and results on slow magnetization dynamics obtained with Glauber's theory are discussed in detail. (reviews of topical problems)

  11. Susceptibility and magnetization of a random Ising model

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, D; Srivastava, V [Roorkee Univ. (India). Dept. of Physics

    1977-08-01

    The susceptibility of a bond disordered Ising model is calculated by configurationally averaging an Ornstein-Zernike type of equation for the two spin correlation function. The equation for the correlation function is derived using a diagrammatic method due to Englert. The averaging is performed using bond CPA. The magnetization is also calculated by averaging in a similar manner a linearised molecular field equation.

  12. Phase diagrams of a nonequilibrium mixed spin-3/2 and spin-2 Ising system in an oscillating magnetic field

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Polat, Yasin

    2009-01-01

    The phase diagrams of the nonequilibrium mixed spin-3/2 and spin-2 Ising ferrimagnetic system on square lattice under a time-dependent external magnetic field are presented by using the Glauber-type stochastic dynamics. The model system consists of two interpenetrating sublattices of spins σ=3/2 and S=2, and we take only nearest-neighbor interactions between pairs of spins. The system is in contact with a heat bath at absolute temperature T abs and the exchange of energy with the heat bath occurs via one-spin flip of the Glauber dynamics. First, we investigate the time variations of average order parameters to find the phases in the system and then the thermal behavior of the dynamic order parameters to obtain the dynamic phase transition (DPT) points as well as to characterize the nature (first- or second-order) phase transitions. The dynamic phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p), ferrimagnetic (i 1 , i 2 , i 3 ) phases, and three coexistence or mixed phase regions, namely i 1 +p, i 2 +p and i 3 +p mixed phases that strongly depend on interaction parameters.

  13. Phase diagrams of a nonequilibrium mixed spin-3/2 and spin-2 Ising system in an oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr; Polat, Yasin [Institutes of Science, Erciyes University, 38039 Kayseri (Turkey)

    2009-12-15

    The phase diagrams of the nonequilibrium mixed spin-3/2 and spin-2 Ising ferrimagnetic system on square lattice under a time-dependent external magnetic field are presented by using the Glauber-type stochastic dynamics. The model system consists of two interpenetrating sublattices of spins {sigma}=3/2 and S=2, and we take only nearest-neighbor interactions between pairs of spins. The system is in contact with a heat bath at absolute temperature T{sub abs} and the exchange of energy with the heat bath occurs via one-spin flip of the Glauber dynamics. First, we investigate the time variations of average order parameters to find the phases in the system and then the thermal behavior of the dynamic order parameters to obtain the dynamic phase transition (DPT) points as well as to characterize the nature (first- or second-order) phase transitions. The dynamic phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p), ferrimagnetic (i{sub 1}, i{sub 2}, i{sub 3}) phases, and three coexistence or mixed phase regions, namely i{sub 1}+p, i{sub 2}+p and i{sub 3}+p mixed phases that strongly depend on interaction parameters.

  14. Magnetic properties of a single transverse Ising ferrimagnetic nanoparticle

    International Nuclear Information System (INIS)

    Bouhou, S.; El Hamri, M.; Essaoudi, I.; Ainane, A.; Ahuja, R.

    2015-01-01

    Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation function, the thermal and the magnetic properties of a single Ising nanoparticle consisting of a ferromagnetic core, a ferromagnetic surface shell and a ferrimagnetic interface coupling are examined. The effect of the transverse field in the surface shell, the exchange interactions between core/shell and in surface shell on the free energy, thermal magnetization, specific heat and susceptibility are studied. A number of interesting phenomena have been found such as the existence of the compensation phenomenon and the magnetization profiles exhibit P-type, N-type and Q-type behaviors

  15. Specific heat of the Ising linear chain in a Random field

    International Nuclear Information System (INIS)

    Silva, P.R.; Sa Barreto, F.C. de

    1984-01-01

    Starting from correlation identities for the Ising model the effect of a random field on the one dimension version of the model is studied. Explicit results for the magnetization, the two-particle correlation function and the specific heat are obtained for an uncorrelated distribution of the random fields. (Author) [pt

  16. Ground states, magnetization plateaus and bipartite entanglement of frustrated spin-1/2 Ising-Heisenberg and Heisenberg triangular tubes

    International Nuclear Information System (INIS)

    Alécio, Raphael C.; Lyra, Marcelo L.; Strečka, Jozef

    2016-01-01

    The ground-state phase diagram, magnetization process and bipartite entanglement of the frustrated spin-1/2 Ising-Heisenberg and Heisenberg triangular tube (three-leg ladder) are investigated in a non-zero external magnetic field. The exact ground-state phase diagram of the spin-1/2 Ising-Heisenberg tube with Heisenberg intra-rung and Ising inter-rung couplings consists of six distinct gapped phases, which manifest themselves in a magnetization curve as intermediate plateaus at zero, one-third and two-thirds of the saturation magnetization. Four out of six available ground states exhibit quantum entanglement between two spins from the same triangular unit evidenced by a non-zero concurrence. Density-matrix renormalization group calculations are used in order to construct the ground-state phase diagram of the analogous but purely quantum spin-1/2 Heisenberg tube with Heisenberg intra- and inter-rung couplings, which consists of four gapped and three gapless phases. The Heisenberg tube shows a continuous change of the magnetization instead of a plateau at zero magnetization, while the intermediate one-third and two-thirds plateaus may be present or not in the zero-temperature magnetization curve. - Highlights: • Ground-state properties of Ising-Heisenberg and full Heisenberg spin tubes are studied. • Phases with 1/3 and 2/3 magnetization plateaus are present in both models. • We unveil the region in the parameter space on which inter-rung quantum fluctuations are relevant. • The full Heisenberg tube exhibits quantum bipartite entanglement between intra- as well as inter-rung spins.

  17. Quasi-realistic distribution of interaction fields leading to a variant of Ising spin glass model

    International Nuclear Information System (INIS)

    Tanasa, Radu; Enachescu, Cristian; Stancu, Alexandru; Linares, Jorge; Varret, Francois

    2004-01-01

    The distribution of interaction fields of an Ising-like system, obtained by Monte Carlo entropic sampling is used for modeling the hysteretic behavior of patterned media made of magnetic particles with a common anisotropy axis; a variant of the canonical Edwards-Anderson Ising spin glass model is introduced

  18. Monte Carlo study of the three-dimensional spatially anisotropic Ising superantiferromagnet in the presence of a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Salmon, Octavio D.R., E-mail: octaviors@gmail.com [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); Neto, Minos A., E-mail: minosneto@pq.cnpq.br [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); Viana, J. Roberto, E-mail: vianafisica@bol.com.br [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); Padilha, Igor T., E-mail: igorfis@ufam.edu.br [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); Sousa, J. Ricardo de, E-mail: jsousa@ufam.edu.br [Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000 Manaus-AM (Brazil)

    2013-11-01

    The phase transition of the three-dimensional spatially anisotropic Ising antiferromagnetic model in the presence of an uniform longitudinal magnetic field H is studied by using the traditional Monte Carlo (MC) simulation for sizes L=16, 32 and 64. The model consists of ferromagnetic interactions J{sub z}=λ{sub 2}J{sub x} in the x(z) direction and antiferromagnetic interactions J{sub y}=λ{sub 1}J{sub x} in the y direction (Ising superantiferromagnetic). For the particular case λ{sub 1}=λ{sub 2}=1 we obtain the phase diagram in the T–H plane. Was observed first- and second-order transitions in the low and high temperature limits, respectively, with the presence of a tricritical point.

  19. Magnetic properties of the three-dimensional Ising model with an interface amorphization

    International Nuclear Information System (INIS)

    Benyoussef, A.; El Kenz, A.; Saber, M.

    1993-09-01

    A three-dimensional ferromagnetic Ising model with an interface amorphization is investigated with the use of the effective field theory. Phase diagrams and reduced magnetization curves of interface and bulks are studied. We obtain a number of characteristic behaviour such as the possibility of the reentrant phenomena and a large depression of interface magnetization. (author). 21 refs, 5 figs

  20. The spin-3/2 Ising model AFM/AFM two-layer lattice with crystal field

    International Nuclear Information System (INIS)

    Yigit, A.; Albayrak, E.

    2010-01-01

    The spin-3/2 Ising model is investigated for the case of antiferromagnetic (AFM/AFM) interactions on the two-layer Bethe lattice by using the exact recursion relations in a pairwise approach for given coordination numbers q=3, 4 and 6 when the layers are under the influences of equal external magnetic and equal crystal fields. The ground state (GS) phase diagrams are obtained on the different planes in detail and then the temperature dependent phase diagrams of the system are calculated accordingly. It is observed that the system presents both second- and first-order phase transitions for all q, therefore, tricritical points. It was also found that the system exhibits double-critical end points and isolated points. The model also presents two Neel temperatures, TN, and the existence of which leads to the reentrant behavior.

  1. Giant magnetocaloric effect, magnetization plateaux and jumps of the regular Ising polyhedra

    International Nuclear Information System (INIS)

    Strečka, Jozef; Karľová, Katarína; Madaras, Tomáš

    2015-01-01

    Magnetization process and adiabatic demagnetization of the antiferromagnetic Ising spin clusters with the shape of regular polyhedra (Platonic solids) are exactly examined within the framework of a simple graph-theoretical approach. While the Ising cube as the only unfrustrated (bipartite) spin cluster shows just one trivial plateau at zero magnetization, the other regular Ising polyhedra (tetrahedron, octahedron, icosahedron and dodecahedron) additionally display either one or two intermediate plateaux at fractional values of the saturation magnetization. The nature of highly degenerate ground states emergent at intermediate plateaux owing to a geometric frustration is clarified. It is evidenced that the regular Ising polyhedra exhibit a giant magnetocaloric effect in a vicinity of magnetization jumps, whereas the Ising octahedron and dodecahedron belong to the most prominent geometrically frustrated spin clusters that enable an efficient low-temperature refrigeration by the process of adiabatic demagnetization

  2. Magnetic field line draping in the plasma depletion layer

    Science.gov (United States)

    Sibeck, D. G.; Lepping, R. P.; Lazarus, A. J.

    1990-01-01

    Simultaneous IMP 8 solar wind and ISEE 1/2 observations for a northern dawn ISEE 1/2 magnetopause crossing on November 6, 1977. During this crossing, ISEE 1/2 observed quasi-periodic pulses of magnetosheathlike plasma on northward magnetic field lines. The ISEE 1/2 observations were originally interpreted as evidence for strong diffusion of magnetosheath plasma across the magnetopause and the Kelvin-Helmholtz instability at the inner edge of the low-latitude boundary layer. An alternate explanation, in terms of magnetic field merging and flux transfer events, has also been advocated. In this paper, a third interpretation is proposed in terms of quasi-periodic magnetopause motion which causes the satellites to repeatedly exit the magnetosphere and observe draped northward magnetosheath magnetic field lines in the plasma depletion layer.

  3. Magnetization plateaus and phase diagrams of the Ising model on the Shastry–Sutherland lattice

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Seyma Akkaya, E-mail: sadeviren@nevsehir.edu.tr

    2015-11-01

    The magnetization properties of a two-dimensional spin-1/2 Ising model on the Shastry–Sutherland lattice are studied within the effective-field theory (EFT) with correlations. The thermal behavior of the magnetizations is investigated in order to characterize the nature (the first- or second-order) of the phase transitions as well as to obtain the phase diagrams of the model. The internal energy, specific heat, entropy and free energy of the system are also examined numerically as a function of the temperature in order to confirm the stability of the phase transitions. The applied field dependence of the magnetizations is also examined to find the existence of the magnetization plateaus. For strong enough magnetic fields, several magnetization plateaus are observed, e.g., at 1/9, 1/8, 1/3 and 1/2 of the saturation. The phase diagrams of the model are constructed in two different planes, namely (h/|J|, |J′|/|J|) and (h/|J|, T/|J|) planes. It was found that the model exhibits first- and second-order phase transitions; hence tricitical point is also observed in additional to the zero-temperature critical point. Moreover the Néel order (N), collinear order (C) and ferromagnetic (F) phases are also found with appropriate values of the system parameters. The reentrant behavior is also obtained whenever model displays two Néel temperatures. These results are compared with some theoretical and experimental works and a good overall agreement has been obtained. - Highlights: • Magnetization properties of spin-1/2 Ising model on SS lattice are investigated. • The magnetization plateaus of the 1/9, 1/8, 1/3 and 1/2 are observed. • The phase diagrams of the model are constructed in two different planes. • The model exhibits the tricitical and zero-temperature critical points. • The reentrant behavior is obtained whenever model displays two Neel temperatures.

  4. Dynamical response of the Ising model to the time dependent magnetic field with white noise

    Science.gov (United States)

    Akıncı, Ümit

    2018-03-01

    The effect of the white noise in time dependent magnetic field on the dynamic behavior of the Ising model has been investigated within the effective field theory based on Glauber type of stochastic process. Discrete white noise has been chosen from both Gaussian and uniform probability distributions. Detailed investigation on probability distribution of dynamical order parameter results that, both type of noise distributions yield the same probability distribution related to the dynamical order parameter, namely Gaussian probability distribution. The variation of the parameters that describe the probability distribution of dynamical order parameter (mean value and standard deviation) with temperature and strength of the noise have been inspected. Also, it has been shown that, rising strength of the noise can induce dynamical phase transition in the system.

  5. Robust extrapolation scheme for fast estimation of 3D Ising field partition functions: application to within subject fMRI data

    Energy Technology Data Exchange (ETDEWEB)

    Risser, L.; Vincent, T.; Ciuciu, Ph. [NeuroSpin CEA, F-91191 Gif sur Yvette (France); Risser, L.; Vincent, T. [Laboratoire de Neuroimagerie Assistee par Ordinateur (LNAO) CEA - DSV/I2BM/NEUROSPIN (France); Risser, L. [Institut de mecanique des fluides de Toulouse (IMFT), CNRS: UMR5502 - Universite Paul Sabatier - Toulouse III - Institut National Polytechnique de Toulouse - INPT (France); Idier, J. [Institut de Recherche en Communications et en Cybernetique de Nantes (IRCCyN) CNRS - UMR6597 - Universite de Nantes - ecole Centrale de Nantes - Ecole des Mines de Nantes - Ecole Polytechnique de l' Universite de Nantes (France)

    2009-07-01

    In this paper, we present a first numerical scheme to estimate Partition Functions (PF) of 3D Ising fields. Our strategy is applied to the context of the joint detection-estimation of brain activity from functional Magnetic Resonance Imaging (fMRI) data, where the goal is to automatically recover activated regions and estimate region-dependent, hemodynamic filters. For any region, a specific binary Markov random field may embody spatial correlation over the hidden states of the voxels by modeling whether they are activated or not. To make this spatial regularization fully adaptive, our approach is first based upon it, classical path-sampling method to approximate a small subset of reference PFs corresponding to pre-specified regions. Then, file proposed extrapolation method allows its to approximate the PFs associated with the Ising fields defined over the remaining brain regions. In comparison with preexisting approaches, our method is robust; to topological inhomogeneities in the definition of the reference regions. As a result, it strongly alleviates the computational burden and makes spatially adaptive regularization of whole brain fMRI datasets feasible. (authors)

  6. Quasi-one-dimensional magnetic behaviour of the Ising system CsFeCl3.2aq

    NARCIS (Netherlands)

    Kopinga, K.; Steiner, M.; Jonge, de W.J.M.

    1985-01-01

    The magnetic behaviour of the quasi-one-dimensional system CsFeCl3.2aq(aq=H2O, D2O) has been investigated by heat capacity measurements, quasi-elastic neutron scattering and spin-cluster resonance. the experiments demonstrate that below 25K the compound is a very good realisation of an (S=1/2) Ising

  7. Neutron diffraction study of antiferromagnetic ErNi3Ga9 in magnetic fields

    Science.gov (United States)

    Ninomiya, Hiroki; Sato, Takaaki; Matsumoto, Yuji; Moyoshi, Taketo; Nakao, Akiko; Ohishi, Kazuki; Kousaka, Yusuke; Akimitsu, Jun; Inoue, Katsuya; Ohara, Shigeo

    2018-05-01

    We report specific heat, magnetization, magnetoresistance, and neutron diffraction measurements of single crystals of ErNi3Ga9. This compound crystalizes in a chiral structure with space group R 32 . The erbium ions form a two-dimensional honeycomb structure. ErNi3Ga9 displays antiferromagnetic order below 6.4 K. We determined that the magnetic structure is slightly amplitude-modulated as well as antiferromagnetic with q = (0 , 0 , 0.5) . The magnetic properties are described by an Ising-like model in which the magnetic moment is always along the c-axis owing to the large uniaxial anisotropy caused by the crystalline electric field effect in the low temperature region. When the magnetic field is applied along the c-axis, a metamagnetic transition is observed around 12 kOe at 2 K. ErNi3Ga9 possesses crystal chirality, but the antisymmetric magnetic interaction, the so-called Dzyaloshinskii-Moriya (DM) interaction, does not contribute to the magnetic structure, because the magnetic moments are parallel to the DM-vector.

  8. Restoration of dimensional reduction in the random-field Ising model at five dimensions

    Science.gov (United States)

    Fytas, Nikolaos G.; Martín-Mayor, Víctor; Picco, Marco; Sourlas, Nicolas

    2017-04-01

    The random-field Ising model is one of the few disordered systems where the perturbative renormalization group can be carried out to all orders of perturbation theory. This analysis predicts dimensional reduction, i.e., that the critical properties of the random-field Ising model in D dimensions are identical to those of the pure Ising ferromagnet in D -2 dimensions. It is well known that dimensional reduction is not true in three dimensions, thus invalidating the perturbative renormalization group prediction. Here, we report high-precision numerical simulations of the 5D random-field Ising model at zero temperature. We illustrate universality by comparing different probability distributions for the random fields. We compute all the relevant critical exponents (including the critical slowing down exponent for the ground-state finding algorithm), as well as several other renormalization-group invariants. The estimated values of the critical exponents of the 5D random-field Ising model are statistically compatible to those of the pure 3D Ising ferromagnet. These results support the restoration of dimensional reduction at D =5 . We thus conclude that the failure of the perturbative renormalization group is a low-dimensional phenomenon. We close our contribution by comparing universal quantities for the random-field problem at dimensions 3 ≤D equality at all studied dimensions.

  9. Ising model with competing axial interactions in the presence of a field

    International Nuclear Information System (INIS)

    Yokoi, C.S.O.; Salinas, S.R.A.; Coutinho Filho, M.D.

    1980-09-01

    A layered Ising model is studied with competing interactions between nearest and next-nearest layers in the presence of a magnetic field. The analysis is carried out in the mean-field approximation with one effective field for each layer. The high-temperature region is studied analytically. The low-temperature region is studied numerically. T-H phase diagrams are constructed, which exhibit a variety of modulated phases, for various values of the ratio of the strength of the competing interactions. Numerical evidence of the devil's staircase behavior is found either as a function of temperature or applied magnetic field. (Author) [pt

  10. Effective-field theory on the kinetic Ising model

    International Nuclear Information System (INIS)

    Shi Xiaoling; Wei Guozhu; Li Lin

    2008-01-01

    As an analytical method, the effective-field theory (EFT) is used to study the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field. The effective-field equations of motion of the average magnetization are given for the square lattice (Z=4) and the simple cubic lattice (Z=6), respectively. The dynamic order parameter, the hysteresis loop area and the dynamic correlation are calculated. In the field amplitude h 0 /ZJ-temperature T/ZJ plane, the phase boundary separating the dynamic ordered and the disordered phase has been drawn, and the dynamical tricritical point has been observed. We also make the compare results of EFT with that given by using the mean field theory (MFT)

  11. Magnetization plateaus and ground-state phase diagrams of the S=1 Ising model on the Shastry Sutherland lattice

    Science.gov (United States)

    Deviren, Seyma Akkaya

    2017-02-01

    In this research, we have investigated the magnetic properties of the spin-1 Ising model on the Shastry Sutherland lattice with the crystal field interaction by using the effective-field theory with correlations. The effects of the applied field on the magnetization are examined in detail in order to obtain the magnetization plateaus, thus different types of magnetization plateaus, such as 1/4, 1/3, 1/2, 3/5, 2/3 and 7/9 of the saturation, are obtained for strong enough magnetic fields (h). Magnetization plateaus exhibit single, triple, quintuplet and sextuple forms according to the interaction parameters, hence the magnetization plateaus originate from the competition between the crystal field (D) and exchange interaction parameters (J, J‧). The ground-state phase diagrams of the system are presented in three varied planes, namely (h/J, J‧/J), (h/J, D/J) and (D/J, J‧/J) planes. These phase diagrams display the Néel (N), collinear (C) and ferromagnetic (F) phases for certain values of the model parameters. The obtained results are in good agreement with some theoretical and experimental studies.

  12. Detect genuine multipartite entanglement in the one-dimensional transverse-field Ising model

    International Nuclear Information System (INIS)

    Deng Dongling; Gu Shijian; Chen Jingling

    2010-01-01

    Recently Seevinck and Uffink argued that genuine multipartite entanglement (GME) had not been established in the experiments designed to confirm GME. In this paper, we use the Bell-type inequalities introduced by Seevinck and Svetlichny [M. Seevinck, G. Svetlichny, Phys. Rev. Lett. 89 (2002) 060401] to investigate the GME problem in the one-dimensional transverse-field Ising model. We show explicitly that the ground states of this model violate the inequality when the external transverse magnetic field is weak, which indicate that the ground states in this model with weak magnetic field are fully entangled. Since this model can be simulated with nuclear magnetic resonance, our results provide a fresh approach to experimental test of GME.

  13. Global mean-field phase diagram of the spin-1 Ising ferromagnet in a random crystal field

    Science.gov (United States)

    Borelli, M. E. S.; Carneiro, C. E. I.

    1996-02-01

    We study the phase diagram of the mean-field spin-1 Ising ferromagnet in a uniform magnetic field H and a random crystal field Δi, with probability distribution P( Δi) = pδ( Δi - Δ) + (1 - p) δ( Δi). We analyse the effects of randomness on the first-order surfaces of the Δ- T- H phase diagram for different values of the concentration p and show how these surfaces are affected by the dilution of the crystal field.

  14. The effective-field study of a mixed spin-1 and spin-5/2 Ising ferrimagnetic system

    International Nuclear Information System (INIS)

    Deviren, Bayram; Bati, Mehmet; Keskin, Mustafa

    2009-01-01

    An effective-field theory with correlations is developed for a mixed spin-1 and spin-5/2 Ising ferrimagnetic system on the honeycomb (δ=3) and square (δ=4) lattices in the absence and presence of a longitudinal magnetic field. The ground-state phase diagram of the model is obtained in the longitudinal magnetic field (h) and a single-ion potential or crystal-field interaction (Δ) plane. We also investigate the thermal variations of the sublattice magnetizations, and present the phase diagrams in the (Δ/|J|,k B T/|J|) plane. The susceptibility, internal energy and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the absence and presence of the applied longitudinal magnetic field. Moreover, the system undergoes second- and first-order phase transition; hence, the system gives a tricritical point. The system also exhibits reentrant behavior.

  15. The effective-field study of a mixed spin-1 and spin-5/2 Ising ferrimagnetic system

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram; Bati, Mehmet [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr

    2009-06-15

    An effective-field theory with correlations is developed for a mixed spin-1 and spin-5/2 Ising ferrimagnetic system on the honeycomb ({delta}=3) and square ({delta}=4) lattices in the absence and presence of a longitudinal magnetic field. The ground-state phase diagram of the model is obtained in the longitudinal magnetic field (h) and a single-ion potential or crystal-field interaction ({delta}) plane. We also investigate the thermal variations of the sublattice magnetizations, and present the phase diagrams in the ({delta}/|J|,k{sub B}T/|J|) plane. The susceptibility, internal energy and specific heat of the system are numerically examined, and some interesting phenomena in these quantities are found due to the absence and presence of the applied longitudinal magnetic field. Moreover, the system undergoes second- and first-order phase transition; hence, the system gives a tricritical point. The system also exhibits reentrant behavior.

  16. Hysteretic features of Ising-type segmented nanostructure with alternating magnetic wires

    International Nuclear Information System (INIS)

    Kantar, Ersin

    2016-01-01

    In the present study, a theoretical approach to investigate the hysteresis behaviors in segmented nanowires is described and applied to spin-1/2 and spin-1 hexagonal nanowire. The hysteresis loop, coercive field and remanent magnetization of a segmented Ising nanowire (SIN) are obtained by using the effective-field theory with correlations. The effects of the temperature, crystal field and geometrical parameters of nanowires on the hysteresis behaviors of the system are investigated. A number of characteristic behaviors are found, such as the occurrence of single and triple hysteresis loops for appropriate values of the crystal field. The hysteresis behaviors are also strongly dependent on geometrical parameters. Comparisons between the obtained theoretical results and some experimental works of segmented nanowire arrays with hysteresis behaviors are made and a very good agreement is obtained. - Highlights: • The hysteresis behaviors of a segmented Ising nanowire are obtained. • The effective-field theory with correlations are used to calculations. • The effects of the temperature and crystal field on the system are investigated. • The geometrical parameters have a significant effect on the system are observed. • The single and triple loops for appropriate values of the crystal field are obtained.

  17. Excitations in the quantum paramagnetic phase of the quasi-one-dimensional Ising magnet CoNb2O6 in a transverse field: Geometric frustration and quantum renormalization effects

    Science.gov (United States)

    Cabrera, I.; Thompson, J. D.; Coldea, R.; Prabhakaran, D.; Bewley, R. I.; Guidi, T.; Rodriguez-Rivera, J. A.; Stock, C.

    2014-07-01

    The quasi-one-dimensional (1D) Ising ferromagnet CoNb2O6 has recently been driven via applied transverse magnetic fields through a continuous quantum phase transition from spontaneous magnetic order to a quantum paramagnet, and dramatic changes were observed in the spin dynamics, characteristic of weakly perturbed 1D Ising quantum criticality. We report here extensive single-crystal inelastic neutron scattering measurements of the magnetic excitations throughout the three-dimensional (3D) Brillouin zone in the quantum paramagnetic phase just above the critical field to characterize the effects of the finite interchain couplings. In this phase, we observe that excitations have a sharp, resolution-limited line shape at low energies and over most of the dispersion bandwidth, as expected for spin-flip quasiparticles. We map the full bandwidth along the strongly dispersive chain direction and resolve clear modulations of the dispersions in the plane normal to the chains, characteristic of frustrated interchain couplings in an antiferromagnetic isosceles triangular lattice. The dispersions can be well parametrized using a linear spin-wave model that includes interchain couplings and further neighbor exchanges. The observed dispersion bandwidth along the chain direction is smaller than that predicted by a linear spin-wave model using exchange values determined at zero field, and this effect is attributed to quantum renormalization of the dispersion beyond the spin-wave approximation in fields slightly above the critical field, where quantum fluctuations are still significant.

  18. Dynamics of the diluted Ising antiferromagnet Fe0.42Zn0.58F2 at strong fields

    International Nuclear Information System (INIS)

    Rosales-Rivera, A.; Ferreira, J.M.; Montenegro, F.C.

    2001-01-01

    The random-field Ising model (RFIM) system Fe 0.42 Zn 0.58 F 2 is studied by magnetization and AC susceptibility measurements, under finite DC applied fields (H). For weak random fields (corresponding to H c (H) is accompanied by the critical slowing down inherent to the random field problem. For higher H, the PT is destroyed and a glassy dynamics dominates the magnetic behavior

  19. Phase diagram of the Ising model on a Cayley tree in the presence of competing interactions and magnetic field

    International Nuclear Information System (INIS)

    Mariz, A.M.; Tsallis, C.; Albuquerque, E.L. de.

    1984-01-01

    The phae diagram for the Ising Model on a Cayley tree with competing nearest-neighbour interactions J 1 and next-nearest-neighbour interactions J 2 and J 3 in the presence of an external magnetic field is studied. To perform this study, an iterative scheme similar to that appearing in real space renormalization group frameworks is established; it recovers, as particular cases, previous works by Vannimenus and by Inawashiro et al. At vanishing temperature, the phase diagram is fully determined, for all values and signs of J 2 /J 1 and J 3 /J 2 ; in particular, it is verified that values of J 3 /J 2 high enough favour the paramagnetic phase. At finite temperatures, several interesting features (evolution of re-entrances, separation of the modulated region in two disconnected pieces, etc.) are exhibited for typical values of J 2 /J 1 and J 3 /J 2 . (Author) [pt

  20. On the formation and evolution of plasmoids: A survey of ISEE 3 geotail data

    International Nuclear Information System (INIS)

    Moldwin, M.B.; Hughes, W.J.

    1992-01-01

    ISEE 3 magnetometer and electron plasma measurements from the 1983 Geotail Mission were surveyed to determine the magnetic and plasma properties of plasmoids and their evolution with distance downtail. Events were selected on the basis of a bipolar magnetic signature in either the geocentric solar magnetospheric B z and/or B y component; most had B z bipolar signatures. The authors found 366 events consistent with this signature while ISEE 3 was in the plasma sheet. Plasmoid length was determined using both the magnetometer and the electron plasma velocity data. They found the average length of plasmoids is 16.7 ± 13.0 R E , significantly smaller than previous estimates. Many plasmoids have a well-defined magnetic core field, characterized by a field strength maximum at the center of the pass through the structure. The size, velocity, magnetic core strength, and B z field amplitude of plasmoids do not depend on distance beyond 100 R E downtail. The average electron temperature inside plasmoids drops by a factor of 2 and the electron density increases by a factor of 2 as plasmoids propagate from near Earth distances (within 100 R E of the Earth) to the deep tail. They conclude that the stable size of the plasmoids, the density increase and the temperature decrease are consistent with a flux of cold electrons into the plasmoid. The strong correlation of interplanetary magnetic field B y an hour before the event with the strength and direction of B y observed inside plasmoids, the existence of events with the bipolar signature in both the B y and B z components, and the possible mass flux all are consistent with plasmoids being 'open' magnetic structures

  1. Dynamic magnetic properties of the mixed spin-1 and spin-3/2 Ising system on a two-layer square lattice

    International Nuclear Information System (INIS)

    Temizer, Ümüt

    2014-01-01

    In this study, the dynamic critical behavior of the mixed spin-1 and spin-3/2 Ising system on a bilayer square lattice is studied by using the Glauber-type stochastic dynamics for both ferromagnetic/ferromagnetic (FM/FM) and antiferromagnetic/ferromagnetic (AFM/FM) interactions in the presence of a time-varying external magnetic field. The dynamic equations describing the time-dependencies of the average magnetizations are derived from the Master equation. The phases in the system are obtained by solving these dynamic equations. The temperature dependence of the dynamic magnetizations is investigated in order to characterize the nature (first- or second-order) of the dynamic phase transitions and to obtain the dynamic phase transition temperatures. The dynamic phase diagrams are constructed in seven different planes for both FM/FM and AFM/FM interactions and the effects of the related interaction parameters on the dynamic phase diagrams are examined. It is found that the dynamic phase diagrams display many dynamic critical points, such as tricritical point, triple point (TP), quadruple point (QP), double critical end point (B), multicritical point (A) and tetracritical point (M). Moreover, the reentrant behavior is observed for AFM/FM interaction in the system. - Highlights: • The mixed spin (1, 3/2) Ising system is studied on a two-layer square lattice. • The Glauber transition rates are employed to construct the dynamic equations. • The dynamic phase diagrams are presented in seven different planes. • The system displays many dynamic critical points. • The reentrant behavior is observed for AFM/FM interaction

  2. Propagation of ULF waves through the ionosphere: Inductive effect for oblique magnetic fields

    Directory of Open Access Journals (Sweden)

    M. D. Sciffer

    2004-04-01

    Full Text Available Solutions for ultra-low frequency (ULF wave fields in the frequency range 1–100mHz that interact with the Earth's ionosphere in the presence of oblique background magnetic fields are described. Analytic expressions for the electric and magnetic wave fields in the magnetosphere, ionosphere and atmosphere are derived within the context of an inductive ionosphere. The inductive shielding effect (ISE arises from the generation of an "inductive" rotational current by the induced part of the divergent electric field in the ionosphere which reduces the wave amplitude detected on the ground. The inductive response of the ionosphere is described by Faraday's law and the ISE depends on the horizontal scale size of the ULF disturbance, its frequency and the ionosphere conductivities. The ISE for ULF waves in a vertical background magnetic field is limited in application to high latitudes. In this paper we examine the ISE within the context of oblique background magnetic fields, extending studies of an inductive ionosphere and the associated shielding of ULF waves to lower latitudes. It is found that the dip angle of the background magnetic field has a significant effect on signals detected at the ground. For incident shear Alfvén mode waves and oblique background magnetic fields, the horizontal component of the field-aligned current contributes to the signal detected at the ground. At low latitudes, the ISE is larger at smaller conductivity values compared with high latitudes.

    Key words. Ionosphere (ionosphere-magnetosphere interactions; electric fields and currents; wave propagation

  3. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Keskin, M.; Canko, O.; Gueldal, S.

    2009-01-01

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  4. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, M., E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Canko, O. [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Gueldal, S. [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)

    2009-12-14

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  5. Phase transitions and Heisenberg limited metrology in an Ising chain interacting with a single-mode cavity field

    DEFF Research Database (Denmark)

    Gammelmark, Søren; Mølmer, Klaus

    2011-01-01

    We investigate the thermodynamics of a combined Dicke and Ising model that exhibits a rich phenomenology arising from the second-order and quantum phase transitions from the respective models. The partition function is calculated using mean-field theory, and the free energy is analyzed in detail...... to determine the complete phase diagram of the system. The analysis reveals both first- and second-order Dicke phase transitions into a super-radiant state, and the cavity mean field in this regime acts as an effective magnetic field, which restricts the Ising chain dynamics to parameter ranges away from...... the Ising phase transition. Physical systems with first-order phase transitions are natural candidates for metrology and calibration purposes, and we apply filter theory to show that the sensitivity of the physical system to temperature and external fields reaches the 1/N Heisenberg limit....

  6. Monte Carlo study of dynamic phase transition in Ising metamagnet driven by oscillating magnetic field

    International Nuclear Information System (INIS)

    Acharyya, Muktish

    2011-01-01

    The dynamical responses of Ising metamagnet (layered antiferromagnet) in the presence of a sinusoidally oscillating magnetic field are studied by Monte Carlo simulation. The time average staggered magnetisation plays the role of dynamic order parameter. A dynamical phase transition was observed and a phase diagram was plotted in the plane formed by field amplitude and temperature. The dynamical phase boundary is observed to shrink inward as the relative antiferromagnetic strength decreases. The results are compared with that obtained from pure ferromagnetic system. The shape of dynamic phase boundary observed to be qualitatively similar to that obtained from previous meanfield calculations. - Highlights: → The time average staggered magnetisation plays the role of dynamic order parameter. → A dynamical phase transition was observed and a phase diagram was plotted in the plane formed by field amplitude and temperature. → The dynamical phase boundary is observed to shrink inward as the relative antiferromagnetic strength decreases. → The results are compared with that obtained from pure ferromagnetic system. → The shape of dynamic phase boundary observed to be qualitatively similar to that obtained from previous meanfield calculation.

  7. Thue-Morse quantum Ising model

    International Nuclear Information System (INIS)

    Doria, M.M.; Nori, F.; Satija, I.I.

    1989-01-01

    We study the one-dimensional quantum Ising model in a transverse magnetic field where the exchange couplings are ordered according to the Thue-Morse (TM) sequence. At zero temperature, this model is equivalent to a two-dimensional classical Ising model in a magnetic field with TM aperiodicity along one direction. We compute the order parameter (magnetization) of the chain and the scaling behavior of the energy spectrum when the system undergoes a phase transition. Analogous to the quasiperiodic (QP) quantum Ising chain, the onset of long-range order is signaled by a nonanaliticity in the exponent δ which describes the scaling of the total bandwidth with the size of the chain. The critical spin-coupling can be computed analytically and it is found to be lower than the QP case. Furthermore, the energy bands are found to be narrower than the corresponding QP chain. The former and latter results are consistent with the fact that the present structure has a degree of ordering intermediate between QP and random

  8. Phase diagrams of a spin-1/2 transverse Ising model with three-peak random field distribution

    International Nuclear Information System (INIS)

    Bassir, A.; Bassir, C.E.; Benyoussef, A.; Ez-Zahraouy, H.

    1996-07-01

    The effect of the transverse magnetic field on the phase diagrams structures of the Ising model in a random longitudinal magnetic field with a trimodal symmetric distribution is investigated within a finite cluster approximation. We find that a small magnetizations ordered phase (small ordered phase) disappears completely for a sufficiently large value of the transverse field or/and large value of the concentration of the disorder of the magnetic field. Multicritical behaviour and reentrant phenomena are discussed. The regions where the tricritical, reentrant phenomena and the small ordered phase persist are delimited as a function of the transverse field and the concentration p. Longitudinal magnetizations are also presented. (author). 33 refs, 6 figs

  9. The square Ising model with second-neighbor interactions and the Ising chain in a transverse field

    International Nuclear Information System (INIS)

    Grynberg, M.D.; Tanatar, B.

    1991-06-01

    We consider the thermal and critical behaviour of the square Ising lattice with frustrated first - and second-neighbor interactions. A low-temperature domain wall analysis including kinks and dislocations shows that there is a close relation between this classical model and the Hamiltonian of an Ising chain in a transverse field provided that the ratio of the next-nearest to nearest-neighbor coupling, is close to 1/2. Due to the field inversion symmetry of the Ising chain Hamiltonian, the thermal properties of the classical system are symmetrical with respect to this coupling ratio. In the neighborhood of this regime critical exponents of the model turn out to belong to the Ising universality class. Our results are compared with previous Monte Carlo simulations. (author). 23 refs, 6 figs

  10. Monte Carlo steps per spin vs. time in the master equation II: Glauber kinetics for the infinite-range ising model in a static magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Suhk Kun [Chungbuk National University, Chungbuk (Korea, Republic of)

    2006-01-15

    As an extension of our previous work on the relationship between time in Monte Carlo simulation and time in the continuous master equation in the infinit-range Glauber kinetic Ising model in the absence of any magnetic field, we explored the same model in the presence of a static magnetic field. Monte Carlo steps per spin as time in the MC simulations again turns out to be proportional to time in the master equation for the model in relatively larger static magnetic fields at any temperature. At and near the critical point in a relatively smaller magnetic field, the model exhibits a significant finite-size dependence, and the solution to the Suzuki-Kubo differential equation stemming from the master equation needs to be re-scaled to fit the Monte Carlo steps per spin for the system with different numbers of spins.

  11. Electron heat flux dropouts in the solar wind: Evidence for interplanetary magnetic field reconnection?

    International Nuclear Information System (INIS)

    McComas, D.J.; Gosling, J.T.; Phillips, J.L.; Bame, S.J.; Luhmann, J.G.; Smith, E.J.

    1989-01-01

    Electron heat flux dropout events have been observed in the solar wind using the ISEE 3 plasma electron data set. These events manifest themselves as dropouts of the solar wind halo electrons which are normally found streaming outward along the local magnetic field. These dropouts leave nearly isotropic distributions of solar wind halo electrons, and consequently, the heat flux in these events is reduced to near the observational noise level. We have examined ISEE 3 data from shortly after launch (August 16, 1978) through the end of 1978 and identified 25 such events ranging in duration from 20 min to over 11 hours. Comparison with the ISEE 3 magnetometer data indicates that these intervals nearly always occur in conjunction with large rotations of the interplanetary magnetic field. Statistical analyses of the plasma and magnetic field data for the 25 dropout intervals indicate that heat flux dropouts generally occur in association with high plasma densities low plasma velocities, low ion and electron temperatures, and low magnetic field magnitudes. A second set of 25 intervals chosen specifically to lie at large field rotations, but at times at which not heat flux dropouts were observed, do not show these characteristic plalsma variations. This suggests that the dropout intervals comprise a unique set of events. Since the hot halo electrons normally found streaming outward from the Sun along the interplanetary magnetic field (the solar wind electron heat flux) are a result of direct magnetic connection to the hot solar corona, heat flux dropout intervals may indicate that the spacecraft is sampling plasma regimes which are magnetically disconnected from the Sun and instead are connected to the outer heliosphere at both ends

  12. The ferromagnet spin-1/2 Ising superlattice in a transverse field

    International Nuclear Information System (INIS)

    Bouziane, T.; Saber, M.; Belaaraj, A.; Ainane, A.

    1998-09-01

    The phase transitions of a ferromagnet spin-1/2 Ising superlattice consisting of two different materials in a transverse field is examined with the use of effective field theory that accounts for the self-spin function correlation. The critical temperature of the system is studied as a function of the thickness of the constituents in a unit cell and of exchange interactions in each material. A critical interface exchange interaction above which the interface magnetism appears is found. The effects of a uniform transverse field and the interface exchange interaction on the parameters of the system are also investigated. (author)

  13. Critical behavior of magnetization in URhAl: Quasi-two-dimensional Ising system with long-range interactions

    Science.gov (United States)

    Tateiwa, Naoyuki; Pospíšil, Jiří; Haga, Yoshinori; Yamamoto, Etsuji

    2018-02-01

    The critical behavior of dc magnetization in the uranium ferromagnet URhAl with the hexagonal ZrNiAl-type crystal structure has been studied around the ferromagnetic transition temperature TC. The critical exponent β for the temperature dependence of the spontaneous magnetization below TC,γ for the magnetic susceptibility, and δ for the magnetic isotherm at TC, have been obtained with a modified Arrott plot, a Kouvel-Fisher plot, the critical isotherm analysis, and the scaling analysis. We have determined the critical exponents as β =0.287 ±0.005 , γ =1.47 ±0.02 , and δ =6.08 ±0.04 by the scaling analysis and the critical isotherm analysis. These critical exponents satisfy the Widom scaling law δ =1 +γ /β . URhAl has strong uniaxial magnetic anisotropy, similar to its isostructural UCoAl that has been regarded as a three-dimensional (3D) Ising system in previous studies. However, the universality class of the critical phenomenon in URhAl does not belong to the 3D Ising model (β =0.325 , γ =1.241 , and δ =4.82 ) with short-range exchange interactions between magnetic moments. The determined exponents can be explained with the results of the renormalization group approach for a two-dimensional (2D) Ising system coupled with long-range interactions decaying as J (r ) ˜r-(d +σ ) with σ =1.44 . We suggest that the strong hybridization between the uranium 5 f and rhodium 4 d electrons in the U-RhI layer in the hexagonal crystal structure is a source of the low-dimensional magnetic property. The present result is contrary to current understandings of the physical properties in a series of isostructural UTX uranium ferromagnets (T: transition metals, X: p -block elements) based on the 3D Ising model.

  14. Dynamic compensation temperature in the kinetic spin-1 Ising model in an oscillating external magnetic field on alternate layers of a hexagonal lattice

    International Nuclear Information System (INIS)

    Temizer, Umuet; Keskin, Mustafa; Canko, Osman

    2009-01-01

    The dynamic behavior of a two-sublattice spin-1 Ising model with a crystal-field interaction (D) in the presence of a time-varying magnetic field on a hexagonal lattice is studied by using the Glauber-type stochastic dynamics. The lattice is formed by alternate layers of spins σ=1 and S=1. For this spin arrangement, any spin at one lattice site has two nearest-neighbor spins on the same sublattice, and four on the other sublattice. The intersublattice interaction is antiferromagnetic. We employ the Glauber transition rates to construct the mean-field dynamical equations. Firstly, we study time variations of the average magnetizations in order to find the phases in the system, and the temperature dependence of the average magnetizations in a period, which is also called the dynamic magnetizations, to obtain the dynamic phase transition (DPT) points as well as to characterize the nature (continuous and discontinuous) of transitions. Then, the behavior of the total dynamic magnetization as a function of the temperature is investigated to find the types of the compensation behavior. Dynamic phase diagrams are calculated for both DPT points and dynamic compensation effect. Phase diagrams contain the paramagnetic (p) and antiferromagnetic (af) phases, the p+af and nm+p mixed phases, nm is the non-magnetic phase, and the compensation temperature or the L-type behavior that strongly depend on the interaction parameters. For D 0 >3.8275, H 0 is the magnetic field amplitude, the compensation effect does not appear in the system.

  15. Dynamic compensation temperature in the kinetic spin-1 Ising model in an oscillating external magnetic field on alternate layers of a hexagonal lattice

    Energy Technology Data Exchange (ETDEWEB)

    Temizer, Umuet [Department of Physics, Bozok University, 66100 Yozgat (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2009-10-15

    The dynamic behavior of a two-sublattice spin-1 Ising model with a crystal-field interaction (D) in the presence of a time-varying magnetic field on a hexagonal lattice is studied by using the Glauber-type stochastic dynamics. The lattice is formed by alternate layers of spins {sigma}=1 and S=1. For this spin arrangement, any spin at one lattice site has two nearest-neighbor spins on the same sublattice, and four on the other sublattice. The intersublattice interaction is antiferromagnetic. We employ the Glauber transition rates to construct the mean-field dynamical equations. Firstly, we study time variations of the average magnetizations in order to find the phases in the system, and the temperature dependence of the average magnetizations in a period, which is also called the dynamic magnetizations, to obtain the dynamic phase transition (DPT) points as well as to characterize the nature (continuous and discontinuous) of transitions. Then, the behavior of the total dynamic magnetization as a function of the temperature is investigated to find the types of the compensation behavior. Dynamic phase diagrams are calculated for both DPT points and dynamic compensation effect. Phase diagrams contain the paramagnetic (p) and antiferromagnetic (af) phases, the p+af and nm+p mixed phases, nm is the non-magnetic phase, and the compensation temperature or the L-type behavior that strongly depend on the interaction parameters. For D<2.835 and H{sub 0}>3.8275, H{sub 0} is the magnetic field amplitude, the compensation effect does not appear in the system.

  16. Effect of External Economic-Field Cycle and Market Temperature on Stock-Price Hysteresis: Monte Carlo Simulation on the Ising Spin Model

    Science.gov (United States)

    Punya Jaroenjittichai, Atchara; Laosiritaworn, Yongyut

    2017-09-01

    In this work, the stock-price versus economic-field hysteresis was investigated. The Ising spin Hamiltonian was utilized as the level of ‘disagreement’ in describing investors’ behaviour. The Ising spin directions were referred to an investor’s intention to perform his action on trading his stock. The periodic economic variation was also considered via the external economic-field in the Ising model. The stochastic Monte Carlo simulation was performed on Ising spins, where the steady-state excess demand and supply as well as the stock-price were extracted via the magnetization. From the results, the economic-field parameters and market temperature were found to have significant effect on the dynamic magnetization and stock-price behaviour. Specifically, the hysteresis changes from asymmetric to symmetric loops with increasing market temperature and economic-field strength. However, the hysteresis changes from symmetric to asymmetric loops with increasing the economic-field frequency, when either temperature or economic-field strength is large enough, and returns to symmetric shape at very high frequencies. This suggests competitive effects among field and temperature factors on the hysteresis characteristic, implying multi-dimensional complicated non-trivial relationship among inputs-outputs. As is seen, the results reported (over extensive range) can be used as basis/guideline for further analysis/quantifying how economic-field and market-temperature affect the stock-price distribution on the course of economic cycle.

  17. Localized magnetic excitations for a line of magnetic impurities in a transverse Ising thin film ferromagnet

    International Nuclear Information System (INIS)

    Leite, R.V.; Oliveira Filho, L.O. de; Milton Pereira, J.; Cottam, M.G.; Costa Filho, R.N.

    2009-01-01

    A Green's function method is used to obtain the spectrum of spin excitations associated with a linear array of magnetic impurities implanted in a ferromagnetic thin film. The equations of motion for the Green's functions of the anisotropic film are written in the framework of the Ising model in a transverse field. The frequencies of localized modes are calculated as a function of the interaction parameters for the exchange coupling between impurity-spin pairs, host-spin pairs, and impurity-host neighbors, as well as the effective field parameter at the impurity sites.

  18. The order parameters of a spin-1 Ising film in a transverse field

    International Nuclear Information System (INIS)

    Saber, A.; Ainane, A.; Dujardin, F.; Saber, M.; Stebe, B.

    1998-08-01

    Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions, the layer longitudinal magnetizations and quadrupolar moments of a spin-1 Ising film and their averages are examined. These quantities as functions of the temperature, the ratio of the surface exchange interactions to the bulk ones, the strength of the transverse field and the film thickness are calculated numerically and some interesting results are obtained. (author)

  19. Radiative corrections to the quark masses in the ferromagnetic Ising and Potts field theories

    Directory of Open Access Journals (Sweden)

    Sergei B. Rutkevich

    2017-10-01

    Full Text Available We consider the Ising Field Theory (IFT, and the 3-state Potts Field Theory (PFT, which describe the scaling limits of the two-dimensional lattice q-state Potts model with q=2, and q=3, respectively. At zero magnetic field h=0, both field theories are integrable away from the critical point, have q degenerate vacua in the ferromagnetic phase, and q(q−1 particles of the same mass – the kinks interpolating between two different vacua. Application of a weak magnetic field induces confinement of kinks into bound states – the “mesons” (for q=2,3 consisting predominantly of two kinks, and “baryons” (for q=3, which are essentially the three-kink excitations. The kinks in the confinement regime are also called “the quarks”. We review and refine the Form Factor Perturbation Theory (FFPT, adapting it to the analysis of the confinement problem in the limit of small h, and apply it to calculate the corrections to the kink (quark masses induced by the multi-kink fluctuations caused by the weak magnetic field. It is shown that the subleading third-order ∼h3 correction to the kink mass vanishes in the IFT. The leading second order ∼h2 correction to the kink mass in the 3-state PFT is estimated by truncation the infinite form factor expansion at the first term representing contribution of the two-kink fluctuations into the kink self-energy.

  20. Radiative corrections to the quark masses in the ferromagnetic Ising and Potts field theories

    Science.gov (United States)

    Rutkevich, Sergei B.

    2017-10-01

    We consider the Ising Field Theory (IFT), and the 3-state Potts Field Theory (PFT), which describe the scaling limits of the two-dimensional lattice q-state Potts model with q = 2, and q = 3, respectively. At zero magnetic field h = 0, both field theories are integrable away from the critical point, have q degenerate vacua in the ferromagnetic phase, and q (q - 1) particles of the same mass - the kinks interpolating between two different vacua. Application of a weak magnetic field induces confinement of kinks into bound states - the "mesons" (for q = 2 , 3) consisting predominantly of two kinks, and "baryons" (for q = 3), which are essentially the three-kink excitations. The kinks in the confinement regime are also called "the quarks". We review and refine the Form Factor Perturbation Theory (FFPT), adapting it to the analysis of the confinement problem in the limit of small h, and apply it to calculate the corrections to the kink (quark) masses induced by the multi-kink fluctuations caused by the weak magnetic field. It is shown that the subleading third-order ∼h3 correction to the kink mass vanishes in the IFT. The leading second order ∼h2 correction to the kink mass in the 3-state PFT is estimated by truncation the infinite form factor expansion at the first term representing contribution of the two-kink fluctuations into the kink self-energy.

  1. Zero-temperature renormalization method for quantum systems. I. Ising model in a transverse field in one dimension

    International Nuclear Information System (INIS)

    Jullien, R.; Pfeuty, P.; Fields, J.N.; Doniach, S.

    1978-01-01

    A zero-temperature real-space renormalization-group method is presented and applied to the quantum Ising model with a transverse field in one dimension. The transition between the low-field and high-field regimes is studied. Magnetization components, spin correlation functions, and critical exponents are derived and checked against the exact results. It is shown that increasing the size of the blocks in the iterative procedure yields more accurate results, especially for the critical ''magnetic'' exponents near the transition

  2. Kinetic Ising model in a time-dependent oscillating external magnetic field: effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Canko, Osman; Keskin, Mustafa

    2010-01-01

    Recently, Shi et al. [2008 Phys. Lett. A 372 5922] have studied the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field and presented the dynamic phase diagrams by using an effective-field theory (EFT) and a mean-field theory (MFT). The MFT results are in conflict with those of the earlier work of Tomé and de Oliveira, [1990 Phys. Rev. A 41 4251]. We calculate the dynamic phase diagrams and find that our results are similar to those of the earlier work of Tomé and de Oliveira; hence the dynamic phase diagrams calculated by Shi et al. are incomplete within both theories, except the low values of frequencies for the MFT calculation. We also investigate the influence of external field frequency (ω) and static external field amplitude (h 0 ) for both MFT and EFT calculations. We find that the behaviour of the system strongly depends on the values of ω and h 0 . (general)

  3. Large deviations of the finite-time magnetization of the Curie-Weiss random-field Ising model

    Science.gov (United States)

    Paga, Pierre; Kühn, Reimer

    2017-08-01

    We study the large deviations of the magnetization at some finite time in the Curie-Weiss random field Ising model with parallel updating. While relaxation dynamics in an infinite-time horizon gives rise to unique dynamical trajectories [specified by initial conditions and governed by first-order dynamics of the form mt +1=f (mt) ] , we observe that the introduction of a finite-time horizon and the specification of terminal conditions can generate a host of metastable solutions obeying second-order dynamics. We show that these solutions are governed by a Newtonian-like dynamics in discrete time which permits solutions in terms of both the first-order relaxation ("forward") dynamics and the backward dynamics mt +1=f-1(mt) . Our approach allows us to classify trajectories for a given final magnetization as stable or metastable according to the value of the rate function associated with them. We find that in analogy to the Freidlin-Wentzell description of the stochastic dynamics of escape from metastable states, the dominant trajectories may switch between the two types (forward and backward) of first-order dynamics. Additionally, we show how to compute rate functions when uncertainty in the quenched disorder is introduced.

  4. Dynamic magnetizations and dynamic phase transitions in a transverse cylindrical Ising nanowire

    International Nuclear Information System (INIS)

    Deviren, Bayram; Ertaş, Mehmet; Keskin, Mustafa

    2012-01-01

    In this paper, we extend the paper of Kaneyoshi (2010 J. Magn. Magn. Mater. 322 3410-5) to investigate the dynamic magnetizations and dynamic phase transitions of a transverse cylindrical Ising nanowire system by using the effective field theory with correlations and the Glauber-type stochastic dynamics under a time-dependent oscillating external magnetic field. The dynamic effective field equations for the average longitudinal and transverse magnetizations on the surface shell and core are derived by using the Glauber transition rates. Temperature dependences of the dynamic longitudinal magnetizations, the transverse magnetizations and the total magnetizations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system is strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, four different types of compensation behaviors in the Néel classification nomenclature exist in the system. The results are compared with some theoretical works and good overall agreement is observed. (paper)

  5. Spatial distribution of electron plasma oscillations in the Earth`s foreshock at ISEE 3

    Energy Technology Data Exchange (ETDEWEB)

    Greenstadt, E.W.; Moses, S.L.; Coroniti, F.V. [TRW, Redondo Beach, CA (United States)] [and others

    1995-10-01

    Electric field oscillations recorded by the 10-56 kHz channels of TRW`s plasma wave detector during parts of two of the ISEE 3 circumterrestrial orbits in 1983 have been used to make the first mapping of Earth`s electron plasma wave foreshock. By combining data from the two trajectory segments, each of which provided relatively meager spatial sampling outside the bow shock, but high variation of interplanetary magnetic field (IMF) direction, a first-order pattern of occurrence of electron plasma waves, hence also backstreaming electrons, has been determined. The authors depict the pattern with an adaptation of the mapping program previously used for the Venus electron foreshock. As at Venus, plasma wave activity was concentrated most densely along the IMF line tangent to the bow shock. Their mappings with three additional ISEE 3 channels surrounding the local electron plasma frequency indicate a richer distribution of waves in the foreshock than the single electron frequency channel of Pioneer Venus Orbiter could detect around Venus. 14 refs., 4 figs.

  6. Zero-field-cooled/field-cooled magnetization study of Dendrimer model

    Energy Technology Data Exchange (ETDEWEB)

    Arejdal, M., E-mail: arejdal.achdad@gmail.com [Laboratory of Magnetism and Physics of High Energies, Department of Physics, L.M.P.H.E (URAC-12), Faculty of Sciences, Mohammed V University, Rabat (Morocco); Bahmad, L. [Laboratory of Magnetism and Physics of High Energies, Department of Physics, L.M.P.H.E (URAC-12), Faculty of Sciences, Mohammed V University, Rabat (Morocco); Benyoussef, A. [Hassan II Academy of Science and Technology, Rabat (Morocco)

    2017-01-01

    Being motivated by Dendrimer model with mixed spins σ=3 and S=7/2, we investigated the magnetic nanoparticle system in this study. We analyzed and discussed the ground-state phase diagrams and the stable phases. Then, we elaborated and explained the magnetic properties of the system by using Monte Carlo Simulations (MCS) in the framework of the Ising model. In this way, we determined the blocking temperature, which is deduced through studying the partial-total magnetization and susceptibility as a function of the temperature, and we established the effects of both the exchange coupling interaction and the crystal field on the hysteresis loop.

  7. Effective-field renormalization-group method for Ising systems

    Science.gov (United States)

    Fittipaldi, I. P.; De Albuquerque, D. F.

    1992-02-01

    A new applicable effective-field renormalization-group (ERFG) scheme for computing critical properties of Ising spins systems is proposed and used to study the phase diagrams of a quenched bond-mixed spin Ising model on square and Kagomé lattices. The present EFRG approach yields results which improves substantially on those obtained from standard mean-field renormalization-group (MFRG) method. In particular, it is shown that the EFRG scheme correctly distinguishes the geometry of the lattice structure even when working with the smallest possible clusters, namely N'=1 and N=2.

  8. Ising model on tangled chain - 2: Magnetization and susceptibility

    International Nuclear Information System (INIS)

    Mejdani, R.

    1993-05-01

    In the preceding paper we have considered an Ising model defined on tangled chain to study the behaviour of the free energy and entropy, particularly in the zero-field and zero-temperature limit. In this paper, following the main line and basing on some results of the previous work, we shall study in the ''language'' of state configurations the behaviour of the magnetization and the susceptibility for different conditions of the model, to understand better the competition between the ferromagnetic bonds along the chain and the antiferromagnetic additional bonds across the chain. Particularly interesting is the behaviour of the susceptibility in the zero-field and zero-temperature limit. Exact solutions for the magnetization and susceptibility, generated by analytical calculations and iterative algorithms, are described. The additional bonds, introduced as a form of perfectly disorder, indicate a particular effect on the spin correlation. We found that the condition J=-J' between the ferromagnetic interaction J along the chain and the antiferromagnetic interaction J' across the chain is somewhat as a ''transition-region'' condition for this behaviour. (author). 16 refs, 14 figs

  9. Effect of Ising-type Tb.sup.3+./sup. ions on the low-temperature magnetism of La, Ca cobaltite

    Czech Academy of Sciences Publication Activity Database

    Knížek, Karel; Jirák, Zdeněk; Hejtmánek, Jiří; Veverka, Miroslav; Kaman, Ondřej; Maryško, Miroslav; Šantavá, Eva; André, G.

    2014-01-01

    Roč. 26, č. 11 (2014), "116003-1"-"116003-9" ISSN 0953-8984 R&D Projects: GA ČR(CZ) GAP204/11/0713 Institutional support: RVO:68378271 Keywords : perovskite cobaltites * neutron diffraction * magnetic ordering * Ising moments * linear specific heat Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.346, year: 2014

  10. Computational Analysis of 3D Ising Model Using Metropolis Algorithms

    International Nuclear Information System (INIS)

    Sonsin, A F; Cortes, M R; Nunes, D R; Gomes, J V; Costa, R S

    2015-01-01

    We simulate the Ising Model with the Monte Carlo method and use the algorithms of Metropolis to update the distribution of spins. We found that, in the specific case of the three-dimensional Ising Model, methods of Metropolis are efficient. Studying the system near the point of phase transition, we observe that the magnetization goes to zero. In our simulations we analyzed the behavior of the magnetization and magnetic susceptibility to verify the phase transition in a paramagnetic to ferromagnetic material. The behavior of the magnetization and of the magnetic susceptibility as a function of the temperature suggest a phase transition around KT/J ≈ 4.5 and was evidenced the problem of finite size of the lattice to work with large lattice. (paper)

  11. Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

    International Nuclear Information System (INIS)

    Kocakaplan, Yusuf; Keskin, Mustafa

    2014-01-01

    The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement

  12. Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

    Energy Technology Data Exchange (ETDEWEB)

    Kocakaplan, Yusuf [Graduate School of Natural and Applied Sciences, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2014-09-07

    The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement.

  13. Generic Ising trees

    DEFF Research Database (Denmark)

    Durhuus, Bergfinnur Jøgvan; Napolitano, George Maria

    2012-01-01

    The Ising model on a class of infinite random trees is defined as a thermodynamiclimit of finite systems. A detailed description of the corresponding distribution of infinite spin configurations is given. As an application, we study the magnetization properties of such systems and prove that they......The Ising model on a class of infinite random trees is defined as a thermodynamiclimit of finite systems. A detailed description of the corresponding distribution of infinite spin configurations is given. As an application, we study the magnetization properties of such systems and prove...... that they exhibit no spontaneous magnetization. Furthermore, the values of the Hausdorff and spectral dimensions of the underlying trees are calculated and found to be, respectively,¯dh =2 and¯ds = 4/3....

  14. Magnetization in quenched bond-mixed Ising ferromagnetic with anisotropic coupling constants

    International Nuclear Information System (INIS)

    Sarmento, E.F.; Tsallis, C.

    1982-01-01

    Within the framework of an effective field theory the phase diagram (ferromagnetic phase stability limit) and magnetization of a quenched bond-mixed spin 1 / 2 Ising model in anisotropic simple cubic lattice for both competing and non competing interactions is dicussed. Although analytically simple, the present formalism is superior to the standard Mean Field Approximation regarding at least two important features, namely it is capable of providing: (i) vanishing critical temperatures for one-dimensional systems; (ii) expected non uniform convergences in the highly diluted and highly anisotropic limits. The largeness of the model under consideration enables the exhibition of a certain amount of physically interesting crossovers (dimensionality changements, (dilute) - (non dilute) behavior, or even mixed situations) at both the phase diagram and magnetization levels. Whenever comparison is possible a satisfactory qualitative (and to a certain extent quantitative) agreement is observed with results available in the literature. (Author) [pt

  15. Magnetization plateaus of the frustrated Ising Shastry–Sutherland system: Wang–Landau simulation

    International Nuclear Information System (INIS)

    Lin, W.S.; Yang, T.H.; Wang, Y.; Qin, M.H.; Liu, J.-M.; Ren, Zhifeng

    2014-01-01

    The Wang–Landau algorithm is used to study the magnetic properties of the Ising model on the Shastry–Sutherland lattice in order to understand the interesting magnetization plateaus observed in TmB 4 . The simulated results demonstrate that the equilibrium state of the model produces only the 1/3 and 1/2 magnetization plateaus at low temperatures even when the random-exchange term or the long-range interactions are taken into account. This confirms our earlier conclusion (Huang et al., 2013) [20] that those fractional plateaus observed in experiments may be due to the magnetization dynamics. - Highlights: • The magnetic behaviors of TmB 4 are investigated using the Wang–Landau method. • The equilibrium state only produces the 1/3 and 1/2 magnetization plateaus. • Those fractional plateaus must arise from the non-equilibrium magnetization

  16. Magnetization plateaus of the frustrated Ising Shastry–Sutherland system: Wang–Landau simulation

    Energy Technology Data Exchange (ETDEWEB)

    Lin, W.S.; Yang, T.H.; Wang, Y. [Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Qin, M.H., E-mail: qinmh@scnu.edu.cn [Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Department of Physics and TcSUH, University of Houston, Houston, TX 77204 (United States); Liu, J.-M. [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Ren, Zhifeng, E-mail: zren@uh.edu [Department of Physics and TcSUH, University of Houston, Houston, TX 77204 (United States)

    2014-07-04

    The Wang–Landau algorithm is used to study the magnetic properties of the Ising model on the Shastry–Sutherland lattice in order to understand the interesting magnetization plateaus observed in TmB{sub 4}. The simulated results demonstrate that the equilibrium state of the model produces only the 1/3 and 1/2 magnetization plateaus at low temperatures even when the random-exchange term or the long-range interactions are taken into account. This confirms our earlier conclusion (Huang et al., 2013) [20] that those fractional plateaus observed in experiments may be due to the magnetization dynamics. - Highlights: • The magnetic behaviors of TmB{sub 4} are investigated using the Wang–Landau method. • The equilibrium state only produces the 1/3 and 1/2 magnetization plateaus. • Those fractional plateaus must arise from the non-equilibrium magnetization.

  17. An effective correlated mean-field theory applied in the spin-1/2 Ising ferromagnetic model

    Energy Technology Data Exchange (ETDEWEB)

    Roberto Viana, J.; Salmon, Octávio R. [Universidade Federal do Amazonas – UFAM, Manaus 69077-000, AM (Brazil); Ricardo de Sousa, J. [Universidade Federal do Amazonas – UFAM, Manaus 69077-000, AM (Brazil); National Institute of Science and Technology for Complex Systems, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Neto, Minos A.; Padilha, Igor T. [Universidade Federal do Amazonas – UFAM, Manaus 69077-000, AM (Brazil)

    2014-11-15

    We developed a new treatment for mean-field theory applied in spins systems, denominated effective correlated mean-field (ECMF). We apply this theory to study the spin-1/2 Ising ferromagnetic model with nearest-neighbor interactions on a square lattice. We use clusters of finite sizes and study the criticality of the ferromagnetic system, where we obtain a convergence of critical temperature for the value k{sub B}T{sub c}/J≃2.27905±0.00141. Also the behavior of magnetic and thermodynamic properties, using the condition of minimum energy of the physical system is obtained. - Highlights: • We developed spin models to study real magnetic systems. • We study the thermodynamic and magnetic properties of the ferromagnetism. • We enhanced a mean-field theory applied in spins models.

  18. Large-scale Ising-machines composed of magnetic neurons

    Science.gov (United States)

    Mizushima, Koichi; Goto, Hayato; Sato, Rie

    2017-10-01

    We propose Ising-machines composed of magnetic neurons, that is, magnetic bits in a recording track. In large-scale machines, the sizes of both neurons and synapses need to be reduced, and neat and smart connections among neurons are also required to achieve all-to-all connectivity among them. These requirements can be fulfilled by adopting magnetic recording technologies such as race-track memories and skyrmion tracks because the area of a magnetic bit is almost two orders of magnitude smaller than that of static random access memory, which has normally been used as a semiconductor neuron, and the smart connections among neurons are realized by using the read and write methods of these technologies.

  19. Magnetic properties and thermodynamics of decorated Ising chain with pendants of arbitrary spin

    Energy Technology Data Exchange (ETDEWEB)

    Li Wei, E-mail: liwei-b09@mails.gucas.ac.c [College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049 (China); Department of Physics, Beihang University, Beijing 100191 (China); Gong Shoushu [College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049 (China); Chen Ziyu [Department of Physics, Beihang University, Beijing 100191 (China); Zhao Yang [College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049 (China); Su Gang, E-mail: gsu@gucas.ac.c [College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049 (China)

    2010-05-31

    The decorated Ising chain with pendants of arbitrary spin and the single-ion anisotropy is exactly solved by the transfer matrix method. The solutions reveal abundant novel properties than the conventional one-dimensional Ising model. It is compared with the experimental data of a necklace-like molecule-based magnet, that gives a qualitative consistency.

  20. Magnetic properties and thermodynamics of decorated Ising chain with pendants of arbitrary spin

    International Nuclear Information System (INIS)

    Li Wei; Gong Shoushu; Chen Ziyu; Zhao Yang; Su Gang

    2010-01-01

    The decorated Ising chain with pendants of arbitrary spin and the single-ion anisotropy is exactly solved by the transfer matrix method. The solutions reveal abundant novel properties than the conventional one-dimensional Ising model. It is compared with the experimental data of a necklace-like molecule-based magnet, that gives a qualitative consistency.

  1. Universal amplitude ratios in the 3D Ising model

    International Nuclear Information System (INIS)

    Caselle, M.; Hasenbusch, M.

    1998-01-01

    We present a high precision Monte Carlo study of various universal amplitude ratios of the three dimensional Ising spin model. Using state of the art simulation techniques we studied the model close to criticality in both phases. Great care was taken to control systematic errors due to finite size effects and correction to scaling terms. We obtain C + /C - =4.75(3), f +,2nd /f -,2nd =1.95(2) and u * =14.3(1). Our results are compatible with those obtained by field theoretic methods applied to the φ 4 theory and high and low temperature series expansions of the Ising model. (orig.)

  2. Wave properties near the subsolar magnetopause - Pc 3-4 energy coupling for northward interplanetary magnetic field

    Science.gov (United States)

    Song, P.; Russell, C. T.; Strangeway, R. J.; Wygant, J. R.; Cattell, C. A.; Fitzenreiter, R. J.; Anderson, R. R.

    1993-01-01

    Strong slow mode waves in the Pc 3-4 frequency range are found in the magnetosheath close to the magnetopause. We have studied these waves at one of the ISEE subsolar magnetopause crossings using the magnetic field, electric field, and plasma measurements. We use the pressure balance at the magnetopause to calibrate the Fast Plasma Experiment data versus the magnetometer data. When we perform such a calibration and renormalization, we find that the slow mode structures are not in pressure balance and small scale fluctuations in the total pressure still remain in the Pc 3-4 range. Energy in the total pressure fluctuations can be transmitted through the magnetopause by boundary motions. The Poynting flux calculated from the electric and magnetic field measurements suggests that a net Poynting flux is transmitted into the magnetopause. The two independent measurements show a similar energy transmission coefficient. The transmitted energy flux is about 18 percent of the magnetic energy flux of the waves in the magnetosheath. Part of this transmitted energy is lost in the sheath transition layer before it enters the closed field line region. The waves reaching the boundary layer decay rapidly. Little wave power is transmitted into the magnetosphere.

  3. Particles and scaling for lattice fields and Ising models

    International Nuclear Information System (INIS)

    Glimm, J.; Jaffe, A.

    1976-01-01

    The conjectured inequality GAMMA 6 4 -fields and the scaling limit for d-dimensional Ising models. Assuming GAMMA 6 = 6 these phi 4 fields are free fields unless the field strength renormalization Z -1 diverges. (orig./BJ) [de

  4. Dynamic magnetic behavior of the mixed-spin bilayer system in an oscillating field within the mean-field theory

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Keskin, Mustafa

    2012-01-01

    The dynamic magnetic behavior of the mixed Ising bilayer system (σ=2 and S=5/2), with a crystal-field interaction in an oscillating field are studied, within the mean-field approach, by using the Glauber-type stochastic dynamics for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior depending on interaction parameters. -- Highlights: ► Dynamic magnetic behavior of the mixed Ising bilayer system is investigated within the Glauber-type stochastic dynamics. ► The time variations of average magnetizations are studied to find the phases. ► The temperature dependence of the dynamic magnetizations is investigated to obtain the dynamic phase transition points. ► The dynamic phase diagrams are presented and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior.

  5. Dynamic magnetic behavior of the mixed-spin bilayer system in an oscillating field within the mean-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-07-23

    The dynamic magnetic behavior of the mixed Ising bilayer system (σ=2 and S=5/2), with a crystal-field interaction in an oscillating field are studied, within the mean-field approach, by using the Glauber-type stochastic dynamics for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior depending on interaction parameters. -- Highlights: ► Dynamic magnetic behavior of the mixed Ising bilayer system is investigated within the Glauber-type stochastic dynamics. ► The time variations of average magnetizations are studied to find the phases. ► The temperature dependence of the dynamic magnetizations is investigated to obtain the dynamic phase transition points. ► The dynamic phase diagrams are presented and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior.

  6. A unified effective-field renormalization-group framework approach for the quenched diluted Ising models

    Science.gov (United States)

    de Albuquerque, Douglas F.; Fittipaldi, I. P.

    1994-05-01

    A unified effective-field renormalization-group framework (EFRG) for both quenched bond- and site-diluted Ising models is herein developed by extending recent works. The method, as in the previous works, follows up the same strategy of the mean-field renormalization-group scheme (MFRG), and is achieved by introducing an alternative way for constructing classical effective-field equations of state, based on rigorous Ising spin identities. The concentration dependence of the critical temperature, Tc(p), and the critical concentrations of magnetic atoms, pc, at which the transition temperature goes to zero, are evaluated for several two- and three-dimensional lattice structures. The obtained values of Tc and pc and the resulting phase diagrams for both bond and site cases are much more accurate than those estimated by the standard MFRG approach. Although preserving the same level of simplicity as the MFRG, it is shown that the present EFRG method, even by considering its simplest size-cluster version, provides results that correctly distinguishes those lattices that have the same coordination number, but differ in dimensionality or geometry.

  7. Phase transitions in the random field Ising model in the presence of a transverse field

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, A.; Chakrabarti, B.K. [Saha Institute of Nuclear Physics, Bidhannagar, Calcutta (India); Stinchcombe, R.B. [Saha Institute of Nuclear Physics, Bidhannagar, Calcutta (India); Department of Physics, Oxford (United Kingdom)

    1996-09-07

    We have studied the phase transition behaviour of the random field Ising model in the presence of a transverse (or tunnelling) field. The mean field phase diagram has been studied in detail, and in particular the nature of the transition induced by the tunnelling (transverse) field at zero temperature. Modified hyper-scaling relation for the zero-temperature transition has been derived using the Suzuki-Trotter formalism and a modified 'Harris criterion'. Mapping of the model to a randomly diluted antiferromagnetic Ising model in uniform longitudinal and transverse field is also given. (author)

  8. Crystal-field study of magnetization and specific heat properties of frustrated pyrochlore Pr2Zr2O7

    International Nuclear Information System (INIS)

    Alam, J.; Jana, Y.M.; Biswas, A. Ali

    2016-01-01

    The experimental results of temperature dependent dc magnetic susceptibility, field dependent isothermal magnetization, magnetic specific heat and entropy of the pyrochlore Pr 2 Zr 2 O 7 are simulated and analyzed using appropriate D 3d crystal-field (CF) and anisotropic molecular field tensors at Pr-sites in the self-consistent mean-field approach involving four magnetically non-equivalent rare-earth spins on the tetrahedral unit of the pyrochlore structure. CF level pattern and wave-functions of the ground 3 H 4 multiplet of the Pr 3+ ions are obtained considering intermediate coupling between different Russell-Saunders terms of the 4f 2 electronic configurations of Pr-ion and J-mixing effects. CF analysis shows that the CF ground-state of the Pr 3+ ion in Pr 2 Zr 2 O 7 is a well-isolated doublet, with significant admixtures of terms coming from |M J =±4〉 and |M J =±1〉, and the Pr-spins are effectively Ising-like along the local <111> axes. Magnetic specific heat in zero-field is simulated by considering a temperature dependence of the exchange splitting of the ground doublet. - Highlights: • Full CF diagonalization using intermediate coupling and J-mixing. • Pr-spins are Ising-like along local [111] axis. • Magnetic specific heat is due to temperature dependence exchange splitting of ground CF doublet.

  9. Power laws in Ising nanostripes

    International Nuclear Information System (INIS)

    Drzewinski, A.; Sznajd, J.; Szota, K.

    2005-01-01

    The results of high accuracy density-matrix renormalization-group calculations for infinite Ising stripes of finite widths 100 ≤ L ≤ 400 are presented. It is shown that in the presence of the small external magnetic field the infinite system critical power laws can be observed for L of order hundreds nm. The single power law describes the field dependence of the magnetization or the longitudinal correlation length only on the infinite system critical isotherm independently of the value of L. The approximate power law which describes how the magnetization varies with a distance from the infinite system critical point for several directions in the plane (temperature, external field) is also studied. (author)

  10. Size effects in spin-crossover nanoparticles in framework of 2D and 3D Ising-like breathing crystal field model

    International Nuclear Information System (INIS)

    Gudyma, Iu.; Maksymov, A.; Spinu, L.

    2015-01-01

    Highlights: • We study the thermal hysteresis in spin-crossover nanoparticles with stochastic perturbation. • The dependence of system behavior on its dimensionality and size were examined. • The spin-crossover compounds where described by breathing crystal field Ising-like model. • The fluctuations may enlarge the hysteresis width which is dependent on the system size. - Abstract: The spin-crossover nanoparticles of different sizes and stochastic perturbations in external field taking into account the influence of the dimensionality of the lattice was studied. The analytical tools used for the investigation of spin-crossover system are based on an Ising-like model described using of the breathing crystal field concept. The changes of transition temperatures characterizing the systems’ bistable properties for 2D and 3D lattices, and their dependence on its size and fluctuations strength were obtained. The state diagrams with hysteretic and non-hysteretic behavior regions have also been determined.

  11. Size effects in spin-crossover nanoparticles in framework of 2D and 3D Ising-like breathing crystal field model

    Energy Technology Data Exchange (ETDEWEB)

    Gudyma, Iu. [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Maksymov, A., E-mail: maxyartur@gmail.com [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Advanced Material Research Institute (AMRI), University of New Orleans, New Orleans, LA 70148 (United States); Spinu, L. [Advanced Material Research Institute (AMRI), University of New Orleans, New Orleans, LA 70148 (United States); Department of Physics, University of New Orleans, New Orleans, LA 70148 (United States)

    2015-10-15

    Highlights: • We study the thermal hysteresis in spin-crossover nanoparticles with stochastic perturbation. • The dependence of system behavior on its dimensionality and size were examined. • The spin-crossover compounds where described by breathing crystal field Ising-like model. • The fluctuations may enlarge the hysteresis width which is dependent on the system size. - Abstract: The spin-crossover nanoparticles of different sizes and stochastic perturbations in external field taking into account the influence of the dimensionality of the lattice was studied. The analytical tools used for the investigation of spin-crossover system are based on an Ising-like model described using of the breathing crystal field concept. The changes of transition temperatures characterizing the systems’ bistable properties for 2D and 3D lattices, and their dependence on its size and fluctuations strength were obtained. The state diagrams with hysteretic and non-hysteretic behavior regions have also been determined.

  12. Effective field treatment of the annealed bond-dilute transverse Ising model

    International Nuclear Information System (INIS)

    Silva, P.R.; Sa Barreto, F.C. de

    1983-01-01

    The dilution of the spin-1/2 transverse Ising Model is studied by means of an effective field type treatment based on an extension of Callen's relation to the present model. The thermodynamics of the diluted model is obtained and the results are shown to be an improvement over the standard mean field treatment. The results are also compared with the Monte Carlo calculation for the spin-infinite transverse Ising Model. (Author) [pt

  13. Self-dual cluster renormalization group approach for the square lattice Ising model specific heat and magnetization

    International Nuclear Information System (INIS)

    Martin, H.O.; Tsallis, C.

    1981-01-01

    A simple renormalization group approach based on self-dual clusters is proposed for two-dimensional nearest-neighbour 1/2 - spin Ising model on the square lattice; it reproduces the exact critical point. The internal energy and the specific heat for vanishing external magnetic field, spontaneous magnetization and the thermal (Y sub(T)) and magnetic (Y sub(H)) critical exponents are calculated. The results obtained from the first four smallest cluster sizes strongly suggest the convergence towards the exact values when the cluster sizes increases. Even for the smallest cluster, where the calculation is very simple, the results are quite accurate, particularly in the neighbourhood of the critical point. (Author) [pt

  14. Dynamics of the Random Field Ising Model

    Science.gov (United States)

    Xu, Jian

    The Random Field Ising Model (RFIM) is a general tool to study disordered systems. Crackling noise is generated when disordered systems are driven by external forces, spanning a broad range of sizes. Systems with different microscopic structures such as disordered mag- nets and Earth's crust have been studied under the RFIM. In this thesis, we investigated the domain dynamics and critical behavior in two dipole-coupled Ising ferromagnets Nd2Fe14B and LiHoxY 1-xF4. With Tc well above room temperature, Nd2Fe14B has shown reversible disorder when exposed to an external transverse field and crosses between two universality classes in the strong and weak disorder limits. Besides tunable disorder, LiHoxY1-xF4 has shown quantum tunneling effects arising from quantum fluctuations, providing another mechanism for domain reversal. Universality within and beyond power law dependence on avalanche size and energy were studied in LiHo0.65Y0.35 F4.

  15. Universal scaling for the quantum Ising chain with a classical impurity

    Science.gov (United States)

    Apollaro, Tony J. G.; Francica, Gianluca; Giuliano, Domenico; Falcone, Giovanni; Palma, G. Massimo; Plastina, Francesco

    2017-10-01

    We study finite-size scaling for the magnetic observables of an impurity residing at the end point of an open quantum Ising chain with transverse magnetic field, realized by locally rescaling the field by a factor μ ≠1 . In the homogeneous chain limit at μ =1 , we find the expected finite-size scaling for the longitudinal impurity magnetization, with no specific scaling for the transverse magnetization. At variance, in the classical impurity limit μ =0 , we recover finite scaling for the longitudinal magnetization, while the transverse one basically does not scale. We provide both analytic approximate expressions for the magnetization and the susceptibility as well as numerical evidences for the scaling behavior. At intermediate values of μ , finite-size scaling is violated, and we provide a possible explanation of this result in terms of the appearance of a second, impurity-related length scale. Finally, by going along the standard quantum-to-classical mapping between statistical models, we derive the classical counterpart of the quantum Ising chain with an end-point impurity as a classical Ising model on a square lattice wrapped on a half-infinite cylinder, with the links along the first circle modified as a function of μ .

  16. Tricritical behavior in the diluted transverse spin-1 Ising model with a longitudinal crystal field

    International Nuclear Information System (INIS)

    Htoutou, K.; Oubelkacem, A.; Ainane, A.; Saber, M.

    2005-01-01

    The transverse spin-1 Ising model with a longitudinal crystal field exhibits a tricritical behavior. Within the effective field theory with a probability distribution technique that accounts for the self-spin correlations, we have studied the influence of site dilution on this behavior and have calculated the temperature-transverse field-longitudinal crystal field-concentration phase diagrams and determined, in particular, the influence of the concentration of magnetic atoms c on the tricritical behavior. We have found that the tricritical point appears for large values of the concentration c of magnetic atoms and disappears with the increase in dilution (small values of c). Results for square lattice are calculated numerically and some interesting results are obtained. In certain ranges of values of the strength of the longitudinal crystal field D/J when it becomes sufficiently negative, we found re-entrant phenomenon, which disappears with increase in the value of the strength of the transverse field

  17. Multi-step magnetization of the Ising model on a Shastry-Sutherland lattice: a Monte Carlo simulation

    International Nuclear Information System (INIS)

    Huang, W C; Huo, L; Tian, G; Qian, H R; Gao, X S; Qin, M H; Liu, J-M

    2012-01-01

    The magnetization behaviors and spin configurations of the classical Ising model on a Shastry-Sutherland lattice are investigated using Monte Carlo simulations, in order to understand the fascinating magnetization plateaus observed in TmB 4 and other rare-earth tetraborides. The simulations reproduce the 1/2 magnetization plateau by taking into account the dipole-dipole interaction. In addition, a narrow 2/3 magnetization step at low temperature is predicted in our simulation. The multi-step magnetization can be understood as the consequence of the competitions among the spin-exchange interaction, the dipole-dipole interaction, and the static magnetic energy.

  18. Characterization of switching field distributions in Ising-like magnetic arrays

    Science.gov (United States)

    Fraleigh, Robert D.; Kempinger, Susan; Lammert, Paul E.; Zhang, Sheng; Crespi, Vincent H.; Schiffer, Peter; Samarth, Nitin

    2017-04-01

    The switching field distribution within arrays of single-domain ferromagnetic islands incorporates both island-island interactions and quenched disorder in island geometry. Separating these two contributions is important for disentangling the effects of disorder and interactions in the magnetization dynamics of island arrays. Using submicron, spatially resolved Kerr imaging in an external magnetic field for islands with perpendicular magnetic anisotropy, we map out the evolution of island arrays during hysteresis loops. Resolving and tracking individual islands across four different lattice types and a range of interisland spacings, we can extract the individual switching fields of every island and thereby quantitatively determine the contributions of interactions and quenched disorder in the arrays. The width of the switching field distribution is found to be well fitted by a simple model comprising the sum of an array-independent contribution (interpreted as disorder induced) and a term proportional to the maximum field the entire rest of the array could exert on a single island, i.e., in a fully polarized state. This supports the claim that disorder in these arrays is primarily a single-island property and provides a methodology by which to quantify such disorder.

  19. Effective field theory with differential operator technique for dynamic phase transition in ferromagnetic Ising model

    International Nuclear Information System (INIS)

    Kinoshita, Takehiro; Fujiyama, Shinya; Idogaki, Toshihiro; Tokita, Masahiko

    2009-01-01

    The non-equilibrium phase transition in a ferromagnetic Ising model is investigated by use of a new type of effective field theory (EFT) which correctly accounts for all the single-site kinematic relations by differential operator technique. In the presence of a time dependent oscillating external field, with decrease of the temperature the system undergoes a dynamic phase transition, which is characterized by the period averaged magnetization Q, from a dynamically disordered state Q = 0 to the dynamically ordered state Q ≠ 0. The results of the dynamic phase transition point T c determined from the behavior of the dynamic magnetization and the Liapunov exponent provided by EFT are improved than that of the standard mean field theory (MFT), especially for the one dimensional lattice where the standard MFT gives incorrect result of T c = 0 even in the case of zero external field.

  20. Mixed spin-5/2 and spin-2 Ising ferrimagnetic system on the Bethe lattice

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, PB 63 46000, Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2015-11-01

    The magnetic properties of spins-S and σ Ising model on the Bethe lattice have been investigated by using the Monte Carlo simulation. The thermal total magnetization and magnetization of spins S and σ with the different exchange interactions, different external magnetic field and different temperatures have been studied. The critical temperature and compensation temperature have been deduced. The magnetic hysteresis cycle of Ising ferrimagnetic system on the Bethe lattice has been deduced for different values of exchange interactions between the spins S and σ, for different values of crystal field and for different sizes. The magnetic coercive filed has been deduced. - Highlights: • The magnetic properties of Bethe lattice have been investigated. • The critical temperature and compensation temperature have been deduced. • The magnetic coercive filed has been deduced.

  1. Variable field-to-normal angles in the shock foreshock boundary observed by ISEE 1 and 2

    International Nuclear Information System (INIS)

    Greenstadt, E.W.; Mellot, M.M.

    1985-01-01

    Saturated ULF waves in the foreshock, with amplitudes comparable to the magnitude of the average field, are convected by the solar wind to the quasi-parallel shock where the average field-normal angle is less than, or about, 45 0 . Several examples from ISEE 1 and 2 magnetometer data show waves that defined local, instantaneous field-normal angles very different periodically from the average. Local geometric conditions at the nominally quasi-parallel shock varied from nearly parallel to nearly perpendicular, at the periods of typical upstream waves. Clear magnetic shock transitions occurred under temporarily quasi-perpendicular geometry

  2. Ground-state magnetization of the Ising spin glass: A recursive numerical method and Chen-Ma scaling

    Science.gov (United States)

    Sepehrinia, Reza; Chalangari, Fartash

    2018-03-01

    The ground-state properties of quasi-one-dimensional (Q1D) Ising spin glass are investigated using an exact numerical approach and analytical arguments. A set of coupled recursive equations for the ground-state energy are introduced and solved numerically. For various types of coupling distribution, we obtain accurate results for magnetization, particularly in the presence of a weak external magnetic field. We show that in the weak magnetic field limit, similar to the 1D model, magnetization exhibits a singular power-law behavior with divergent susceptibility. Remarkably, the spectrum of magnetic exponents is markedly different from that of the 1D system even in the case of two coupled chains. The magnetic exponent makes a crossover from being dependent on a distribution function to a constant value independent of distribution. We provide an analytic theory for these observations by extending the Chen-Ma argument to the Q1D case. We derive an analytical formula for the exponent which is in perfect agreement with the numerical results.

  3. ISEE observations of radiation at twice the solar wind plasma frequency

    International Nuclear Information System (INIS)

    Lacombe, C.; Harvey, C.C.; Hoang, S.

    1988-01-01

    Radiation produced in the vicinity of the Earth's bow shock at twice the solar wind electron plasma frequency f p is seen by both ISEE-1 and ISEE-3, respectively at about 20 and about 200 R E from the Earth. This electromagnetic radiation is due to the presence, in the electron foreshock, of electrons reflected and accelerated at the Earth's bow shock. We show that the source is near the upstream boundary of the foreshock, the surface where the magnetic field lines are tangent to the bow shock. A typical diameter of the source is 120-150 R E . Emissivity is given. The angular size of the source, seen by ISEE-3, is increased by scattering of the 2f p radio waves on the solar wind density fluctuations. We examine whether the bandwidth and directivity predicted by current source models are consistent with our observations

  4. Bidirectional electron anisotropies in the distant tail: ISEE-3 observations of polar rain

    International Nuclear Information System (INIS)

    Baker, D.N.; Bame, S.J.; Feldman, W.C.; Gosling, J.T.; Zwickl, R.D.; Slavin, J.A.; Smith, E.J.

    1985-01-01

    A detailed observational treatment of bidirectional electrons (50 approx.500 eV) in the distant magnetotail (r greater than or equal to 100 R/sub E/) is presented. It is found that electrons in this energy range commonly exhibit strong, field-aligned anisotropies in the tail lobes. Because of large tail motions, the ISEE-3 data provide extensive sampling of both the north and south lobes in rapid succession, demonstrating directly the strong asymmetries that exist between the north and south lobes at any one time. The bidirectional fluxes are found to occur predominantly in the lobe directly connected to the sunward IMF in the open magnetosphere model (north lobe for away sectors and south lobe for toward sectors). Electron anisotropy and magnetic field data are presented which show the transition from unidirectional (sheath) electron populations to bidirectional (lobe) populations. Taken together, the present evidence suggests that the bidirectional electrons that we observe in the distant tail are closely related to the polar rain electrons observed previously at lower altitudes. Furthermore, these data provide strong evidence that the distant tail is comprised largely of open magnetic field lines in contradistinction to some recently advanced models

  5. Replica symmetry breaking solution for two-sublattice fermionic Ising spin glass models in a transverse field

    International Nuclear Information System (INIS)

    Zimmer, F.M.; Magalhaes, S.G.

    2007-01-01

    The one-step replica symmetry breaking is used to study the competition between spin glass (SG) and antiferromagnetic order (AF) in two-sublattice fermionic Ising SG models in the presence of a transverse Γ and a parallel H magnetic fields. Inter- and intra-sublattice exchange interactions following Gaussian distributions are considered. The problem is formulated in a Grassmann path integral formalism within the static ansatz. Results show that H favors the non-ergodic mixed phase (AF+SG) and it destroys the AF. The Γ suppresses the magnetic orders, and the intra-sublattice interaction can introduce a discontinuous phase transition

  6. Phase diagrams of diluted transverse Ising nanowire

    International Nuclear Information System (INIS)

    Bouhou, S.; Essaoudi, I.; Ainane, A.; Saber, M.; Ahuja, R.; Dujardin, F.

    2013-01-01

    In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J cs exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated. - Highlights: ► We use the EFT to investigate the phase diagrams of Ising transverse nanowire. ► Ferrimagnetic and ferromagnetic cases are investigated. ► The effects of the dilution and the transverse fields in core and shell are studied. ► Behavior of the transition temperature with the exchange interaction is given

  7. Effective field renormalization group approach for Ising lattice spin systems

    Science.gov (United States)

    Fittipaldi, Ivon P.

    1994-03-01

    A new applicable real-space renormalization group framework (EFRG) for computing the critical properties of Ising lattice spin systems is presented. The method, which follows up the same strategy of the mean-field renormalization group scheme (MFRG), is based on rigorous Ising spin identities and utilizes a convenient differential operator expansion technique. Within this scheme, in contrast with the usual mean-field type of equation of state, all the relevant self-spin correlations are taken exactly into account. The results for the critical coupling and the critical exponent v, for the correlation length, are very satisfactory and it is shown that this technique leads to rather accurate results which represent a remarkable improvement on those obtained from the standard MFRG method. In particular, it is shown that the present EFRG approach correctly distinguishes the geometry of the lattice structure even when employing its simplest size-cluster version. Owing to its simplicity we also comment on the wide applicability of the present method to problems in crystalline and disordered Ising spin systems.

  8. The diluted tri-dimensional spin-one Ising model with crystal field interactions

    International Nuclear Information System (INIS)

    Saber, M.

    1988-09-01

    3D spin-one Ising models with nearest-neighbour ferromagnetic interactions with crystal-field exhibit tricritical behaviour. A new method that applies to a wide class of random systems is used to study the influence of site and bond dilution on this behaviour. We have calculated temperature-crystal-field-concentration phase diagrams and determined, in particular, the influence of dilution on the zero temperature tricritical temperature. (author). 10 refs, 8 figs

  9. Q-deformed Grassmann field and the two-dimensional Ising model

    International Nuclear Information System (INIS)

    Bugrij, A.I.; Shadura, V.N.

    1994-01-01

    In this paper we construct the exact representation of the Ising partition function in form of the SL q (2,R)-invariant functional integral for the lattice free q-fermion field theory (q=-1). It is shown that the proposed method of q-fermionization allows one to re-express the partition function of the eight vertex model in external field through the functional integral with four-fermion interaction. For the construction of these representation we define a lattice (l,q,s)-deformed Grassmann bi spinor field and extend the Berezin integration rules for this field. At q = - 1, l = s 1 we obtain the lattice q-fermion field which allows to fermionize the two-dimensional Ising model. We show that Gaussian integral over (q,s)-Grassmann variables is expressed through the (q,s)-deformed Pfaffian which is equal to square root of the determinant of some matrix at q = ± 1, s = ±1. (author). 39 refs

  10. Quantum simulation of transverse Ising models with Rydberg atoms

    Science.gov (United States)

    Schauss, Peter

    2018-04-01

    Quantum Ising models are canonical models for the study of quantum phase transitions (Sachdev 1999 Quantum Phase Transitions (Cambridge: Cambridge University Press)) and are the underlying concept for many analogue quantum computing and quantum annealing ideas (Tanaka et al Quantum Spin Glasses, Annealing and Computation (Cambridge: Cambridge University Press)). Here we focus on the implementation of finite-range interacting Ising spin models, which are barely tractable numerically. Recent experiments with cold atoms have reached the interaction-dominated regime in quantum Ising magnets via optical coupling of trapped neutral atoms to Rydberg states. This approach allows for the tunability of all relevant terms in an Ising spin Hamiltonian with 1/{r}6 interactions in transverse and longitudinal fields. This review summarizes the recent progress of these implementations in Rydberg lattices with site-resolved detection. Strong correlations in quantum Ising models have been observed in several experiments, starting from a single excitation in the superatom regime up to the point of crystallization. The rapid progress in this field makes spin systems based on Rydberg atoms a promising platform for quantum simulation because of the unmatched flexibility and strength of interactions combined with high control and good isolation from the environment.

  11. Strong electron bidirectional anisotropies in the distant tail: ISEE 3 observations of polar rain

    International Nuclear Information System (INIS)

    Baker, D.N.; Bame, S.J.; Feldman, W.C.; Gosling, J.T.; Zwickl, R.D.; Slavin, J.A.; Smith, E.J.

    1986-01-01

    A detailed observational treatment of bidirectional electrons (--50 to 50 eV)in the distant magnetotail (rapprox. >100 R/sub E/) is presented. It is found that electrons in this energy range commonly exhibit strong, field-aligned anisotropies in the tail lobes. Because of large tail motions, the ISEE 3 data provide extensive sampling of both the north and south lobes in rapid succession. These data demonstrate directly the strong asymmetries that exist between the north and south lobes at any one time. The bidirectional fluxes are found to occur predominantly in the lobe directly connected to the sunward interplanetary magnetic field in the open magnetosphere model (north lobe for away sectors and south lobe for toward sectors). Electron anisotropy and magnetic field data are presented which show the transition from unidirectional (sheath) electron populations to bidirectional (lobe) populations. Thus we demonstrate the open nature of the distant magnetopause and show that the source of the higher-energy, bidirectional lobe electrons is the tailward directed electron heat flux population in the distant magnetosheath. Taken together, the present evidence suggests that the bidirectional electrons that we observe in the distant tail are closely related to the polar rain electrons observed previously at lower altitudes. Furthermore, these data provide strong evidence that the distant tail is composed largely of open magnetic field lines in contradistinction to some recently advanced models

  12. Phase diagrams of diluted transverse Ising nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Bouhou, S.; Essaoudi, I. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Ainane, A., E-mail: ainane@pks.mpg.de [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Saber, M. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Ahuja, R. [Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden); Dujardin, F. [Laboratoire de Chimie et Physique des Milieux Complexes (LCPMC), Institut de Chimie, Physique et Matériaux (ICPM), 1 Bd. Arago, 57070 Metz (France)

    2013-06-15

    In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J{sub cs} exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated. - Highlights: ► We use the EFT to investigate the phase diagrams of Ising transverse nanowire. ► Ferrimagnetic and ferromagnetic cases are investigated. ► The effects of the dilution and the transverse fields in core and shell are studied. ► Behavior of the transition temperature with the exchange interaction is given.

  13. Spin excitations and quantum criticality in the quasi-one-dimensional Ising-like ferromagnet CoCl2·2D2O in a transverse field

    DEFF Research Database (Denmark)

    Larsen, J.; Schäffer, T. K.; Hansen, U. B.

    2017-01-01

    We present experimental evidence for a quantum phase transition in the easy-axis S = 3/2 anisotropic quasione-dimensional ferromagnet CoCl2 · 2D2O in a transverse field. Elastic neutron scattering shows that the magnetic order parameter vanishes at a transverse critical field μ0Hc = 16.05(4) T......, while inelastic neutron scattering shows that the gap in the magnetic excitation spectrum vanishes at the same field value, and reopens for H>Hc. The field dependence of the order parameter and the gap are well described by critical exponents β = 0.45 ± 0.09 and zν close to 1/2, implying...... that the quantum phase transition in CoCl2 · 2D2O differs significantly from the textbook version of a S = 1/2 Ising chain in a transverse field. We attribute the difference to weak but finite three-dimensionality of the magnetic interactions....

  14. Thermodynamic behavior and enhanced magnetocaloric effect in a frustrated spin-1/2 Ising-Heisenberg triangular tube

    Science.gov (United States)

    Alécio, Raphael Cavalcante; Strečka, Jozef; Lyra, Marcelo L.

    2018-04-01

    The thermodynamic behavior of an Ising-Heisenberg triangular tube with Heisenberg intra-rung and Ising inter-rung interactions is exactly obtained in an external magnetic field within the framework of the transfer-matrix method. We report rigorous results for the temperature dependence of the magnetization, entropy, pair correlations and specific heat, as well as typical iso-entropic curves. The discontinuous field-driven ground-state phase transitions are reflected in some anomalous thermodynamic behavior as for instance a striking low-temperature peak of the specific heat and an enhanced magnetocaloric effect. It is demonstrated that the intermediate magnetization plateaus shrink in and the relevant sharp edges associated with the magnetization jump round off upon increasing temperature.

  15. Electromagnetic waves with frequencies near the local proton gyrofrequency: ISEE-3 1 AU observations

    Science.gov (United States)

    Tsurutani, Bruce T.; Arballo, John K.; Mok, John; Smith, Edward J.; Mason, Glenn M.; Tan, Lun C.

    1994-01-01

    Low Frequency (LF) electromagnetic waves with periods near the local proton gyrofrequency have been detected in interplanetary space by the magnetometer onboard International-Sun-Earth-Explorer-3 (ISEE-3). Transverse peak-to-peak amplitudes as large as delta vector B/absolute value of B approximately 0.4 have been noted with compressional components (Delta absolute value of B/absolute value of B) typically less than or = 0.1. Generally, the waves have even smaller amplitudes, or are not detectable within the solar wind turbulence. The waves are elliptically/linearly polarized and are often, but not always, found to propagate nearly along vector B(sub zero). Both right- and left-hand polarizations in the spacecraft-frame have been detected. The waves are observed during all orientations of the interplanetary magnetic field, with the Parker spiral orientation being the most common case. Because the waves are detected at and near the local proton cyclotron frequency, the generation mechanism must almost certainly be solar wind pickup of freshly created hydrogen ions. Possible sources for the hydrogen are the Earth's atmosphere, coronal mass ejections from the Sun, comets and interstellar neutral atoms. At this time it is not obvious which potential source is the correct one. Statistical tests employing over one year of ISEE-3 data will be done in the near future to eliminate/confirm some of these possibilities.

  16. Phi4 lattice field theory as an asymptotic expansion about the Ising limit

    International Nuclear Information System (INIS)

    Caginalp, G.

    1980-01-01

    For a d-dimensional phi 4 lattice field theory consisting of N spins, an asymptotic expansion of expectations about the Ising limit is established in inverse powers of the bare coupling constant lambda. In the thermodynamic limit (N→infinity), the expansion is expected to be valid in the noncritical region of the Ising system

  17. Phase diagrams in mixed spin-3/2 and spin-2 Ising system with two alternative layers within the effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Polat, Yasin; Keskin, Mustafa

    2011-01-01

    The phase diagrams in the mixed spin-3/2 and spin-2 Ising system with two alternative layers on a honeycomb lattice are investigated and discussed by the use of the effective-field theory with correlations. The interaction of the nearest-neighbour spins of each layer is taken to be positive (ferromagnetic interaction) and the interaction of the adjacent spins of the nearest-neighbour layers is considered to be either positive or negative (ferromagnetic or anti-ferromagnetic interaction). The temperature dependence of the layer magnetizations of the system is examined to characterize the nature (continuous or discontinuous) of the phase transitions and obtain the phase transition temperatures. The system exhibits both second- and first-order phase transitions besides triple point (TP), critical end point (E), multicritical point (A), isolated critical point (C) and reentrant behaviour depending on the interaction parameters. We have also studied the temperature dependence of the total magnetization to find the compensation points, as well as to determine the type of behaviour, and N-type behaviour in Néel classification nomenclature existing in the system. The phase diagrams are constructed in eight different planes and it is found that the system also presents the compensation phenomena depending on the sign of the bilinear exchange interactions. (general)

  18. Magnetization of the Ising model on the Sierpinski pastry-shell

    Science.gov (United States)

    Chame, Anna; Branco, N. S.

    1992-02-01

    Using a real-space renormalization group approach, we calculate the approximate magnetization in the Ising model on the Sierpinski Pastry-shell. We consider, as an approximation, only two regions of the fractal: the internal surfaces, or walls (sites on the border of eliminated areas), with coupling constants JS, and the bulk (all other sites), with coupling constants Jv. We obtain the mean magnetization of the two regions as a function of temperature, for different values of α= JS/ JV and different geometric parameters b and l. Curves present a step-like behavior for some values of b and l, as well as different universality classes for the bulk transition.

  19. ISEE-magnetopause observations - workshop results

    International Nuclear Information System (INIS)

    Paschmann, G.

    1982-01-01

    A brief history of ISEE magnetopause workshops held during 1977-1981 is presented, and an assessment of the activity of these workshops is made. Workshop results are surveyed, with attention given to magnetopause thickness and speed, large-scale reconnection, small-scale reconnection, magnetic field topology, plasma waves, boundary layer structure, surface waves, plasma origin, and the relationship between magnetopause and particle boundaries. Finally, a few topics that require particular attention in the future are mentioned

  20. Testing Lorentz Invariance Emergence in the Ising Model using Monte Carlo simulations

    CERN Document Server

    Dias Astros, Maria Isabel

    2017-01-01

    In the context of the Lorentz invariance as an emergent phenomenon at low energy scales to study quantum gravity a system composed by two 3D interacting Ising models (one with an anisotropy in one direction) was proposed. Two Monte Carlo simulations were run: one for the 2D Ising model and one for the target model. In both cases the observables (energy, magnetization, heat capacity and magnetic susceptibility) were computed for different lattice sizes and a Binder cumulant introduced in order to estimate the critical temperature of the systems. Moreover, the correlation function was calculated for the 2D Ising model.

  1. Dendrimer-magnetic nanostructure: a Monte Carlo simulation

    Science.gov (United States)

    Jabar, A.; Masrour, R.

    2017-11-01

    In this paper, the magnetic properties of ternary mixed spins (σ,S,q) Ising model on a dendrimer nanostructure are studied using Monte Carlo simulations. The ground state phase diagrams of dendrimer nanostructure with ternary mixed spins σ = 1/2, S = 1 and q = 3/2 Ising model are found. The variation of the thermal total and partial magnetizations with the different exchange interactions, the external magnetic fields and the crystal fields have been also studied. The reduced critical temperatures have been deduced. The magnetic hysteresis cycles have been discussed. In particular, the corresponding magnetic coercive filed values have been deduced. The multiples hysteresis cycles are found. The dendrimer nanostructure has several applications in the medicine.

  2. ISEE/IMP Observations of simultaneous upstream ion events

    International Nuclear Information System (INIS)

    Mitchel, D.G.; Roelof, E.C.; Sanderson, T.R.; Reinhard, R.; Wenzel, K.

    1983-01-01

    Propagation of upstream energetic (50--200 keV) ions is analyzed in sixteen events observed simulataneously by solid state detectors on ISEE 3 at approx.200 R/sub E/ and on IMP 8 at approx.35 R/sub E/ from the earth. Conclusions are based on comparisons of the pitch angle distributions observed at the two spacecraft and transformed into the solar wind frame. They are beamlike at ISEE 3 and are confined to the outward hemisphere. When IMP 8 is furtherest from the bow shock, they are also usually beamlike, or hemispheric. However, when IMP 8 is closer to the bow shock, pancakelike distributions are observed. This systematic variation in the IMP 8 pitch angle distributions delimits a scattering region l< or approx. =14 R/sub E/ upstream of the earth's bow shock (l measured along the interplanetary magnetic field) that dominates ion propagation, influences the global distribution of fluxes in the foreshock, and may play a role in acceleration of the ions. When IMP 8 is beyond lapprox.15 R/sub E/, the propagation appears to be essentially scatter-free between IMP 8 and ISEE 3; this is deduced from the absence of earthward fluxes at IMP 8 as well as the tendency for the spin-averaged fluxes to be comparable at the two spacecraft

  3. Contingency plans for the ISEE-3 libration-point mission

    Science.gov (United States)

    Dunham, D. W.

    1979-01-01

    During the planning stage of the International Sun-Earth Explorer-3 (ISEE-3) mission, a recovery strategy was developed in case the Delta rocket underperformed during the launch phase. If a large underburn had occurred, the ISEE-3 spacecraft would have been allowed to complete one revolution of its highly elliptical earth orbit. The recovery plan called for a maneuver near perigee to increase the energy of the off-nominal orbit; a relatively small second maneuver would then insert the spacecraft into a new transfer trajectory toward the desired halo orbit target, and a third maneuver would place the spacecraft in the halo orbit. Results of the study showed that a large range of underburns could be corrected for a total nominal velocity deviation cost within the ISEE-3 fuel budget.

  4. Ferrimagnetism and compensation points in a decorated 3D Ising model

    International Nuclear Information System (INIS)

    Oitmaa, J.; Zheng, W.

    2003-01-01

    Full text: Ferrimagnets are materials where ions on different sublattices have opposing magnetic moments which do not exactly cancel even at zero temperature. An intriguing possibility then is the existence of a compensation point, below the Curie temperature, where the net moment changes sign. This has obvious technological significance. Most theoretical studies of such systems have used mean-field approaches, making it difficult to distinguish real properties of the model from artefacts of the approximation. For this reason a number of simpler models have been proposed, where treatments beyond mean-field theory are possible. Of particular interest are decorated systems, which can be mapped exactly onto simpler models and, in this way, either solved exactly or to a high degree of numerical precision. We use this approach to study a ferrimagnetic Ising system with spins 1/2 at the sites of a simple cubic lattice and spins S=1 or 3/2 located on the bonds. Our results, which are exact to high numerical precision, show a number of surprising and interesting features: for S=1 the possibility of zero, one or two compensation points, re-entrant behaviour, and up to three critical points; for S=3/2 always a simple critical point and zero or one compensation point

  5. Ladder Ising spin configurations. Pt. 1. Heat capacity

    International Nuclear Information System (INIS)

    Mejdani, R.; Lambros, A.

    1996-01-01

    We consider a ladder Ising spin model (with two coupled Ising spin chains), characterized by two couplings (interchain and intrachain couplings), to study in detail, in an analytical way, its thermal behaviour and particularly the variation of the specific heat versus temperature, the ratio of interaction constants, and the magnetic field. It is interesting that when the competition between interchain and intrachain interactions is strong the specific heat exhibits a double peak and when the competition is not so strong the specific heat has a single peak. Further, without entering into details, we give, in a numerical way, some similar results for more complicated ladder configurations (with more than two linear Ising chains). The spin-1/2 ladders or systems of spin chains may be realized in nature by vanadyl pyrophosphate ((VO) 2 P 2 O 7 ) or similar materials. All these intermediate systems are today important to gain further insight into the physics of one-dimensional spin chains and two-dimensional high-T c spin systems, both of which have shown interesting and unusual magnetic and superconducting properties. It is plausible that experimental and theoretical studies of ladders may lead to other interesting physical phenomena. (orig.)

  6. Efficient generation of series expansions for ±J Ising spin glasses in a classical or a quantum field

    Science.gov (United States)

    Singh, R. R. P.; Young, A. P.

    2017-12-01

    We discuss generation of series expansions for Ising spin glasses with a symmetric ±J (i.e., bimodal) distribution on d -dimensional hypercubic lattices using linked-cluster methods. Simplifications for the bimodal distribution allow us to go to higher order than for a general distribution. We discuss two types of problems, one classical and one quantum. The classical problem is that of the Ising spin glass in a longitudinal magnetic field h , for which we obtain high temperature series expansions in variables tanh(J /T ) and tanh(h /T ) . The quantum problem is a T =0 study of the Ising spin glass in a transverse magnetic field hT for which we obtain a perturbation theory in powers of J /hT . These methods require (i) enumeration and counting of all connected clusters that can be embedded in the lattice up to some order n , and (ii) an evaluation of the contribution of each cluster for the quantity being calculated, known as the weight. We discuss a general method that takes the much smaller list (and count) of all no free-end (NFE) clusters on a lattice up to some order n and automatically generates all other clusters and their counts up to the same order. The weights for finite clusters in both cases have a simple graphical interpretation that allows us to proceed efficiently for a general configuration of the ±J bonds and at the end perform suitable disorder averaging. The order of our computations is limited by the weight calculations for the high-temperature expansions of the classical model, while they are limited by graph counting for the T =0 quantum system. Details of the calculational methods are presented.

  7. The topology of intrasector reversals of the interplanetary magnetic field

    Science.gov (United States)

    Kahler, S. W.; Crooker, N. U.; Gosling, J. T.

    1996-11-01

    A technique has been developed recently to determine the polarities of interplanetary magnetic fields relative to their origins at the Sun by comparing energetic electron flow directions with local magnetic field directions. Here we use heat flux electrons from the Los Alamos National Laboratory (LANL) plasma detector on the ISEE 3 spacecraft to determine the field polarities. We examine periods within well-defined magnetic sectors when the field directions appear to be reversed from the normal spiral direction of the sector. About half of these intrasector field reversals (IFRs) are cases in which the polarities match those of the surrounding sectors, indicating that those fields have been folded back toward the Sun. The more interesting cases are those with polarity reversals. We find no clear cases of isolated reverse polarity fields, which suggests that islands of reverse polarity in the solar source dipole field probably do not exist. The IFRs with polarity reversals are strongly associated with periods of bidirectional electron flows, suggesting that those fields occur only in conjunction with closed fields. We propose that both those IFRs and the bidirectional flows are signatures of coronal mass ejections (CMEs). In that case, many interplanetary CMEs are larger and more complex than previously thought, consisting of both open and closed field components.

  8. Monte Carlo study of alternate mixed spin-5/2 and spin-2 Ising ferrimagnetic system on the Bethe lattice

    Energy Technology Data Exchange (ETDEWEB)

    Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, PB 63 46000 Safi (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2016-01-01

    The magnetic properties of alternate mixed spin-5/2 and spin-2 Ising model on the Bethe lattice have been studied by using the Monte Carlo simulations. The ground state phase diagrams of alternate mixed spin-5/2 and spin-2 Ising model on the Bethe lattice has been obtained. The thermal total magnetization and magnetization of spins-5/2 and spin-2 with the different exchange interactions, external magnetic field and temperatures have been studied. The critical temperature have been deduced. The magnetic hysteresis cycle on the Bethe lattice has been deduced for different values of exchange interactions, for different values of crystal field and for different sizes. The magnetic coercive field has been deduced. - Highlights: • The alternate mixed spin-5/2 and -2 on the Bethe lattice is studied. • The critical temperature has been deduced. • The magnetic coercive filed has been deduced.

  9. Statistical mechanics of the cluster Ising model

    International Nuclear Information System (INIS)

    Smacchia, Pietro; Amico, Luigi; Facchi, Paolo; Fazio, Rosario; Florio, Giuseppe; Pascazio, Saverio; Vedral, Vlatko

    2011-01-01

    We study a Hamiltonian system describing a three-spin-1/2 clusterlike interaction competing with an Ising-like antiferromagnetic interaction. We compute free energy, spin-correlation functions, and entanglement both in the ground and in thermal states. The model undergoes a quantum phase transition between an Ising phase with a nonvanishing magnetization and a cluster phase characterized by a string order. Any two-spin entanglement is found to vanish in both quantum phases because of a nontrivial correlation pattern. Nevertheless, the residual multipartite entanglement is maximal in the cluster phase and dependent on the magnetization in the Ising phase. We study the block entropy at the critical point and calculate the central charge of the system, showing that the criticality of the system is beyond the Ising universality class.

  10. Statistical mechanics of the cluster Ising model

    Energy Technology Data Exchange (ETDEWEB)

    Smacchia, Pietro [SISSA - via Bonomea 265, I-34136, Trieste (Italy); Amico, Luigi [CNR-MATIS-IMM and Dipartimento di Fisica e Astronomia Universita di Catania, C/O ed. 10, viale Andrea Doria 6, I-95125 Catania (Italy); Facchi, Paolo [Dipartimento di Matematica and MECENAS, Universita di Bari, I-70125 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); Fazio, Rosario [NEST, Scuola Normale Superiore and Istituto Nanoscienze - CNR, 56126 Pisa (Italy); Center for Quantum Technology, National University of Singapore, 117542 Singapore (Singapore); Florio, Giuseppe; Pascazio, Saverio [Dipartimento di Fisica and MECENAS, Universita di Bari, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); Vedral, Vlatko [Center for Quantum Technology, National University of Singapore, 117542 Singapore (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU (United Kingdom)

    2011-08-15

    We study a Hamiltonian system describing a three-spin-1/2 clusterlike interaction competing with an Ising-like antiferromagnetic interaction. We compute free energy, spin-correlation functions, and entanglement both in the ground and in thermal states. The model undergoes a quantum phase transition between an Ising phase with a nonvanishing magnetization and a cluster phase characterized by a string order. Any two-spin entanglement is found to vanish in both quantum phases because of a nontrivial correlation pattern. Nevertheless, the residual multipartite entanglement is maximal in the cluster phase and dependent on the magnetization in the Ising phase. We study the block entropy at the critical point and calculate the central charge of the system, showing that the criticality of the system is beyond the Ising universality class.

  11. The dilute random field Ising model by finite cluster approximation

    International Nuclear Information System (INIS)

    Benyoussef, A.; Saber, M.

    1987-09-01

    Using the finite cluster approximation, phase diagrams of bond and site diluted three-dimensional simple cubic Ising models with a random field have been determined. The resulting phase diagrams have the same general features for both bond and site dilution. (author). 7 refs, 4 figs

  12. Elastic and inelastic neutron scattering studies on 3d and 4f magnetic compounds

    International Nuclear Information System (INIS)

    Erkelens, W.A.C.

    1987-01-01

    First, some theoretical aspects of neutron scattering techniques are given, and the cyrogenic equipment and the neutron spectrometers employed are described. Experiments on a 3-d Ising system are described, performed at very low temperatures and in a magnetic field. Experimental proof has been obtained for the theoretical prediction that the critical behaviour of a d-dimensional Ising system in a transverse magnetic field near T=0 is identical to that of a d+1 dimensional Ising system as a function of temperature in zero field. Experiments are described on a Ni 2+ compound which represents a good example of a 1-d antiferromagnetic Heisenberg (HAF), spin s=1, system. The results give evidence for the so called 'Haldane conjecture', a theory which predicts that the ground state of HAF systems with integer spin is a nonmagnetic many-body singlet. The excited states are separated from the ground state by an energy gap. Contrastingly, half-integer spin systems are predicted to have no such gap. A short introduction is given to phenomena in rare earth, 4f compunds, like the Kondo effect and heavy fermion behaviour. Experimental results on the RE hexaborides are reported, among which CeB 6 , a typical Kondo system with complex magnetic orderings. Furthermore, inelastic neutron scattering experiments on NdB 6 and CeB 6 , performed in order to get insight in the various reaction mechanisms, are presented. Finally a report is given on magnetic correlations and excitations in two nonmagnetically ordered heavy fermion compounds, CeCu 6 and CeRu 2 Si 2 and their interpretation in the light of existing theories. 201 refs.; 61 figs.; 4 tabs

  13. Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.

    Science.gov (United States)

    Asaba, Tomoya; Wang, Yongjie; Li, Gang; Xiang, Ziji; Tinsman, Colin; Chen, Lu; Zhou, Shangnan; Zhao, Songrui; Laleyan, David; Li, Yi; Mi, Zetian; Li, Lu

    2018-04-25

    In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe 2 ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe 2 thin films with a high precision rotation stage, we map the upper critical field H c2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field H c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H c2 in Ising superconductors.

  14. Phase transitions of a spin-one Ising ferromagnetic superlattice

    International Nuclear Information System (INIS)

    Saber, A.

    2001-09-01

    Using the effective field theory with a probability distribution technique, the magnetic properties in an infinite superlattice consisting of two different ferromagnets are studied in a spin-one Ising model. The dependence of the Curie temperatures are calculated as a function of two slabs in one period and as a function of the intra- and interlayer exchange interactions. A critical value of the exchange reduced interaction above which the interface magnetism appears is found. (author)

  15. New relation for critical exponents in the Ising model

    International Nuclear Information System (INIS)

    Pishtshev, A.

    2007-01-01

    The Ising model in a transverse field is considered at T=0. From the analysis of the power low behaviors of the energy gap and the order parameter as functions of the field a new relation between the respective critical exponents, β>=1/(8s 2 ), is derived. By using the Suzuki equivalence from this inequality a new relation for critical exponents in the Ising model, β>=1/(8ν 2 ), is obtained. A number of numerical examples for different cases illustrates the generality and validity of the relation. By applying this relation the estimation ν=(1/4) 1/3 ∼0.62996 for the 3D-Ising model is proposed

  16. Dynamic magnetic behavior of the mixed spin (2, 5/2) Ising system with antiferromagnetic/antiferromagnetic interactions on a bilayer square lattice

    International Nuclear Information System (INIS)

    Ertaş Mehmet; Keskin Mustafa

    2013-01-01

    Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin (2, 5/2) Ising system for the antiferromagnetic/antiferromagnetic (AFM/AFM) interactions on the bilayer square lattice under a time varying (sinusoidal) magnetic field. The time dependence of average magnetizations and the thermal variation of the dynamic magnetizations are examined to calculate the dynamic phase diagrams. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and the effects of interlayer coupling interaction on the critical behavior of the system are investigated. We also investigate the influence of the frequency and find that the system displays richer dynamic critical behavior for higher values of frequency than that of the lower values of it. We perform a comparison with the ferromagnetic/ferromagnetic (FM/FM) and AFM/FM interactions in order to see the effects of AFM/AFM interaction and observe that the system displays richer and more interesting dynamic critical behaviors for the AFM/AFM interaction than those for the FM/FM and AFM/FM interactions. (general)

  17. Effective-field theory of the Ising model with three alternative layers on the honeycomb and square lattices

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Institute of Science, Erciyes University, Kayseri 38039 (Turkey); Canko, Osman [Department of Physics, Erciyes University, Kayseri 38039 (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, Kayseri 38039 (Turkey)], E-mail: keskin@erciyes.edu.tr

    2008-09-15

    The Ising model with three alternative layers on the honeycomb and square lattices is studied by using the effective-field theory with correlations. We consider that the nearest-neighbor spins of each layer are coupled ferromagnetically and the adjacent spins of the nearest-neighbor layers are coupled either ferromagnetically or anti-ferromagnetically depending on the sign of the bilinear exchange interactions. We investigate the thermal variations of the magnetizations and present the phase diagrams. The phase diagrams contain the paramagnetic, ferromagnetic and anti-ferromagnetic phases, and the system also exhibits a tricritical behavior.

  18. Effective-field theory of the Ising model with three alternative layers on the honeycomb and square lattices

    International Nuclear Information System (INIS)

    Deviren, Bayram; Canko, Osman; Keskin, Mustafa

    2008-01-01

    The Ising model with three alternative layers on the honeycomb and square lattices is studied by using the effective-field theory with correlations. We consider that the nearest-neighbor spins of each layer are coupled ferromagnetically and the adjacent spins of the nearest-neighbor layers are coupled either ferromagnetically or anti-ferromagnetically depending on the sign of the bilinear exchange interactions. We investigate the thermal variations of the magnetizations and present the phase diagrams. The phase diagrams contain the paramagnetic, ferromagnetic and anti-ferromagnetic phases, and the system also exhibits a tricritical behavior

  19. Critical phenomena in Ising-type thin films by Monte Carlo study

    International Nuclear Information System (INIS)

    Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.

    2016-01-01

    The magnetic properties of ferrimagnetic spin-2 and 3/2 Ising-typed thin films are studied by Monte Carlo simulation. The critical temperature is obtained for different values of thickness of the thin film and for different exchange interactions. The total magnetization has been determined for different values of exchange interactions in surface and in bulk and different temperatures. The magnetic hysteresis cycle is obtained for different values of exchange interactions ferro and antiferromagnetic in the surface and in the bulk and for different values of temperatures for a fixed size of the film thickness. The coercive field increase with increasing the film thickness. - Highlights: • The magnetic properties of thin films are studied by Monte Carlo simulation. • The critical temperature is obtained for different values of thickness of thin film. • The magnetic hysteresis cycle is obtained in the surface and in the bulk. • The coercive field increase with increasing the thin film thickness.

  20. Critical phenomena in Ising-type thin films by Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63, 46000 Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2016-04-01

    The magnetic properties of ferrimagnetic spin-2 and 3/2 Ising-typed thin films are studied by Monte Carlo simulation. The critical temperature is obtained for different values of thickness of the thin film and for different exchange interactions. The total magnetization has been determined for different values of exchange interactions in surface and in bulk and different temperatures. The magnetic hysteresis cycle is obtained for different values of exchange interactions ferro and antiferromagnetic in the surface and in the bulk and for different values of temperatures for a fixed size of the film thickness. The coercive field increase with increasing the film thickness. - Highlights: • The magnetic properties of thin films are studied by Monte Carlo simulation. • The critical temperature is obtained for different values of thickness of thin film. • The magnetic hysteresis cycle is obtained in the surface and in the bulk. • The coercive field increase with increasing the thin film thickness.

  1. Correlation effects in the Ising model in an external field

    International Nuclear Information System (INIS)

    Borges, H.E.; Silva, P.R.

    1983-01-01

    The thermodynamic properties of the spin-1/2 Ising Model in an external field are evaluated through the use of the exponential differential operator method and Callen's exact relations. The correlations effects are treated in a phenomenological approach and the results are compared with other treatments. (Author) [pt

  2. Generation of Control by SU(2) Reduction for the Anisotropic Ising Model

    International Nuclear Information System (INIS)

    Delgado, F

    2016-01-01

    Control of entanglement is fundamental in Quantum Information and Quantum Computation towards scalable spin-based quantum devices. For magnetic systems, Ising interaction with driven magnetic fields modifies entanglement properties of matter based quantum systems. This work presents a procedure for dynamics reduction on SU(2) subsystems using a non-local description. Some applications for Quantum Information are discussed. (paper)

  3. Antiferromagnetic Ising model with transverse and longitudinal field

    International Nuclear Information System (INIS)

    Kischinhevsky, M.

    1985-01-01

    We study the quantum hamiltonian version of the Ising Model in one spacial dimension under an external longitudinal (uniform) field at zero temperature. A phenomenological renormalization group procedure is used to obtain the phase diagram; the transverse and longitudinal zero field limits are studied and we verify the validity of universality at non zero transverse fields, where two-dimensional critical behaviour is obtained. To perform the numerical calculations we use the Lanczos scheme, which gives highly precise results with rather short processing times. We also analyse the possibility of using these techniques to extend the present work to the quantum hamiltonian version of the q-state Potts Model (q>2) in larger system. (author) [pt

  4. The high-temperature expansion of the classical Ising model with Sz2 term

    Directory of Open Access Journals (Sweden)

    M.T. Thomaz

    2012-03-01

    Full Text Available We derive the high-temperature expansion of the Helmholtz free energy up to order β17 of the one-dimensional spin-S Ising model, with single-ion anisotropy term, in the presence of a longitudinal magnetic field. We show that the values of some thermodynamical functions for the ferromagnetic models, in the presence of a weak magnetic field, are not small corrections to their values with h=0. This model with S=3 was applied by Kishine et al. [J.-i. Kishine et al., Phys. Rev. B, 2006, 74, 224419] to analyze experimental data of the single-chain magnet [Mn (saltmen]2 [Ni(pac2 (py2] (PF62 for T<40 K. We show that for T<35 K the thermodynamic functions of the large-spin limit model are poor approximations to their analogous spin-3 functions.

  5. Investigation of phase diagrams for cylindrical Ising nanotube using cellular automata

    Science.gov (United States)

    Astaraki, M.; Ghaemi, M.; Afzali, K.

    2018-05-01

    Recent developments in the field of applied nanoscience and nanotechnology have heightened the need for categorizing various characteristics of nanostructures. In this regard, this paper establishes a novel method to investigate magnetic properties (phase diagram and spontaneous magnetization) of a cylindrical Ising nanotube. Using a two-layer Ising model and the core-shell concept, the interactions within nanotube has been modelled. In the model, both ferromagnetic and antiferromagnetic cases have been considered. Furthermore, the effect of nanotube's length on the critical temperature is investigated. The model has been simulated using cellular automata approach and phase diagrams were constructed for different values of inter- and intra-layer couplings. For the antiferromagnetic case, the possibility of existence of compensation point is observed.

  6. Quenched bond-dilute Ising ferromagnet in square lattice: thermodynamical properties

    International Nuclear Information System (INIS)

    Honmura, R.; Sarmento, E.F.; Tsallis, C.

    1982-01-01

    Within an effective field framework which improves the Molecular Field Approximation, the phase diagram, magnetization, specific heat and susceptibility associated with the quenched bond-dilute Ising ferromagnet in square lattice is calculated. The results are qualitatively (and within certain extent quantitatively) satisfactory; in particular the effects, on the specific heat and susceptibility, of the (eventually) coexisting finite and infinite clusters are exhibited. (Author) [pt

  7. 3D Biomimetic Magnetic Structures for Static Magnetic Field Stimulation of Osteogenesis

    Directory of Open Access Journals (Sweden)

    Irina Alexandra Paun

    2018-02-01

    Full Text Available We designed, fabricated and optimized 3D biomimetic magnetic structures that stimulate the osteogenesis in static magnetic fields. The structures were fabricated by direct laser writing via two-photon polymerization of IP-L780 photopolymer and were based on ellipsoidal, hexagonal units organized in a multilayered architecture. The magnetic activity of the structures was assured by coating with a thin layer of collagen-chitosan-hydroxyapatite-magnetic nanoparticles composite. In vitro experiments using MG-63 osteoblast-like cells for 3D structures with gradients of pore size helped us to find an optimum pore size between 20–40 µm. Starting from optimized 3D structures, we evaluated both qualitatively and quantitatively the effects of static magnetic fields of up to 250 mT on cell proliferation and differentiation, by ALP (alkaline phosphatase production, Alizarin Red and osteocalcin secretion measurements. We demonstrated that the synergic effect of 3D structure optimization and static magnetic stimulation enhances the bone regeneration by a factor greater than 2 as compared with the same structure in the absence of a magnetic field.

  8. 3D Biomimetic Magnetic Structures for Static Magnetic Field Stimulation of Osteogenesis.

    Science.gov (United States)

    Paun, Irina Alexandra; Popescu, Roxana Cristina; Calin, Bogdan Stefanita; Mustaciosu, Cosmin Catalin; Dinescu, Maria; Luculescu, Catalin Romeo

    2018-02-07

    We designed, fabricated and optimized 3D biomimetic magnetic structures that stimulate the osteogenesis in static magnetic fields. The structures were fabricated by direct laser writing via two-photon polymerization of IP-L780 photopolymer and were based on ellipsoidal, hexagonal units organized in a multilayered architecture. The magnetic activity of the structures was assured by coating with a thin layer of collagen-chitosan-hydroxyapatite-magnetic nanoparticles composite. In vitro experiments using MG-63 osteoblast-like cells for 3D structures with gradients of pore size helped us to find an optimum pore size between 20-40 µm. Starting from optimized 3D structures, we evaluated both qualitatively and quantitatively the effects of static magnetic fields of up to 250 mT on cell proliferation and differentiation, by ALP (alkaline phosphatase) production, Alizarin Red and osteocalcin secretion measurements. We demonstrated that the synergic effect of 3D structure optimization and static magnetic stimulation enhances the bone regeneration by a factor greater than 2 as compared with the same structure in the absence of a magnetic field.

  9. Simultaneous observations of solar MeV particles in a magnetic cloud and in the earth's northern tail lobe - Implications for the global field line topology of magnetic clouds and for the entry of solar particles into the magnetosphere during cloud passage

    Science.gov (United States)

    Farrugia, C. J.; Richardson, I. G.; Burlaga, L. F.; Lepping, R. P.; Osherovich, V. A.

    1993-01-01

    Simultaneous ISEE 3 and IMP 8 spacecraft observations of magnetic fields and flow anisotropies of solar energetic protons and electrons during the passage of an interplanetary magnetic cloud show various particle signature differences at the two spacecraft. These differences are interpretable in terms of the magnetic line topology of the cloud, the connectivity of the cloud field lines to the solar surface, and the interconnection between the magnetic fields of the magnetic clouds and of the earth. These observations are consistent with a magnetic cloud model in which these mesoscale configurations are curved magnetic flux ropes attached at both ends to the sun's surface, extending out to 1 AU.

  10. Hamiltonian truncation approach to quenches in the Ising field theory

    Directory of Open Access Journals (Sweden)

    T. Rakovszky

    2016-10-01

    Full Text Available In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1+1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations not only for small, but even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while in the paramagnetic phase the single magnon excitation governs the dynamics, allowing us to capture the time evolution of the magnetisation using a combination of known results from perturbation theory and form factor based methods. We point out that the dominance of low lying excitations allows for the numerical or experimental determination of the mass spectra through the study of the quench dynamics.

  11. Hysteresis and compensation behaviors of mixed spin-2 and spin-1 hexagonal Ising nanowire core–shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Bahmad, L. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco)

    2015-09-01

    The magnetic behaviors of a mixed spins (2-1) hexagonal Ising nanowire with core–shell structure are investigated by using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperatures of core–shell are studied for different values of crystal field and exchange interactions. The thermal and magnetic hysteresis cycles are given for different values of the crystal field. - Highlights: • Critical temperature increase when exchange interaction increasing in core-shell. • Hysteresis loop areas decrease at above transition temperature. • Magnetic coercive field decrease when crystal field increasing. • Magnetic coercive field increase when exchange interaction increasing.

  12. Initial ISEE magnetometer results: shock observation

    International Nuclear Information System (INIS)

    Russell, C.T.

    1979-01-01

    ISEE-1 and -2 magnetic field profiles across 6 terrestrial bow shock and one interplanetary shock are examined. The inteplanetary shock illustrates the behavior of a low Mach number shock. Three examples of low or moderate β, high Mach number, quasi-perpendicular shocks are examined. These did not have upstream waves, but rather had waves growing in the field gradient. Two examples of high β shocks showed little coherence in field variation even though the two vehicles were only a few hundred kilometers apart. The authors present the joint behavior of wave, particle and field data across some of these shocks to show some of the myriad of shock features whose behavior they are now beginning to investigate. (Auth.)

  13. Test of quantum thermalization in the two-dimensional transverse-field Ising model.

    Science.gov (United States)

    Blaß, Benjamin; Rieger, Heiko

    2016-12-01

    We study the quantum relaxation of the two-dimensional transverse-field Ising model after global quenches with a real-time variational Monte Carlo method and address the question whether this non-integrable, two-dimensional system thermalizes or not. We consider both interaction quenches in the paramagnetic phase and field quenches in the ferromagnetic phase and compare the time-averaged probability distributions of non-conserved quantities like magnetization and correlation functions to the thermal distributions according to the canonical Gibbs ensemble obtained with quantum Monte Carlo simulations at temperatures defined by the excess energy in the system. We find that the occurrence of thermalization crucially depends on the quench parameters: While after the interaction quenches in the paramagnetic phase thermalization can be observed, our results for the field quenches in the ferromagnetic phase show clear deviations from the thermal system. These deviations increase with the quench strength and become especially clear comparing the shape of the thermal and the time-averaged distributions, the latter ones indicating that the system does not completely lose the memory of its initial state even for strong quenches. We discuss our results with respect to a recently formulated theorem on generalized thermalization in quantum systems.

  14. Surface magnetization of the Ising ferromagnet in semi-infinite cubic lattice: renormalization group approach

    International Nuclear Information System (INIS)

    Chame, A.M.N.; Tsallis, C.

    1988-01-01

    The behaviour of the spontaneous surface and bulk magnetizations as function of the temperature for the Ising ferromagnet in a semi-infinitre cubic lattice for various ratios JS/JB (JS and JB are the surface and bulk coupling constants, respectively), is studied. The extraordinary transition where the surface maintains its magnetization as the bulk disorders, was study, in particular; a discontinuity on the first derivative of the surface magnetization at the bulk transition temperature was found. The criticality of the system (universality classes, critical exponents and amplitudes) is discussed. An unexpected slight lack of monotonicity of the surface magnetization as a function of JS/JB for JS/JB [pt

  15. First steps towards a state classification in the random-field Ising model

    International Nuclear Information System (INIS)

    Basso, Vittorio; Magni, Alessandro; Bertotti, Giorgio

    2006-01-01

    The properties of locally stable states of the random-field Ising model are studied. A map is defined for the dynamics driven by the field starting from a locally stable state. The fixed points of the map are connected with the limit hysteresis loops that appear in the classification of the states

  16. The order parameter and susceptibility of the 3D Ising-like system in an external field near the phase transition point

    Directory of Open Access Journals (Sweden)

    M.P. Kozlovskii

    2010-01-01

    Full Text Available The present work is devoted to the investigation of the 3D Ising-like model in the presence of an external field in the vicinity of critical point. The method of collective variables is used. General expressions for the order parameter and susceptibility are calculated as functions of temperature and the external field as well as scaling functions of that are explicitly obtained. The results are compared with the ones obtained within the framework of parametric representation of the equation of state and Monte Carlo simulations. New expression for the exit point from critical regime of the order parameter fluctuations is proposed and used for the calculation.

  17. Phase transition in Ising, XY and Heisenberg magnetic films

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Route Sidi Bouzid - BP 63 46000 Safi (Morocco); LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Hamedoun, M. [Institute for Nanomaterials and Nanotechnologies, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco); Benyoussef, A. [LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Institute for Nanomaterials and Nanotechnologies, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco)

    2012-01-01

    The phase transition and magnetic properties of a ferromagnet spin-S, a disordered diluted thin and semi-infinite film with a face-centered cubic lattice are investigated using the high-temperature series expansions technique extrapolated with Pade approximants method for Heisenberg, XY and Ising models. The reduced critical temperature of the system {tau}{sub c} is studied as function of the thickness of the thin film and the exchange interactions in the bulk, and within the surfaces J{sub b}, J{sub s} and J{sub Up-Tack }, respectively. It is found that {tau}{sub c} increases with the exchange interactions of surface. The magnetic phase diagrams ({tau}{sub c} versus the dilution x) and the percolation threshold are obtained. The shifts of the critical temperatures T{sub c}(l) from the bulk value (T{sub c}({infinity})/T{sub c}(l) - 1) can be described by a power law l{sup -{lambda}}, where {lambda} = 1/{upsilon} is the inverse of the correlation length exponent.

  18. Dynamics of asymmetric kinetic Ising systems revisited

    International Nuclear Information System (INIS)

    Huang, Haiping; Kabashima, Yoshiyuki

    2014-01-01

    The dynamics of an asymmetric kinetic Ising model is studied. Two schemes for improving the existing mean-field description are proposed. In the first scheme, we derive the formulas for instantaneous magnetization, equal-time correlation, and time-delayed correlation, considering the correlation between different local fields. To derive the time-delayed correlation, we emphasize that the small-correlation assumption adopted in previous work (Mézard and Sakellariou, 2011 J. Stat. Mech. L07001) is in fact not required. To confirm the prediction efficiency of our method, we perform extensive simulations on single instances with either temporally constant external driving fields or sinusoidal external fields. In the second scheme, we develop an improved mean-field theory for instantaneous magnetization prediction utilizing the notion of the cavity system in conjunction with a perturbative expansion approach. Its efficiency is numerically confirmed by comparison with the existing mean-field theory when partially asymmetric couplings are present. (paper)

  19. Exact form factors for the scaling ZN-Ising and the affine AN-1-Toda quantum field theories

    International Nuclear Information System (INIS)

    Babujian, H.; Karowski, M.

    2003-01-01

    Previous results on form factors for the scaling Ising and the sinh-Gordon models are extended to general Z N -Ising and affine A N-1 -Toda quantum field theories. In particular result for order, disorder parameters and para-Fermi fields σ Q (x), μ Q-tilde (x) and ψ Q (x) are presented for the Z N -model. For the A N-1 -Toda model form factors for exponentials of the Toda fields are proposed. The quantum field equation of motion is proved and the mass and wave function renormalization are calculated exactly

  20. Dynamical TAP equations for non-equilibrium Ising spin glasses

    DEFF Research Database (Denmark)

    Roudi, Yasser; Hertz, John

    2011-01-01

    We derive and study dynamical TAP equations for Ising spin glasses obeying both synchronous and asynchronous dynamics using a generating functional approach. The system can have an asymmetric coupling matrix, and the external fields can be time-dependent. In the synchronously updated model, the TAP...... equations take the form of self consistent equations for magnetizations at time t+1, given the magnetizations at time t. In the asynchronously updated model, the TAP equations determine the time derivatives of the magnetizations at each time, again via self consistent equations, given the current values...... of the magnetizations. Numerical simulations suggest that the TAP equations become exact for large systems....

  1. BCS wave function, matrix product states, and the Ising conformal field theory

    Science.gov (United States)

    Montes, Sebastián; Rodríguez-Laguna, Javier; Sierra, Germán

    2017-11-01

    We present a characterization of the many-body lattice wave functions obtained from the conformal blocks (CBs) of the Ising conformal field theory (CFT). The formalism is interpreted as a matrix product state using continuous ancillary degrees of freedom. We provide analytic and numerical evidence that the resulting states can be written as BCS states. We give a complete proof that the translationally invariant 1D configurations have a BCS form and we find suitable parent Hamiltonians. In particular, we prove that the ground state of the finite-size critical Ising transverse field (ITF) Hamiltonian can be obtained with this construction. Finally, we study 2D configurations using an operator product expansion (OPE) approximation. We associate these states to the weak pairing phase of the p +i p superconductor via the scaling of the pairing function and the entanglement spectrum.

  2. Singular ferromagnetic susceptibility of the transverse-field Ising antiferromagnet on the triangular lattice

    Science.gov (United States)

    Biswas, Sounak; Damle, Kedar

    2018-02-01

    A transverse magnetic field Γ is known to induce antiferromagnetic three-sublattice order of the Ising spins σz in the triangular lattice Ising antiferromagnet at low enough temperature. This low-temperature order is known to melt on heating in a two-step manner, with a power-law ordered intermediate temperature phase characterized by power-law correlations at the three-sublattice wave vector Q : ˜cos(Q .R ⃗) /|R⃗| η (T ) with the temperature-dependent power-law exponent η (T )∈(1 /9 ,1 /4 ) . Here, we use a quantum cluster algorithm to study the ferromagnetic easy-axis susceptibility χu(L ) of an L ×L sample in this power-law ordered phase. Our numerical results are consistent with a recent prediction of a singular L dependence χu(L ) ˜L2 -9 η when η (T ) is in the range (1 /9 ,2 /9 ) . This finite-size result implies, via standard scaling arguments, that the ferromagnetic susceptibility χu(B ) to a uniform field B along the easy axis is singular at intermediate temperatures in the small B limit, χu(B ) ˜|B| -4/-18 η 4 -9 η for η (T )∈(1 /9 ,2 /9 ) , although there is no ferromagnetic long-range order in the low temperature state. Additionally we establish similar two-step melting behavior (via a study of the order parameter susceptibility χQ) in the case of the ferrimagnetic three-sublattice ordered phase which is stabilized by ferromagnetic next-neighbor couplings (J2) and confirm that the ferromagnetic susceptibility obeys the predicted singular form in the associated power-law ordered phase.

  3. Form factors of Ising spin and disorder fields on the Poincare disc

    International Nuclear Information System (INIS)

    Doyon, Benjamin

    2004-01-01

    Using recent results concerning form factors of certain scaling fields in the massive Dirac theory on the Poincare disc, we find expressions for the form factors of Ising spin and disorder fields in the massive Majorana theory on the Poincare disc. In particular, we verify that these recent results agree with the factorization properties of the fields in the Dirac theory representing tensor products of spin and of disorder fields in the Majorana theory

  4. A search for upstream pressure pulses associated with flux transfer events: An AMPTE/ISEE case study

    Science.gov (United States)

    Elphic, R. C.; Baumjohann, W.; Cattell, C. A.; Luehr, H.; Smith, M. F.

    1994-01-01

    On September 19, 1984, the Active Magnetospheric Particle Tracers Explorers (AMPTE) United Kingdom Satellite (UKS) and Ion Release Module (IRM) and International Sun Earth Explorers (ISEE) 1 and 2 spacecraft passed outbound through the dayside magnetopause at about the same time. The AMPTE spacecraft pair crossed first and were in the near-subsolar magnetosheath for more than an hour. Meanwhile the ISEE pair, about 5 R(sub E) to the south, observed flux transfer event (FTE) signatures. We use the AMPTE UKS and IRM plasma and field observations of magnetosheath conditions directly upstream of the subsolar magnetopause to check whether pressure pulses are responsible for the FTE signatures seen at ISEE. Pulses in both the ion thermal pressure and the dynamic pressure are observed in the magnetosheath early on when IRM and UKS are close to the magnetopause, but not later. These large pulses appear to be related to reconnection going on at the magnetopause nearby. AMPTE magnetosheath data far from the magnetopause do not show a pressure pulse correlation with FTEs at ISEE. Moreover, the magnetic pressure and tension effects seen in the ISEE FTEs are much larger than any pressure effects seen in the magnetosheath. A superposed epoch analysis based on small-amplitude peaks in the AMPTE magnetosheath total static pressure (nkT + B(exp 2)/2 mu(sub 0)) hint at some boundary effects, less than 5 nT peak-to-peak variations in the ISEE 1 and 2 B(sub N) signature starting about 1 min after the pressure peak epoch. However, these variations are much smaller than the standard deviations of the B(sub N) field component. Thus the evidence from this case study suggests that upstream magnetosheath pressure pulses do not give rise to FTEs, but may produce very small amplitude signatures in the magnetic field at the magnetopause.

  5. Testing ground for fluctuation theorems: The one-dimensional Ising model

    Science.gov (United States)

    Lemos, C. G. O.; Santos, M.; Ferreira, A. L.; Figueiredo, W.

    2018-04-01

    In this paper we determine the nonequilibrium magnetic work performed on a Ising model and relate it to the fluctuation theorem derived some years ago by Jarzynski. The basic idea behind this theorem is the relationship connecting the free energy difference between two thermodynamic states of a system and the average work performed by an external agent, in a finite time, through nonequilibrium paths between the same thermodynamic states. We test the validity of this theorem by considering the one-dimensional Ising model where the free energy is exactly determined as a function of temperature and magnetic field. We have found that the Jarzynski theorem remains valid for all the values of the rate of variation of the magnetic field applied to the system. We have also determined the probability distribution function for the work performed on the system for the forward and reverse processes and verified that predictions based on the Crooks relation are equally correct. We also propose a method to calculate the lag between the current state of the system and that of the equilibrium based on macroscopic variables. We have shown that the lag increases with the sweeping rate of the field at its final value for the reverse process, while it decreases in the case of the forward process. The lag increases linearly with the size of the chain and with a slope decreasing with the inverse of the rate of variation of the field.

  6. Casting the Coronal Magnetic Field Reconstructions with Magnetic Field Constraints above the Photosphere in 3D Using MHD Bifrost Model

    Science.gov (United States)

    Fleishman, G. D.; Anfinogentov, S.; Loukitcheva, M.; Mysh'yakov, I.; Stupishin, A.

    2017-12-01

    Measuring and modeling coronal magnetic field, especially above active regions (ARs), remains one of the central problems of solar physics given that the solar coronal magnetism is the key driver of all solar activity. Nowadays the coronal magnetic field is often modelled using methods of nonlinear force-free field reconstruction, whose accuracy has not yet been comprehensively assessed. Given that the coronal magnetic probing is routinely unavailable, only morphological tests have been applied to evaluate performance of the reconstruction methods and a few direct tests using available semi-analytical force-free field solution. Here we report a detailed casting of various tools used for the nonlinear force-free field reconstruction, such as disambiguation methods, photospheric field preprocessing methods, and volume reconstruction methods in a 3D domain using a 3D snapshot of the publicly available full-fledged radiative MHD model. We take advantage of the fact that from the realistic MHD model we know the magnetic field vector distribution in the entire 3D domain, which enables us to perform "voxel-by-voxel" comparison of the restored magnetic field and the true magnetic field in the 3D model volume. Our tests show that the available disambiguation methods often fail at the quiet sun areas, where the magnetic structure is dominated by small-scale magnetic elements, while they work really well at the AR photosphere and (even better) chromosphere. The preprocessing of the photospheric magnetic field, although does produce a more force-free boundary condition, also results in some effective `elevation' of the magnetic field components. The effective `elevation' height turns out to be different for the longitudinal and transverse components of the magnetic field, which results in a systematic error in absolute heights in the reconstructed magnetic data cube. The extrapolation performed starting from actual AR photospheric magnetogram (i.e., without preprocessing) are

  7. A portable, low-cost, 3D-printed main magnetic field system for magnetic imaging.

    Science.gov (United States)

    Iksung Kang

    2017-07-01

    In this paper, a portable, low-cost, 3D-printed system for main magnetic field is proposed to suggest a solution for accessibility problems of current magnetic imaging systems, e.g. MRI scanner, their size and cost. The system consists of twelve pairs of NdFeB N35 permanent magnets arranged in a Halbach array in a 3D-printed, cylindrical container based on FEM simulation results by COMSOL Multiphysics 4.4b. Its magnetic field homogeneity and field strength were measured by Hall sensors, WSH-135 XPAN2 by Wilson Semiconductor, and the container was printed by 3DISON H700 by Rokit. The system generated a 5-mm imaging quality FOV and main magnetic field of 120 mT with a 12 % error in the field strength. Also, a hundred dollar was enough for the manufacture of the system with a radius of 6 cm and height of 10 cm. Given the results, I believe the system will be useful for some magnetic imaging applications, e.g. EPRI and low-field MRI.

  8. Accurate Mapping of Multilevel Rydberg Atoms on Interacting Spin-1 /2 Particles for the Quantum Simulation of Ising Models

    Science.gov (United States)

    de Léséleuc, Sylvain; Weber, Sebastian; Lienhard, Vincent; Barredo, Daniel; Büchler, Hans Peter; Lahaye, Thierry; Browaeys, Antoine

    2018-03-01

    We study a system of atoms that are laser driven to n D3 /2 Rydberg states and assess how accurately they can be mapped onto spin-1 /2 particles for the quantum simulation of anisotropic Ising magnets. Using nonperturbative calculations of the pair potentials between two atoms in the presence of electric and magnetic fields, we emphasize the importance of a careful selection of experimental parameters in order to maintain the Rydberg blockade and avoid excitation of unwanted Rydberg states. We benchmark these theoretical observations against experiments using two atoms. Finally, we show that in these conditions, the experimental dynamics observed after a quench is in good agreement with numerical simulations of spin-1 /2 Ising models in systems with up to 49 spins, for which numerical simulations become intractable.

  9. Quantum transitions driven by one-bond defects in quantum Ising rings.

    Science.gov (United States)

    Campostrini, Massimo; Pelissetto, Andrea; Vicari, Ettore

    2015-04-01

    We investigate quantum scaling phenomena driven by lower-dimensional defects in quantum Ising-like models. We consider quantum Ising rings in the presence of a bond defect. In the ordered phase, the system undergoes a quantum transition driven by the bond defect between a magnet phase, in which the gap decreases exponentially with increasing size, and a kink phase, in which the gap decreases instead with a power of the size. Close to the transition, the system shows a universal scaling behavior, which we characterize by computing, either analytically or numerically, scaling functions for the low-level energy differences and the two-point correlation function. We discuss the implications of these results for the nonequilibrium dynamics in the presence of a slowly varying parallel magnetic field h, when going across the first-order quantum transition at h=0.

  10. Exact solution of the Ising model in a fully frustrated two-dimensional lattice

    International Nuclear Information System (INIS)

    Silva, N.R. da; Medeiros e Silva Filho, J.

    1983-01-01

    A straightforward extension of the Onsager method allows us to solve exactly the Ising problem in a fully frustated square lattice in the absence of external magnetic field. It is shown there is no singularity in the thermodynamic functions for non-zero temperature. (Author) [pt

  11. Quenched random-bond ising ferromagnet

    International Nuclear Information System (INIS)

    Sarmento, E.F.; Honmura, R.; Tsallis, C.; Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro)

    1984-01-01

    A effective-field framework which, without mathematical complexities, enables the calculation of the phase diagram (and magnetization) associated with a quenched bond-mixed spin - 1/2 Ising model in an anisotropic simple cubic lattice have been recently introduced. The case corresponding to anisotropic coupling constants but isotropic concentrations was discussed in detail. Herein the case corresponding to isotropic coupling constants but anisotropic concentrations is discussed. A certain amount of interesting phase diagrams are exhibited; whenever comparison with available data is possible, the present results provide a satisfactory qualitative (and to a certain extent quantitative) agreement. (Author) [pt

  12. Mixed spin-3/2 and spin-5/2 Ising system on the Bethe lattice

    International Nuclear Information System (INIS)

    Albayrak, Erhan; Yigit, Ali

    2006-01-01

    In order to study the critical behaviors of the half-integer mixed spin-3/2 and spin-5/2 Blume-Capel Ising ferrimagnetic system, we have used the exact recursion relations on the Bethe lattice. The system was studied for the coordination numbers with q=3, 4, 5 and 6, and the obtained phase diagrams are illustrated on the (kT c /|J|,D A /|J|) plane for constant values of D B /|J|, the reduced crystal field of the sublattice with spin-5/2, and on the (kT c /|J|,D B /|J|) plane for constant values of D A /|J|, the reduced crystal field of the sublattice with spin-3/2, for q=3 only, since the cases corresponding to q=4, 5 and 6 reproduce results similar to the case for q=3. In addition we have also presented the phase diagram with equal strengths of the crystal fields for q=3, 4, 5 and 6. Besides the second- and first-order phase transitions, the system also exhibits compensation temperatures for appropriate values of the crystal fields. In this mixed spin system while the second-order phase transition lines never cut the reduced crystal field axes as in the single spin type spin-3/2 and spin-5/2 Ising models separately, the first-order phase transition lines never connect to the second-order phase transition lines and they end at the critical points, therefore the system does not give any tricritical points. In addition to this, this mixed-spin model exhibits one or two compensation temperatures depending on the values of the crystal fields, as a result the compensation temperature lines show reentrant behavior

  13. Test of quantum thermalization in the two-dimensional transverse-field Ising model

    Science.gov (United States)

    Blaß, Benjamin; Rieger, Heiko

    2016-01-01

    We study the quantum relaxation of the two-dimensional transverse-field Ising model after global quenches with a real-time variational Monte Carlo method and address the question whether this non-integrable, two-dimensional system thermalizes or not. We consider both interaction quenches in the paramagnetic phase and field quenches in the ferromagnetic phase and compare the time-averaged probability distributions of non-conserved quantities like magnetization and correlation functions to the thermal distributions according to the canonical Gibbs ensemble obtained with quantum Monte Carlo simulations at temperatures defined by the excess energy in the system. We find that the occurrence of thermalization crucially depends on the quench parameters: While after the interaction quenches in the paramagnetic phase thermalization can be observed, our results for the field quenches in the ferromagnetic phase show clear deviations from the thermal system. These deviations increase with the quench strength and become especially clear comparing the shape of the thermal and the time-averaged distributions, the latter ones indicating that the system does not completely lose the memory of its initial state even for strong quenches. We discuss our results with respect to a recently formulated theorem on generalized thermalization in quantum systems. PMID:27905523

  14. The influence of further-neighbor spin-spin interaction on a ground state of 2D coupled spin-electron model in a magnetic field

    Science.gov (United States)

    Čenčariková, Hana; Strečka, Jozef; Gendiar, Andrej; Tomašovičová, Natália

    2018-05-01

    An exhaustive ground-state analysis of extended two-dimensional (2D) correlated spin-electron model consisting of the Ising spins localized on nodal lattice sites and mobile electrons delocalized over pairs of decorating sites is performed within the framework of rigorous analytical calculations. The investigated model, defined on an arbitrary 2D doubly decorated lattice, takes into account the kinetic energy of mobile electrons, the nearest-neighbor Ising coupling between the localized spins and mobile electrons, the further-neighbor Ising coupling between the localized spins and the Zeeman energy. The ground-state phase diagrams are examined for a wide range of model parameters for both ferromagnetic as well as antiferromagnetic interaction between the nodal Ising spins and non-zero value of external magnetic field. It is found that non-zero values of further-neighbor interaction leads to a formation of new quantum states as a consequence of competition between all considered interaction terms. Moreover, the new quantum states are accompanied with different magnetic features and thus, several kinds of field-driven phase transitions are observed.

  15. Ising critical behaviour in the one-dimensional frustrated quantum XY model

    International Nuclear Information System (INIS)

    Granato, E.

    1993-06-01

    A generalization of the one-dimensional frustrated quantum XY model is considered in which the inter and intra-chain coupling constants of the two infinite XY (planar rotor) chains have different strengths. The model can describe the superconductor-insulator transition due to charging effects in a ladder of Josephson junctions in a magnetic field with half a flux quantum per plaquette. From a fluctuation-effective action, this transition is expected to be in the universality class of the two-dimensional classical XY-Ising model. The critical behaviour is studied using a Monte Carlo transfer matrix applied to the path-integral representation of the model and a finite-size-scaling analysis of data on small system sizes. It is found that, unlike the previous studied case of equal inter and intra-chain coupling constants, the XY and Ising-like excitations of the quantum model decouple for large interchain coupling, giving rise to pure Ising model critical behaviour for the chirality order parameter in good agreement with the results for the XY-Ising model. (author). 18 refs, 4 figs

  16. High critical magnetic field superconductor La3S4

    International Nuclear Information System (INIS)

    Westerholt, K.; Bach, H.; Wendemuth, R.; Methfessel, S.

    1979-01-01

    A report is presented on electrical conductivity, specific heat and magnetization measurements on La 3 S 4 single crystals. The results show that La 3 S 4 is a strong coupling superconductor with a BCS coherence length of 132 A. This extremely low value makes La 3 S 4 an intrinsic high critical magnetic field superconductor with a Landau-Ginsburg parameter of 20. For the temperature gradient of the upper critical magnetic field at the transition temperature values are found up to 35 kG/K. (author)

  17. The Ising model and its applications to a phase transition of biological interest

    International Nuclear Information System (INIS)

    Cabrera, G.G.; Stein-Barana, A.M.; Zuckermann, M.J.

    1984-01-01

    It is investigated a gel-liquid crystal phase transition employing a two-state model equivalent to the Spin 1/2 Ising Model with applied magnetic field. The model is studied from the standpoint of the cluster variational method of Kikuchi for cooperative phenomena. (M.W.O.) [pt

  18. Dynamics of the directed Ising chain

    International Nuclear Information System (INIS)

    Godrèche, Claude

    2011-01-01

    The study by Glauber of the time-dependent statistics of the Ising chain is extended to the case where each spin is influenced unequally by its nearest neighbours. The asymmetry of the dynamics implies the failure of the detailed balance condition. The functional form of the rate at which an individual spin changes its state is constrained by the global balance condition with respect to the equilibrium measure of the Ising chain. The local magnetization, the equal-time and two-time correlation functions and the linear response to an external magnetic field obey linear equations which are solved explicitly. The behaviour of these quantities and the relation between the correlation and response functions are analysed both in the stationary state and in the zero-temperature scaling regime. In the stationary state, a transition between two behaviours of the correlation function occurs when the amplitude of the asymmetry crosses a critical value, with the consequence that the limit fluctuation-dissipation ratio decays continuously from the value 1, for the equilibrium state in the absence of asymmetry, to 0 for this critical value. At zero temperature, under asymmetric dynamics, the system loses its critical character, yet keeping many of the characteristic features of a coarsening system

  19. PREFACE: 3rd International Workshop on Materials Analysis and Processing in Magnetic Fields (MAP3)

    Science.gov (United States)

    Sakka, Yoshio; Hirota, Noriyuki; Horii, Shigeru; Ando, Tsutomu

    2009-07-01

    The 3rd International Workshop on Materials Analysis and Processing in Materials Fields (MAP3) was held on 14-16 May 2008 at the University of Tokyo, Japan. The first was held in March 2004 at the National High Magnetic Field Laboratory in Tallahassee, USA. Two years later the second took place in Grenoble, France. MAP3 was held at The University of Tokyo International Symposium, and jointly with MANA Workshop on Materials Processing by External Stimulation, and JSPS CORE Program of Construction of the World Center on Electromagnetic Processing of Materials. At the end of MAP3 it was decided that the next MAP4 will be held in Atlanta, USA in 2010. Processing in magnetic fields is a rapidly expanding research area with a wide range of promising applications in materials science. MAP3 focused on the magnetic field interactions involved in the study and processing of materials in all disciplines ranging from physics to chemistry and biology: Magnetic field effects on chemical, physical, and biological phenomena Magnetic field effects on electrochemical phenomena Magnetic field effects on thermodynamic phenomena Magnetic field effects on hydrodynamic phenomena Magnetic field effects on crystal growth Magnetic processing of materials Diamagnetic levitation Magneto-Archimedes effect Spin chemistry Application of magnetic fields to analytical chemistry Magnetic orientation Control of structure by magnetic fields Magnetic separation and purification Magnetic field-induced phase transitions Materials properties in high magnetic fields Development of NMR and MRI Medical application of magnetic fields Novel magnetic phenomena Physical property measurement by Magnetic fields High magnetic field generation> MAP3 consisted of 84 presentations including 16 invited talks. This volume of Journal of Physics: Conference Series contains the proceeding of MAP3 with 34 papers that provide a scientific record of the topics covered by the conference with the special topics (13 papers) in

  20. Probability distribution of magnetization in the one-dimensional Ising model: effects of boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Antal, T [Physics Department, Simon Fraser University, Burnaby, BC V5A 1S6 (Canada); Droz, M [Departement de Physique Theorique, Universite de Geneve, CH 1211 Geneva 4 (Switzerland); Racz, Z [Institute for Theoretical Physics, Eoetvoes University, 1117 Budapest, Pazmany setany 1/a (Hungary)

    2004-02-06

    Finite-size scaling functions are investigated both for the mean-square magnetization fluctuations and for the probability distribution of the magnetization in the one-dimensional Ising model. The scaling functions are evaluated in the limit of the temperature going to zero (T {yields} 0), the size of the system going to infinity (N {yields} {infinity}) while N[1 - tanh(J/k{sub B}T)] is kept finite (J being the nearest neighbour coupling). Exact calculations using various boundary conditions (periodic, antiperiodic, free, block) demonstrate explicitly how the scaling functions depend on the boundary conditions. We also show that the block (small part of a large system) magnetization distribution results are identical to those obtained for free boundary conditions.

  1. Light induced kickoff of magnetic domain walls in Ising chains

    Science.gov (United States)

    Bogani, Lapo

    2012-02-01

    Controlling the speed at which systems evolve is a challenge shared by all disciplines, and otherwise unrelated areas use common theoretical frameworks towards this goal. A particularly widespread model is Glauber dynamics, which describes the time evolution of the Ising model and can be applied to any binary system. Here we show, using molecular nanowires under irradiation, that Glauber dynamics can be controlled by a novel domain-wall kickoff mechanism. Contrary to known processes, the kickoff has unambiguous fingerprints, slowing down the spin-flip attempt rate by several orders of magnitude, and following a scaling law. The required irradiation power is very low, a substantial improvement over present methods of magnetooptical switching: in our experimental demonstration we switched molecular nanowires with light, using powers thousands of times lower than in previous optical switching methods. This manipulation of stochastic dynamic processes is extremely clean, leading to fingerprint signatures and scaling laws. These observations can be used, in material science, to better study domain-wall displacements and solitons in discrete lattices. These results provide a new way to control and study stochastic dynamic processes. Being general for Glauber dynamics, they can be extended to different kinds of magnetic nanowires and to a myriad of fields, ranging from social evolution to neural networks and chemical reactivity. For nanoelectronics and molecular spintronics the kickoff affords external control of molecular spin-valves and a magnetic fingerprint in single molecule measurements. It can also be applied to the dynamics of mechanical switches and the related study of phasons and order-disorder transitions.

  2. Thermodynamic and critical properties of an antiferromagnetically stacked triangular Ising antiferromagnet in a field

    Science.gov (United States)

    Žukovič, M.; Borovský, M.; Bobák, A.

    2018-05-01

    We study a stacked triangular lattice Ising model with both intra- and inter-plane antiferromagnetic interactions in a field, by Monte Carlo simulation. We find only one phase transition from a paramagnetic to a partially disordered phase, which is of second order and 3D XY universality class. At low temperatures we identify two highly degenerate phases: at smaller (larger) fields the system shows long-range ordering in the stacking direction (within planes) but not in the planes (stacking direction). Nevertheless, crossovers to these phases do not have a character of conventional phase transitions but rather linear-chain-like excitations.

  3. An Ising model for metal-organic frameworks

    Science.gov (United States)

    Höft, Nicolas; Horbach, Jürgen; Martín-Mayor, Victor; Seoane, Beatriz

    2017-08-01

    We present a three-dimensional Ising model where lines of equal spins are frozen such that they form an ordered framework structure. The frame spins impose an external field on the rest of the spins (active spins). We demonstrate that this "porous Ising model" can be seen as a minimal model for condensation transitions of gas molecules in metal-organic frameworks. Using Monte Carlo simulation techniques, we compare the phase behavior of a porous Ising model with that of a particle-based model for the condensation of methane (CH4) in the isoreticular metal-organic framework IRMOF-16. For both models, we find a line of first-order phase transitions that end in a critical point. We show that the critical behavior in both cases belongs to the 3D Ising universality class, in contrast to other phase transitions in confinement such as capillary condensation.

  4. Magnetic behavior of the diluted antiferromagnet Mn0.39Zn0.61F2 at strong fields

    International Nuclear Information System (INIS)

    Rosales-Rivera, A.; Ferreira, J.M.; Montenegro, F.C.; Ramos, C.A.

    2001-01-01

    The magnetic phase boundaries of the random-field Ising model (RFIM) system Mn 0.39 Zn 0.61 F 2 are determined using magnetization measurements, under finite DC applied fields (H). At low fields (H<12 kOe), our results support a critical phase boundary, separating an ordered antiferromagnetic (AF) phase from the paramagnetic (P) one. For intermediate fields (12< H<18 kOe), the AF ordering coexists with a spin-flop (SF) clustering. For higher H, a spin-flop phase dominates the upper part of the (H,T) phase diagram

  5. Transverse spin correlations of the random transverse-field Ising model

    Science.gov (United States)

    Iglói, Ferenc; Kovács, István A.

    2018-03-01

    The critical behavior of the random transverse-field Ising model in finite-dimensional lattices is governed by infinite disorder fixed points, several properties of which have already been calculated by the use of the strong disorder renormalization-group (SDRG) method. Here we extend these studies and calculate the connected transverse-spin correlation function by a numerical implementation of the SDRG method in d =1 ,2 , and 3 dimensions. At the critical point an algebraic decay of the form ˜r-ηt is found, with a decay exponent being approximately ηt≈2 +2 d . In d =1 the results are related to dimer-dimer correlations in the random antiferromagnetic X X chain and have been tested by numerical calculations using free-fermionic techniques.

  6. Effective field approach to the Ising film in a transverse field

    International Nuclear Information System (INIS)

    Peliti, L.; Saber, M.

    1998-05-01

    Within the framework of the effective field theory, we examine the phase transitions of the spin -1/2 Ising film in a transverse field. We study the critical temperature of the film as a function of the exchange interactions, the transverse field and the film thickness. We find that, if the ratio of the surface exchange interactions to the bulk ones R=J s /J is smaller that a critical value R c , the critical temperature T c /J of the film is smaller that the bulk critical temperature T B c /J and as R is increased further, T c /J approaches T B c /J. On the other hand, if R>R c ,T c /J is larger than the bulk T B c /J and the surface T S c /J critical temperatures of the corresponding semi-infinite system and as R is increased further, T c /J approaches the surface critical temperature T S c /J. (author)

  7. Phase transitions of ferromagnetic Ising films with amorphous surfaces

    International Nuclear Information System (INIS)

    Saber, M.; Ainane, A.; Dujardin, F.; Stebe, B.

    1997-08-01

    The critical behavior of a ferromagnetic Ising film with amorphous surfaces is studied within the framework of the effective field theory. The dependence of the critical temperature on exchange interaction strength ratio, film thickness, and structural fluctuation parameter is presented. It is found that an order-disorder magnetic transition occurs by varying the thickness of the film. Such a result is in agreement with experiments performed recently on Fe-films. (author). 39 refs, 4 figs

  8. Heisenberg spin-1/2 XXZ chain in the presence of electric and magnetic fields

    Science.gov (United States)

    Thakur, Pradeep; Durganandini, P.

    2018-02-01

    We study the interplay of electric and magnetic order in the one-dimensional Heisenberg spin-1/2 XXZ chain with large Ising anisotropy in the presence of the Dzyaloshinskii-Moriya (DM) interaction and with longitudinal and transverse magnetic fields, interpreting the DM interaction as a coupling between the local electric polarization and an external electric field. We obtain the ground state phase diagram using the density matrix renormalization group method and compute various ground state quantities like the magnetization, staggered magnetization, electric polarization and spin correlation functions, etc. In the presence of both longitudinal and transverse magnetic fields, there are three different phases corresponding to a gapped Néel phase with antiferromagnetic (AF) order, gapped saturated phase, and a critical incommensurate gapless phase. The external electric field modifies the phase boundaries but does not lead to any new phases. Both external magnetic fields and electric fields can be used to tune between the phases. We also show that the transverse magnetic field induces a vector chiral order in the Néel phase (even in the absence of an electric field) which can be interpreted as an electric polarization in a direction parallel to the AF order.

  9. RFID Antenna Near-field Characterization Using a New 3D Magnetic Field Probe

    Directory of Open Access Journals (Sweden)

    Kassem Jomaa

    2017-05-01

    Full Text Available In this paper the design of a new 3D magnetic field (H-field probe with a near-field scanning system is presented, then the near electromagnetic fields radiated by a Library RFID system is characterized. The proposed system is developed in order to determine the magnetic near-field emitted by electronic devices. The designed isotropic H-field probe consists of three orthogonal and identical loops each of diameter of 6 mm having 3 turns. The antenna factor of the designed probe is presented for a frequency range from 10 MHz to 1 GHz. The designed probe is tested and validated using a standard passive circuit as a device under test. An RFID reader antenna is also designed and simulated on HFSS (high frequency structural simulator and the radiated magnetic field, obtained by simulations, is then compared to the real measured one above the fabricated circuit. The obtained levels are checked if they satisfy the European and ICNIRP Electromagnetic Fields Guidelines.

  10. Magnetic field computations for ISX using GFUN-3D

    International Nuclear Information System (INIS)

    Cain, W.D.

    1977-01-01

    This paper presents a comparison between measured magnetic fields and the magnetic fields calculated by the three-dimensional computer program GFUN-3D for the Impurity Study Experiment (ISX). Several iron models are considered ranging in sophistication from 50 to 222 tetrahedra iron elements. The effects of air gaps and the efforts made to simulate effects of grain orientation and packing factor are detailed. The results obtained are compared with the measured magnetic fields, and explanations are presented to account for the variations which occur

  11. Open and disconnected magnetic field lines within coronal mass ejections in the solar wind: Evidence for 3-dimensional reconnection

    Science.gov (United States)

    Gosling, J. T.; Birn, J.; McComas, D. J.; Phillips, J. L.; Hesse, M.

    1995-01-01

    Measurements of suprathermal electron fluxes in the solar wind at energies greater than approximatley 80 eV indicate that magnetic field lines within coronal mass ejections. CMEs, near and beyond 1 AU are normally connected to the Sun at both ends. However, a preliminary reexamination of events previously identified as CMEs in the ISEE 3 data reveals that about 1/4 of all such events contain limited regions where field lines appear to be either connected to the Sun at only one end or connected to the outer heliosphere at both ends. Similar intervals of open and disconnected field lines within CMEs have been identified in the Ulysses observations. We believe that these anomalous field topologies within CMEs are most naturally interpreted in terms of 3-dimensional reconnection behind CMEs close to the Sun. Such reconnection also provides a natural explanation both for the flux rope topology of many CMEs as well as the coronal loops formed during long-duration solar soft X ray events. Although detailed numerical simulations of 3-dimensional reconnection behind CMEs are not yet available, such simulations have been done for the qualitatively similar geometry that prevails within the geomagnetic tail. Those simulations of plasmoid formation in the geomagnetic tail do produce the mixture of field topologies within plasmoids discussed here for CMEs.

  12. 1/3 magnetization plateau in a one-dimensional anisotropic ferrimagnet

    Energy Technology Data Exchange (ETDEWEB)

    Tonegawa, T [Department of Mechanical Engineering, Fukui University of Technology, Fukui 910-8505 (Japan); Sakai, T [Japan Atomic Energy Agency (JAEA), Spring-8, Hyogo 679-5148, and Crest JST, Japan (Japan); Okamoto, K [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551 (Japan); Kaburagi, M [Faculty of Cross-Cultural Studies, Kobe University, Kobe 657-8501 (Japan)

    2006-11-15

    Using mainly numerical methods, we investigate the ground-state magnetization curve of a mixed spin chain with uniaxial single-ion anisotropies, where S = 1 and S = 2 spins are alternating and coupled antiferromagnetically. Special attention is paid to the magnetization plateau, the 1/3-plateau, which appears at one third of the saturation magnetization in the magnetization curve. It is found that there appear three kinds of 1/3-plateaux, one of which has a quantum nature, while the remaining two have a classical (Ising) nature.

  13. Spin-phonon induced magnetic order in magnetized Spin Ice systems

    International Nuclear Information System (INIS)

    Albarracín, F A Gómez; Cabra, D C; Rosales, H D; Rossini, G L

    2014-01-01

    We study the behavior of spin ice pyrochlore systems above the well known [111] 1/3 plateau, under slight deviations of the direction of the external field. We model the relevant degrees of freedom by Ising spins on the kagome lattice. We propose the inclusion of lattice deformations, which imply phononic degrees of freedom in the adiabatic limit. We use analytical calculations to estimate how these new degrees of freedom affect the short and long range spin interactions in the presence of an external magnetic field. We then obtain the magnetization curves, explore the phases and the ground states of this system in the presence of magnetic field by Monte Carlo simulations. We discuss comparisons with experimental results

  14. Ferromagnetic transitions of a spin-one Ising film in a surface and bulk transverse fields

    International Nuclear Information System (INIS)

    Saber, A.; Lo Russo, S.; Mattei, G.; Mattoni, A.

    2002-01-01

    Using the effective field theory method, we have calculated the Curie temperature of a spin-one Ising ferromagnetic film in a surface and bulk transverse fields. Numerical calculations give phase diagrams under various parameters. Surface exchange enhancement is considered. The dependence of the critical transverse field on film thickness, and phase diagrams in the fields, critical surface transverse field versus the bulk one are presented

  15. Aging, rejuvenation, and memory effects in short-range Ising spin glass: Cu_0.5Co_0.5Cl_2-FeCl3 GBIC

    Science.gov (United States)

    Suzuki, M.; Suzuki, I. S.

    2004-03-01

    Cu_0.5Co_0.5Cl_2-FeCl3 GBIC undergoes a spin glass (SG) transition at Tg (= 3.92 ± 0.11 K). The system shows a dynamic behavior that has some similarities and some significant differences compared to a 3D Ising SG.^1 Here we report on non-equilibrium aging dynamics which has been studied using zero-field cooled (ZFC) magnetization and low frequency AC magnetic susceptibility.^2 The time dependence of the relaxation rate S(t) = (1/H)dM_ZFC/dln t for the ZFC magnetization after the ZFC aging protocol, shows a peak at a characteristic time t_cr near a wait time t_w, corresponding to a crossover from quasi equilibrium dynamics to non-equilibrium. The time t_cr strongly depends on t_w, temperature, magnetic field, and the temperature shift. The rejuvenation effect is observed in both i^' and i^'' under the T-shift and H-shift procedures. The memory of the specific spin configurations imprinted during the ZFC aging protocol can be recalled when the system is re-heated at a constant heating rate. The aging, rejuvenation, and memory effects are discussed in terms of the scaling concepts derived from numerical studies on 3D Edwards-Anderson spin glass model. 1. I.S. Suzuki and M. Suzuki, Phys. Rev. B 68, 094424 (2003) 2. M. Suzuki and I.S. Suzuki, cond-mat/0308285

  16. An effective field study of the magnetic properties and critical behaviour at the surface Ising film

    International Nuclear Information System (INIS)

    Bengrine, M.; Benyoussef, A.; Ez-Zahraouy, H.; Mhirech, F.

    1998-09-01

    The influence of corrugation and disorder at the surface on the critical behaviour of a ferromagnetic spin-1/2 Ising film is investigated using mean-field theory and finite cluster approximation. It is found that the critical surface exponent β 1 follows closely the one of a perfect surface, in the two cases: corrugated surface and random equiprobable coupling surface. However, in the case of flat surface with random interactions the surface critical exponent β 1 depends on the concentration p of the strong interaction for p>p c =0,5, while for p≤p c , such critical exponent is independent on the value of p and is equal to the one of the perfect surface. Moreover, in the case of corrugated surface, the effective exponent for a layer z, β eff J(z,n), is calculated as a function of the number of steps at the surface. (author)

  17. 3D Biomimetic Magnetic Structures for Static Magnetic Field Stimulation of Osteogenesis

    OpenAIRE

    Irina Alexandra Paun; Roxana Cristina Popescu; Bogdan Stefanita Calin; Cosmin Catalin Mustaciosu; Maria Dinescu; Catalin Romeo Luculescu

    2018-01-01

    We designed, fabricated and optimized 3D biomimetic magnetic structures that stimulate the osteogenesis in static magnetic fields. The structures were fabricated by direct laser writing via two-photon polymerization of IP-L780 photopolymer and were based on ellipsoidal, hexagonal units organized in a multilayered architecture. The magnetic activity of the structures was assured by coating with a thin layer of collagen-chitosan-hydroxyapatite-magnetic nanoparticles composite. In vitro experime...

  18. Dynamic phase transitions and dynamic phase diagrams of the Ising model on the Shastry-Sutherland lattice

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Şeyma Akkaya, E-mail: sadeviren@nevsehir.edu.tr [Department of Science Education, Education Faculty, Nevsehir Hacı Bektaş Veli University, 50300 Nevşehir (Turkey); Deviren, Bayram [Department of Physics, Nevsehir Hacı Bektaş Veli University, 50300 Nevsehir (Turkey)

    2016-03-15

    The dynamic phase transitions and dynamic phase diagrams are studied, within a mean-field approach, in the kinetic Ising model on the Shastry-Sutherland lattice under the presence of a time varying (sinusoidal) magnetic field by using the Glauber-type stochastic dynamics. The time-dependence behavior of order parameters and the behavior of average order parameters in a period, which is also called the dynamic order parameters, as a function of temperature, are investigated. Temperature dependence of the dynamic magnetizations, hysteresis loop areas and correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic phase transitions as well as to obtain the dynamic phase transition temperatures. We present the dynamic phase diagrams in the magnetic field amplitude and temperature plane. The phase diagrams exhibit a dynamic tricritical point and reentrant phenomena. The phase diagrams also contain paramagnetic (P), Néel (N), Collinear (C) phases, two coexistence or mixed regions, (N+C) and (N+P), which strongly depend on interaction parameters. - Highlights: • Dynamic magnetization properties of spin-1/2 Ising model on SSL are investigated. • Dynamic magnetization, hysteresis loop area, and correlation have been calculated. • The dynamic phase diagrams are constructed in (T/|J|, h/|J|) plane. • The phase diagrams exhibit a dynamic tricritical point and reentrant phenomena.

  19. Dimensional expansion for the Ising limit of quantum field theory

    International Nuclear Information System (INIS)

    Bender, C.M.; Boettcher, S.

    1993-01-01

    A recently proposed technique, called dimensional expansion, uses the space-time dimension D as an expansion parameter to extract nonperturbative results in quantum field theory. Here we apply dimensional-expansion methods to examine the Ising limit of a self-interacting scalar field theory. We compute the first few coefficients in the dimensional expansion of γ 2n , the renormalized 2n-point Green's function at zero momentum, for n=2, 3, 4, and 5. Because the exact results for γ 2n are known at D=1 we can compare the predictions of the dimensional expansion at this value of D. We find typical accuracies of less than 5%. The radius of convergence of the dimensional expansion for γ 2n appears to be 2n/(n-1). As a function of the space-time dimension D, γ 2n appears to rise monotonically with increasing D and we conjecture that it becomes infinite at D=2n/(n-1). We presume that for values of D greater than this critical value γ 2n vanishes identically because the corresponding φ 2n scalar quantum field theory is free for D>2n/(n-1)

  20. Synthesis of Fe3O4 particle-chain microwires in applied magnetic field

    International Nuclear Information System (INIS)

    Li Fashen; Wang Ying; Wang Tao

    2007-01-01

    Fe 3 O 4 particle-chain microwires are firstly synthesized under magnetic field by a simple coprecipitation method. The increase of magnetic field caused the lengthening of the wires, and doubled densities of starting solution lead to a halved diameter. It was supposed that the magnetic field gradient and the particular growing process of particles are the main factors of the formation of these microwires. Magnetic hysteresis curves of Fe 3 O 4 microwires were also measured. - Graphical abstract: Fe 3 O 4 particle-chain microwires are firstly synthesized under magnetic field by a simple coprecipitation method. It was supposed that the magnetic field gradient and the particular growing process of particles are the main factors of the formation of these microwires. Magnetic hysteresis curves of Fe 3 O 4 microwires were also measured

  1. Magnetic properties of Fe–Al for quenched diluted spin-1 Ising model

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, A.S. [Departamento de Física, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil); Coordenadoria de Física, Instituto Federal de Sergipe, 49400-000 Lagarto, SE (Brazil); Albuquerque, Douglas F. de, E-mail: douglas@ufs.br [Departamento de Física, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil); Departamento de Matemática, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil); Fittipaldi, I.P. [Representação Regional do Ministério da Ciência, Tecnologia e Inovação no Nordeste - ReNE, 50740-540 Recife, PE (Brazil); Moreno, N.O. [Departamento de Física, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil)

    2014-08-01

    We study the phase diagram of Fe{sub 1−q}Al{sub q} alloys via the quenched site diluted spin-1 ferromagnetic Ising model by employing effective field theory. One suggests a new approach to exchange interaction between nearest neighbors of Fe that depends on the powers of the Al (q) instead of the linear dependence proposed in other papers. In such model we propose the same kind of the exchange interaction in which the iron–nickel alloys obtain an excellent theoretical description of the experimental data of the T–q phase diagram for all Al concentration q. - Highlights: • We apply the quenched Ising model spin-1 to study the properties of Fe–Al. • We employ the EFT and suggest a new approach to ferromagnetic coupling. • The new probability distribution is considered. • The phase diagram is obtained for all values of q in T–q plane.

  2. Magnetic properties of Fe–Al for quenched diluted spin-1 Ising model

    International Nuclear Information System (INIS)

    Freitas, A.S.; Albuquerque, Douglas F. de; Fittipaldi, I.P.; Moreno, N.O.

    2014-01-01

    We study the phase diagram of Fe 1−q Al q alloys via the quenched site diluted spin-1 ferromagnetic Ising model by employing effective field theory. One suggests a new approach to exchange interaction between nearest neighbors of Fe that depends on the powers of the Al (q) instead of the linear dependence proposed in other papers. In such model we propose the same kind of the exchange interaction in which the iron–nickel alloys obtain an excellent theoretical description of the experimental data of the T–q phase diagram for all Al concentration q. - Highlights: • We apply the quenched Ising model spin-1 to study the properties of Fe–Al. • We employ the EFT and suggest a new approach to ferromagnetic coupling. • The new probability distribution is considered. • The phase diagram is obtained for all values of q in T–q plane

  3. The magnetic field of cloud 3 in L204

    Energy Technology Data Exchange (ETDEWEB)

    Cashman, Lauren R.; Clemens, D. P., E-mail: lcashman@bu.edu, E-mail: clemens@bu.edu [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)

    2014-10-01

    The L204 dark cloud complex is a nearby filamentary structure in Ophiuchus North that has no signs of active star formation. Past studies show that L204 is interacting with the nearby runaway O star, ζ Oph, and hosts a magnetic field that is coherent across parsec-length scales. Near-infrared H-band (1.6 μm) linear polarization measurements were obtained for 3896 background stars across a 1° × 1.°5 region centered on the dense Cloud 3 in L204, using the Mimir near-infrared instrument on the 1.8 m Perkins Telescope. Analysis of these observations reveals both large-scale properties and small-scale changes in the magnetic field direction in Cloud 3. In the northern and western ζ Oph facing regions of the cloud, the magnetic field appears to be pushed up against the face of the cloud. This may indicate that the UV flux from ζ Oph has compressed the magnetic field on the western edge of L204. The plane-of-sky magnetic field strength is estimated to be ∼11-26 μG using the Chandrasekhar-Fermi method. The polarimetry data also reveal that the polarization efficiency (PE ≡ P {sub H}/A {sub V}) steadily decreases with distance from ζ Oph (–0.09% ± 0.03% mag{sup –1} pc{sup –1}). Additionally, power-law fits of PE versus A {sub V} for localized samples of probe stars show steeper negative indices with distance from ζ Oph. Both findings highlight the importance of external illumination, here from ζ Oph, in aligning dust grains to embedded magnetic fields.

  4. Effects of interplanetary magnetic field and magnetospheric substorm variations on the dayside aurora

    Science.gov (United States)

    Sandholt, P. E.; Egeland, A.; Lybekk, B.; Deehr, C. S.; Sivjee, G. G.; Romick, G. J.

    1983-11-01

    Photometric auroral observations and geomagnetic measurements obtained simultaneously on the dayside in Norway and the nightside in the USSR, Alaska, and Canada are combined with ISEE-1 and 3 data on the interplanetary magnetic field (IMF) to study the relative importance of substorm perturbations and IMF in determining dayside auroral (DA) motion. Ten events from December, 1978, and January and December, 1979, are characterized, the data are presented in tables, illustrated with charts and graphs, and summarized. The equatorward and poleward motion of the DA is correlated with the growth and decay of DP2-mode geomagnetic disturbances and changes in the north-south component of the IMF. Discrete DA forms appear in a region of sunward-convecting field lines. A detailed model of DA motion is developed which explains these phenomena as the result of a direct global response of the magnetospheric electromagnetic state to the solar-wind magnetic field. Using the model, the potential drop, Pedersen current, and Joule heat-dissipation rate of the polar-cap ionosphere are estimated as 125 kV, 800,000 A, and 100 GW, respectively.

  5. The ground-state phase diagrams of the spin-3/2 Ising model

    International Nuclear Information System (INIS)

    Canko, Osman; Keskin, Mustafa

    2003-01-01

    The ground-state spin configurations are obtained for the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic exchange interactions and a single-ion crystal field. The interactions are assumed to be only between nearest-neighbors. The calculated ground-state phase diagrams are presented on diatomic lattices, such as the square, honeycomb and sc lattices, and triangular lattice in the (Δ/z vertical bar J vertical bar ,K/ vertical bar J vertical bar) and (H/z vertical bar J vertical bar, K/ vertical bar J vertical bar) planes

  6. Critical Behavior of the Annealed Ising Model on Random Regular Graphs

    Science.gov (United States)

    Can, Van Hao

    2017-11-01

    In Giardinà et al. (ALEA Lat Am J Probab Math Stat 13(1):121-161, 2016), the authors have defined an annealed Ising model on random graphs and proved limit theorems for the magnetization of this model on some random graphs including random 2-regular graphs. Then in Can (Annealed limit theorems for the Ising model on random regular graphs, arXiv:1701.08639, 2017), we generalized their results to the class of all random regular graphs. In this paper, we study the critical behavior of this model. In particular, we determine the critical exponents and prove a non standard limit theorem stating that the magnetization scaled by n^{3/4} converges to a specific random variable, with n the number of vertices of random regular graphs.

  7. The Peierls argument for higher dimensional Ising models

    International Nuclear Information System (INIS)

    Bonati, Claudio

    2014-01-01

    The Peierls argument is a mathematically rigorous and intuitive method to show the presence of a non-vanishing spontaneous magnetization in some lattice models. This argument is typically explained for the D = 2 Ising model in a way which cannot be easily generalized to higher dimensions. The aim of this paper is to present an elementary discussion of the Peierls argument for the general D-dimensional Ising model. (paper)

  8. Low field magnetic resonance experiments in superfluid 3He--A

    International Nuclear Information System (INIS)

    Gully, W.J. Jr.

    1976-01-01

    Measurements of the longitudinal and transverse nuclear magnetic resonance signals have been made on the A phase of liquid 3 He. They were performed on a sample of 3 He self-cooled by the Pomeranchuk effect to the critical temperature of the superfluid at 2.7 m 0 K. The longitudinal resonance is a magnetic mode of the liquid excited by radio frequency magnetic fields applied in the direction of the static magnetic field. Frequency profiles of this resonance were indirectly obtained by contour techniques from signals recorded by sweeping the temperature. Its frequency is found to be related to the frequency shift of the transverse resonance in agreement with theoretical predictions for the ABM pairing state. Its linewidth also agrees with theoretical predictions based upon dissipative phenomena peculiar to the superfluid phase. An analysis of the linewidth of the longitudinal resonance yields a value for the quasiparticle collision time. Transverse NMR lines were also studied. In low magnetic fields (20 Oersted) these lines were found to become extremely broad. This is shown to be a manifestation of the same collisional processes that broaden the longitudinal resonance lines. Also, the effects of various textures on the resonance lines are discussed, including the results of an attempt to create a single domain of 3 He with crossed electric and magnetic fields

  9. Magnetic field simulation and shimming analysis of 3.0T superconducting MRI system

    Science.gov (United States)

    Yue, Z. K.; Liu, Z. Z.; Tang, G. S.; Zhang, X. C.; Duan, L. J.; Liu, W. C.

    2018-04-01

    3.0T superconducting magnetic resonance imaging (MRI) system has become the mainstream of modern clinical MRI system because of its high field intensity and high degree of uniformity and stability. It has broad prospects in scientific research and other fields. We analyze the principle of magnet designing in this paper. We also perform the magnetic field simulation and shimming analysis of the first 3.0T/850 superconducting MRI system in the world using the Ansoft Maxwell simulation software. We guide the production and optimization of the prototype based on the results of simulation analysis. Thus the magnetic field strength, magnetic field uniformity and magnetic field stability of the prototype is guided to achieve the expected target.

  10. Enhancement of crystallinity and magnetization in Fe3O4 nanoferrites induced by a high synthesized magnetic field

    Science.gov (United States)

    Ma, Xinxiu; Zhang, Zhanxian; Chen, Shijie; Lei, Wei; Xu, Yan; Lin, Jia; Luo, Xiaojing; Liu, Yongsheng

    2018-05-01

    A one-step hydrothermal method in different dc magnetic fields was used to prepare the Fe3O4 nanoparticles. Under the magnetic field, the average particle size decreased from 72.9 to 41.6 nm, meanwhile, the particle crystallinity is greatly improved. The magnetic field enhances its saturation magnetization and coercivity. The high magnetic field induce another magnetic structure. At room temperature, these nanoparticles exhibit superparamagnetism whose critical size (D sp) is about 26 nm. The Verwey transition is observed in the vicinity of 120 K of Fe3O4 nanoparticles. The effective magnetic anisotropy decreases with the increase of the test temperature because of the H c decreased.

  11. Antiferromagnetic Ising model decorated with D-vector spins: Transversal and longitudinal local fields effects

    International Nuclear Information System (INIS)

    Vasconcelos Dos Santos, R.J.; Coutinho, S.

    1995-01-01

    The effect of a local field acting on decorating classical D-vector bond spins of an antiferromagnetic Ising model on the square lattice is studied for both the annealed isotropic and the axial decorated cases. In both models the effect on the phase diagrams of the transversal and the longitudinal components of the local field acting on the decorating spins are fully analyzed and discussed

  12. One-dimensional Ising model with multispin interactions

    Science.gov (United States)

    Turban, Loïc

    2016-09-01

    We study the spin-1/2 Ising chain with multispin interactions K involving the product of m successive spins, for general values of m. Using a change of spin variables the zero-field partition function of a finite chain is obtained for free and periodic boundary conditions and we calculate the two-spin correlation function. When placed in an external field H the system is shown to be self-dual. Using another change of spin variables the one-dimensional Ising model with multispin interactions in a field is mapped onto a zero-field rectangular Ising model with first-neighbour interactions K and H. The 2D system, with size m × N/m, has the topology of a cylinder with helical BC. In the thermodynamic limit N/m\\to ∞ , m\\to ∞ , a 2D critical singularity develops on the self-duality line, \\sinh 2K\\sinh 2H=1.

  13. Effects of the amorphization on hysteresis loops of the amorphous spin-1/2 Ising system

    International Nuclear Information System (INIS)

    Essaoudi, I.; Ainane, A.; Saber, M.; Miguel, J.J. de

    2009-01-01

    We examine the effects of the amorphization on the hysteresis loops of the amorphous spin-1/2 Ising system using the effective field theory within a probability distribution technique that accounts for the self-spin correlation functions. The magnetization, the transverse and longitudinal susceptibilities, and pyromagnetic coefficient are also studied in detail

  14. 3D print of polymer bonded rare-earth magnets, and 3D magnetic field scanning with an end-user 3D printer

    Science.gov (United States)

    Huber, C.; Abert, C.; Bruckner, F.; Groenefeld, M.; Muthsam, O.; Schuschnigg, S.; Sirak, K.; Thanhoffer, R.; Teliban, I.; Vogler, C.; Windl, R.; Suess, D.

    2016-10-01

    3D print is a recently developed technique, for single-unit production, and for structures that have been impossible to build previously. The current work presents a method to 3D print polymer bonded isotropic hard magnets with a low-cost, end-user 3D printer. Commercially available isotropic NdFeB powder inside a PA11 matrix is characterized, and prepared for the printing process. An example of a printed magnet with a complex shape that was designed to generate a specific stray field is presented, and compared with finite element simulation solving the macroscopic Maxwell equations. For magnetic characterization, and comparing 3D printed structures with injection molded parts, hysteresis measurements are performed. To measure the stray field outside the magnet, the printer is upgraded to a 3D magnetic flux density measurement system. To skip an elaborate adjusting of the sensor, a simulation is used to calibrate the angles, sensitivity, and the offset of the sensor. With this setup, a measurement resolution of 0.05 mm along the z-axes is achievable. The effectiveness of our calibration method is shown. With our setup, we are able to print polymer bonded magnetic systems with the freedom of having a specific complex shape with locally tailored magnetic properties. The 3D scanning setup is easy to mount, and with our calibration method we are able to get accurate measuring results of the stray field.

  15. Magnetic hysteresis scaling in thulium: Implication of irreversibility-related scaling for soliton wall motion in an Ising system

    International Nuclear Information System (INIS)

    Kobayashi, Satoru

    2013-01-01

    We report low-field magnetic hysteresis scaling in thulium with strong uniaxial anisotropy. A power-law hysteresis scaling with an exponent of 1.13±0.02 is found between hysteresis loss and remanent flux density of minor loops in the low-temperature ferrimagnetic phase. This exponent value is slightly lower than 1.25–1.4 observed previously for ferromagnets and helimagnets. Unlike spiral and/or Bloch walls with a finite transition width, typical for Dy, Tb, and Ho with planar anisotropy, a soliton wall with a sudden phase shift between neighboring domains may dominate in Tm due to its Ising-like character. The observations imply the presence of universality class of hysteresis scaling that depends on the type of magnetic anisotropy. - Highlights: ► We observe magnetic hysteresis scaling in thulium with a power law exponent of 1.13. ► Irreversibility of soliton walls dominates owing to its strong uniaxial anisotropy. ► The exponent is lower than those for Bloch wall and spiral wall. ► The results imply the presence of universality class that depends on the wall type.

  16. Exact solutions to plaquette Ising models with free and periodic boundaries

    International Nuclear Information System (INIS)

    Mueller, Marco; Johnston, Desmond A.; Janke, Wolfhard

    2017-01-01

    An anisotropic limit of the 3d plaquette Ising model, in which the plaquette couplings in one direction were set to zero, was solved for free boundary conditions by Suzuki (1972) , who later dubbed it the fuki-nuke, or “no-ceiling”, model. Defining new spin variables as the product of nearest-neighbour spins transforms the Hamiltonian into that of a stack of (standard) 2d Ising models and reveals the planar nature of the magnetic order, which is also present in the fully isotropic 3d plaquette model. More recently, the solution of the fuki-nuke model was discussed for periodic boundary conditions, which require a different approach to defining the product spin transformation, by Castelnovo et al. (2010) . We clarify the exact relation between partition functions with free and periodic boundary conditions expressed in terms of original and product spin variables for the 2d plaquette and 3d fuki-nuke models, noting that the differences are already present in the 1d Ising model. In addition, we solve the 2d plaquette Ising model with helical boundary conditions. The various exactly solved examples illustrate how correlations can be induced in finite systems as a consequence of the choice of boundary conditions.

  17. Enhancement of switching speed of BiFeO3 capacitors by magnetic fields

    Directory of Open Access Journals (Sweden)

    E. J. Guo

    2014-09-01

    Full Text Available The effect of a magnetic field on the ferroelectric switching kinetics of BiFeO3 (BFO capacitors with La0.8Ca0.2MnO3 (LCMO bottom electrode and Pt top contact has been investigated. We find a strong dependence of the remnant polarization and coercive field on the magnetic field. The switching time can be systematically tuned by magnetic field and reaches a tenfold reduction around the Curie temperature of LCMO at 4 T. We attribute this behavior to the splitting of the voltage drops across the BFO film and the LCMO bottom electrode, which can be strongly influenced by an external magnetic field due to the magnetoresistance. Further experiments on the BFO capacitors with SrRuO3 bottom electrodes show little magnetic field dependence of ferroelectric switching confirming our interpretation. Our results provide an efficient route to control the ferroelectric switching speed through the magnetic field, implying potential application in multifunctional devices.

  18. Thermal Entanglement and Critical Behavior of Magnetic Properties on a Triangulated Kagomé Lattice

    Directory of Open Access Journals (Sweden)

    N. Ananikian

    2011-01-01

    Full Text Available The equilibrium magnetic and entanglement properties in a spin-1/2 Ising-Heisenberg model on a triangulated Kagomé lattice are analyzed by means of the effective field for the Gibbs-Bogoliubov inequality. The calculation is reduced to decoupled individual (clusters trimers due to the separable character of the Ising-type exchange interactions between the Heisenberg trimers. The concurrence in terms of the three qubit isotropic Heisenberg model in the effective Ising field in the absence of a magnetic field is non-zero. The magnetic and entanglement properties exhibit common (plateau, peak features driven by a magnetic field and (antiferromagnetic exchange interaction. The (quantum entangled and non-entangled phases can be exploited as a useful tool for signalling the quantum phase transitions and crossovers at finite temperatures. The critical temperature of order-disorder coincides with the threshold temperature of thermal entanglement.

  19. Random field Ising chain and neutral networks with synchronous dynamics

    International Nuclear Information System (INIS)

    Skantzos, N.S.; Coolen, A.C.C.

    2001-01-01

    We first present an exact solution of the one-dimensional random-field Ising model in which spin-updates are made fully synchronously, i.e. in parallel (in contrast to the more conventional Glauber-type sequential rules). We find transitions where the support of local observables turns from a continuous interval into a Cantor set and we show that synchronous and sequential random-field models lead asymptotically to the same physical states. We then proceed to an application of these techniques to recurrent neural networks where 1D short-range interactions are combined with infinite-range ones. Due to the competing interactions these models exhibit phase diagrams with first-order transitions and regions with multiple locally stable solutions for the macroscopic order parameters

  20. Finite-size effects on the dynamic susceptibility of CoPhOMe single-chain molecular magnets in presence of a static magnetic field

    Science.gov (United States)

    Pini, M. G.; Rettori, A.; Bogani, L.; Lascialfari, A.; Mariani, M.; Caneschi, A.; Sessoli, R.

    2011-09-01

    The static and dynamic properties of the single-chain molecular magnet Co(hfac)2NITPhOMe (CoPhOMe) (hfac = hexafluoroacetylacetonate, NITPhOMe = 4'-methoxy-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) are investigated in the framework of the Ising model with Glauber dynamics, in order to take into account both the effect of an applied magnetic field and a finite size of the chains. For static fields of moderate intensity and short chain lengths, the approximation of a monoexponential decay of the magnetization fluctuations is found to be valid at low temperatures; for strong fields and long chains, a multiexponential decay should rather be assumed. The effect of an oscillating magnetic field, with intensity much smaller than that of the static one, is included in the theory in order to obtain the dynamic susceptibility χ(ω). We find that, for an open chain with N spins, χ(ω) can be written as a weighted sum of N frequency contributions, with a sum rule relating the frequency weights to the static susceptibility of the chain. Very good agreement is found between the theoretical dynamic susceptibility and the ac susceptibility measured in moderate static fields (Hdc≤2 kOe), where the approximation of a single dominating frequency for each segment length turns out to be valid. For static fields in this range, data for the relaxation time, τ versus Hdc, of the magnetization of CoPhOMe at low temperature are also qualitatively reproduced by theory, provided that finite-size effects are included.

  1. Magnetic Field Effects on CaCO3 Precipitation Process in Hard Water

    Directory of Open Access Journals (Sweden)

    Nelson Saksono

    2010-10-01

    Full Text Available Magnetic treatment is applied as physical water treatment for scale prevention especially CaCO3, from hard water in piping equipment by reducing its hardness.Na2CO3 and CaCl2 solution sample was used in to investigate the magnetic fields influence on the formation of particle of CaCO3. By changing the strength of magnetic fields, exposure time and concentration of samples solution, this study presents quantitative results of total scale deposit, total precipitated CaCO3 and morphology of the deposit. This research was run by comparing magnetically and non-magnetically treated  samples. The results showed an increase of deposits formation rate and total number of precipitated CaCO3 of magnetically treated samples. The increase of concentration solution sample will also raised the deposit under magnetic  field. Microscope images showed a greater number but smaller size of CaCO3 deposits form in magnetically treated samples, and aggregation during the processes. X-ray diffraction (XRD analysis showed that magnetically samples were dominated by calcite. But, there was a significant decrease of calcite’s peak intensities from magnetized  samples that indicated the decrease of the amount of calcite and an increase of total amorphous of deposits. This result  showed that magnetization of hard water leaded to the decreasing of ion Ca2+ due to the increasing of total CaCO3 precipitation process.

  2. Neutron scattering study of magnetic and crystalline electirc field interactions in RCrO3

    International Nuclear Information System (INIS)

    Shamir, N.

    1978-05-01

    Magnetic and crystalline electric field interactions in the compounds RCrO 3 (R-rare earth) , were studied by neutron scattering. Elastic neutron scattering was utilized in the study of the temperature dependence of the Cr 3+ and Ho 3+ magnetic reflections in Lu CrO 3 and HoCrO 3 , respectively. Analysis of this temperature dependence yielde constant canting angles for the Cr 3+ and Ho 3+ magnetic moments. Molecular magnetic field constants and crystalline electric field splitting were also calculated from the temperature dependence of the Ho 3+ magnetic reflection. These parameters were obtained directly by inelastic neutron scattering measurement. Inelastic neutron scattering measurements of crystlline electric field transitions of R 3+ (R=Pr, Nd, Tb, Ho, Er, Tm, Yb) in RCrO 3 , formed the basis for the calculation of the common crystalline electirc field parameters of the heavy R 3+ ions. (author)

  3. Magnetic properties of a ferromagnet spin-S, Ising, XY and Heisenberg models semi-infinites systems

    International Nuclear Information System (INIS)

    Masrour, R.; Hamedoun, M.; Hourmatallah, A.; Bouslykhane, K.; Benzakour, N.

    2008-01-01

    The magnetic properties of a ferromagnet spin-S a disordered semi-infinite system with a face-centered cubic lattice are investigated using the high-temperature series expansions technique extrapolated with Pade approximants method for Heisenberg, XY and Ising models. The reduced critical temperature of the system τ c =(k B T c )/(2S(S+1)J b ) is studied as function of the thickness of the film and the exchange interactions in the bulk, and within the surfaces J b ,J s and J perpendicular , respectively. It is found that τ c increases with the exchange interactions of surface. The magnetic phase diagrams (τ c versus the dilution x) and the percolation threshold are obtained

  4. Simple explanation for the reentrant magnetic phase transition in Pr ...

    Indian Academy of Sciences (India)

    The reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite is explained using the Ising spin model on the square lattice with mixed ferromagnetic and antiferromagnetic exchange interactions. It is shown using numerical calculations that this effect is strongly affected by the external magnetic field and ...

  5. OpenCL Implementation of NeuroIsing

    Science.gov (United States)

    Zapart, C. A.

    Recent advances in graphics card hardware combined with anintroduction of the OpenCL standard promise to accelerate numerical simulations across diverse scientific disciplines. One such field benefiting from new hardware/software paradigms is econophysics. The paper describes an OpenCL implementation of a selected econophysics model: NeuroIsing, which has been designed to execute in parallel on a vendor-independent graphics card. Originally introduced in the paper [C.~A.~Zapart, ``Econophysics in Financial Time Series Prediction'', PhD thesis, Graduate University for Advanced Studies, Japan (2009)], at first it was implemented on a CELL processor running inside a SONY PS3 games console. The NeuroIsing framework can be applied to predicting and trading foreign exchange as well as stock market index futures.

  6. Ising model for packet routing control

    International Nuclear Information System (INIS)

    Horiguchi, Tsuyoshi; Takahashi, Hideyuki; Hayashi, Keisuke; Yamaguchi, Chiaki

    2004-01-01

    For packet routing control in computer networks, we propose an Ising model which is defined in order to express competition among a queue length and a distance from a node with a packet to its destination node. By introducing a dynamics for a mean-field value of an Ising spin, we show by computer simulations that effective control of packet routing through priority links is possible

  7. Ising game: Nonequilibrium steady states of resource-allocation systems

    Science.gov (United States)

    Xin, C.; Yang, G.; Huang, J. P.

    2017-04-01

    Resource-allocation systems are ubiquitous in the human society. But how external fields affect the state of such systems remains poorly explored due to the lack of a suitable model. Because the behavior of spins pursuing energy minimization required by physical laws is similar to that of humans chasing payoff maximization studied in game theory, here we combine the Ising model with the market-directed resource-allocation game, yielding an Ising game. Based on the Ising game, we show theoretical, simulative and experimental evidences for a formula, which offers a clear expression of nonequilibrium steady states (NESSs). Interestingly, the formula also reveals a convertible relationship between the external field (exogenous factor) and resource ratio (endogenous factor), and a class of saturation as the external field exceeds certain limits. This work suggests that the Ising game could be a suitable model for studying external-field effects on resource-allocation systems, and it could provide guidance both for seeking more relations between NESSs and equilibrium states and for regulating human systems by choosing NESSs appropriately.

  8. The spectrum of massive excitations of 3d 3-state Potts model and universality

    International Nuclear Information System (INIS)

    Falcone, R.; Fiore, R.; Gravina, M.; Papa, A.

    2007-01-01

    We consider the mass spectrum of the 3d 3-state Potts model in the broken phase (a) near the second order Ising critical point in the temperature-magnetic field plane and (b) near the weakly first order transition point at zero magnetic field. In the case (a), we compare the mass spectrum with the prediction from universality of mass ratios in the 3d Ising class; in the case (b), we determine a mass ratio to be compared with the corresponding one in the spectrum of screening masses of the (3+1)d SU(3) pure gauge theory at finite temperature in the deconfined phase near the transition. The agreement in the comparison in the case (a) would represent a non-trivial test of validity of the conjecture of spectrum universality. A positive answer to the comparison in the case (b) would suggest the possibility to extend this conjecture to weakly first order phase transitions

  9. Finite-temperature spin dynamics in a perturbed quantum critical Ising chain with an E₈ symmetry.

    Science.gov (United States)

    Wu, Jianda; Kormos, Márton; Si, Qimiao

    2014-12-12

    A spectrum exhibiting E₈ symmetry is expected to arise when a small longitudinal field is introduced in the transverse-field Ising chain at its quantum critical point. Evidence for this spectrum has recently come from neutron scattering measurements in cobalt niobate, a quasi-one-dimensional Ising ferromagnet. Unlike its zero-temperature counterpart, the finite-temperature dynamics of the model has not yet been determined. We study the dynamical spin structure factor of the model at low frequencies and nonzero temperatures, using the form factor method. Its frequency dependence is singular, but differs from the diffusion form. The temperature dependence of the nuclear magnetic resonance (NMR) relaxation rate has an activated form, whose prefactor we also determine. We propose NMR experiments as a means to further test the applicability of the E₈ description for CoNb₂O₆.

  10. Solving the 3d Ising Model with the Conformal Bootstrap II. c-Minimization and Precise Critical Exponents

    CERN Document Server

    El-Showk, Sheer; Poland, David; Rychkov, Slava; Simmons-Duffin, David; Vichi, Alessandro

    2014-01-01

    We use the conformal bootstrap to perform a precision study of the operator spectrum of the critical 3d Ising model. We conjecture that the 3d Ising spectrum minimizes the central charge c in the space of unitary solutions to crossing symmetry. Because extremal solutions to crossing symmetry are uniquely determined, we are able to precisely reconstruct the first several Z2-even operator dimensions and their OPE coefficients. We observe that a sharp transition in the operator spectrum occurs at the 3d Ising dimension Delta_sigma=0.518154(15), and find strong numerical evidence that operators decouple from the spectrum as one approaches the 3d Ising point. We compare this behavior to the analogous situation in 2d, where the disappearance of operators can be understood in terms of degenerate Virasoro representations.

  11. Exact solution of the mixed spin-1/2 and spin-S Ising-Heisenberg diamond chain

    Directory of Open Access Journals (Sweden)

    L. Čanová

    2009-01-01

    Full Text Available The geometric frustration in a class of the mixed spin-1/2 and spin-S Ising-Heisenberg diamond chains is investigated by combining three exact analytical techniques: Kambe projection method, decoration-iteration transformation and transfer-matrix method. The ground state, the magnetization process and the specific heat as a function of the external magnetic field are particularly examined for different strengths of the geometric frustration. It is shown that the increase of the Heisenberg spin value S raises the number of intermediate magnetization plateaux, which emerge in magnetization curves provided that the ground state is highly degenerate on behalf of a sufficiently strong geometric frustration. On the other hand, all intermediate magnetization plateaux merge into a linear magnetization versus magnetic field dependence in the limit of classical Heisenberg spin S → ∞. The enhanced magnetocaloric effect with cooling rate exceeding the one of paramagnetic salts is also detected when the disordered frustrated phase constitutes the ground state and the external magnetic field is small enough.

  12. The Glauber dynamics for a spin-1 metamagnetic Ising system with bilinear and biquadratic interactions

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Kantar, Ersin [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)

    2009-06-15

    We present a study, within a mean-field approximation, of the dynamics of a spin-1 metamagnetic Ising system with bilinear and biquadratic interactions in the presence of a time-dependent oscillating external magnetic field. First, we employ the Glauber transition rates to construct the set of mean-field dynamic equations. Then, we study the time variation of the average order parameters to find the phases in the system. We also investigate the thermal behavior of dynamic order parameters to characterize the nature (first- or second-order) of the dynamic transitions. The dynamic phase transitions are obtained and the phase diagrams are constructed in two different the planes. The phase diagrams contain a disordered and ordered phases, and four different mixed phases that strongly depend on interaction parameters. Phase diagrams also display one or two dynamic tricritical points, a dynamic double critical end and dynamic quadruple points. A comparison is made with the results of the other metamagnetic Ising systems.

  13. The Glauber dynamics for a spin-1 metamagnetic Ising system with bilinear and biquadratic interactions

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Canko, Osman; Kantar, Ersin

    2009-01-01

    We present a study, within a mean-field approximation, of the dynamics of a spin-1 metamagnetic Ising system with bilinear and biquadratic interactions in the presence of a time-dependent oscillating external magnetic field. First, we employ the Glauber transition rates to construct the set of mean-field dynamic equations. Then, we study the time variation of the average order parameters to find the phases in the system. We also investigate the thermal behavior of dynamic order parameters to characterize the nature (first- or second-order) of the dynamic transitions. The dynamic phase transitions are obtained and the phase diagrams are constructed in two different the planes. The phase diagrams contain a disordered and ordered phases, and four different mixed phases that strongly depend on interaction parameters. Phase diagrams also display one or two dynamic tricritical points, a dynamic double critical end and dynamic quadruple points. A comparison is made with the results of the other metamagnetic Ising systems.

  14. Quantum Ising model on hierarchical structures

    International Nuclear Information System (INIS)

    Lin Zhifang; Tao Ruibao.

    1989-11-01

    A quantum Ising chain with both the exchange couplings and the transverse fields arranged in a hierarchical way is considered. Exact analytical results for the critical line and energy gap are obtained. It is shown that when R 1 not= R 2 , where R 1 and R 2 are the hierarchical parameters for the exchange couplings and the transverse fields, respectively, the system undergoes a phase transition in a different universality class from the pure quantum Ising chain with R 1 =R 2 =1. On the other hand, when R 1 =R 2 =R, there exists a critical value R c dependent on the furcating number of the hierarchy. In case of R > R c , the system is shown to exhibit as Ising-like critical point with the critical behaviour the same as in the pure case, while for R c the system belongs to another universality class. (author). 19 refs, 2 figs

  15. Fermions as generalized Ising models

    Directory of Open Access Journals (Sweden)

    C. Wetterich

    2017-04-01

    Full Text Available We establish a general map between Grassmann functionals for fermions and probability or weight distributions for Ising spins. The equivalence between the two formulations is based on identical transfer matrices and expectation values of products of observables. The map preserves locality properties and can be realized for arbitrary dimensions. We present a simple example where a quantum field theory for free massless Dirac fermions in two-dimensional Minkowski space is represented by an asymmetric Ising model on a euclidean square lattice.

  16. The susceptibilities in the spin-S Ising model

    International Nuclear Information System (INIS)

    Ainane, A.; Saber, M.

    1995-08-01

    The susceptibilities of the spin-S Ising model are evaluated using the effective field theory introduced by Tucker et al. for studying general spin-S Ising model. The susceptibilities are studied for all spin values from S = 1/2 to S = 5/2. (author). 12 refs, 4 figs

  17. Bona Fide Thermodynamic Temperature in Nonequilibrium Kinetic Ising Models

    OpenAIRE

    Sastre, Francisco; Dornic, Ivan; Chaté, Hugues

    2003-01-01

    We show that a nominal temperature can be consistently and uniquely defined everywhere in the phase diagram of large classes of nonequilibrium kinetic Ising spin models. In addition, we confirm the recent proposal that, at critical points, the large-time ``fluctuation-dissipation ratio'' $X_\\infty$ is a universal amplitude ratio and find in particular $X_\\infty \\approx 0.33(2)$ and $X_\\infty = 1/2$ for the magnetization in, respectively, the two-dimensional Ising and voter universality classes.

  18. Phase diagrams of a spin-1 Ising superlattice with alternating transverse field

    International Nuclear Information System (INIS)

    Saber, A.; Ez-Zahraouy, H.; Lo Russo, S.; Mattei, G.; Ainane, A.

    2003-01-01

    The effects of alternating transverse fields Ω a and Ω b on the critical behavior of an alternating spin-1 Ising superlattice are studied within an effective field theory with a probability distribution technique that accounts for the single-site spin correlation. Critical temperatures are calculated as a function of the thickness of the superlattice and the strength of the transverse field. Depending on the values of the transverse fields Ω a and Ω b , the critical temperature can increase or decrease with increasing the thickness of the film, such result is not obtained in the uniform transverse field case (Ω a = Ω b ). Furthermore, for each thickness L of the film, a long range ordered phase persist at low temperature for selected values of the transverse field Ω a and arbitrary values of Ω b . The effects of interlayer and intralayer exchange interactions are also examined

  19. Phase diagrams of a spin-1 Ising superlattice with alternating transverse field

    International Nuclear Information System (INIS)

    Saber, A.; Ez-Zahraouy, H.

    2000-09-01

    The effects of alternating transverse fields Ω a and Ω b on the critical behavior of an alternating spin-1 Ising superlattice are studied within an effective field theory with a probability distribution technique that accounts for the single-site spin correlations. Critical temperatures are calculated as a function of the thickness of the superlattice and the strength of the transverse field. Depending on the values of the transverse fields Ω a and Ω b , the critical temperature can increase or decrease with increasing the thickness of the film, such result is not obtained in the uniform transverse field case (Ω a = Ω b ). Furthermore, for each thickness L of the film, a long range ordered phase persists at low temperature for selected values of the transverse field Ω a and arbitrary values of Ω b . The effects of interlayer and intralayer exchange interactions are also examined. (author)

  20. Dynamic of Ising model with transverse field for two coupled sublattices in disordered phase

    International Nuclear Information System (INIS)

    Sa Motta, C.E.H. de.

    1984-02-01

    The dynamics of the two coupled sublattices tridimensional Ising model in a transverse field was studied by means of a continued fraction expansion for coupled operators. The static Correlation Functions necessary for studying the dynamics were calculated with the Green's Functions Method in the Random Phase Approximation (RPA). The spectral function was calculated in the region T c → . (Author) [pt

  1. Visualization tool for three-dimensional plasma velocity distributions (ISEE_3D) as a plug-in for SPEDAS

    Science.gov (United States)

    Keika, Kunihiro; Miyoshi, Yoshizumi; Machida, Shinobu; Ieda, Akimasa; Seki, Kanako; Hori, Tomoaki; Miyashita, Yukinaga; Shoji, Masafumi; Shinohara, Iku; Angelopoulos, Vassilis; Lewis, Jim W.; Flores, Aaron

    2017-12-01

    This paper introduces ISEE_3D, an interactive visualization tool for three-dimensional plasma velocity distribution functions, developed by the Institute for Space-Earth Environmental Research, Nagoya University, Japan. The tool provides a variety of methods to visualize the distribution function of space plasma: scatter, volume, and isosurface modes. The tool also has a wide range of functions, such as displaying magnetic field vectors and two-dimensional slices of distributions to facilitate extensive analysis. The coordinate transformation to the magnetic field coordinates is also implemented in the tool. The source codes of the tool are written as scripts of a widely used data analysis software language, Interactive Data Language, which has been widespread in the field of space physics and solar physics. The current version of the tool can be used for data files of the plasma distribution function from the Geotail satellite mission, which are publicly accessible through the Data Archives and Transmission System of the Institute of Space and Astronautical Science (ISAS)/Japan Aerospace Exploration Agency (JAXA). The tool is also available in the Space Physics Environment Data Analysis Software to visualize plasma data from the Magnetospheric Multiscale and the Time History of Events and Macroscale Interactions during Substorms missions. The tool is planned to be applied to data from other missions, such as Arase (ERG) and Van Allen Probes after replacing or adding data loading plug-ins. This visualization tool helps scientists understand the dynamics of space plasma better, particularly in the regions where the magnetohydrodynamic approximation is not valid, for example, the Earth's inner magnetosphere, magnetopause, bow shock, and plasma sheet.

  2. Effect of a magnetic field on fourth sound in 3He

    International Nuclear Information System (INIS)

    Daly, K.

    1988-01-01

    The influence of a magnetic field on the propagation of fourth sound in superfluid 3 He is studied. The field and temperature dependences of the average superfluid density /anti rho//sub s///rho/ and fourth sound Q are measured. The field dependence of /anti rho//sub s///rho/ is very different in a porous medium than predicted by Ginzburg-Landau theory applied to bulk liquid. In particular, a magnetic suppression of /anti rho//sub s///rho/ is observed in the temperature and pressure ranges corresponding to the A phase in bulk liquid. There is strong evidence of a magnetic suppression of T/sub c/ itself. The measured /anti rho//sub s///rho/ has a slight history dependence in a magnetic field, but none in zero field. The fourth-sound Q values are compared to the theoretical work of Smith, Jensen, and Wolfle. Quantitative confirmation of their work is problematic

  3. Wetting and layering transitions of a spin-1/2 Ising model in a random transverse field

    International Nuclear Information System (INIS)

    Bahmad, L.; Benyoussef, A.; El-Kenz, A.; Ez-Zahraouy, H.

    2000-09-01

    The effect of a random transverse field (RTF) on the wetting and layering transitions of a spin-1/2 Ising model, in the presence of bulk and surface fields, is studied within an effective field theory by using the differential operator technique. Indeed, the dependencies of the wetting temperature and wetting transverse field on the probability of the presence of a transverse field are established. For specific values of the surface field we show the existence of a critical probability p, above which wetting and layering transitions disappear. (author)

  4. Orthodontic brackets in high field MR imaging: experimental evaluation of magnetic field interactions at 3.0 tesla

    International Nuclear Information System (INIS)

    Kemper, J.; Adam, G.; Klocke, A.; Kahl-Nieke, B.

    2005-01-01

    Purpose: To evaluate static magnetic field interactions for 32 commonly used orthodontic brackets in a 3.0 T magnetic resonance imaging (MRI) system. Materials and methods: 32 orthodontic brackets consisting of a steel alloy (n=27), a cobalt-chromium alloy (n=2), ceramic (n=1), ceramic with a steel slot (n=1), and titanium (n=1) from 13 different manufacturers were tested for magnetic field interactions in a static magnetic field at 3.0 T (Gyroscan Intera 3.0 T, Philips Medical Systems, Best, Netherlands). The magnetic deflection force F Z [mN] was evaluated by determining the deflection angle β[ ] using the established deflection angle test according to the ASTM guidelines. The magnetic-field-induced rotational force F rot or torque was qualitatively determined using a 5-point grading scale (0: no torque; +4: very strong torque). Results: In 18 of the 32 brackets, the deflection angle β was found to be > 45 and the translational force exceeded the gravitational force F G on the particular bracket (F Z : 1.2-45.7 mN). The translational force F Z was found to be up to 68.5 times greater than the gravitational force F G (F Z /F G : 1.4-68.5). The rotational force F rot was correspondingly high (+3/+4) for those brackets. For the remaining 14 objects, the deflection angles were < 45 and the torque measurements ranged from 0 to +2. The static magnetic field did not affect the titanium bracket and the ceramic bracket. No measurable translational and rotational forces were found. (orig.)

  5. A theory of solving TAP equations for Ising models with general invariant random matrices

    DEFF Research Database (Denmark)

    Opper, Manfred; Çakmak, Burak; Winther, Ole

    2016-01-01

    We consider the problem of solving TAP mean field equations by iteration for Ising models with coupling matrices that are drawn at random from general invariant ensembles. We develop an analysis of iterative algorithms using a dynamical functional approach that in the thermodynamic limit yields...... the iteration dependent on a Gaussian distributed field only. The TAP magnetizations are stable fixed points if a de Almeida–Thouless stability criterion is fulfilled. We illustrate our method explicitly for coupling matrices drawn from the random orthogonal ensemble....

  6. 3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum

    Energy Technology Data Exchange (ETDEWEB)

    Kramar, Maxim [Physics Department, The Catholic University of America, Washington, DC (United States); Airapetian, Vladimir [Department of Physics and Astronomy, George Mason University, Fairfax, VA (United States); NASA/Goddard Space Flight Center, Code 671, Greenbelt, MD (United States); Lin, Haosheng, E-mail: vladimir.airapetian@nasa.gov [College of Natural Sciences, Institute for Astronomy, University of Hawaii at Manoa, Pukalani, HI (United States)

    2016-08-09

    Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal dynamic phenomena at all scales. We employ STEREO/COR1 data obtained near maximum of solar activity in December 2012 (Carrington rotation, CR 2131) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from 1.5 to 4 R{sub ⊙} using a tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 Å band obtained by tomography for the same CR period. We find that the magnetic field configuration during CR 2131 has a tendency to become radially open at heliocentric distances below ~2.5 R{sub ⊙}. We compared the reconstructed 3D coronal structures over the CR near the solar maximum to the one at deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.

  7. 3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum

    Directory of Open Access Journals (Sweden)

    Maxim Kramar

    2016-08-01

    Full Text Available Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal dynamic phenomena at all scales. We employ STEREO/COR1 data obtained near maximum of solar activity in December 2012 (Carrington rotation, CR 2131 to retrieve and analyze the three-dimensional (3D coronal electron density in the range of heights from $1.5$ to $4 R_odot$ using a tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 AA band obtained by tomography for the same CR period. We find that the magnetic field configuration during CR 2131 has a tendency to become radially open at heliocentric distances below $sim 2.5 R_odot$. We compared the reconstructed 3D coronal structures over the CR near the solar maximum to the one at deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.

  8. Electric Field Controlled Magnetism in BiFeO3/Ferromagnet Films

    Science.gov (United States)

    Holcomb, M. B.; Chu, Y. H.; Martin, L. W.; Gajek, M.; Seidel, J.; Ramesh, R.; Scholl, A.; Fraile-Rodriguez, A.

    2008-03-01

    Electric field control of magnetism is a hot technological topic at the moment due to its potential to revolutionize today's devices. Magnetoelectric materials, those having both electric and magnetic order and the potential for coupling between the two, are a promising avenue to approach electric control. BiFeO3, both a ferroelectric and an antiferromagnet, is the only single phase room temperature magnetoelectric that is currently known. In addition to other possibilities, its multiferroic nature has potential in the very active field of exchange bias, where an antiferromagnetic thin film pins the magnetic direction of an adjoining ferromagnetic layer. Since this antiferromagnet is electrically tunable, this coupling could allow electric-field control of the ferromagnetic magnetization. Direction determination of antiferromagnetic domains in BFO has recently been shown using linear and circular dichroism studies. Recently, this technique has been extended to look at the magnetic domains of a ferromagnetic grown on top of BFO. The clear magnetic changes induced by application of electric fields reveal the possibility of electric control.

  9. Complex-network description of thermal quantum states in the Ising spin chain

    Science.gov (United States)

    Sundar, Bhuvanesh; Valdez, Marc Andrew; Carr, Lincoln D.; Hazzard, Kaden R. A.

    2018-05-01

    We use network analysis to describe and characterize an archetypal quantum system—an Ising spin chain in a transverse magnetic field. We analyze weighted networks for this quantum system, with link weights given by various measures of spin-spin correlations such as the von Neumann and Rényi mutual information, concurrence, and negativity. We analytically calculate the spin-spin correlations in the system at an arbitrary temperature by mapping the Ising spin chain to fermions, as well as numerically calculate the correlations in the ground state using matrix product state methods, and then analyze the resulting networks using a variety of network measures. We demonstrate that the network measures show some traits of complex networks already in this spin chain, arguably the simplest quantum many-body system. The network measures give insight into the phase diagram not easily captured by more typical quantities, such as the order parameter or correlation length. For example, the network structure varies with transverse field and temperature, and the structure in the quantum critical fan is different from the ordered and disordered phases.

  10. Self-organization of domain growth in the Ising model with impurities

    DEFF Research Database (Denmark)

    Andersen, Jørgen Vitting; Mouritsen, Ole G.

    1992-01-01

    We have studied avalanchelike rearrangements of domain patterns in the two-dimensional Ising model with static impurities, which is quenched to low temperatures. When breaking the up-down symmetry of the spins by a small applied field, the mere fluctuation of a single spin eventually results...... in a cascade of spin flips at the domain boundaries. We have analyzed the lifetime and size distribution functions for the avalanches and related the results to the general phenomena of self-organized criticality and to recent experiments on cellular magnetic domain patterns in magnetic garnet films. Our...... results suggest that the self-organized state in this system appears to be subcritical, in agreement with a recent theory....

  11. Quench Modeling in High-field Nb3Sn Accelerator Magnets

    Science.gov (United States)

    Bermudez, S. Izquierdo; Bajas, H.; Bottura, L.

    The development of high-field magnets is on-going in the framework of the LHC luminosity upgrade. The resulting peak field, in the range of 12 T to 13 T, requires the use Nb3Sn as superconductor. Due to the high stored energy density (compact winding for cost reduction) and the low stabilizer fraction (to achieve the desired margins), quench protection becomes a challenging problem. Accurate simulation of quench transientsin these magnets is hence crucial to the design choices, the definition of priority R&D and to prove that the magnets are fit for operation. In this paper we focus on the modelling of quench initiation and propagation, we describe approaches that are suitable for magnet simulation, and we compare numerical results with available experimental data.

  12. Numerical estimation of structure constants in the three-dimensional Ising conformal field theory through Markov chain uv sampler

    Science.gov (United States)

    Herdeiro, Victor

    2017-09-01

    Herdeiro and Doyon [Phys. Rev. E 94, 043322 (2016), 10.1103/PhysRevE.94.043322] introduced a numerical recipe, dubbed uv sampler, offering precise estimations of the conformal field theory (CFT) data of the planar two-dimensional (2D) critical Ising model. It made use of scale invariance emerging at the critical point in order to sample finite sublattice marginals of the infinite plane Gibbs measure of the model by producing holographic boundary distributions. The main ingredient of the Markov chain Monte Carlo sampler is the invariance under dilation. This paper presents a generalization to higher dimensions with the critical 3D Ising model. This leads to numerical estimations of a subset of the CFT data—scaling weights and structure constants—through fitting of measured correlation functions. The results are shown to agree with the recent most precise estimations from numerical bootstrap methods [Kos, Poland, Simmons-Duffin, and Vichi, J. High Energy Phys. 08 (2016) 036, 10.1007/JHEP08(2016)036].

  13. Entanglement of two blocks of spins in the critical Ising model

    Science.gov (United States)

    Facchi, P.; Florio, G.; Invernizzi, C.; Pascazio, S.

    2008-11-01

    We compute the entropy of entanglement of two blocks of L spins at a distance d in the ground state of an Ising chain in an external transverse magnetic field. We numerically study the von Neumann entropy for different values of the transverse field. At the critical point we obtain analytical results for blocks of size L=1 and 2. In the general case, the critical entropy is shown to be additive when d→∞ . Finally, based on simple arguments, we derive an expression for the entropy at the critical point as a function of both L and d . This formula is in excellent agreement with numerical results.

  14. Hexagonal type Ising nanowire with mixed spins: Some dynamic behaviors

    International Nuclear Information System (INIS)

    Kantar, Ersin; Kocakaplan, Yusuf

    2015-01-01

    The dynamic behaviors of a mixed spin (1/2–1) hexagonal Ising nanowire (HIN) with core–shell structure in the presence of a time dependent magnetic field are investigated by using the effective-field theory with correlations based on the Glauber-type stochastic dynamics (DEFT). According to the values of interaction parameters, temperature dependence of the dynamic magnetizations, the hysteresis loop areas and the dynamic correlations are investigated to characterize the nature (first- or second-order) of the dynamic phase transitions (DPTs). Dynamic phase diagrams, including compensation points, are also obtained. Moreover, from the thermal variations of the dynamic total magnetization, the five compensation types can be found under certain conditions, namely the Q-, R-, S-, P-, and N-types. - Highlights: • Dynamic behaviors of mixed spin HIN system are obtained within the EFT. • The system exhibits i, p and nm fundamental phases. • The dynamic phase diagrams are presented in (h, T), (D, T), (Δ S , T) and (r, T) planes. • The dynamic phase diagrams exhibit the dynamic tricritical point (TCP). • Different dynamic compensation types are obtained

  15. Thermal conductivity of Ca3Co2O6 single crystals

    Science.gov (United States)

    Che, H. L.; Shi, J.; Wu, J. C.; Rao, X.; Liu, X. G.; Zhao, X.; Sun, X. F.

    2018-05-01

    Ca3Co2O6 is a rare example of one-dimensional Ising spin-chain material with the moments preferentially aligned along the c axis. In this work, we study the c-axis thermal conductivity (κc) of Ca3Co2O6 single crystal at low temperatures down to 0.3 K and in magnetic fields up to 14 T. The zero-field κc(T) shows a large phonon peak and can be well fitted by using the classical Debye model, which indicates that the heat transport is purely phononic. Moreover, the low-T κc(H) isotherms with H || c display a field-independent behavior. These results indicate that there is no contribution of magnetic excitations to the thermal conductivity in Ca3Co2O6, neither carrying heat nor scattering phonons, which can be attributed to the Ising-like spin anisotropy.

  16. Probing α -RuCl3 Beyond Magnetic Order: Effects of Temperature and Magnetic Field

    Science.gov (United States)

    Winter, Stephen M.; Riedl, Kira; Kaib, David; Coldea, Radu; Valentí, Roser

    2018-02-01

    Recent studies have brought α -RuCl3 to the forefront of experimental searches for materials realizing Kitaev spin-liquid physics. This material exhibits strongly anisotropic exchange interactions afforded by the spin-orbit coupling of the 4 d Ru centers. We investigate the dynamical response at finite temperature and magnetic field for a realistic model of the magnetic interactions in α -RuCl3 . These regimes are thought to host unconventional paramagnetic states that emerge from the suppression of magnetic order. Using exact diagonalization calculations of the quantum model complemented by semiclassical analysis, we find a very rich evolution of the spin dynamics as the applied field suppresses the zigzag order and stabilizes a quantum paramagnetic state that is adiabatically connected to the fully polarized state at high fields. At finite temperature, we observe large redistributions of spectral weight that can be attributed to the anisotropic frustration of the model. These results are compared to recent experiments and provide a road map for further studies of these regimes.

  17. Magnetic field effects in UNi.sub.1/3./sub.Ru.sub.2/3./sub.Al

    Czech Academy of Sciences Publication Activity Database

    Alsmadi, A. M.; El-Khatib, S.; de Chatel, P.F.; Nakotte, H.; Lacerda, A. H.; Jung, M. H.; Andreev, Alexander V.; Honda, F.; Sechovský, V.

    2005-01-01

    Roč. 97, - (2005), 10A919/1-10A919/3 ISSN 0021-8979 R&D Projects: GA ČR(CZ) GA202/02/0739 Keywords : UNi 1/3 Ru 2/3 Al * magnetic field effects Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.498, year: 2005

  18. The anisotropic magnetic property and Faraday rotation in Er3Ga5O12 under high magnetic field

    International Nuclear Information System (INIS)

    Wang Wei; Zhang Xijuan; Liu Gongqiang

    2005-01-01

    A theoretical investigation on the anisotropic magnetic property and Faraday rotation in Er 3 Ga 5 O 12 (ErGaG) is presented. With particular consideration of the anisotropy of the exchange interaction between rare-earth ions (Er 3+ ), the magnetization, based on the quantum theory, in ErGaG under high magnetic field (HMF) is calculated. Theoretical calculations show that the appropriate choice of the crystal field (CF) parameters is of great importance. A novel three-level model is presented, and in terms of this model the Faraday rotation under HMF is calculated. In addition, it is demonstrated that the Faraday rotation (θ) depends not only on the magnetization (M) but also on the magnetic field (H e ). The theory is in good agreement with the experiment

  19. On the equivalence of dilute antiferromagnets and ferromagnets in random external fields: Curie-Weiss models

    International Nuclear Information System (INIS)

    Perez, J.F.; Pontin, L.F.; Segundo, J.A.B.

    1985-01-01

    Using a method proposed by van Hemmen the free energy of the Curie-Weiss version of the site-dilute antiferromagnetic Ising model is computed, in the presence of an uniform magnetic field. The solution displays an exact correspondence between this model and the Curie-Weiss version of the Ising model in the presence of a random magnetic field. The phase diagrams are discussed and a tricritical point is shown to exist. (Author) [pt

  20. Quantum phase transition of the transverse-field quantum Ising model on scale-free networks.

    Science.gov (United States)

    Yi, Hangmo

    2015-01-01

    I investigate the quantum phase transition of the transverse-field quantum Ising model in which nearest neighbors are defined according to the connectivity of scale-free networks. Using a continuous-time quantum Monte Carlo simulation method and the finite-size scaling analysis, I identify the quantum critical point and study its scaling characteristics. For the degree exponent λ=6, I obtain results that are consistent with the mean-field theory. For λ=4.5 and 4, however, the results suggest that the quantum critical point belongs to a non-mean-field universality class. Further simulations indicate that the quantum critical point remains mean-field-like if λ>5, but it continuously deviates from the mean-field theory as λ becomes smaller.

  1. Chiral symmetry breaking in d=3 NJL model in external gravitational and magnetic fields

    OpenAIRE

    Gitman, D. M.; Odintsov, S. D.; Shil'nov, Yu. I.

    1996-01-01

    The phase structure of $d=3$ Nambu-Jona-Lasinio model in curved spacetime with magnetic field is investigated in the leading order of the $1/N$-expansion and in linear curvature approximation (an external magnetic field is treated exactly). The possibility of the chiral symmetry breaking under the combined action of the external gravitational and magnetic fields is shown explicitly. At some circumstances the chiral symmetry may be restored due to the compensation of the magnetic field by the ...

  2. Field-dependent spin chirality and frustration in V3 and Cu3 nanomagnets in transverse magnetic field. 2. Spin configurations, chirality and intermediate spin magnetization in distorted trimers

    International Nuclear Information System (INIS)

    Belinsky, Moisey I.

    2014-01-01

    Highlights: • Distorted spin configurations determine field behavior of the variable chiralities. • Distortions change spin chiralities, intermediate M 12 ± and staggered magnetization. • Magnetizations, distorted vector and scalar chiralities are strongly correlated. • Distorted V 3 , Cu 3 nanomagnets possess large vector chirality in the ground state in B ⊥ . • Chiralities and distortions in EPR, INS and NMR spectra were considered. - Abstract: Correlated spin configurations, magnetizations, frustration, vector κ ¯ z and scalar χ ¯ chiralities are considered for distorted V ‾ 3 , /Cu 3 / anisotropic DM nanomagnets in transverse B x ‖X and longitudinal B‖Z fields. Different planar configurations in the ground and excited states of distorted nanomagnets in B x determine different field behavior of the vector chiralities and the degenerate frustration in these states correlated with the M ~ 12 ± (B x ) intermediate spin (IS) magnetization which describes the S 12 characteristics, χ=0. Distortion results in the reduced κ ¯ z <1 chirality in the ground distorted configuration and in the maximum κ z =±1 in the excited states with the planar 120° configurations at avoided level crossing. In B‖Z, distorted longitudinal spin-collinear configurations are characterized by the reduced degenerate frustration, out-of-plane staggered and IS M ~ 12 ± (B z ) magnetizations, and in-plane toroidal moments, correlated with the κ ¯ z , χ ¯ chiralities, χ ¯ =±|κ ¯ z |. The chiralities and IS magnetization in EPR, INS and NMR spectra are considered. The quantitative correlations describe variable spin chirality, frustration and field manipulation of chiralities in nanomagnets

  3. Trapped field recovery of bulk superconductor magnets by static field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Z., E-mail: zigang@kaiyodai.ac.jp [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Tokyo 135-8533 (Japan); Tsuzuki, K.; Miki, M.; Felder, B.; Hara, S.; Izumi, M. [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Tokyo 135-8533 (Japan)

    2011-11-15

    A series of initial trapped fields after ZFC or FC magnetization are used to simulate the attenuated trapped field. It is possible and easy to recover the lost trapped field and regain the best trapped field performance as before. In the re-magnetization process, the initial magnetic flux inside the bulk magnets will help to recover the trapped field. The optimum recovery field is recommended to be 2.5 times the saturation field of the bulk at LN2 temperature. Thanks to the trapped field of bulk high-temperature superconductors, they can be used as field-pole magnets in the high temperature superconducting (HTS) rotating machines. For example, an output power of 10 kW at 720 rpm was realized by an average trapped field of 0.56 T of eight melt-textured GdBa{sub 2}Cu{sub 3}O{sub y} (Gd-123) bulks at liquid nitrogen temperature in TUMSAT in 2004. Similarly to the HTS machines involving 1G or 2G wires, the trapped field of the bulk is possibly sensitive and even can be attenuated by the AC component field during the operation. Hence, it is necessary to recover the trapped field once being decreased to some extent in the practical application. From this point, we have investigated the trapped field recovery of HTS bulk magnets by static field magnetization in the paper. A series of different initial trapped fields after zero-field-cooling or field-cooling magnetization are used to simulate the attenuated trapped field. By comparing the trapped field peak and its distribution, the trapped field was found to be able to recover by the static field magnetization method with a stronger excitation field and the initial trapped flux inside the bulk also has an influence on the recovery process. The optimum recovery field was found to be about 2.5 times the saturated trapped field of the bulk at liquid nitrogen temperature, by which the bulk can regain the former best trapped field performance.

  4. Local probe (170Yb3+) measurements of magnetic fields in YBa2Cu3Ox

    International Nuclear Information System (INIS)

    Hodges, J.A.; Bonville, P.; Vincent, E.

    1989-01-01

    We introduce the technique of studying the field dependence of the electro-nuclear energy levels of a rare earth to measure the magnetic field present at the rare earth/yttrium site in YBa 2 Cu 3 O x . Measurements were made by 170 Yb spectroscopy. The hyperfine spectrum of the ground state Kramers doublet for Yb 3+ ions diluted into this matrix is sensitive to fields in the range 100 to 2000G. Flux penetration and trapping at the local site level have been measured in superconducting samples. A molecular field exists on the rare earth site in non superconducting samples suggesting that the ordered Cu2 magnetic moments are intrinsically non colinear

  5. 3D analytical field calculation using triangular magnet segments applied to a skewed linear permanent magnet actuator

    NARCIS (Netherlands)

    Janssen, J.L.G.; Paulides, J.J.H.; Lomonova, E.

    2010-01-01

    This paper presents novel analytical expressions which describe the 3D magnetic field of arbitrarily magnetized triangular-shaped charged surfaces. These versatile expressions are suitable to model triangularshaped permanent magnets and can be expanded to any polyhedral shape. Many applications are

  6. 3D Analytical field calculation using triangular magnet segments applied to a skewed linear permanent magnet actuator

    NARCIS (Netherlands)

    Janssen, J.L.G.; Paulides, J.J.H.; Lomonova, E.

    2009-01-01

    This paper presents novel analytical expressions which describe the 3D magnetic field of arbitrarily magnetized triangular-shaped charged surfaces. These versatile expressions are suitable to model triangularshaped permanent magnets and can be expanded to any polyhedral shape. Many applications are

  7. Magnetic resonance imaging: effects of magnetic field strength

    International Nuclear Information System (INIS)

    Crooks, L.E.; Arakawa, M.; Hoenninger, J.; McCarten, B.; Watts, J.; Kaufman, L.

    1984-01-01

    Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. For any one spin echo sequence, gray/white matter contrast decreases and muscle/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then change more slowly, actually dropping for muscle. The optimum field for magnetic resonance imaging depends on tissue type, body part, and imaging sequence, so that it does not have a unique value. Magnetic resonance systems that operate in the 3.0-5.0 kgauss range achieve most or all of the gains that can be achieved by higher magnetic fields

  8. Size effect on magnetic properties of a nano-graphene bilayer structure: A Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R. [Laboratory of Materials, Process, Environment and Quality, Cady Ayyad University, National School of Applied Sciences, Safi (Morocco); Laboratoire de Magnetisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Universite Mohammed V-Agdal, Faculte des Sciences, B.P. 1014 Rabat (Morocco); Bahmad, L., E-mail: bahmad@fsr.ac.ma [Laboratoire de Magnetisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Universite Mohammed V-Agdal, Faculte des Sciences, B.P. 1014 Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnetisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Universite Mohammed V-Agdal, Faculte des Sciences, B.P. 1014 Rabat (Morocco)

    2012-11-15

    In this paper we use the Monte Carlo simulations to investigate the magnetic properties of an Ising ferromagnetic-antiferromagnetic model. The system is based on a nano-graphene structure-like bilayer with two bloc sizes: N=24 and 42 spins. For each size N, the upper layer A is formed with spin -3/2, whereas the lower layer B is composed of spin -5/2. We only consider the first nearest-neighbor interactions between the sites i and j. The magnetic properties are studied, in the absence as well as in the presence of a crystal magnetic field, and an external magnetic field. The increasing temperature and crystal field as well as the inter-layer coupling constant, are also studied for this system sizes N=24 and 42 spins. The zero-field-cooled and the field cooled magnetization behaviors are investigated for different values of external magnetic field and a fixed value of exchange interaction between the two blocs. The magnetizations as well as the magnetic susceptibilities versus the temperature are used in order to obtain blocking temperature. The saturation magnetization and coercive field are also obtained for the two sizes of the studied system. It is found that the blocking temperature decreases on increasing the crystal magnetic field and/or the external magnetic field, for a fixed system size. On the other hand, it is found that the blocking temperature increases on increasing the system size from N=24 to 42 spins, for fixed values of external and the crystal magnetic fields. - Highlights: Black-Right-Pointing-Pointer Magnetic properties of an Ising ferromagnetic-antiferromagnetic bilayer is studied. Black-Right-Pointing-Pointer Monte Carlo simulations are used. Black-Right-Pointing-Pointer Zero-field-cooled (ZFC) and field cooled (FC) magnetization behaviors for nano-graphene are obtained.

  9. An extended chain Ising model and its Glauber dynamics

    International Nuclear Information System (INIS)

    Zhao Xing-Yu; Fan Xiao-Hui; Huang Yi-Neng; Huang Xin-Ru

    2012-01-01

    It was first proposed that an extended chain Ising (ECI) model contains the Ising chain model, single spin double-well potentials and a pure phonon heat bath of a specific energy exchange with the spins. The extension method is easy to apply to high dimensional cases. Then the single spin-flip probability (rate) of the ECI model is deduced based on the Boltzmann principle and general statistical principles of independent events and the model is simplified to an extended chain Glauber—Ising (ECGI) model. Moreover, the relaxation dynamics of the ECGI model were simulated by the Monte Carlo method and a comparison with the predictions of the special chain Glauber—Ising (SCGI) model was presented. It was found that the results of the two models are consistent with each other when the Ising chain length is large enough and temperature is relative low, which is the most valuable case of the model applications. These show that the ECI model will provide a firm physical base for the widely used single spin-flip rate proposed by Glauber and a possible route to obtain the single spin-flip rate of other form and even the multi-spin-flip rate. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  10. The random transverse field Ising model in d = 2: analysis via boundary strong disorder renormalization

    International Nuclear Information System (INIS)

    Monthus, Cécile; Garel, Thomas

    2012-01-01

    To avoid the complicated topology of surviving clusters induced by standard strong disorder RG in dimension d > 1, we introduce a modified procedure called ‘boundary strong disorder RG’ where the order of decimations is chosen a priori. We apply this modified procedure numerically to the random transverse field Ising model in dimension d = 2. We find that the location of the critical point, the activated exponent ψ ≃ 0.5 of the infinite-disorder scaling, and the finite-size correlation exponent ν FS ≃ 1.3 are compatible with the values obtained previously using standard strong disorder RG. Our conclusion is thus that strong disorder RG is very robust with respect to changes in the order of decimations. In addition, we analyze the RG flows within the two phases in more detail, to show explicitly the presence of various correlation length exponents: we measure the typical correlation exponent ν typ ≃ 0.64 for the disordered phase (this value is very close to the correlation exponent ν pure Q (d=2)≅0.6 3 of the pure two-dimensional quantum Ising model), and the typical exponent ν h ≃ 1 for the ordered phase. These values satisfy the relations between critical exponents imposed by the expected finite-size scaling properties at infinite-disorder critical points. We also measure, within the disordered phase, the fluctuation exponent ω ≃ 0.35 which is compatible with the directed polymer exponent ω DP (1+1)= 1/3 in (1 + 1) dimensions. (paper)

  11. Diagonalization of replicated transfer matrices for disordered Ising spin systems

    International Nuclear Information System (INIS)

    Nikoletopoulos, T; Coolen, A C C

    2004-01-01

    We present an alternative procedure for solving the eigenvalue problem of replicated transfer matrices describing disordered spin systems with (random) 1D nearest neighbour bonds and/or random fields, possibly in combination with (random) long range bonds. Our method is based on transforming the original eigenvalue problem for a 2 n x 2 n matrix (where n → 0) into an eigenvalue problem for integral operators. We first develop our formalism for the Ising chain with random bonds and fields, where we recover known results. We then apply our methods to models of spins which interact simultaneously via a one-dimensional ring and via more complex long-range connectivity structures, e.g., (1 + ∞)-dimensional neural networks and 'small-world' magnets. Numerical simulations confirm our predictions satisfactorily

  12. Magnetic field enhanced photothermal effect of Fe3O4 nanoparticles

    Science.gov (United States)

    Pan, Pengfei; Lin, Yawen; Gan, Zhixing; Luo, Xiaobin; Zhou, Weiping; Zhang, Ning

    2018-03-01

    Photothermal and magnetothermal effects are promising in hyperthermia for cancer therapy. However, the development of safe treatments with limited side-effects requires a relatively-high thermal efficiency triggered by mild near-infrared (NIR) light and alternating magnetic field (HAC), which remains a formidable challenge. In this work, a magnetic field enhanced photothermal effect (MFEP) of Fe3O4 nanoparticles is proposed and investigated systematically. The results suggest remarkable temperature increments of 9.59 to 36.90 °C under irradiation of NIR with different light power densities (808 nm, 0-6.98 W/cm2) combined with a certain magnetic field (HAC = 1.5 kA/m at 90 kHz). The rise of temperature induced by MFEP is substantially larger than the sum of isolated photothermal and magnetothermal effects, which is attributed to the hot-phonon bottleneck effect. The MFEP of Fe3O4 nanoparticles could serve as an effective treatment for cancer therapy in the future.

  13. Mixed spin Ising model with four-spin interaction and random crystal field

    International Nuclear Information System (INIS)

    Benayad, N.; Ghliyem, M.

    2012-01-01

    The effects of fluctuations of the crystal field on the phase diagram of the mixed spin-1/2 and spin-1 Ising model with four-spin interactions are investigated within the finite cluster approximation based on a single-site cluster theory. The state equations are derived for the two-dimensional square lattice. It has been found that the system exhibits a variety of interesting features resulting from the fluctuation of the crystal field interactions. In particular, for low mean value D of the crystal field, the critical temperature is not very sensitive to fluctuations and all transitions are of second order for any value of the four-spin interactions. But for relatively high D, the transition temperature depends on the fluctuation of the crystal field, and the system undergoes tricritical behaviour for any strength of the four-spin interactions. We have also found that the model may exhibit reentrance for appropriate values of the system parameters.

  14. Orthodontic springs and auxiliary appliances: assessment of magnetic field interactions associated with 1.5 T and 3 T magnetic resonance systems

    International Nuclear Information System (INIS)

    Kemper, J.; Priest, A.N.; Adam, G.; Schulze, D.; Kahl-Nieke, B.; Klocke, A.

    2007-01-01

    The objective of this paper is to evaluate magnetic field interactions at 1.5 and 3 T for 20 orthodontic devices used for fixed orthodontic therapy. Twenty springs and auxiliary parts made from varying ferromagnetic alloys were tested for magnetic field interactions in the static magnetic field at 1.5 and 3 T. Magnetic translational force F z (in millinewtons) was evaluated by determining the deflection angle β [American Society for Testing and Materials (ASTM standard test method)]. Magnetic-field-induced rotational force F rot was qualitatively determined using a five-point scale. β was found to be >45 in 13(15) devices at 1.5(3) T and translational force F z exceeded gravitational force F g on the particular object [F z 10.17-261.4 mN (10.72-566.4 mN) at 1.5(3) T]. F z was found to be up to 24.1(47.5)-fold higher than F g at 1.5(3) T. Corresponding to this, F rot on the objects was shown to be high at both field strengths (≥ +3). Three objects (at 1.5 T) and one object (at 3 T) showed deflection angles rot was found to be ≥ +3 at both field strengths. For the remaining objects, β was below 45 and torque measurements ranged from 0 to +2. Of 20 objects investigated for magnetic field interactions at 1.5(3) T, 13(15) were unsafe in magnetic resonance (MR), based on the ASTM criteria of F z . The implications of these results for orthodontic patients undergoing MRI are discussed. (orig.)

  15. Orthodontic springs and auxiliary appliances: assessment of magnetic field interactions associated with 1.5 T and 3 T magnetic resonance systems

    Energy Technology Data Exchange (ETDEWEB)

    Kemper, J.; Priest, A.N.; Adam, G. [University Medical Center of Hamburg-Eppendorf, Clinic of Diagnostic and Interventional Radiology, Hamburg (Germany); Schulze, D. [University Hospital of Freiburg, Department of Oral and Maxillofacial Surgery, Freiburg (Germany); Kahl-Nieke, B.; Klocke, A. [University Medical Center of Hamburg-Eppendorf, Department of Orthodontics, Hamburg (Germany)

    2007-02-15

    The objective of this paper is to evaluate magnetic field interactions at 1.5 and 3 T for 20 orthodontic devices used for fixed orthodontic therapy. Twenty springs and auxiliary parts made from varying ferromagnetic alloys were tested for magnetic field interactions in the static magnetic field at 1.5 and 3 T. Magnetic translational force F{sub z} (in millinewtons) was evaluated by determining the deflection angle {beta} [American Society for Testing and Materials (ASTM standard test method)]. Magnetic-field-induced rotational force F{sub rot} was qualitatively determined using a five-point scale. {beta} was found to be >45 in 13(15) devices at 1.5(3) T and translational force F{sub z} exceeded gravitational force F{sub g} on the particular object [F{sub z} 10.17-261.4 mN (10.72-566.4 mN) at 1.5(3) T]. F{sub z} was found to be up to 24.1(47.5)-fold higher than F{sub g} at 1.5(3) T. Corresponding to this, F{sub rot} on the objects was shown to be high at both field strengths ({>=} +3). Three objects (at 1.5 T) and one object (at 3 T) showed deflection angles <45 , but F{sub rot} was found to be {>=} +3 at both field strengths. For the remaining objects, {beta} was below 45 and torque measurements ranged from 0 to +2. Of 20 objects investigated for magnetic field interactions at 1.5(3) T, 13(15) were unsafe in magnetic resonance (MR), based on the ASTM criteria of F{sub z}. The implications of these results for orthodontic patients undergoing MRI are discussed. (orig.)

  16. Evidence for magnetic field reconnection at the earth's magnetopause

    Science.gov (United States)

    Sonnerup, B. U. O.; Paschmann, G.; Papamastorakis, I.; Sckopke, N.; Haerendel, G.; Bame, S. J.; Asbridge, J. R.; Gosling, J. T.; Russell, C. T.

    1981-01-01

    Eleven Northern Hemisphere crossings of the dayside magnetopause by the ISEE spacecraft are examined to test the hypothesis that the large plasma flow speeds observed in the magnetopause and boundary layer are the result of the plasma acceleration intrinsic to the magnetic field reconnection process. In several cases energetic magnetospheric particles with the proper flow anisotropy, and in one case, reflected magnetosheath particles, were observed outside the magnetopause but adjacent to it. All results support the reconnection hypothesis. The energetic particles were also used to identify the outer separatrix surface, in one case of which is was possible to conclude from its location relative to the magnetopause that the reconnection site was in the vicinity of the equatorial plane rather than in the cusp. The electric field tangential to the magnetopause is inferred to be in the 0.4-2.8 mV/m range.

  17. On the S matrix of the subleading magnetic deformation of the tricritical ising model in two dimensions

    International Nuclear Information System (INIS)

    Colomo, F.; Mussardo, G.

    1992-01-01

    In this paper, the authors compute the S matrix of the tricritical Ising model perturbed by the subleading magnetic operator using Smirnov's RSOS reduction of the Izergin-Korepin model. The massive model contains kink excitations which interpolate between two degenerate asymmetric vacua. As a consequence of the different structure of the two vacua, the crossing symmetry is implemented in a nontrivial way. The authors use finite-size techniques to compare their results with the numerical data obtained by the truncated conformal space approach and find good agreement

  18. Magnetic resonance of field-frozen and zero-field-frozen magnetic fluids

    International Nuclear Information System (INIS)

    Pereira, A.R.; Pelegrini, F.; Neto, K. Skeff; Buske, N.; Morais, P.C.

    2004-01-01

    In this study magnetic resonance was used to investigate magnetic fluid samples frozen under zero and non-zero (15 kG) external fields. The magnetite-based sample containing 2x10 17 particle/cm 3 was investigated from 100 to 400 K. Analysis of the temperature dependence of the resonance field revealed bigger magnetic structures in the frozen state than in the liquid phase. Also, differences in the mesoscopic organization in the frozen state may explain the data obtained from samples frozen under zero and non-zero fields

  19. Electrical Transport on the Shastry-Sutherland Lattice in Ising-type Rare Earth Tetraborides

    Science.gov (United States)

    Ye, Linda; Suzuki, Takehito; Checkelsky, Joseph. G.

    In the presence of a magnetic field, frustrated spin systems may exhibit plateaus at fractional values of their saturation magnetization. Study of the magnetic ordering and excitations at such plateaus are key to understanding the nature of the underlying ground states in these systems. Here we study the magnetization plateaus in metallic rare earth tetraborides RB4 with Ising-type anisotropy (R = Er, Tm) in which R resides on a Shastry-Sutherland lattice. We focus on electrical transport and find that the response reflects scattering of charge carriers with the static and dynamic plateau structure. Modeling of these results is consistent with the expected strong uniaxial anisotropy and provides a framework for the study of plateau states in metallic frustrated systems. We thank NSF Grant No. DMR-1231319, Tsinghua Education Foundation, Moore foundation Grant No. GBMF3848 for support.

  20. The phase diagrams of the site-diluted spin-1/2 Ising superlattice

    International Nuclear Information System (INIS)

    Saber, A.; Essaoudi, I.; Ainane, A.; Dujardin, F.; Saber, M.; Stebe, B.

    1998-08-01

    Using the effective field theory with a probability distribution technique that accounts for the single-site spin correlations, the critical behavior of a diluted spin-1/2 Ising superlattice consisting of two different ferromagnet materials is examined. The critical temperature of the system is studied as a function of the thickness of the constituents in a unit cell, the concentration of magnetic atoms, and the exchange interactions in each material. It is shown that the properties of the diluted system are different from those of the corresponding pure system. (author)

  1. Heat transfer enhancement of Fe{sub 3}O{sub 4} ferrofluids in the presence of magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Fadaei, Farzad; Shahrokhi, Mohammad; Molaei Dehkordi, Asghar, E-mail: amolaeid@sharif.edu; Abbasi, Zeinab

    2017-05-01

    In this article, three-dimensional (3D) forced-convection heat transfer of magnetic nanofluids in a pipe subject to constant wall heat flux in the presence of single or double permanent magnet(s) or current-carrying wire has been investigated and compared. In this regard, laminar fluid flow and equilibrium magnetization for the ferrofluid were considered. In addition, variations of magnetic field in different media were taken into account and the assumption of having a linear relationship of magnetization with applied magnetic field intensity was also relaxed. Effects of magnetic field intensity, nanoparticle volume fraction, Reynolds number value, and the type of magnetic field source (i.e., a permanent magnet or current-carrying wire) on the forced-convection heat transfer of magnetic nanofluids were carefully investigated. It was found that by applying the magnetic field, the fluid mixing could be intensified that leads to an increase in the Nusselt number value along the pipe length. Moreover, the obtained simulation results indicate that applying the magnetic field induced by two permanent magnets with a magnetization of 3×10{sup 5} (A/m) (for each one), the fully developed Nusselt number value can be increased by 196%. - Highlights: • 3D forced-convection heat transfer of magnetic nanofluids is investigated. • Effects of single or double permanent magnet on the heat transfer are studied. • Influences of magnetic field induced by a current-carrying wire are studied. • Effects of magnetic field intensity and Reynolds number value are studied. • Variations of magnetic field in different media are taken into account.

  2. 3D Printing of Polymer-Bonded Rare-Earth Magnets With a Variable Magnetic Compound Fraction for a Predefined Stray Field.

    Science.gov (United States)

    Huber, Christian; Abert, Claas; Bruckner, Florian; Groenefeld, Martin; Schuschnigg, Stephan; Teliban, Iulian; Vogler, Christoph; Wautischer, Gregor; Windl, Roman; Suess, Dieter

    2017-08-25

    Additive manufacturing of polymer-bonded magnets is a recently developed technique, for single-unit production, and for structures that have been impossible to manufacture previously. Also, new possibilities to create a specific stray field around the magnet are triggered. The current work presents a method to 3D print polymer-bonded magnets with a variable magnetic compound fraction distribution. This means the saturation magnetization can be adjusted during the printing process to obtain a required external field of the manufactured magnets. A low-cost, end-user 3D printer with a mixing extruder is used to mix permanent magnetic filaments with pure polyamide (PA12) filaments. The magnetic filaments are compounded, extruded, and characterized for the printing process. To deduce the quality of the manufactured magnets with a variable magnetic compound fraction, an inverse stray field framework is developed. The effectiveness of the printing process and the simulation method is shown. It can also be used to manufacture magnets that produce a predefined stray field in a given region. This opens new possibilities for magnetic sensor applications. This setup and simulation framework allows the design and manufacturing of polymer-bonded permanent magnets, which are impossible to create with conventional methods.

  3. Magnetic-field-assisted synthesis of Co{sub 3}O{sub 4} nanoneedles with superior electrochemical capacitance

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Tao; Xie, Yan; Zhang, Guoxiong; He, Zhenni; Lu, Yisheng; Guo, Haibo [Shanghai University, Department of Electronic Information Materials, School of Materials Science and Engineering (China); Lin, Chuan [GE Global Research, China Technology Center (China); Chen, Yigang, E-mail: yigangchen@shu.edu.cn [Shanghai University, Department of Electronic Information Materials, School of Materials Science and Engineering (China)

    2015-12-15

    Nanostructured Co{sub 3}O{sub 4} films have been deposited on nickel foam in a magnetic-field-assisted hydrothermal process followed by annealing in air. The magnetic field strength is varied to study its relationship with nanostructures, morphology, and electrochemical properties of the Co{sub 3}O{sub 4} electrodes. The Co{sub 3}O{sub 4} films synthesized in the weak magnetic fields consist of dispersed nanoneedles, which are different from clustered nanoneedles when the magnetic field is absent. Moreover, the magnetic fields (of several millitesla) induced substantial changes in the nanostructures and electrochemical properties of the Co{sub 3}O{sub 4} films. A possible formation mechanism of Co{sub 3}O{sub 4} nanoneedles is proposed by comparing the morphologies and nanostructures of the films synthesized with and without the magnetic fields. Among these electrodes, the optimal one has a high specific capacitance (970.8 F g{sup −1} at 0.5 A g{sup −1}), good power capability (847.5 F g{sup −1} at 6.0 A g{sup −1}), and an excellent retention ratio (93.7 % over 1000 cycles). All these impressive results demonstrate that magnetic fields may be an economic and effective tool in hydrothermal synthesis of Co{sub 3}O{sub 4} electrodes for high-performance supercapacitors.

  4. Strong coupling expansion for scattering phases in hamiltonian lattice field theories. Pt. 1. The (d+1)-dimensional Ising model

    International Nuclear Information System (INIS)

    Dahmen, Bernd

    1994-01-01

    A systematic method to obtain strong coupling expansions for scattering quantities in hamiltonian lattice field theories is presented. I develop the conceptual ideas for the case of the hamiltonian field theory analogue of the Ising model, in d space and one time dimension. The main result is a convergent series representation for the scattering states and the transition matrix. To be explicit, the special cases of d=1 and d=3 spatial dimensions are discussed in detail. I compute the next-to-leading order approximation for the phase shifts. The application of the method to investigate low-energy scattering phenomena in lattice gauge theory and QCD is proposed. ((orig.))

  5. Spin Chirality of Cu3 and V3 Nanomagnets. 1. Rotation Behavior of Vector Chirality, Scalar Chirality, and Magnetization in the Rotating Magnetic Field, Magnetochiral Correlations.

    Science.gov (United States)

    Belinsky, Moisey I

    2016-05-02

    The rotation behavior of the vector chirality κ, scalar chirality χ, and magnetization M in the rotating magnetic field H1 is considered for the V3 and Cu3 nanomagnets, in which the Dzialoshinsky-Moriya coupling is active. The polar rotation of the field H1 of the given strength H1 results in the energy spectrum characterized by different vector and scalar chiralities in the ground and excited states. The magnetochiral correlations between the vector and scalar chiralities, energy, and magnetization in the rotating field were considered. Under the uniform polar rotation of the field H1, the ground-state chirality vector κI performs sawtooth oscillations and the magnetization vector MI performs the sawtooth oscillating rotation that is accompanied by the correlated transformation of the scalar chirality χI. This demonstrates the magnetochiral effect of the joint rotation behavior and simultaneous frustrations of the spin chiralities and magnetization in the rotating field, which are governed by the correlation between the chiralities and magnetization.

  6. IceBridge Scintrex CS-3 Cesium Magnetometer L0 Raw Magnetic Field, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA IceBridge Scintrex CS-3 Cesium Magnetometer L0 Raw Magnetic Field data set contains magnetic field readings and fluxgate values taken over Greenland using...

  7. Electronic transport on the Shastry-Sutherland lattice in Ising-type rare-earth tetraborides

    Science.gov (United States)

    Ye, Linda; Suzuki, Takehito; Checkelsky, Joseph G.

    2017-05-01

    In the presence of a magnetic field frustrated spin systems may exhibit plateaus at fractional values of saturation magnetization. Such plateau states are stabilized by classical and quantum mechanisms including order by disorder, triplon crystallization, and various competing order effects. In the case of electrically conducting systems, free electrons represent an incisive probe for the plateau states. Here we study the electrical transport of Ising-type rare-earth tetraborides R B4 (R =Er , Tm), a metallic Shastry-Sutherland lattice showing magnetization plateaus. We find that the longitudinal and transverse resistivities reflect scattering with both the static and the dynamic plateau structure. We model these results consistently with the expected strong uniaxial anisotropy on a quantitative level, providing a framework for the study of plateau states in metallic frustrated systems.

  8. 2D-Ising critical behavior in mixtures of water and 3-methylpyridine

    International Nuclear Information System (INIS)

    Sadakane, Koichiro; Iguchi, Kazuya; Nagao, Michihiro; Seto, Hideki

    2011-01-01

    The effect of an antagonistic salt on the phase behavior and nanoscale structure of a mixture of D 2 O and 3-methylpyridine was investigated by visual inspection and small-angle neutron scattering (SANS). The addition of the antagonistic salt, namely sodium tetraphenylborate (NaBPh 4 ), induces the shrinking of the two-phase region in contrast to the case in which a normal (hydrophilic) salt is added. Below the phase separation point, the SANS profiles cannot be described by the Ornstein-Zernike function owing to the existence of a long-range periodic structure. With increasing salt concentration, the critical exponents change from the values of 3D-Ising and approach those of 2D-Ising. These results suggest that the concentration fluctuation of the mixture of solvents is limited to a quasi two-dimensional space by the periodic structure induced by the adding the salt. The same behaviors were also observed in mixtures composed of water, 3-methylpyridine, and ionic surfactant.

  9. Non-conserved magnetization operator and 'fire-and-ice' ground states in the Ising-Heisenberg diamond chain

    Science.gov (United States)

    Torrico, Jordana; Ohanyan, Vadim; Rojas, Onofre

    2018-05-01

    We consider the diamond chain with S = 1/2 XYZ vertical dimers which interact with the intermediate sites via the interaction of the Ising type. We also suppose all four spins form the diamond-shaped plaquette to have different g-factors. The non-uniform g-factors within the quantum spin dimer as well as the XY-anisotropy of the exchange interaction lead to the non-conserving magnetization for the chain. We analyze the effects of non-conserving magnetization as well as the effects of the appearance of negative g-factors among the spins from the unit cell. A number of unusual frustrated states for ferromagnetic couplings and g-factors with non-uniform signs are found out. These frustrated states generalize the "half-fire-half-ice" state introduced in reference Yin et al. (2015). The corresponding zero-temperature ground state phase diagrams are presented.

  10. The behaviour of the L3 muon chambers in a magnetic field

    International Nuclear Information System (INIS)

    Onvlee, J.

    1989-01-01

    L3 is one of the four detectors at LEP. It consists of many parts, each of which measures a specific property of the particles produced in the electron positron collisions. One of the specialities of the L3 detector is the high precision measurement of the momenta of the muons produced in the collisions. In order to curve the muon trajectories the detector is placed in a magnetic field of about 0.5 Tesla. The behaviour of the L3 muon drift chambers in this magnetic field is the main subject of this thesis. (author). 45 refs.; 47 figs.; 12 tabs

  11. Magnetic properties of checkerboard lattice: a Monte Carlo study

    Science.gov (United States)

    Jabar, A.; Masrour, R.; Hamedoun, M.; Benyoussef, A.

    2017-12-01

    The magnetic properties of ferrimagnetic mixed-spin Ising model in the checkerboard lattice are studied using Monte Carlo simulations. The variation of total magnetization and magnetic susceptibility with the crystal field has been established. We have obtained a transition from an order to a disordered phase in some critical value of the physical variables. The reduced transition temperature is obtained for different exchange interactions. The magnetic hysteresis cycles have been established. The multiples hysteresis cycle in checkerboard lattice are obtained. The multiples hysteresis cycle have been established. The ferrimagnetic mixed-spin Ising model in checkerboard lattice is very interesting from the experimental point of view. The mixed spins system have many technological applications such as in domain opto-electronics, memory, nanomedicine and nano-biological systems. The obtained results show that that crystal field induce long-range spin-spin correlations even bellow the reduced transition temperature.

  12. On the quantum symmetry of the chiral Ising model

    Science.gov (United States)

    Vecsernyés, Peter

    1994-03-01

    We introduce the notion of rational Hopf algebras that we think are able to describe the superselection symmetries of rational quantum field theories. As an example we show that a six-dimensional rational Hopf algebra H can reproduce the fusion rules, the conformal weights, the quantum dimensions and the representation of the modular group of the chiral Ising model. H plays the role of the global symmetry algebra of the chiral Ising model in the following sense: (1) a simple field algebra F and a representation π on Hπ of it is given, which contains the c = {1}/{2} unitary representations of the Virasoro algebra as subrepresentations; (2) the embedding U: H → B( Hπ) is such that the observable algebra π( A) - is the invariant subalgebra of B( Hπ) with respect to the left adjoint action of H and U(H) is the commutant of π( A); (3) there exist H-covariant primary fields in B( Hπ), which obey generalized Cuntz algebra properties and intertwine between the inequivalent sectors of the observables.

  13. On the phase transition nature in compressible Ising models

    International Nuclear Information System (INIS)

    Ota, A.T.

    1985-01-01

    The phase transition phenomenon is analysed in a compressible ferromagnetic Ising model at null field, through the mean-field approximation. The model studied is d-dimensional under the magnetic point of view and one-dimensional under the elastic point of view. This is achieved keeping the compressive interactions among the ions and rejecting annealing forces completely. The exchange parameter J is linear and the elastic potential quadratic in relation to the microscopic shifts of the lattice. In the one-dimensional case, this model shows no phase transition. In the two-dimensional case, the role of the S i spin of the i-the ion is crucial: a) for spin 1/2 the transitions are of second order; b) for spin 1, desides the second order transitions there is a three-critical point and a first-order transitions line. (L.C.) [pt

  14. Trapped field recovery of bulk superconductor magnets by static field magnetization

    Science.gov (United States)

    Deng, Z.; Tsuzuki, K.; Miki, M.; Felder, B.; Hara, S.; Izumi, M.

    2011-11-01

    Thanks to the trapped field of bulk high-temperature superconductors, they can be used as field-pole magnets in the high temperature superconducting (HTS) rotating machines. For example, an output power of 10 kW at 720 rpm was realized by an average trapped field of 0.56 T of eight melt-textured GdBa2Cu3Oy (Gd-123) bulks at liquid nitrogen temperature in TUMSAT in 2004. Similarly to the HTS machines involving 1G or 2G wires, the trapped field of the bulk is possibly sensitive and even can be attenuated by the AC component field during the operation. Hence, it is necessary to recover the trapped field once being decreased to some extent in the practical application. From this point, we have investigated the trapped field recovery of HTS bulk magnets by static field magnetization in the paper. A series of different initial trapped fields after zero-field-cooling or field-cooling magnetization are used to simulate the attenuated trapped field. By comparing the trapped field peak and its distribution, the trapped field was found to be able to recover by the static field magnetization method with a stronger excitation field and the initial trapped flux inside the bulk also has an influence on the recovery process. The optimum recovery field was found to be about 2.5 times the saturated trapped field of the bulk at liquid nitrogen temperature, by which the bulk can regain the former best trapped field performance.

  15. An approach to 3D magnetic field calculation using numerical and differential algebra methods

    International Nuclear Information System (INIS)

    Caspi, S.; Helm, M.; Laslett, L.J.; Brady, V.O.

    1992-01-01

    Motivated by the need for new means for specification and determination of 3D fields that are produced by electromagnetic lens elements in the region interior to coil windings and seeking to obtain techniques that will be convenient for accurate conductor placement and dynamical study of particle motion, we have conveniently gene the representation of a 2D magnetic field to 3D. We have shown that the 3 dimensioal magnetic field components of a multipole magnet in the curl-fire divergence-fire region near the axis r=0 can be derived from one dimensional functions A n (z) and their derivatives (part 1). In the region interior to coil windings of accelerator magnets the three spatial components of magnet fields can be expressed in terms of ''harmonic components'' proportional to functions sin (nθ) or cos (nθ) of the azimuthal angle. The r,z dependence of any such component can then be expressed in terms of powers of r times functions A n (z) and their derivatives. For twodimensional configurations B z of course is identically zero, the derivatives of A n (z) vanish, and the harmonic components of the transverse field then acquire a simple proportionality B r,n ∝ r n-1 sin (nθ),B θ,n ∝ r n-1 cos (nθ), whereas in a 3-D configuration the more complex nature of the field gives rise to additional so-called ''psuedomultipole'' components as judged by additional powers of r required in the development of the field. Computation of the 3-D magnetic field arising at a sequence of field points, as a direct result of a specified current configuration or coil geometry, can be calculated explicitly through use of the Biot-Savart law and from such data the coefficients can then be derived for a general development of the type indicated above. We indicate, discuss, and illustrate two means by which this development may be performed

  16. Ising model with conserved magnetization on the human connectome: Implications on the relation structure-function in wakefulness and anesthesia

    Science.gov (United States)

    Stramaglia, S.; Pellicoro, M.; Angelini, L.; Amico, E.; Aerts, H.; Cortés, J. M.; Laureys, S.; Marinazzo, D.

    2017-04-01

    Dynamical models implemented on the large scale architecture of the human brain may shed light on how a function arises from the underlying structure. This is the case notably for simple abstract models, such as the Ising model. We compare the spin correlations of the Ising model and the empirical functional brain correlations, both at the single link level and at the modular level, and show that their match increases at the modular level in anesthesia, in line with recent results and theories. Moreover, we show that at the peak of the specific heat (the critical state), the spin correlations are minimally shaped by the underlying structural network, explaining how the best match between the structure and function is obtained at the onset of criticality, as previously observed. These findings confirm that brain dynamics under anesthesia shows a departure from criticality and could open the way to novel perspectives when the conserved magnetization is interpreted in terms of a homeostatic principle imposed to neural activity.

  17. Semi-local invariance in Ising models with multi-spin interaction

    International Nuclear Information System (INIS)

    Lipowski, A.

    1996-08-01

    We examine implications of semi-local invariance in Ising models with multispin interaction. In ergodic models all spin-spin correlation functions vanish and the local symmetry is the same as in locally gauge-invariant models. The d = 3 model with four-spin interaction is nonergodic at low temperature but the magnetic symmetry remains unbroken. The d = 3 model with eight-spin interaction is ergodic but undergoes the phase transition and most likely its low-temperature phase is characterized by a nonlocal order parameter. (author). 7 refs, 1 fig

  18. Nb3Sn High Field Magnets for the High Luminosity LHC Upgrade Project

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Giorgio

    2015-06-01

    The High Luminosity upgrade of the Large Hadron Collider at CERN requires a new generation of high field superconducting magnets. High field large aperture quadrupoles (MQXF) are needed for the low-beta triplets close to the ATLAS and CMS detectors, and high field two-in-one dipoles (11 T dipoles) are needed to make room for additional collimation. The MQXF quadrupoles, with a field gradient of 140 T/m in 150 mm aperture, have a peak coil field of 12.1 T at nominal current. The 11 T dipoles, with an aperture of 60 mm, have a peak coil field of 11.6 T at nominal current. Both magnets require Nb3Sn conductor and are the first applications of this superconductor to actual accelerator magnets.

  19. Quantum correlated cluster mean-field theory applied to the transverse Ising model.

    Science.gov (United States)

    Zimmer, F M; Schmidt, M; Maziero, Jonas

    2016-06-01

    Mean-field theory (MFT) is one of the main available tools for analytical calculations entailed in investigations regarding many-body systems. Recently, there has been a surge of interest in ameliorating this kind of method, mainly with the aim of incorporating geometric and correlation properties of these systems. The correlated cluster MFT (CCMFT) is an improvement that succeeded quite well in doing that for classical spin systems. Nevertheless, even the CCMFT presents some deficiencies when applied to quantum systems. In this article, we address this issue by proposing the quantum CCMFT (QCCMFT), which, in contrast to its former approach, uses general quantum states in its self-consistent mean-field equations. We apply the introduced QCCMFT to the transverse Ising model in honeycomb, square, and simple cubic lattices and obtain fairly good results both for the Curie temperature of thermal phase transition and for the critical field of quantum phase transition. Actually, our results match those obtained via exact solutions, series expansions or Monte Carlo simulations.

  20. Spin-glass polyamorphism induced by a magnetic field in LaMnO3 single crystal

    Science.gov (United States)

    Eremenko, V. V.; Sirenko, V. A.; Baran, A.; Čižmár, E.; Feher, A.

    2018-05-01

    We present experimental evidence of field-driven transition in spin-glass state, similar to pressure-induced transition between amorphous phases in structural and metallic glasses, attributed to the polyamorphism phenomena. Cusp in temperature dependences of ac magnetic susceptibility of weakly disordered LaMnO3 single crystal is registered below the temperature of magnetic ordering. Frequency dependence of the cusp temperature proves its spin-glass origin. The transition induced by a magnetic field in spin-glass state, is manifested by peculiarity in dependence of cusp temperature on applied magnetic field. Field dependent maximum of heat capacity is observed in the same magnetic field and temperature range.

  1. Dynamical replica analysis of processes on finitely connected random graphs: II. Dynamics in the Griffiths phase of the diluted Ising ferromagnet

    International Nuclear Information System (INIS)

    Mozeika, A; Coolen, A C C

    2009-01-01

    We study the Glauber dynamics of Ising spin models with random bonds, on finitely connected random graphs. We generalize a recent dynamical replica theory with which to predict the evolution of the joint spin-field distribution, to include random graphs with arbitrary degree distributions. The theory is applied to Ising ferromagnets on randomly diluted Bethe lattices, where we study the evolution of the magnetization and the internal energy. It predicts a prominent slowing down of the flow in the Griffiths phase, it suggests a further dynamical transition at lower temperatures within the Griffiths phase, and it is verified quantitatively by the results of Monte Carlo simulations

  2. Anomalous aspects of magnetosheath flow and of the shape and oscillations of the magnetopause during an interval of strongly northward interplanetary magnetic field

    Science.gov (United States)

    Chen, Sheng-Hsien; Kivelson, Margaret G.; Gosling, Jack T.; Walker, Raymond T.; Lazarus, Allan J.

    1992-01-01

    On 15 Feb. 1978, the orientation of the interplanetary magnetic field (IMF) remained steadily northward for more than 12 hours. The ISEE 1 and 2 spacecraft were located near apogee on the dawn side flank of the magnetotail. IMP 8 was almost symmetrically located in the magnetosheath on the dusk flank and IMP 7 was upstream in the solar wind. Using plasma and magnetic field data, we show the following: (1) the magnetosheath flow speed on the flanks of the magnetotail steadily exceeded the solar wind speed by 20 percent; (2) surface waves with approximately a 5-min period and very non-sinusoidal waveform were persistently present on the dawn magnetopause and waves of similar period were present in the dusk magnetosheath; and (3) the magnetotail ceased to flare at an antisunward distance of 15 R(sub E). We propose that the acceleration of the magnetosheath flow is achieved by magnetic tension in the draped field configuration for northward IMF and that the reduction of tail flaring is consistent with a decreased amount of open magnetic flux and a larger standoff distance of the subsolar magnetopause. Results of a three-dimensional magnetohydrodynamic simulation support this phenomenological model.

  3. Magnetic islands in the near geomagnetic tail and its implications for the mechanism of 1054 UT CDAW 6 substorm

    Science.gov (United States)

    Lin, N.; Walker, R. J.; Mcpherron, R. L.; Kivelson, M. G.

    1990-01-01

    During the 1054 UT CDAW 6 substorm event, two ISEE spacecraft observed dynamic changes in the magnetic field and in the flux of energetic particles in the near-earth plasma sheet. In the substorm growth phase, the magnetic field at both ISEE spacecraft became tail-like. Following expansion phase onset, two small scale magnetic islands were observed moving tailward at a velocity of about 580 km/s. The passage of these two magnetic islands was coincident with bursts of tailward streaming energetic particles. The length of the magnetic loops was estimated to have been about 2 to 3 earth radii while the height of the loops was less than 0.5 earth radii. The magnetic islands were produced by multipoint reconnection processes in the near tail plasma sheet which may have been associated with the formation of the near-earth neutral line and the subsequent formation of a large scale plasmoid. The near-earth neutral line retreated tailward later in the expansion phase, as suggested by the reversal of the streaming of energetic particles.

  4. Phase diagram and re-entrant fermionic entanglement in a hybrid Ising-Hubbard ladder

    Science.gov (United States)

    Sousa, H. S.; Pereira, M. S. S.; de Oliveira, I. N.; Strečka, J.; Lyra, M. L.

    2018-05-01

    The degree of fermionic entanglement is examined in an exactly solvable Ising-Hubbard ladder, which involves interacting electrons on the ladder's rungs described by Hubbard dimers at half-filling on each rung, accounting for intrarung hopping and Coulomb terms. The coupling between neighboring Hubbard dimers is assumed to have an Ising-like nature. The ground-state phase diagram consists of four distinct regions corresponding to the saturated paramagnetic, the classical antiferromagnetic, the quantum antiferromagnetic, and the mixed classical-quantum phase. We have exactly computed the fermionic concurrence, which measures the degree of quantum entanglement between the pair of electrons on the ladder rungs. The effects of the hopping amplitude, the Coulomb term, temperature, and magnetic fields on the fermionic entanglement are explored in detail. It is shown that the fermionic concurrence displays a re-entrant behavior when quantum entanglement is being generated at moderate temperatures above the classical saturated paramagnetic ground state.

  5. Substorm-associated large-scale magnetic field changes in the magnetotail: a prerequisite for "magnetotail deflation" events

    Directory of Open Access Journals (Sweden)

    H. Nakai

    Full Text Available An attempt is made to search for a critical condition in the lobe magnetic field to initiate large-scale magnetic field changes associated with substorm expansions. Using data from ISEE-1 for 1978, sudden decreases in the lobe magnetic field accompanied by magnetic field dipolarizations are identified. In this study, such events are designated as the magnetotail deflation. The magnetic field component parallel to the equatorial plane, BE , is normalized to a fixed geocentric distance, BEN , and is corrected for the compression effect of the solar wind dynamic pres-sure, BENC . It is shown that the BENC value just prior to a magnetotail deflation correlates well with the Dst index; BENC = 37.5 - 0.217 Dst0, where Dst0 denotes the Dst value corrected for the solar wind dynamic pressure. This regression function appears to delineate the upper limit of BENC values, when they are sorted by the Dst0 index. On the basis of this finding it is suggested that a prerequisite condition for magnetotail deflations must exist in the magnetosphere.

    Key words. Magnetospheric physics (magnetotail; current systems; storms and substorms

  6. Electric Field Tuning Non-volatile Magnetism in Half-Metallic Alloys Co2FeAl/Pb(Mg1/3Nb2/3)O3-PbTiO3 Heterostructure

    Science.gov (United States)

    Dunzhu, Gesang; Wang, Fenglong; Zhou, Cai; Jiang, Changjun

    2018-03-01

    We reported the non-volatile electric field-mediated magnetic properties in the half-metallic Heusler alloy Co2FeAl/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructure at room temperature. The remanent magnetization with different applied electric field along [100] and [01-1] directions was achieved, which showed the non-volatile remanent magnetization driven by an electric field. The two giant reversible and stable remanent magnetization states were obtained by applying pulsed electric field. This can be attributed to the piezostrain effect originating from the piezoelectric substrate, which can be used for magnetoelectric-based memory devices.

  7. Fe3O4/BSA particles induce osteogenic differentiation of mesenchymal stem cells under static magnetic field.

    Science.gov (United States)

    Jiang, Pengfei; Zhang, Yixian; Zhu, Chaonan; Zhang, Wenjing; Mao, Zhengwei; Gao, Changyou

    2016-12-01

    Differentiation of stem cells is influenced by many factors, yet uptake of the magnetic particles with or without magnetic field is rarely tackled. In this study, iron oxide nanoparticles-loaded bovine serum albumin (BSA) (Fe 3 O 4 /BSA) particles were prepared, which showed a spherical morphology with a diameter below 200 nm, negatively charged surface, and tunable magnetic property. The particles could be internalized into bone marrow mesenchymal stem cells (MSCs), and their release from the cells was significantly retarded under external magnetic field, resulting in almost twice intracellular amount of the particles within 21 d compared to that of the magnetic field free control. Uptake of the Fe 3 O 4 /BSA particles enhanced significantly the osteogenic differentiation of MSCs under a static magnetic field, as evidenced by elevated alkaline phosphatase (ALP) activity, calcium deposition, and expressions of collagen type I and osteocalcin at both mRNA and protein levels. Therefore, uptake of the Fe 3 O 4 /BSA particles brings significant influence on the differentiation of MSCs under magnetic field, and thereby should be paid great attention for practical applications. Differentiation of stem cells is influenced by many factors, yet uptake of the magnetic particles with or without magnetic field is rarely tackled. In this study, iron oxide nanoparticles-loaded bovine serum albumin (BSA) (Fe 3 O 4 /BSA) particles with a diameter below 200nm, negatively charged surface, tunable Fe 3 O 4 content and subsequently adjustable magnetic property were prepared. The particles could be internalized into bone marrow mesenchymal stem cells (MSCs), and their release from the cells was significantly retarded under external magnetic field. Uptake of the Fe 3 O 4 /BSA particles enhanced significantly the osteogenic differentiation of MSCs under a constant static magnetic field, while the magnetic particles and external magnetic field alone do not influence significantly the

  8. Casting the Coronal Magnetic Field Reconstruction Tools in 3D Using the MHD Bifrost Model

    Energy Technology Data Exchange (ETDEWEB)

    Fleishman, Gregory D.; Loukitcheva, Maria [Physics Department, Center for Solar-Terrestrial Research, New Jersey Institute of Technology Newark, NJ, 07102-1982 (United States); Anfinogentov, Sergey; Mysh’yakov, Ivan [Institute of Solar-Terrestrial Physics (ISZF), Lermontov st., 126a, Irkutsk, 664033 (Russian Federation); Stupishin, Alexey [Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034 (Russian Federation)

    2017-04-10

    Quantifying the coronal magnetic field remains a central problem in solar physics. Nowadays, the coronal magnetic field is often modeled using nonlinear force-free field (NLFFF) reconstructions, whose accuracy has not yet been comprehensively assessed. Here we perform a detailed casting of the NLFFF reconstruction tools, such as π -disambiguation, photospheric field preprocessing, and volume reconstruction methods, using a 3D snapshot of the publicly available full-fledged radiative MHD model. Specifically, from the MHD model, we know the magnetic field vector in the entire 3D domain, which enables us to perform a “voxel-by-voxel” comparison of the restored and the true magnetic fields in the 3D model volume. Our tests show that the available π -disambiguation methods often fail in the quiet-Sun areas dominated by small-scale magnetic elements, while they work well in the active region (AR) photosphere and (even better) chromosphere. The preprocessing of the photospheric magnetic field, although it does produce a more force-free boundary condition, also results in some effective “elevation” of the magnetic field components. This “elevation” height is different for the longitudinal and transverse components, which results in a systematic error in absolute heights in the reconstructed magnetic data cube. The extrapolations performed starting from the actual AR photospheric magnetogram are free from this systematic error, while other metrics are comparable with those for extrapolations from the preprocessed magnetograms. This finding favors the use of extrapolations from the original photospheric magnetogram without preprocessing. Our tests further suggest that extrapolations from a force-free chromospheric boundary produce measurably better results than those from a photospheric boundary.

  9. The CMS Magnetic Field Map Performance

    CERN Document Server

    Klyukhin, V.I.; Andreev, V.; Ball, A.; Cure, B.; Herve, A.; Gaddi, A.; Gerwig, H.; Karimaki, V.; Loveless, R.; Mulders, M.; Popescu, S.; Sarycheva, L.I.; Virdee, T.

    2010-04-05

    The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive featuresinclude a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field ...

  10. Generation of high magnetic fields using superconducting magnets

    International Nuclear Information System (INIS)

    Kiyoshi, T.; Otsuka, A.; Kosuge, M.; Yuyama, M.; Nagai, H.; Matsumoto, F.

    2006-01-01

    High-field superconducting magnets have opened new frontiers for several kinds of applications, such as fusion reactors, particle accelerators, and nuclear magnetic resonance (NMR) spectrometers. The present record for the highest field in a fully superconducting state is 23.4 T. It was achieved with a combination of NbTi, Nb 3 Sn, and Bi-2212 conductors in 1999. Since high T c (critical temperature) superconductors (HTS) have sufficiently high critical current density even in excess of 30 T, they are promising for use as high-field superconducting magnets. However, several problems still remain to be resolved for practical applications, and the use of HTS coils will be limited to the inner part of a high-field magnet system in the near future. The required technologies to develop a high-field superconducting magnet with a field of up to 28 T have already been established. Such a magnet is certain to provide information to all leading research areas

  11. Semiconductor of spinons: from Ising band insulator to orthogonal band insulator.

    Science.gov (United States)

    Farajollahpour, T; Jafari, S A

    2018-01-10

    We use the ionic Hubbard model to study the effects of strong correlations on a two-dimensional semiconductor. The spectral gap in the limit where on-site interactions are zero is set by the staggered ionic potential, while in the strong interaction limit it is set by the Hubbard U. Combining mean field solutions of the slave spin and slave rotor methods, we propose two interesting gapped phases in between: (i) the insulating phase before the Mott phase can be viewed as gapping a non-Fermi liquid state of spinons by the staggered ionic potential. The quasi-particles of underlying spinons are orthogonal to physical electrons, giving rise to the 'ARPES-dark' state where the ARPES gap will be larger than the optical and thermal gap. (ii) The Ising insulator corresponding to ordered phase of the Ising variable is characterized by single-particle excitations whose dispersion is controlled by Ising-like temperature and field dependences. The temperature can be conveniently employed to drive a phase transition between these two insulating phases where Ising exponents become measurable by ARPES and cyclotron resonance. The rare earth monochalcogenide semiconductors where the magneto-resistance is anomalously large can be a candidate system for the Ising band insulator. We argue that the Ising and orthogonal insulating phases require strong enough ionic potential to survive the downward renormalization of the ionic potential caused by Hubbard U.

  12. Semiconductor of spinons: from Ising band insulator to orthogonal band insulator

    Science.gov (United States)

    Farajollahpour, T.; Jafari, S. A.

    2018-01-01

    We use the ionic Hubbard model to study the effects of strong correlations on a two-dimensional semiconductor. The spectral gap in the limit where on-site interactions are zero is set by the staggered ionic potential, while in the strong interaction limit it is set by the Hubbard U. Combining mean field solutions of the slave spin and slave rotor methods, we propose two interesting gapped phases in between: (i) the insulating phase before the Mott phase can be viewed as gapping a non-Fermi liquid state of spinons by the staggered ionic potential. The quasi-particles of underlying spinons are orthogonal to physical electrons, giving rise to the ‘ARPES-dark’ state where the ARPES gap will be larger than the optical and thermal gap. (ii) The Ising insulator corresponding to ordered phase of the Ising variable is characterized by single-particle excitations whose dispersion is controlled by Ising-like temperature and field dependences. The temperature can be conveniently employed to drive a phase transition between these two insulating phases where Ising exponents become measurable by ARPES and cyclotron resonance. The rare earth monochalcogenide semiconductors where the magneto-resistance is anomalously large can be a candidate system for the Ising band insulator. We argue that the Ising and orthogonal insulating phases require strong enough ionic potential to survive the downward renormalization of the ionic potential caused by Hubbard U.

  13. Weak universality in inhomogeneous Ising quantum chains

    International Nuclear Information System (INIS)

    Karevski, Dragi

    2006-01-01

    The Ising quantum chain with arbitrary coupling distribution {λ i } leading to an anisotropic scaling is considered. The smallest gap of the chain is connected to the surface magnetization by the relation Λ 1 = m s ({λ i })m s ({λ -1 i }). For some aperiodic distribution {λ i }, a weak universality of the critical behaviour is found. (letter to the editor)

  14. 2D/3D quench simulation using ANSYS for epoxy impregnated Nb3Sn high field magnets

    Energy Technology Data Exchange (ETDEWEB)

    Ryuji Yamada et al.

    2002-09-19

    A quench program using ANSYS is developed for the high field collider magnet for three-dimensional analysis. Its computational procedure is explained. The quench program is applied to a one meter Nb{sub 3}Sn high field model magnet, which is epoxy impregnated. The quench simulation program is used to estimate the temperature and mechanical stress inside the coil as well as over the whole magnet. It is concluded that for the one meter magnet with the presented cross section and configuration, the thermal effects due to the quench is tolerable. But we need much more quench study and improvements in the design for longer magnets.

  15. Design and development of a 3 axis magnetic field measurement facility using Hall probe

    International Nuclear Information System (INIS)

    Sahoo, Shantonu; Bhattacharyya, Sumantra; Chaddha, Niraj; Mishra, Santosh Kr.; Nandy, Partha P.; Nandi, Chinmay; Bhole, Rajendra B.; Pal, Sarbajit; Pal, Gautam

    2015-01-01

    A 3-axis drive system has been designed and developed in-house to measure the magnetic field with positional accuracy of 0.2 mm in a volume of 1.5 x 1.3 x 0.15 cubic-meter. Hall sensor based magnetometer is used to measure the magnetic field with a precision of 100 μT(1 Gauss). The drive of each axis has linear guide and zero backlash ball screw combination to achieve accurate movement of the hall probe with positional repeatability of +/- 0.2 micron per 50 mm. The hardware and software, also developed in-house, facilitate precise probe positioning and sophisticated visualization of field map. Dedicated microcontroller based motor controllers and encoder read-out cards for each axis have been developed. The facility is integrated with a rich touch-screen based intelligent GUI for automated scanning and data acquisition. This facility can be used for accurate magnetic field mapping of big dipole magnets, solenoids, etc. The facility has been tested successfully to characterize a Dipole Magnet designed for Radioactive Ion Beam (RIB) facility. (author)

  16. Approximating the Ising model on fractal lattices of dimension less than two

    DEFF Research Database (Denmark)

    Codello, Alessandro; Drach, Vincent; Hietanen, Ari

    2015-01-01

    We construct periodic approximations to the free energies of Ising models on fractal lattices of dimension smaller than two, in the case of a zero external magnetic field, based on the combinatorial method of Feynman and Vdovichenko. We show that the procedure is applicable to any fractal obtained...... with, possibly, arbitrary accuracy and paves the way for determination Tc of any fractal of dimension less than two. Critical exponents are more diffcult to determine since the free energy of any periodic approximation still has a logarithmic singularity at the critical point implying α = 0. We also...

  17. Magnetic-Field-Enhanced Incommensurate Magnetic Order in the Underdoped High-Temperature Superconductor YBa2Cu3O6.45

    DEFF Research Database (Denmark)

    Haug, D.; Hinkov, V.; Suchaneck, A.

    2009-01-01

    We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift...

  18. Powder-in-Tube (PIT) Nb3Sn conductors for high-field magnets

    NARCIS (Netherlands)

    Lindenhovius, J.H.; Hornsveld, E.M.; den Ouden, A.; Wessel, Wilhelm A.J.; ten Kate, Herman H.J.

    2000-01-01

    New Nb3Sn conductors, based on the powder-in-tube (PIT) process, have been developed for application in accelerator magnets and high-field solenoids. For application in accelerator magnets, SMI has developed a binary 504 filament PIT conductor by optimizing the manufacturing process and adjustment

  19. Low-field anomalous magnetic phase in the kagome-lattice shandite Co3Sn2S2

    OpenAIRE

    Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

    2017-01-01

    The magnetization process of single crystals of the metallic kagom\\'e ferromagnet Co3Sn2S2 was carefully measured via magnetization and AC susceptibility. Field-dependent anomalous transitions in the magnetization indicate a low-field unconventionally ordered phase stabilized just below TC. The magnetic phase diagrams in applied fields along different crystallographic directions were determined. The magnetic relaxation process studied in frequencies covering five orders of magnitude from 0.01...

  20. TFTR magnetic field design analyses

    International Nuclear Information System (INIS)

    Davies, K.; Iwinski, E.; McWhirter, J.M.

    1975-11-01

    The three main magnetic field windings for the TFTR are the toroidal field (TF) windings, the ohmic heating (OH) winding, and the equilibrium field (EF) winding. The following information is provided for these windings: (1) descriptions, (2) functions, (3) magnetic designs, e.g., number and location of turns, (4) design methods, and (5) descriptions of resulting magnetic fields. This report does not deal with the thermal, mechanical support, or construction details of the windings

  1. Fisher zeros in the Kallen-Lehmann approach to 3D Ising model

    International Nuclear Information System (INIS)

    Astorino, Marco; Canfora, Fabrizio; Giribet, Gaston

    2009-01-01

    The distribution of the Fisher zeros in the Kallen-Lehmann approach to three-dimensional Ising model is studied. It is argued that the presence of a non-trivial angle (a cusp) in the distribution of zeros in the complex temperatures plane near the physical singularity is realized through a strong breaking of the 2D Ising self-duality. Remarkably, the realization of the cusp in the Fisher distribution ultimately leads to an improvement of the results of the Kallen-Lehmann ansatz. In fact, excellent agreement with Monte Carlo predictions both at high and at low temperatures is observed. Besides, agreement between both approaches is found for the predictions of the critical exponent α and of the universal amplitude ratio Δ=A + /A - , within the 3.5% and 7% of the Monte Carlo predictions, respectively

  2. Relaxation theory of spin-3/2 Ising system near phase transition temperatures

    International Nuclear Information System (INIS)

    Canko, Osman; Keskin, Mustafa

    2010-01-01

    Dynamics of a spin-3/2 Ising system Hamiltonian with bilinear and biquadratic nearest-neighbour exchange interactions is studied by a simple method in which the statistical equilibrium theory is combined with the Onsager's theory of irreversible thermodynamics. First, the equilibrium behaviour of the model in the molecular-field approximation is given briefly in order to obtain the phase transition temperatures, i.e. the first- and second-order and the tricritical points. Then, the Onsager theory is applied to the model and the kinetic or rate equations are obtained. By solving these equations three relaxation times are calculated and their behaviours are examined for temperatures near the phase transition points. Moreover, the z dynamic critical exponent is calculated and compared with the z values obtained for different systems experimentally and theoretically, and they are found to be in good agrement. (general)

  3. Solar wind deceleration and MHD turbulence in the earth's foreshock region: ISEE 1 and 2 and IMP 8 observations

    International Nuclear Information System (INIS)

    Bonifazi, C.; Moreno, G.; Russell, C.T.; Lazarus, A.J.; Sullivan, J.D.

    1983-01-01

    The interaction of the solar wind with ions backstreaming from the earth's bow shock is investigated using plasma and magnetic field measurements on ISEE 1 and 2 and IMP 8 at widely separated positions in the earth's foreshock. This technique separates temporal and spatial variations within the foreshock. It is found that the solar wind acceleration associated with backstreaming ions is correlated with the amplitude of the MHD turbulence and that the largest decelerations are seen close to the bow shock. The density of the backstreaming ion beam is stronly correlated with distance from the shock and decreases by about a factor of 3 in a distance of about 3 R/sub E/

  4. Large non-volatile tuning of magnetism mediated by electric field in Fe–Al/Pb(Mg1/3Nb2/3)O3–PbTiO3 heterostructure

    International Nuclear Information System (INIS)

    Chen, Zhendong; Gao, Cunxu; Wei, Yanping; Zhang, Peng; Wang, Yutian; Zhang, Chao; Ma, Zhikun

    2017-01-01

    Electric-field control of magnetism is now an attractive trend to approach a new kind of fast, low-power-cost memory device. In this work, we report a strong non-volatile electric control of magnetism in an Fe–Al/Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 heterostructure. In this system, a 90° rotation of the in-plane uniaxial magnetic anisotropy is exhibited during the increase of the external electric field, which means the easy axis turns into a hard axis and the hard axis turns into an easy one. Additionally, a non-volatile switch of the remanence is observed after a sweeping of the electric field from 0 kV cm −1 to  ±  10 kV cm −1 , then back to 0 kV cm −1 . More interestingly, a 20% non-volatile magnetic state tuning driven by individual pulse electric fields is shown in contrast to large tuning up to 120% caused by pulse electric fields with small assistant pulse magnetic fields, which means a 180° reverse of the magnetization. These remarkable behaviors demonstrated in this heterostructure reveal a promising potential application in magnetic memory devices mediated by electric fields. (paper)

  5. Magnetic field influence on the spin-density wave of the organic conductor (TMTSF)2NO3

    International Nuclear Information System (INIS)

    Tomic, S.; Biskup, N.; Korin-Hamzic, B.; Basletic, M.; Hamzic, A.; Maki, K.; Fabre, J.M.; Bechgaard, K.

    1993-01-01

    We present the influence of a transverse magnetic field on the spin-density wave (SDW) ground state of the organic conductor (TMTSF) 2 NO 3 . Magnetic field increases the single-particle activation energy. A finite magnetic field (H C ) induces discontinuities in the magnetoresistance behaviour and its value is temperature dependent. The threshold electric field (E T ) for the SDW sliding increases in a magnetic field. All observed effects are strongly angle-dependent indicating that they are determined by the magnetic field component along the least-conduction (c * ) direction. We discuss these results in the framework of a theoretical model for the SDW with large imperfect nesting. (orig.)

  6. Design of combined magnetic field system for magnetic-bottle time-of-flight spectrometer

    International Nuclear Information System (INIS)

    Wang Chao; Tian Jinshou; Zhang Meizhi; Kang Yifan

    2011-01-01

    Based on the primary requirement for the magnetic field system in magnetic-bottle time-of-flight spectrometer, an appropriate combined inhomogeneous magnetic field system is designed. The inhomogeneous higher magnetic field part, with the highest field of 1.2 T, is produced by the combination of a permanent magnet and a pole piece with optimized shape. The magnet,known as NdFeB magnet,is one of rare earth permanent magnets in N52. The guiding uniform magnetic field of 1.0 x 10 -3 T is provided by solenoid, with length of 3 m and radius of 3 cm. The pitch between the pole piece and the near end of used solenoid is determined to be 5 cm, which can satisfy the actual engineering needs. (authors)

  7. Ising-type anisotropy and spin state transitions in GdBaCo2O5.5 from first-principles calculations

    International Nuclear Information System (INIS)

    Pardo, V.; Baldomir, D.; Castro, J.; Iglesias, M.; Arias, J.E.

    2007-01-01

    Ising-type behaviour of GdBaCo 2 O 5.5 is analyzed from first principles calculations of the electronic structure of the material. The variations in its magnetic anisotropy properties in the different possible magnetic configurations is analyzed. A possible metallic phase is studied and an analysis of the electronic structure of the Co 3+ ions in that phase is presented

  8. Scaling behaviour of the correlation length for the two-point correlation function in the random field Ising chain

    Energy Technology Data Exchange (ETDEWEB)

    Lange, Adrian; Stinchcombe, Robin [Theoretical Physics, University of Oxford, Oxford (United Kingdom)

    1996-07-07

    We study the general behaviour of the correlation length {zeta}(kT:h) for two-point correlation function of the local fields in an Ising chain with binary distributed fields. At zero field it is shown that {zeta} is the same as the zero-field correlation length for the spin-spin correlation function. For the field-dominated behaviour of {zeta} we find an exponent for the power-law divergence which is smaller than the exponent for the spin-spin correlation length. The entire behaviour of the correlation length can be described by a single crossover scaling function involving the new critical exponent. (author)

  9. Thermo-magnetic instabilities in Nb3Sn Superconducting Accelerator Magnets

    International Nuclear Information System (INIS)

    Bordini, Bernardo; Pisa U.

    2006-01-01

    The advance of High Energy Physics research using circulating accelerators strongly depends on increasing the magnetic bending field which accelerator magnets provide. To achieve high fields, the most powerful present-day accelerator magnets employ NbTi superconducting technology; however, with the start up of Large Hadron Collider (LHC) in 2007, NbTi magnets will have reached the maximum field allowed by the intrinsic properties of this superconductor. A further increase of the field strength necessarily requires a change in superconductor material; the best candidate is Nb 3 Sn. Several laboratories in the US and Europe are currently working on developing Nb 3 Sn accelerator magnets, and although these magnets have great potential, it is suspected that their performance may be fundamentally limited by conductor thermo-magnetic instabilities: an idea first proposed by the Fermilab High Field Magnet group early in 2003. This thesis presents a study of thermo-magnetic instability in high field Nb 3 Sn accelerator magnets. In this chapter the following topics are described: the role of superconducting magnets in High Energy Physics; the main characteristics of superconductors for accelerator magnets; typical measurements of current capability in superconducting strands; the properties of Nb 3 Sn; a description of the manufacturing process of Nb 3 Sn strands; superconducting cables; a typical layout of superconducting accelerator magnets; the current state of the art of Nb 3 Sn accelerator magnets; the High Field Magnet program at Fermilab; and the scope of the thesis

  10. ISEE (InformationsSystem Erneuerbare Energie): Renewable Energy Information System

    International Nuclear Information System (INIS)

    Grebe, R.; Koch, H.

    1991-01-01

    Since the end of 1989 ISET has been operating the title database ISEE. Access to this on-line database may be obtained by any interested party posessing a computer, which is connected to the network of the 'Deutsche TeleCom' by telephone or Datex-P. The command language of ISEE is German. ISET will establish an English version in 1991/1992. In brief attention is paid to the components of the ISEE database, its user groups, the possibilities to access ISEE, and further developments. 3 figs

  11. Structural, electronic and magnetic properties of LaCr2Si2C: Ab initio calculation, mean field approximation and Monte-Carlo simulation

    Science.gov (United States)

    Endichi, A.; Zaari, H.; Benyoussef, A.; El Kenz, A.

    2018-06-01

    The magnetic behavior of LaCr2Si2C compound is investigated in this work, using first principle methods, Monte Carlo simulation (MCS) and mean field approximation (MFA). The structural, electronic and magnetic properties are described using ab initio method in the framework of the Generalized Gradient Approximation (GGA), and the Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method implemented in the WIEN2K packages. We have also computed the coupling terms between magnetic atoms which are used in Hamiltonian model. A theoretical study realized by mean field approximation and Monte Carlo Simulation within the Ising model is used to more understand the magnetic properties of this compound. Thereby, our results showed a ferromagnetic ordering of the Cr magnetic moments below the Curie temperature of 30 K (Tc magnetization, the energy, the specific heat and the susceptibility. This material shows the small sign of supra-conductivity; and future researches could be focused to enhance the transport and magnetic properties of this system.

  12. Sound dispersion in a spin-1 Ising system near the second-order phase transition point

    International Nuclear Information System (INIS)

    Erdem, Ryza; Keskin, Mustafa

    2003-01-01

    Sound dispersion relation is derived for a spin-1 Ising system and its behaviour near the second-order phase transition point or the critical point is analyzed. The method used is a combination of molecular field approximation and Onsager theory of irreversible thermodynamics. If we assume a linear coupling of sound wave with the order parameter fluctuations in the system, we find that the dispersion which is the relative sound velocity change with frequency behaves as ω 0 ε 0 , where ω is the sound frequency and ε the temperature distance from the critical point. In the ordered region, one also observes a frequency-dependent velocity or dispersion minimum which is shifted from the corresponding attenuation maxima. These phenomena are in good agreement with the calculations of sound velocity in other magnetic systems such as magnetic metals, magnetic insulators, and magnetic semiconductors

  13. Quantum dynamics in transverse-field Ising models from classical networks

    Directory of Open Access Journals (Sweden)

    Markus Schmitt, Markus Heyl

    2018-02-01

    Full Text Available The efficient representation of quantum many-body states with classical resources is a key challenge in quantum many-body theory. In this work we analytically construct classical networks for the description of the quantum dynamics in transverse-field Ising models that can be solved efficiently using Monte Carlo techniques. Our perturbative construction encodes time-evolved quantum states of spin-1/2 systems in a network of classical spins with local couplings and can be directly generalized to other spin systems and higher spins. Using this construction we compute the transient dynamics in one, two, and three dimensions including local observables, entanglement production, and Loschmidt amplitudes using Monte Carlo algorithms and demonstrate the accuracy of this approach by comparisons to exact results. We include a mapping to equivalent artificial neural networks, which were recently introduced to provide a universal structure for classical network wave functions.

  14. Cosmic Magnetic Fields

    Science.gov (United States)

    Sánchez Almeida, J.; Martínez González, M. J.

    2018-05-01

    Magnetic fields play an important role in many astrophysical processes. They are difficult to detect and characterize since often their properties have to be inferred through interpreting the polarization of the light. Magnetic fields are also challenging to model and understand. Magnetized plasmas behave following highly non-linear differential equations having no general solution, so that every astrophysical problem represents a special case to be studied independently. Hence, magnetic fields are often an inconvenient subject which is overlooked or simply neglected (the elephant in the room, as they are dubbed in poster of the school). Such difficulty burdens the research on magnetic fields, which has evolved to become a very technical subject, with many small disconnected communities studying specific aspects and details. The school tried to amend the situation by providing a unifying view of the subject. The students had a chance to understand the behavior of magnetic fields in all astrophysical contexts, from cosmology to the Sun, and from starbursts to AGNs. The school was planed to present a balanced yet complete review of our knowledge, with excursions into the unknown to point out present and future lines of research. The subject of Cosmic Magnetic Fields was split into seven different topics: cosmic magnetic field essentials, solar magnetic fields, stellar magnetic fields, the role of magnetic fields on AGN feedback, magnetic fields in galaxies, magnetic fields in galaxy clusters and at larger scales, and primordial magnetic fields and magnetic fields in the early Universe. The corresponding lectures were delivered by seven well known and experienced scientists that have played key roles in the major advances of the field during the last years: F. Cattaneo, P. Judge, O. Kochukhov, R. Keppens, R. Beck, K. Dolag, and F. Finelli. Their lectures were recorded and are freely available at the IAC website: http://iactalks.iac.es/talks/serie/19.

  15. Magnetic-field-induced dose effects in MR-guided radiotherapy systems: dependence on the magnetic field strength.

    Science.gov (United States)

    Raaijmakers, A J E; Raaymakers, B W; Lagendijk, J J W

    2008-02-21

    Several institutes are currently working on the development of a radiotherapy treatment system with online MR imaging (MRI) modality. The main difference between their designs is the magnetic field strength of the MRI system. While we have chosen a 1.5 Tesla (T) magnetic field strength, the Cross Cancer Institute in Edmonton will be using a 0.2 T MRI scanner and the company Viewray aims to use 0.3 T. The magnetic field strength will affect the severity of magnetic field dose effects, such as the electron return effect (ERE): considerable dose increase at tissue air boundaries due to returning electrons. This paper has investigated how the ERE dose increase depends on the magnetic field strength. Therefore, four situations where the ERE occurs have been simulated: ERE at the distal side of the beam, the lateral ERE, ERE in cylindrical air cavities and ERE in the lungs. The magnetic field comparison values were 0.2, 0.75, 1.5 and 3 T. Results show that, in general, magnetic field dose effects are reduced at lower magnetic field strengths. At the distal side, the ERE dose increase is largest for B = 0.75 T and depends on the irradiation field size for B = 0.2 T. The lateral ERE is strongest for B = 3 T but shows no effect for B = 0.2 T. Around cylindrical air cavities, dose inhomogeneities disappear if the radius of the cavity becomes small relative to the in-air radius of the secondary electron trajectories. At larger cavities (r > 1 cm), dose inhomogeneities exist for all magnetic field strengths. In water-lung-water phantoms, the ERE dose increase takes place at the water-lung transition and the dose decreases at the lung-water transition, but these effects are minimal for B = 0.2 T. These results will contribute to evaluating the trade-off between magnetic field dose effects and image quality of MR-guided radiotherapy systems.

  16. Magnetic-field-induced dose effects in MR-guided radiotherapy systems: dependence on the magnetic field strength

    International Nuclear Information System (INIS)

    Raaijmakers, A J E; Raaymakers, B W; Lagendijk, J J W

    2008-01-01

    Several institutes are currently working on the development of a radiotherapy treatment system with online MR imaging (MRI) modality. The main difference between their designs is the magnetic field strength of the MRI system. While we have chosen a 1.5 Tesla (T) magnetic field strength, the Cross Cancer Institute in Edmonton will be using a 0.2 T MRI scanner and the company Viewray aims to use 0.3 T. The magnetic field strength will affect the severity of magnetic field dose effects, such as the electron return effect (ERE): considerable dose increase at tissue air boundaries due to returning electrons. This paper has investigated how the ERE dose increase depends on the magnetic field strength. Therefore, four situations where the ERE occurs have been simulated: ERE at the distal side of the beam, the lateral ERE, ERE in cylindrical air cavities and ERE in the lungs. The magnetic field comparison values were 0.2, 0.75, 1.5 and 3 T. Results show that, in general, magnetic field dose effects are reduced at lower magnetic field strengths. At the distal side, the ERE dose increase is largest for B = 0.75 T and depends on the irradiation field size for B = 0.2 T. The lateral ERE is strongest for B = 3 T but shows no effect for B = 0.2 T. Around cylindrical air cavities, dose inhomogeneities disappear if the radius of the cavity becomes small relative to the in-air radius of the secondary electron trajectories. At larger cavities (r > 1 cm), dose inhomogeneities exist for all magnetic field strengths. In water-lung-water phantoms, the ERE dose increase takes place at the water-lung transition and the dose decreases at the lung-water transition, but these effects are minimal for B = 0.2 T. These results will contribute to evaluating the trade-off between magnetic field dose effects and image quality of MR-guided radiotherapy systems

  17. Comparison of mechanical concepts for $Nb_3Sn$ high field accelerator magnets

    CERN Document Server

    AUTHOR|(CDS)2084469; Peter, Schmolz

    Several magnets using Nb$_{3}$Sn as conductor are currently developed at CERN; these magnets are either slated for future updates of the LHC or for research purposes relating to future accelerators. The mechanical structure is one of the challenging aspects of superconducting high-field magnets. The main purpose of the mechanical structure is to keep the coils in compression till the emergence of the highest electromagnetic forces that are developed in the ultimate field of the magnet. Any loss of pre-compression during the magnet’s excitation would cause too large deformation of the coil and possibly a quench in the conductor owing to relative movements of strands in contact associated with excessive local heat release. However, too high pre-compression would overstrain the conductor and thereby limit the performance of the magnet. This thesis focuses on the mechanical behaviour of three of these magnets. All of them are based on different mechanical designs, “bladder and key” and “collar-based”, ...

  18. Integrals of the Ising class

    International Nuclear Information System (INIS)

    Bailey, D H; Borwein, J M; Crandall, R E

    2006-01-01

    From an experimental-mathematical perspective we analyse 'Ising-class' integrals. These are structurally related n-dimensional integrals we call C n , D n , E n , where D n is a magnetic susceptibility integral central to the Ising theory of solid-state physics. We first analyse C n := 4/(n factorial) ∫ 0 ∞ ... ∫ 0 ∞ 1/(Σ j=1 n (u j + 1/u j )) 2 du 1 /u 1 ... du n /u n . We had conjectured-on the basis of extreme-precision numerical quadrature-that C n has a finite large-n limit, namely C ∞ = 2 e -2γ , with γ being the Euler constant. On such a numerological clue we are able to prove the conjecture. We then show that integrals D n and E n both decay exponentially with n, in a certain rigorous sense. While C n , D n remain unresolved for n ≥ 5, we were able to conjecture a closed form for E 5 . Our experimental results involved extreme-precision, multidimensional quadrature on intricate integrands; thus, a highly parallel computation was required

  19. Quantum Ising model in transverse and longitudinal fields: chaotic wave functions

    International Nuclear Information System (INIS)

    Atas, Y Y; Bogomolny, E

    2017-01-01

    The construction of a statistical model for eigenfunctions of the Ising model in transverse and longitudinal fields is discussed in detail for the chaotic case. When the number of spins is large, each wave function coefficient has the Gaussian distribution with zero mean and variance calculated from the first two moments of the Hamiltonian. The main part of the paper is devoted to the discussion of various corrections to the asymptotic result. One type of correction is related to higher order moments of the Hamiltonian, and can be taken into account by Gibbs-like formulae. Other corrections are due to symmetry contributions, which manifest as different numbers of non-zero real and complex coefficients. The statistical model with these corrections included agrees well with numerical calculations of wave function moments. (paper)

  20. Conformal invariance in the long-range Ising model

    Directory of Open Access Journals (Sweden)

    Miguel F. Paulos

    2016-01-01

    Full Text Available We consider the question of conformal invariance of the long-range Ising model at the critical point. The continuum description is given in terms of a nonlocal field theory, and the absence of a stress tensor invalidates all of the standard arguments for the enhancement of scale invariance to conformal invariance. We however show that several correlation functions, computed to second order in the epsilon expansion, are nontrivially consistent with conformal invariance. We proceed to give a proof of conformal invariance to all orders in the epsilon expansion, based on the description of the long-range Ising model as a defect theory in an auxiliary higher-dimensional space. A detailed review of conformal invariance in the d-dimensional short-range Ising model is also included and may be of independent interest.

  1. Conformal Invariance in the Long-Range Ising Model

    CERN Document Server

    Paulos, Miguel F; van Rees, Balt C; Zan, Bernardo

    2016-01-01

    We consider the question of conformal invariance of the long-range Ising model at the critical point. The continuum description is given in terms of a nonlocal field theory, and the absence of a stress tensor invalidates all of the standard arguments for the enhancement of scale invariance to conformal invariance. We however show that several correlation functions, computed to second order in the epsilon expansion, are nontrivially consistent with conformal invariance. We proceed to give a proof of conformal invariance to all orders in the epsilon expansion, based on the description of the long-range Ising model as a defect theory in an auxiliary higher-dimensional space. A detailed review of conformal invariance in the d-dimensional short-range Ising model is also included and may be of independent interest.

  2. Conformal invariance in the long-range Ising model

    Energy Technology Data Exchange (ETDEWEB)

    Paulos, Miguel F. [CERN, Theory Group, Geneva (Switzerland); Rychkov, Slava, E-mail: slava.rychkov@lpt.ens.fr [CERN, Theory Group, Geneva (Switzerland); Laboratoire de Physique Théorique de l' École Normale Supérieure (LPTENS), Paris (France); Faculté de Physique, Université Pierre et Marie Curie (UPMC), Paris (France); Rees, Balt C. van [CERN, Theory Group, Geneva (Switzerland); Zan, Bernardo [Institute of Physics, Universiteit van Amsterdam, Amsterdam (Netherlands)

    2016-01-15

    We consider the question of conformal invariance of the long-range Ising model at the critical point. The continuum description is given in terms of a nonlocal field theory, and the absence of a stress tensor invalidates all of the standard arguments for the enhancement of scale invariance to conformal invariance. We however show that several correlation functions, computed to second order in the epsilon expansion, are nontrivially consistent with conformal invariance. We proceed to give a proof of conformal invariance to all orders in the epsilon expansion, based on the description of the long-range Ising model as a defect theory in an auxiliary higher-dimensional space. A detailed review of conformal invariance in the d-dimensional short-range Ising model is also included and may be of independent interest.

  3. The quantum transverse spin-2 Ising model with a bimodal random-field in the pair approximation

    International Nuclear Information System (INIS)

    Canko, O.; Albayrak, E.; Keskin, M.

    2005-01-01

    In this paper, we have investigated the bimodal random-field spin-2 Ising system in a transverse field by combining the pair approximation with the discretized path-integral representation. The exact equations for the second-order phase transition lines and tricritical points are obtained in terms of the random field H, the transverse field G and the coordination number z. It is found that there are some critical values for H and G where the tricritical points disappear for given z. We have also observed that the system presents reentrant behavior which may be caused by the quantum effects and randomness. The phase diagram with respect to the random field and the second-order phase transition temperature are studied extensively for given values of the transverse field and the coordination number

  4. Designing magnets with prescribed magnetic fields

    International Nuclear Information System (INIS)

    Liu Liping

    2011-01-01

    We present a novel design method capable of finding the magnetization densities that generate prescribed magnetic fields. The method is based on the solution to a simple variational inequality and the resulting designs have simple piecewise-constant magnetization densities. By this method, we obtain new designs of magnets that generate commonly used magnetic fields: uniform magnetic fields, self-shielding fields, quadrupole fields and sextupole fields. Further, it is worth noting that this method is not limited to the presented examples, and in particular, three-dimensional designs can be constructed in a similar manner. In conclusion, this novel design method is anticipated to have broad applications where specific magnetic fields are important for the performance of the devices.

  5. Critical behavior of ferromagnetic Ising thin films

    International Nuclear Information System (INIS)

    Cossio, P.; Mazo-Zuluaga, J.; Restrepo, J.

    2006-01-01

    In the present work, we study the magnetic properties and critical behavior of simple cubic ferromagnetic thin films. We simulate LxLxd films with semifree boundary conditions on the basis of the Monte Carlo method and the Ising model with nearest neighbor interactions. A Metropolis dynamics was implemented to carry out the energy minimization process. For different film thickness, in the nanometer range, we compute the temperature dependence of the magnetization, the magnetic susceptibility and the fourth order Binder's cumulant. Bulk and surface contributions of these quantities are computed in a differentiated fashion. Additionally, according to finite size scaling theory, we estimate the critical exponents for the correlation length, magnetic susceptibility, and magnetization. Results reveal a strong dependence of critical temperature and critical exponents on the film thickness. The obtained critical exponents are finally compared to those reported in literature for thin films

  6. Topology optimized and 3D printed polymer-bonded permanent magnets for a predefined external field

    Science.gov (United States)

    Huber, C.; Abert, C.; Bruckner, F.; Pfaff, C.; Kriwet, J.; Groenefeld, M.; Teliban, I.; Vogler, C.; Suess, D.

    2017-08-01

    Topology optimization offers great opportunities to design permanent magnetic systems that have specific external field characteristics. Additive manufacturing of polymer-bonded magnets with an end-user 3D printer can be used to manufacture permanent magnets with structures that had been difficult or impossible to manufacture previously. This work combines these two powerful methods to design and manufacture permanent magnetic systems with specific properties. The topology optimization framework is simple, fast, and accurate. It can also be used for the reverse engineering of permanent magnets in order to find the topology from field measurements. Furthermore, a magnetic system that generates a linear external field above the magnet is presented. With a volume constraint, the amount of magnetic material can be minimized without losing performance. Simulations and measurements of the printed systems show very good agreement.

  7. Unsaturated magnetoconductance of epitaxial La0.7Sr0.3MnO3 thin films in pulsed magnetic fields up to 60 T

    Directory of Open Access Journals (Sweden)

    Wei Niu

    2017-05-01

    Full Text Available We report on the temperature and field dependence of resistance of La0.7Sr0.3MnO3 thin films over a wide temperature range and in pulsed magnetic fields up to 60 T. The epitaxial La0.7Sr0.3MnO3 thin films were deposited by laser molecular beam epitaxy. High magnetic field magnetoresistance curves were fitted by the Brillouin function, which indicated the existence of magnetically polarized regions and the underlying hopping mechanism. The unsaturated magnetoconductance was the most striking finding observed in pulsed magnetic fields up to 60 T. These observations can deepen the fundamental understanding of the colossal magnetoresistance in manganites with strong correlation of transport properties and magnetic ordering.

  8. Reconnection at the earth's magnetopause - Magnetic field observations and flux transfer events

    Science.gov (United States)

    Russell, C. T.

    1984-01-01

    Theoretical models of plasma acceleration by magnetic-field-line reconnection at the earth magnetopause and the high-resolution three-dimensional plasma measurements obtained with the ISEE satellites are compared and illustrated with diagrams, graphs, drawings, and histograms. The history of reconnection theory and the results of early satellite observations are summarized; the thickness of the magnetopause current layer is discussed; problems in analyzing the polarization of current-layer rotation are considered; and the flux-transfer events responsible for periods of patchy reconnection are characterized in detail. The need for further observations and refinements of the theory to explain the initiation of reconnection and identify the mechanism determining whether it is patchy or steady-state is indicated.

  9. Acceleration of auroral particles by magnetic-field aligned electric fields

    International Nuclear Information System (INIS)

    Block, L.P.

    1988-01-01

    Measurements on the S3-3 and Viking satellites appear to show that at least a large fraction of magnetic field-aligned potential drops are made up of multiple double layers. Solitons and double layers in U-shaped potential structures give rise to spiky electric fields also perpendicular to the magnetic field in agreement with satellite measurements. The large scale potential structures associated with inverted V-events are built up of many similar short-lived structures on a small scale. Viking measurements indicate that electric fields parallel to the magnetic field are almost always directed upward

  10. Evidence for the ferromagnetic frustration in a classical spin- 1 / 2 system with multisite interaction in external magnetic field: Exact results

    Science.gov (United States)

    Jurčišinová, E.; Jurčišin, M.

    2017-11-01

    We investigate the influence of the multisite interaction among sites within elementary triangles of the kagome-like recursive lattice on the properties of the classical spin- 1 / 2 ferromagnetic Ising model in the external magnetic field. The exact solution of the model is found and it is shown that the model exhibits a nontrivial structure of the first order as well as second order phase transitions in nonzero external magnetic fields related to the multisite interaction. The equation for the exact determination of the positions of the critical points of the second order phase transitions is derived. The thermodynamic properties of the model are investigated in detail and it is shown that the competition between the ferromagnetic interaction and the multisite interaction leads to the appearance of strong ferromagnetic frustration effects represented by the formation of a nontrivial system of macroscopically degenerated plateau-like and single-point-like ground states. The residual entropies of all ground states are found and the kagome spin-ice-like highly macroscopically degenerated plateau state with nonzero magnetization is identified with the exact residual entropy per site s /kB = ln(4 / 3) / 3 ≈ 0 . 095894. The properties of the specific heat are investigated, its Schottky-type behavior near the single-point ground state values of the magnetic field is identified, the existence of large magnetocaloric effect is discussed, and the existence of the first order phase transitions without the specific heat capacity change is demonstrated.

  11. Magnetization, Low Field Instability and Quench of RHQT Nb(3)Al Strands

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, R.; Wake, M.; Kikuchi, A.; Velev, V.; /Fermilab

    2009-01-01

    Since 2005, we made and tested three RHQT Nb{sub 3}Al strands, one with Nb matrix and two with Ta matrix, which are fully stabilized with Cu electroplating. We observed anomalously large magnetization curves extending beyond 1 to 1.5 Tesla with the F1 Nb matrix strand at 4.2 K, when we measured its magnetization with a balanced coil magnetometer. This problem was eliminated with the Ta matrix strands operating at 4.2 K. But with these strands a similar but smaller anomalous magnetization was observed at 1.9 K. We studied these phenomena with FEM. With the F1 Nb matrix strand, it is explained that at low external field, inter-filamentary coupling currents in the outer layers of sub-elements create a shielding effect. It reduces the inside field, keeps the inside Nb matrix superconductive, and stands against a higher outside field beyond the Hc of Nb. At an even higher external field, the superconductivity of the whole Nb matrix collapses and releases a large amount of energy, which may cause a big quench. Depending on the size of the energy in the strand or the cable, a magnet could quench, causing the low field instability. Some attempt to analyze the anomaly with FEM is presented.

  12. Long-range transverse Ising model built with dipolar condensates in two-well arrays

    International Nuclear Information System (INIS)

    Li, Yongyao; Pang, Wei; Xu, Jun; Lee, Chaohong; Malomed, Boris A; Santos, Luis

    2017-01-01

    Dipolar Bose–Einstein condensates in an array of double-well potentials realize an effective transverse Ising model with peculiar inter-layer interactions, that may result under proper conditions in an anomalous first-order ferromagnetic–antiferromagnetic phase transition, and non-trivial phases due to frustration. The considered setup allows as well for the study of Kibble–Zurek defect formation, whose kink statistics follows that expected from the universality class of the mean-field one-dimensional transverse Ising model. Furthermore, random occupation of each layer of the stack leads to random effective Ising interactions and local transverse fields, that may lead to the Anderson-like localization of imbalance perturbations. (paper)

  13. Microstructural, magnetic and magnetostrictive properties of Tb0.3Dy0.7Fe1.95 prepared by solidification in a high magnetic field

    International Nuclear Information System (INIS)

    Liu Tie; Liu Yin; Wang Qiang; Gao Pengfei; He Jicheng; Iwai, Kazuhiko

    2013-01-01

    The microstructure evolution and magnetization and magnetostriction properties of Tb 0.3 Dy 0.7 Fe 1.95 alloy solidified in a high magnetic field were investigated. A cellular microstructure was produced, with the grains highly aligned along the direction of the magnetic field. The (Tb,Dy)Fe 2 phase was highly oriented, with its 〈1 1 1〉 axis along the magnetic field direction. The easy magnetization direction of the alloy lay along the magnetic field direction. The magnetostriction at room temperature significantly increased to double that of the sample prepared without high magnetic field; in addition, a sharp rise in the initial magnetostriction at low fields was observed. Applying a high magnetic field during the solidification process is proposed as an effective route for fabricating 〈1 1 1〉 oriented Tb–Dy–Fe compounds, and improving their magnetic and magnetostrictive properties. (paper)

  14. Plasma and magnetic field variations in the distant magnetotail associated with near-earth substorm effects

    Science.gov (United States)

    Baker, D. N.; Bame, S. J.; Mccomas, D. J.; Zwickl, R. D.; Slavin, J. A.; Smith, E. J.

    1987-01-01

    Examination of many individual event periods in the ISEE 3 deep-tail data set has suggested that magnetospheric substorms produce a characteristic pattern of effects in the distant magnetotail. During the growth, or tail-energy-storage phase of substorms, the magnetotail appears to grow diametrically in size, often by many earth radii. Subsequently, after the substorm expansive phase onset at earth, the distant tail undergoes a sequence of plasma, field, and energetic-particle variations as large-scale plasmoids move rapidly down the tail following their disconnection from the near-earth plasma sheet. ISEE 3 data are appropriate for the study of these effects since the spacecraft remained fixed within the nominal tail location for long periods. Using newly available auroral electrojet indices (AE and AL) and Geo particle data to time substorm onsets at earth, superposed epoch analyses of ISEE 3 and near-earth data prior to, and following, substorm expansive phase onsets have been performed. These analyses quantify and extend substantially the understanding of the deep-tail pattern of response to global substorm-induced dynamical effects.

  15. Strain and electric field mediated manipulation of magnetism in La_(_1_-_x_)Sr_xMnO_3/BaTiO_3 heterostructures

    International Nuclear Information System (INIS)

    Schmitz, Markus

    2016-01-01

    Heterostructures of ferromagnetic La_1_-_xSr_xMnO_3 (LSMO) and ferroelectric BaTiO_3 (BTO) were produced and investigated for their structural and magnetic properties. The combination of these ferroic properties can lead to an artificial multiferroic. Special emphasis was given to the manipulation of magnetic properties by applying electric fields. A magneto-electric coupling could be observed in the heterostructures under investigation. Epitaxial LSMO thin films were grown on BTO substrates using a state-of-the-art oxide molecular beam epitaxy (OMBE) and a high oxygen sputtering system (HOPSS). Stoichiometric La_1_-_xSr_xMnO_3 films with doping levels of x=0.5 and x=0.3 were produced. The film quality in terms of roughness and crystalline structure was confirmed by X-ray scattering methods. The presence of structural domains in the BaTiO_3 single crystal substrate, whose proportion could be altered due to the application of electric fields, was shown by X-ray diffraction. Tensile strain is induced into the epitaxial La_1_-_xSr_xMnO_3 films in the whole temperature range under investigation. The magnetization of LSMO alteres by the variation of strain induced into the film, generated by the different structural phases of single crystal BaTiO_3 substrates. The magnetization shows sharp steps at the structural phase transition temperatures of BTO. The evaluation of magnetic hysteresis loops reveals a change of the magnetic anisotropy of LSMO for each structural phase of BTO, but also within the orthorhombic phase. Special focus was given to the manipulation of magnetic properties by the application of electric fields. A newly established measurement option was used to determine the magnetic response to an applied electric field as a function of temperature and magnetic field. The electrically induced modification of the magnetization is profound near the structural phase transition temperatures. Electrical hysteresis loops give a detailed view on the influence of the

  16. The critical 1-arm exponent for the ferromagnetic Ising model on the Bethe lattice

    Science.gov (United States)

    Heydenreich, Markus; Kolesnikov, Leonid

    2018-04-01

    We consider the ferromagnetic nearest-neighbor Ising model on regular trees (Bethe lattice), which is well-known to undergo a phase transition in the absence of an external magnetic field. The behavior of the model at critical temperature can be described in terms of various critical exponents; one of them is the critical 1-arm exponent ρ which characterizes the rate of decay of the (root) magnetization as a function of the distance to the boundary. The crucial quantity we analyze in this work is the thermal expectation of the root spin on a finite subtree, where the expected value is taken with respect to a probability measure related to the corresponding finite-volume Hamiltonian with a fixed boundary condition. The spontaneous magnetization, which is the limit of this thermal expectation in the distance between the root and the boundary (i.e., in the height of the subtree), is known to vanish at criticality. We are interested in a quantitative analysis of the rate of this convergence in terms of the critical 1-arm exponent ρ. Therefore, we rigorously prove that ⟨σ0⟩ n +, the thermal expectation of the root spin at the critical temperature and in the presence of the positive boundary condition, decays as ⟨σ0 ⟩ n +≈n-1/2 (in a rather sharp sense), where n is the height of the tree. This establishes the 1-arm critical exponent for the Ising model on regular trees (ρ =1/2 ).

  17. Magnetic Field

    DEFF Research Database (Denmark)

    Olsen, Nils

    2015-01-01

    he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics...... of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere, and oceans, and by currents induced...... in the Earth by time-varying external fields. These sources have their specific characteristics in terms of spatial and temporal variations, and their proper separation, based on magnetic measurements, is a major challenge. Such a separation is a prerequisite for remote sensing by means of magnetic field...

  18. Inhomogeneous quenches in the transverse field Ising chain: scaling and front dynamics

    Directory of Open Access Journals (Sweden)

    Márton Kormos

    2017-09-01

    Full Text Available We investigate the non-equilibrium dynamics of the transverse field quantum Ising chain evolving from an inhomogeneous initial state given by joining two macroscopically different semi-infinite chains. We obtain integral expressions for all two-point correlation functions of the Jordan-Wigner Majorana fermions at any time and for any value of the transverse field. Using this result, we compute analytically the profiles of various physical observables in the space-time scaling limit and show that they can be obtained from a hydrodynamic picture based on ballistically propagating quasiparticles. Going beyond the hydrodynamic limit, we analyze the approach to the non-equilibrium steady state and find that the leading late time corrections display a lattice effect. We also study the fine structure of the propagating fronts which are found to be described by the Airy kernel and its derivatives. Near the front we observe the phenomenon of energy back-flow where the energy locally flows from the colder to the hotter region.

  19. Magnetic field effects on electric behavior of [Fe(CN6]3− at bare and membrane-coated electrodes

    Directory of Open Access Journals (Sweden)

    Govindachetty Saravanan, Katsuhiko Fujio and Sumio Ozeki

    2008-01-01

    Full Text Available The cyclic voltammetric behavior of [Fe(CN6]3− was investigated under homogeneous magnetic fields perpendicular to the electrode surface in order to determine the effects of magnetic fields on the distribution of an Fe2+/Fe3+ redox couple. The cathodic current was enhanced much more than the anodic current by a homogeneous magnetic field, suggesting that the concentration gradient of paramagnetic [Fe(CN6]3− and diamagnetic [Fe(CN6]4− formed at an electrode surface may also contribute to the asymmetric current. The apparent diffusion coefficient of the redox couple increased by over 30% in both cathodic and anodic processes upon applying a magnetic field. For a gold electrode coated with dioctadecyldimethylammonium, the application of a magnetic field perpendicular to the surface increased the peak-to-peak separation, and enhanced the asymmetric current. It is inferred that the application of a magnetic field promotes the electron-tunneling process by tilting chain molecules in the barrier membrane.

  20. Quantitative analysis of magnetic resonance imaging susceptibility artifacts caused by neurosurgical biomaterials. Comparison of 0.5, 1.5, and 3.0 tesla magnetic fields

    International Nuclear Information System (INIS)

    Matsuura, Hideki; Inoue, Takashi; Ogasawara, Kuniaki; Sasaki, Makoto; Konno, Hiromu; Kuzu, Yasutaka; Nishimoto, Hideaki; Ogawa, Akira

    2005-01-01

    Magnetic resonance (MR) imaging is an important diagnostic tool for neurosurgical diseases but susceptibility artifacts caused by biomaterial instrumentation frequently causes difficulty in visualizing postoperative changes. The susceptibility artifacts caused by neurosurgical biomaterials were compared quantitatively by 0.5, 1.5, and 3.0 Tesla MR imaging. MR imaging of uniform size and shape of pieces ceramic (zirconia), pure titanium, titanium alloy, and cobalt-based alloy was performed at 0.5, 1.5, and 3.0 Tesla. A linear region of interest was defined across the center of the biomaterial in the transverse direction, and the susceptibility artifact diameter was calculated. Susceptibility artifacts developed around all biomaterials at all magnetic field strengths. The artifact diameters caused by pure titanium, titanium alloy, and cobalt-based alloy increased in the order of 0.5, 1.5, to 3.0 Tesla magnetic fields. The artifact diameter of ceramic was not influenced by magnetic field strength, and was the smallest of all biomaterials at all magnetic field strengths. The artifacts caused by biomaterials except ceramic increase with the magnetic field strength. Ceramic instrumentation will minimize artifacts in all magnetic fields. (author)

  1. The lightcone bootstrap and the spectrum of the 3d Ising CFT

    Energy Technology Data Exchange (ETDEWEB)

    Simmons-Duffin, David [School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey 08540 (United States); Walter Burke Institute for Theoretical Physics, Caltech, Pasadena, California 91125 (United States)

    2017-03-15

    We compute numerically the dimensions and OPE coefficients of several operators in the 3d Ising CFT, and then try to reverse-engineer the solution to crossing symmetry analytically. Our key tool is a set of new techniques for computing infinite sums of SL(2,ℝ) conformal blocks. Using these techniques, we solve the lightcone bootstrap to all orders in an asymptotic expansion in large spin, and suggest a strategy for going beyond the large spin limit. We carry out the first steps of this strategy for the 3d Ising CFT, deriving analytic approximations for the dimensions and OPE coefficients of several infinite families of operators in terms of the initial data {Δ_σ,Δ_ϵ,f_σ_σ_ϵ,f_ϵ_ϵ_ϵ,c_T}. The analytic results agree with numerics to high precision for about 100 low-twist operators (correctly accounting for O(1) mixing effects between large-spin families). Plugging these results back into the crossing equations, we obtain approximate analytic constraints on the initial data.

  2. Magnetic field considerations in fusion power plant environs

    International Nuclear Information System (INIS)

    Liemohn, H.B.; Lessor, D.L.; Duane, B.H.

    1976-09-01

    A summary of magnetic field production mechanisms and effects is given. Discussions are included on the following areas: (1) stray magnetic and electric fields from tokamaks, (2) methods for reducing magnetic fields, (3) economics of magnetic field reductions, (4) forces on magnetizable objects near magnetic confinement fusion reactors, (5) electric field transients in tokamaks, (6) attenuation and decay of electromagnetic fields, and (7) magnetic field transients from tokamak malfunctions

  3. Zero-temperature renormalization of the 2D transverse Ising model

    International Nuclear Information System (INIS)

    Kamieniarz, G.

    1982-08-01

    A zero-temperature real-space renormalization-group method is applied to the transverse Ising model on planar hexagonal, triangular and quadratic lattices. The critical fields and the critical exponents describing low-field large-field transition are calculated. (author)

  4. Terahertz probes of magnetic field induced spin reorientation in YFeO{sub 3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Xian; Jiang, Junjie; Ma, Guohong, E-mail: ghma@staff.shu.edu.cn [Department of Physics, Shanghai University, Shanghai 200444 (China); Jin, Zuanming [Department of Physics, Shanghai University, Shanghai 200444 (China); Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany); Wang, Dongyang; Tian, Zhen; Han, Jiaguang [Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072 (China); Cheng, Zhenxiang [Department of Physics, Shanghai University, Shanghai 200444 (China); Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, New South Wales 2522 (Australia)

    2015-03-02

    Using the terahertz time-domain spectroscopy, we demonstrate the spin reorientation of a canted antiferromagnetic YFeO{sub 3} single crystal, by evaluating the temperature and magnetic field dependence of resonant frequency and amplitude for the quasi-ferromagnetic (FM) and quasi-antiferromagnetic modes (AFM), a deeper insight into the dynamics of spin reorientation in rare-earth orthoferrites is established. Due to the absence of 4f-electrons in Y ion, the spin reorientation of Fe sublattices can only be induced by the applied magnetic field, rather than temperature. In agreement with the theoretical predication, the frequency of FM mode decreases with magnetic field. In addition, an obvious step of spin reorientation phase transition occurs with a relatively large applied magnetic field of 4 T. By comparison with the family members of RFeO{sub 3} (R = Y{sup 3+} or rare-earth ions), our results suggest that the chosen of R would tailor the dynamical rotation properties of Fe ions, leading to the designable spin switching in the orthoferrite antiferromagnetic systems.

  5. Critical magnetic behaviour in one and two dimensions

    International Nuclear Information System (INIS)

    Koebler, U.; Hoser, A.

    2007-01-01

    Critical magnetic data of magnets in which the phase transition is driven by one-dimensional (1D) or two-dimensional (2D) interactions are examined. Characteristic for 1D (2D) phase transitions is that only the longitudinal (in plane) correlation length diverges. The transverse (inter-layer) interactions are then not relevant although they may be finite. The condition for 1D (2D) phase transitions is that the ratio of transverse (inter-layer) to longitudinal (in plane) interactions is below some threshold value. This threshold defines the bandwidth of the 1D (2D) universality class. On the other hand, three-dimensional (3D) magnetic Bragg scattering relies on a finite transverse (inter-layer) correlation length. If this correlation length is relatively long the spin structure appears 3D. For materials with a pure spin moment the dimensionality can now conveniently be inferred from the universal power function by which the order parameter approaches saturation at the stable fixed point T=0. Using this criterion it is concluded that the critical behaviour of 2D magnets is essentially of the 2D Ising type but for 1D magnets of the 3D Ising type. Slight deviations from the ideal model exponents are, however, frequently observed. Universality for T->0 is not of the Ising type in the investigated magnets with a 3D spin

  6. Quantum-information approach to the Ising model: Entanglement in chains of qubits

    International Nuclear Information System (INIS)

    Stelmachovic, Peter; Buzek, Vladimir

    2004-01-01

    Simple physical interactions between spin-1/2 particles may result in quantum states that exhibit exotic correlations that are difficult to find if one simply explores state spaces of multipartite systems. In particular, we present a detailed investigation of the well-known Ising model of a chain (ring) of spin-1/2 particles (qubits) in a transverse magnetic field. We present explicit expressions for eigenstates of the model Hamiltonian for arbitrary number of spin-1/2 particles in the chain in the standard (computer) basis, and we investigate quantum entanglement between individual qubits. We analyze bipartite as well as multipartite entanglement in the ground state of the model. In particular, we show that bipartite entanglement between pairs of qubits of the Ising chain (measured in terms of a concurrence) as a function of the parameter λ has a maximum around the point λ=1, and it monotonically decreases for large values of λ. We prove that in the limit λ→∞ this state is locally unitary equivalent to an N-partite Greenberger-Horn-Zeilinger state. We also analyze a very specific eigenstate of the Ising Hamiltonian with a zero eigenenergy (we denote this eigenstate as the X-state). This X-state exhibits the 'extreme' entanglement in a sense that an arbitrary subset A of k≤n qubits in the Ising chain composed of N=2n+1 qubits is maximally entangled with the remaining qubits (set B) in the chain. In addition, we prove that by performing a local operation just on the subset B, one can transform the X-state into a direct product of k singlets shared by the parties A and B. This property of the X-state can be utilized for new secure multipartite communication protocols

  7. Multi spin-flip dynamics: a solution of the one-dimensional Ising model

    International Nuclear Information System (INIS)

    Novak, I.

    1990-01-01

    The Glauber dynamics of interacting Ising spins (the single spin-flip dynamics) is generalized to p spin-flip dynamics with a simultaneous flip of up to p spins in a single configuration move. The p spin-flip dynamics is studied of the one-dimensional Ising model with uniform nearest-neighbour interaction. For this case, an exact relation is given for the time dependence of magnetization. It was found that the critical slowing down in this model could be avoided when p spin-flip dynamics with p>2 was considered. (author). 17 refs

  8. Monte Carlo study of the magnetic properties of GdSb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi Bouzid, Safi, BP, 46000 63 (Morocco); LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Bahmad, L. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France); Hamedoun, M. [Institute of Layers and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Institute of Layers and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco)

    2014-03-15

    The magnetic properties of antiferromagnetic GdSb layers have been studied using Monte Carlo simulations within the Ising model framework. The considered Hamiltonian includes first nearest-neighbor, an external magnetic field and a crystal field. The thermal magnetizations and magnetic susceptibilities are computed for a fixed size. In addition, the Néel temperature is deduced. The magnetization versus the exchange interactions and crystal field are studied for a fixed system size, N=5, 7 and 9 sites. The magnetic hysteresis cycle versus temperature is also established. - Highlights: • Determination of the Néel temperature of GdSb by MC simulations. • Magnetic hysteresis cycle of GdSb. • Determination of saturation magnetization and field coercive in GdSb.

  9. The enhancement of the magnetic properties of α-Fe{sub 2}O{sub 3} nanocatalyst using an external magnetic field for the production of green ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Alqasem, Bilal, E-mail: bilalalqasem@yahoo.com; Yahya, Noorhana, E-mail: noorhana_yahya@petronas.com.my; Qureshi, Saima, E-mail: saima_qureshi_25@yahoo.com; Irfan, Muhammad, E-mail: irfan-mohammad@hotmail.com; Ur Rehman, Zia, E-mail: zia545@hotmail.com; Soleimani, Hassan, E-mail: hassan.soleimani@petronas.com.my

    2017-03-15

    Highlights: • External magnetic field was applied during syntheses of α-Fe{sub 2}O{sub 3} nanocatalyst. • α-Fe{sub 2}O{sub 3} nanocatalyst with enhanced magnetic properties was synthesized. • Effect of magnetic properties and morphology of α-Fe{sub 2}O{sub 3} on ammonia yield was tested. • α-Fe{sub 2}O{sub 3} nanowires with improved saturation magnetization created high ammonia yield. • A maximum green ammonia yield of 24.174 × 10{sup −3} mol h{sup −1} g cat{sup −1} was produced. - Abstract: Hematite nanocatalysts with improved magnetic properties were synthesized using electrical resistive heating under the presence of a magnetic field and a gaseous environment containing oxygen and nitrogen. The synthesis temperature was varied from 500–850 °C in the absence and presence of a static magnetic field of 0.25 T. VSM hysteresis results showed that there is a clear improve in the magnetic properties of the nanocatalysts when an external magnetic field was used during the synthesis. It also showed that the nanowires amongst other shapes hold the highest saturation magnetization value. The produced α-Fe{sub 2}O{sub 3} nanocatalysts were used for ammonia synthesis under an external magnetic field strength ranging between 0.4–2 T. Correspondingly, (24.174 mmol h{sup −1} g cat{sup −1}) ammonia was yielded by applying an external magnetic field of 1.2 T and using the α-Fe{sub 2}O{sub 3} nanowires synthesized at 700 °C with the highest saturation magnetization value of 189.43 emu/g.

  10. FOREWORD: Focus on Materials Analysis and Processing in Magnetic Fields Focus on Materials Analysis and Processing in Magnetic Fields

    Science.gov (United States)

    Sakka, Yoshio; Hirota, Noriyuki; Horii, Shigeru; Ando, Tsutomu

    2009-03-01

    Recently, interest in the applications of feeble (diamagnetic and paramagnetic) magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in excess of 10 000 times that of conventional 0.1 T permanent magnets. Consequently, many interesting phenomena have been observed over the last decade, such as the Moses effect, magnetic levitation and the alignment of feeble magnetic materials. Researchers in this area are widely spread around the world, but their number in Japan is relatively high, which might explain the success of magnetic field science and technology in Japan. Processing in magnetic fields is a rapidly expanding research area with a wide range of promising applications in materials science. The 3rd International Workshop on Materials Analysis and Processing in Magnetic Fields (MAP3), which was held on 14-16 May 2008 at the University of Tokyo, Japan, focused on various topics including magnetic field effects on chemical, physical, biological, electrochemical, thermodynamic and hydrodynamic phenomena; magnetic field effects on the crystal growth and processing of materials; diamagnetic levitation, the magneto-Archimedes effect, spin chemistry, magnetic orientation, control of structure by magnetic fields, magnetic separation and purification, magnetic-field-induced phase transitions, properties of materials in high magnetic fields, the development of NMR and MRI, medical applications of magnetic fields, novel magnetic phenomena, physical property measurement by magnetic fields, and the generation of high magnetic fields. This focus issue compiles 13 key papers selected from the proceedings of MAP3. Other

  11. MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS

    International Nuclear Information System (INIS)

    2004-01-01

    Several recent applications for fast ramped magnets have been found that require rapid measurement of the field quality during the ramp. (In one instance, accelerator dipoles will be ramped at 1 T/sec, with measurements needed to the accuracy typically required for accelerators.) We have built and tested a new type of magnetic field measuring system to meet this need. The system consists of 16 stationary pickup windings mounted on a cylinder. The signals induced in the windings in a changing magnetic field are sampled and analyzed to obtain the field harmonics. To minimize costs, printed circuit boards were used for the pickup windings and a combination of amplifiers and ADPs used for the voltage readout system. New software was developed for the analysis. Magnetic field measurements of a model dipole developed for the SIS200 accelerator at GSI are presented. The measurements are needed to insure that eddy currents induced by the fast ramps do not impact the field quality needed for successful accelerator operation

  12. Split-Field Magnet facility upgraded

    CERN Multimedia

    CERN PhotoLab

    1977-01-01

    The Split Field Magnet (SFM) was the largest spectrometer for particles from beam-beam collisions in the ISR. It could determine particle momenta in a large solid angle, but was designed mainly for the analysis of forward travelling particles.As the magnet was working on the ISR circulating beams, its magnetic field had to be such as to restore the correct proton orbit.The SFM, therefore, produced zero field at the crossing point and fields of opposite signs upstream and downstream of it and was completed by 2 large and 2 small compensator magnets. The gradient effects were corrected by magnetic channels equipped with movable flaps. The useful magnetic field volume was 28 m3, the induction in the median plane 1.14 T, the gap heigth 1.1 m, the length 10.5 m, the weight about 1000 ton. Concerning the detectors, the SFM was the first massive application of multiwire proportional chambers (about 70000 wires) which filled the main and the large compensator magnets. In 1976 an improved programme was started with tw...

  13. Charge-regulation phase transition on surface lattices of titratable sites adjacent to electrolyte solutions: An analog of the Ising antiferromagnet in a magnetic field

    Science.gov (United States)

    Shore, Joel D.; Thurston, George M.

    2018-01-01

    We report a charge-patterning phase transition on two-dimensional square lattices of titratable sites, here regarded as protonation sites, placed in a low-dielectric medium just below the planar interface between this medium and a salt solution. We calculate the work-of-charging matrix of the lattice with use of a linear Debye-Hückel model, as input to a grand-canonical partition function for the distribution of occupancy patterns. For a large range of parameter values, this model exhibits an approximate inverse cubic power-law decrease of the voltage produced by an individual charge, as a function of its in-lattice separation from neighboring titratable sites. Thus, the charge coupling voltage biases the local probabilities of proton binding as a function of the occupancy of sites for many neighbors beyond the nearest ones. We find that even in the presence of these longer-range interactions, the site couplings give rise to a phase transition in which the site occupancies exhibit an alternating, checkerboard pattern that is an analog of antiferromagnetic ordering. The overall strength W of this canonical charge coupling voltage, per unit charge, is a function of the Debye length, the charge depth, the Bjerrum length, and the dielectric coefficients of the medium and the solvent. The alternating occupancy transition occurs above a curve of thermodynamic critical points in the (pH-pK,W) plane, the curve representing a charge-regulation analog of variation of the Néel temperature of an Ising antiferromagnet as a function of an applied, uniform magnetic field. The analog of a uniform magnetic field in the antiferromagnet problem is a combination of pH-pK and W, and 1/W is the analog of the temperature in the antiferromagnet problem. We use Monte Carlo simulations to study the occupancy patterns of the titratable sites, including interactions out to the 37th nearest-neighbor category (a distance of 74 lattice constants), first validating simulations through

  14. The magnetic field of Mars according to data of Mars-3 and Mars-5 space vehicles

    International Nuclear Information System (INIS)

    Dolginov, Sh.Sh.; Eroshenko, E.G.; Zhuzgov, L.N.

    1975-01-01

    Magnitograms obtained by the space probe ''Mars-5'' on the evening and day sides as well as those from the ''Mars-3'' obtained earlier suggest the following: In the vicinity of Mars there exists a shock front and its disposition is tracked at various angles to the direction to the sun. Magnetometers have registered a region in space where magnetic field features the properties of a magnetosphere field in its topology and action on plasma. The magnetic field in the region of the ''magnitosphere'' does not change its sign when the interplanetary field does shile in adjacent boundary regions the regular part of the field changes its sign when that of the interplanetary field does. The configuration and dimensions of the ''magnitosphere'' depend on thesolar wind intensity. On the day side (''Mars-3'') the magnitospheric field ceases to be registered at an altitude of 2200km, whereas on the night side (''Mars-5'') the regular field is traced up to 7500-9500km from the planet surface. All the above unambiguously suggests that the planet Mars has its own magnetic field. Under the influence of the solar wind the field takes the characteristic form: it is limited on the day side and elongated on the night one. The topology oif force lines is explicable if one assumes that the axis of the Mars magnetic dipole is inclined to the rotation axis at an abgle of 15-20deg. The northern magnetic pole of the dipole is licated in the northern hemisphere, i.e. the Mars fields in their regularity are opposite to the geomagnetic field. The magnetic moment of the Mars dipole is equal to M=2.5x10 22 Gauss.cm 3 . (author)

  15. Tricritical Ising model with a boundary

    International Nuclear Information System (INIS)

    De Martino, A.; Moriconi, M.

    1998-03-01

    We study the integrable and supersymmetric massive φ (1,3) deformation of the tricritical Ising model in the presence of a boundary. We use constraints from supersymmetry in order to compute the exact boundary S-matrices, which turn out to depend explicitly on the topological charge of the supersymmetry algebra. We also solve the general boundary Yang-Baxter equation and show that in appropriate limits the general reflection matrices go over the supersymmetry preserving solutions. Finally, we briefly discuss the possible connection between our reflection matrices and boundary perturbations within the framework of perturbed boundary conformal field theory. (author)

  16. Criticality of the random-site Ising model: Metropolis, Swendsen-Wang and Wolff Monte Carlo algorithms

    Directory of Open Access Journals (Sweden)

    D.Ivaneyko

    2005-01-01

    Full Text Available We apply numerical simulations to study of the criticality of the 3D Ising model with random site quenched dilution. The emphasis is given to the issues not being discussed in detail before. In particular, we attempt a comparison of different Monte Carlo techniques, discussing regions of their applicability and advantages/disadvantages depending on the aim of a particular simulation set. Moreover, besides evaluation of the critical indices we estimate the universal ratio Γ+/Γ- for the magnetic susceptibility critical amplitudes. Our estimate Γ+/Γ- = 1.67 ± 0.15 is in a good agreement with the recent MC analysis of the random-bond Ising model giving further support that both random-site and random-bond dilutions lead to the same universality class.

  17. Magnetic field compression using pinch-plasma

    International Nuclear Information System (INIS)

    Koyama, K.; Tanimoto, M.; Matsumoto, Y.; Veno, I.

    1987-01-01

    In a previous report, the method for ultra-high magnetic field compression by using the pinchplasma was discussed. It is summarized as follows. The experiment is performed with the Mather-type plasma focus device tau/sub 1/4/ = 2 μs, I=880 kA at V=20 kV). An initial DC magnetic field is fed by an electromagnet embedded in the inner electrode. The axial component of the magnetic field diverges from the maximum field of 1 kG on the surface of the inner electrode. The density profile deduced from a Mach-Zehnder interferogram with a 2-ns N/sub 2/-laser shows a density dip lasting for 30 ns along the axes. Using the measured density of 8 x 10/sup 18/ cm/sup -3/, the temperature of 1.5 keV and the pressure balance relation, the magnitude of the trapped magnetic field is estimated to be 1.0 MG. The magnitude of the compressed magnetic field is also measured by Faraday rotation in a single-mode quartz fiber and a magnetic pickup soil. A protective polyethylene tube (3-mm o.d.) is used along the central axis through the inner electrode and the discharge chamber. The peak value of the compressed field range from 150 to 190 kG. No signal of the magnetic field appears up to the instance of the maximum pinch

  18. The optimization of NbTi-Nb/sub 3/Sn high field superconducting magnet used for physics experiments

    International Nuclear Information System (INIS)

    Han, B.; Han, S.; Feng, Z.X.

    1989-01-01

    The approach to the optimum cost design of multigraded NbTi-Nb/sub 3/Sn high field superconducting magnet is proposed. Investigation shows that by reasonably choosing the contribution of NbTi and Nb/sub 3/Sn coils to the central field required and properly increasing the parameters β of both NbTi and Nb/sub 2/Sn coils, the optimum cost design of the NbTi-Nb/sub 3/Sn solenoid magnet can be obtained. This is the base on which the minimum cost design of multi-graded NbTi-Nb/sub 3/Sn high field superconducting magnet is reached. As an example, a calculation of a 14T three graded NbT-Nb/sub 3/Sn superconducting magnet with a bore of 31mm in diameter is given

  19. The interaction of a very large interplanetary magnetic cloud with the magnetosphere and with cosmic rays

    International Nuclear Information System (INIS)

    Lepping, R.P.; Burlaga, L.F.; Ogilvie, K.W.; Tsurutani, B.T.; Lazarus, A.J.; Evans, D.S.; Klein, L.W.

    1991-01-01

    A large interplanetary magnetic cloud has been observed in the mid-December 1982 data from ISEE 3. It is estimated to have a heliocentric radial extent of approx-gt 0.4 AU, making it one of the largest magnetic clouds yet observed at 1 AU. The magnetic field measured throughout the main portion of the cloud was fairly tightly confined to a plane as it changed direction by 174 degree while varying only moderately in magnitude. Throughout nearly the entire duration of the cloud's passage, IMP 8 was located in the Earth's dawn magnetosheath providing observations of this cloud's interaction with the bow shock and magnetopause; the cloud is shown to maintain its solar wind characteristics during the interaction. Near the end of the cloud passage, at 0806 UT on December 17, ISEE 3 (and IMP 8 at nearly the same time) observed an oblique fast forward interplanetary shock closely coincident in time with a geomagnetic storm sudden commencement. The shock, moving much faster than the cloud (radial speeds of 700 and 390 km/s, respectively, on the average), was in the process of overtaking the cloud. The index Dst decreased monotonically by ∼ 130 nT during the 2-day cloud passage by the Earth and was well correlated with the B z component of the interplanetary magnetic field. There was no significant decrease in the cosmic ray intensity recorded by ground-based neutron monitors at this time of rather strong, smoothly changing fields. However, a Forbush decrease did occur immediately after the interplanetary shock, during a period of significant field turbulence. Thus a large, smooth, interplanetary helical magnetic field configuration engulfing the Earth does not necessarily deflect cosmic rays sufficiently to cause a Forbush decrease, but there is a suggestion that such a decrease may be caused by particle scattering by turbulent magnetic fields

  20. A neutron scattering study of the quasi-one-dimensional, dilute Ising-like antiferromagnet CsCo0.83Mg0.17Br3

    International Nuclear Information System (INIS)

    Rogge, R.B.; Gaulin, B.D.; Harrison, A.

    1992-01-01

    Neutron scattering measurements have been performed on a single crystal sample of CsCo 0.83 Mg 0.17 Br 3 , a quasi-one-dimensional, Ising-like antiferromagnet. Residual three-dimensional interactions between the dilute magnetic chains precipitate a phase transition to long range order at T N ∼ 8.5 K, and short range correlations persist as high as 40 K. Relatively high energy inelastic scattering from both ''bulk'' spin wave modes and ''end'' modes is observed from the finite chains. The low energy inelastic spectrum is dominated by soliton scattering due to anti-phase domain walls propagating along the finite chains

  1. Finite-range-scaling analysis of metastability in an Ising model with long-range interactions

    International Nuclear Information System (INIS)

    Gorman, B.M.; Rikvold, P.A.; Novotny, M.A.

    1994-01-01

    We apply both a scalar field theory and a recently developed transfer-matrix method to study the stationary properties of metastability in a two-state model with weak, long-range interactions: the Nx∞ quasi-one-dimensional Ising model. Using the field theory, we find the analytic continuation f of the free energy across the first-order transition, assuming that the system escapes the metastable state by the nucleation of noninteracting droplets. We find that corrections to the field dependence are substantial, and, by solving the Euler-Lagrange equation for the model numerically, we have verified the form of the free-energy cost of nucleation, including the first correction. In the transfer-matrix method, we associate with the subdominant eigenvectors of the transfer matrix a complex-valued ''constrained'' free-energy density f α computed directly from the matrix. For the eigenvector with an associated magnetization most strongly opposed to the applied magnetic field, f α exhibits finite-range scaling behavior in agreement with f over a wide range of temperatures and fields, extending nearly to the classical spinodal. Some implications of these results for numerical studies of metastability are discussed

  2. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru

    2003-01-01

    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  3. Tests of a 3D Self Magnetic Field Solver in the Finite Element Gun Code MICHELLE

    CERN Document Server

    Nelson, Eric M

    2005-01-01

    We have recently implemented a prototype 3d self magnetic field solver in the finite-element gun code MICHELLE. The new solver computes the magnetic vector potential on unstructured grids. The solver employs edge basis functions in the curl-curl formulation of the finite-element method. A novel current accumulation algorithm takes advantage of the unstructured grid particle tracker to produce a compatible source vector, for which the singular matrix equation is easily solved by the conjugate gradient method. We will present some test cases demonstrating the capabilities of the prototype 3d self magnetic field solver. One test case is self magnetic field in a square drift tube. Another is a relativistic axisymmetric beam freely expanding in a round pipe.

  4. Magnetic properties of Ni/Au core/shell studied by Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi Bouzid, Safi, 63 4600 (Morocco); LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Bahmad, L. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France)

    2014-01-10

    The magnetic properties of ferromagnetic Ni/Au core/shell have been studied using Monte Carlo simulations within the Ising model framework. The considered Hamiltonian includes the exchange interactions between Ni–Ni, Au–Au and Ni–Au and the external magnetic field. The thermal total magnetizations and total magnetic susceptibilities of core/shell Ni/Au are computed. The critical temperature is deduced. The exchange interaction between Ni and Au atoms is obtained. In addition, the total magnetizations versus the external magnetic field and crystal filed for different temperature are also established.

  5. Field Quality Measurements of LARP Nb$_{3}$Sn Magnet HQ02

    CERN Document Server

    DiMarco, J; Buehler, M; Chlachidze, G; Orris, D; Sylvester, C; Tartaglia, M; Velev, G; Yu, M; Zlobin, A; Ghosh, A; Schmalzle, J; Wanderer, P; Borgnolutti, F; Cheng, D; Dietderich, D; Felice, H; Godeke, A; Hafalia, R; Joseph, J; Lizarazo, J; Marchevsky, M; Prestemon, S O; Sabbi, G L; Salehi, A,; Wang, X; Ferracin, P; Todesco, E

    2014-01-01

    Large-aperture, high-field, Nb$_{3}$Sn quadrupoles are being developed by the US LHC accelerator research program (LARP) for the High luminosity upgrade of the Large Hadron Collider (HiLumi-LHC). The first 1 m long, 120 mm aperture prototype, HQ01, was assembled with various sets of coils and tested at LBNL and CERN. Based on these results, several design modifications have been introduced to improve the performance for HQ02, the latest model. From the field quality perspective, the most relevant improvements are a cored cable for reduction of eddy current effects, and more uniform coil components and fabrication processes. This paper reports on the magnetic measurements of HQ02 during recent testing at the Vertical Magnet Test Facility at Fermilab. Results of baseline measurements performed with a new multi-layer circuit board probe are compared with the earlier magnet. An analysis of probe and measurement system performance is also presented.

  6. Solar wind deceleration and MHD turbulence in the earth's foreshock region - ISEE 1 and 2 and IMP 8 observations

    Science.gov (United States)

    Bonifazi, C.; Moreno, G.; Russell, C. T.; Lazarus, A. J.; Sullivan, J. D.

    1983-01-01

    The interaction of the solar wind with ions backstreaming from the earth's bow shock is investigated using plasma and magnetic field measurements on ISEE 1 and 2 and IMP 8 at widely separated positions in the earth's foreshock. This technique separates temporal and spatial variations within the foreshock. It is found that the solar wind acceleration associated with backstreaming ions is correlated with the amplitude of the MHD turbulence, and that the largest decelerations are seen close to the bow shock. The density of the backstreaming ion beam is strongly correlated with distance from the shock, and decreases by about a factor of three in a distance of about 3R(e).

  7. Magnetomigration of rare-earth ions in inhomogeneous magnetic fields.

    Science.gov (United States)

    Franczak, Agnieszka; Binnemans, Koen; Jan Fransaer

    2016-10-05

    The effects of external inhomogenous (gradient) magnetic fields on the movement of the rare-earth ions: Dy 3+ , Gd 3+ and Y 3+ , in initially homogeneous aqueous solutions have been investigated. Differences in the migration of rare-earth ions in gradient magnetic fields were observed, depending on the magnetic character of the ions: paramagnetic ions of Dy 3+ and Gd 3+ move towards regions of the sample where the magnetic field gradient is the strongest, while diamagnetic ions of Y 3+ move in the opposite direction. It has been showed that the low magnetic field gradients, such the ones generated by permanent magnets, are sufficient to observe the magnetomigration effects of the ions in solution. The present work clearly establishes the behavior of magnetically different ions in initially homogeneous aqueous solutions exposed to magnetic field gradients. To this avail, a methodology for measuring the local concentration differences of metal ions in liquid samples was developed.

  8. Tripolar electric field Structure in guide field magnetic reconnection

    Science.gov (United States)

    Fu, Song; Huang, Shiyong; Zhou, Meng; Ni, Binbin; Deng, Xiaohua

    2018-03-01

    It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection). In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. The newly emerged electric field is a convective electric field about one ion inertial length away from the neutral sheet. It arises from the disappearance of the Hall electric field due to the substantial modification of the magnetic field and electric current by the imposed guide field. The peak magnitude of this new electric field increases linearly with the increment of guide field strength. Possible applications of these results to space observations are also discussed.

  9. Tripolar electric field Structure in guide field magnetic reconnection

    Directory of Open Access Journals (Sweden)

    S. Fu

    2018-03-01

    Full Text Available It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection. In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg. Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. The newly emerged electric field is a convective electric field about one ion inertial length away from the neutral sheet. It arises from the disappearance of the Hall electric field due to the substantial modification of the magnetic field and electric current by the imposed guide field. The peak magnitude of this new electric field increases linearly with the increment of guide field strength. Possible applications of these results to space observations are also discussed.

  10. Complex microwave conductivity of YBa2Cu3O7 in magnetic fields up to 500T

    International Nuclear Information System (INIS)

    Goettee, J.D.; Zerwekh, W.D.; Kudasov, Y.B.

    1994-01-01

    We have measured the complex conductivity of thin films of YBa 2 cu 3 O 7 (YBCO) superconductor down to temperatures of 4K and magnetic fields up to 500T. The highly oriented films were probed by 94 GHz radiation, with the external magnetic field applied perpendicular to the c-axis. These measurements allowed us to assign a value of 340 ± 40 for the upper critical field at T=O. The measurements were recently carried out at the pulsed field facility of the National High Magnetic Field Laboratory at Los Alamos using both Russian and American magnetic flux compression generators

  11. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  12. ISE and Chemfet sensors in greenhouse cultivation

    NARCIS (Netherlands)

    Gieling, T.H.; Straten, van G.; Janssen, H.J.J.; Wouters, H.

    2005-01-01

    The development and market introduction of ion-specific sensors, like the ion selective electrode (ISE) and ion selective field effect transistor (ISFET) sensor, has paved the way for completely new systems for application of fertilisers to crops in greenhouses. This paper illustrates the usefulness

  13. Fluctuation dynamics near the quantum critical point in the S=1/2 Ising chain CoNb{sub 2}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Harms, Steffen; Engelmayer, Johannes; Lorenz, Thomas; Hemberger, Joachim [II. Physikalisches Institut, Koeln Univ. (Germany)

    2016-07-01

    CoNb{sub 2}O{sub 6} is a model system for quantum phase transitions in magnetic field. Its structure consists of layers of CoO{sub 6} octahedrons separated by non-magnetic NbO{sub 6} layers. The edge-sharing oxygen octahedrons link the Co{sup 2+} spins via Co-O-Co superexchange and form 1D ferromagnetic zigzag chains along the orthorhombic c axis. Crystal field effects lead to an easy-axis anisotropy of the Co{sup 2+} moments in the ac plane and to an effective spin-1/2 chain system. The 1D spin system can be described by the Ising model. At T=0 K a transverse magnetic field can induce a quantum phase transition from a long range ferromagnetic state into a quantum paramagnetic state. Employing measurements of the complex AC-susceptibility in the frequency range 10 MHz < ν < 5 GHz for temperatures down to 50 mK we investigate the slowing down of the magnetic fluctuation dynamics in the vicinity of the critical field at μ{sub 0}H=5.25 T.

  14. Ferroelectric Cathodes in Transverse Magnetic Fields

    International Nuclear Information System (INIS)

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-01-01

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode

  15. Spin flip statistics and spin wave interference patterns in Ising ferromagnetic films: A Monte Carlo study.

    Science.gov (United States)

    Acharyya, Muktish

    2017-07-01

    The spin wave interference is studied in two dimensional Ising ferromagnet driven by two coherent spherical magnetic field waves by Monte Carlo simulation. The spin waves are found to propagate and interfere according to the classic rule of interference pattern generated by two point sources. The interference pattern of spin wave is observed in one boundary of the lattice. The interference pattern is detected and studied by spin flip statistics at high and low temperatures. The destructive interference is manifested as the large number of spin flips and vice versa.

  16. Self-assembly of a 3d-5f trinuclear single-molecule magnet from a pentavalent uranyl complex

    International Nuclear Information System (INIS)

    Chatelain, Lucile; Pecaut, Jacques; Walsh, James P.S.; Tuna, Floriana; Mazzanti, Marinella

    2014-01-01

    Mixed-metal uranium compounds are very attractive candidates in the design of single-molecule magnets (SMMs), but only one 3d-5f hetero-polymetallic SMM containing a uranium center is known. Herein, we report two trimeric heterodimetallic 3d-5f complexes self-assembled by cation-cation interactions between a uranyl(V) complex and a TPA-capped M II complex (M=Mn (1), Cd (2); TPA=tris(2-pyridylmethyl)amine). The metal centers were strategically chosen to promote the formation of discrete molecules rather than extended chains. Compound 1, which contains an almost linear {Mn-O=U=O-Mn} core, exhibits SMM behavior with a relaxation barrier of 81±0.5 K - the highest reported for a mono-uranium system - arising from intramolecular Mn-U exchange interactions combined with the high Ising anisotropy of the uranyl(V) moiety. Compound 1 also exhibits an open magnetic hysteresis loop at temperatures less than 3 K, with a significant coercive field of 1.9 T at 1.8 K.

  17. Self-assembly of a 3d-5f trinuclear single-molecule magnet from a pentavalent uranyl complex

    Energy Technology Data Exchange (ETDEWEB)

    Chatelain, Lucile; Pecaut, Jacques [CEA-Grenoble (France). Lab. de Reconnaissance Ionique et Chimie de Coordination SCIB; Walsh, James P.S.; Tuna, Floriana [Manchester Univ. (United Kingdom). School of Chemistry and Photon Science Inst.; Mazzanti, Marinella [Ecole Polytechnique Federale de Lausanne (EPFL) (Switzerland). Inst. de Sciences et Ingenierie Chimiques

    2014-12-01

    Mixed-metal uranium compounds are very attractive candidates in the design of single-molecule magnets (SMMs), but only one 3d-5f hetero-polymetallic SMM containing a uranium center is known. Herein, we report two trimeric heterodimetallic 3d-5f complexes self-assembled by cation-cation interactions between a uranyl(V) complex and a TPA-capped M{sup II} complex (M=Mn (1), Cd (2); TPA=tris(2-pyridylmethyl)amine). The metal centers were strategically chosen to promote the formation of discrete molecules rather than extended chains. Compound 1, which contains an almost linear {Mn-O=U=O-Mn} core, exhibits SMM behavior with a relaxation barrier of 81±0.5 K - the highest reported for a mono-uranium system - arising from intramolecular Mn-U exchange interactions combined with the high Ising anisotropy of the uranyl(V) moiety. Compound 1 also exhibits an open magnetic hysteresis loop at temperatures less than 3 K, with a significant coercive field of 1.9 T at 1.8 K.

  18. Powder-in-tube (PIT) Nb$_{3}$Sn conductors for high-field magnets

    CERN Document Server

    Lindenhovius, J L H; den Ouden, A; Wessel, W A J; ten Kate, H H J

    2000-01-01

    New Nb/sub 3/Sn conductors, based on the powder-in-tube (PIT) process, have been developed for application in accelerator magnets and high-field solenoids. For application in accelerator magnets, SMI has developed a binary 504 filament PIT conductor by optimizing the manufacturing process and adjustment of the conductor lay-out. It uniquely combines a non-copper current density of 2680 A/mm/sup 2/@10 T with an effective filament diameter of about 20 mu m. This binary conductor may be used in a 10 T, wide bore model separator dipole magnet for the LHC, which is being developed by a collaboration of the University of Twente and CERN. A ternary (Nb/7.5wt%Ta)/sub 3/Sn conductor containing 37 filaments is particularly suited for application in extremely high-field superconducting solenoids. This wire features a copper content of 43%, a non-copper current density of 217 A/mm/sup 2/@20 T and a B/sub c2/ of 25.6 T. The main issues and the experimental results of the development program of PIT Nb/sub 3/Sn conductors a...

  19. Magnetic field effects on the fluorescence of Cr3+ in GdAlO3

    International Nuclear Information System (INIS)

    Helman, J.S.; Carvalho, R.A.; Panepucci, H.; Terrile, M.C.; Aegerter, M.A.; Soarez, E.

    1979-01-01

    The fluorescence spectrum of Cr 3+ in GdAlO 3 has been examined at 4.2 K as a function of magnetic field up to 60 kG. The resulting splitting of the 2 E → 4 A 2 emission lines are explained in terms of a modified molecular field approximation, which incorporates the effect of the spin fluctuations. The exchange constant in the relaxed excited state is found to be 1.2 cm -1 which differs from that reported from absorption data. It is suggested that the difference may be related to the Franck-Condon effect. (author)

  20. Magnetic Field Interactions of Copper-Containing Intrauterine Devices in 3.0-Tesla Magnetic Resonance Imaging: In Vivo Study

    Energy Technology Data Exchange (ETDEWEB)

    Berger-Kulemann, Vanessa; Einspieler, Henrik [Department of Radiology, Medical University of Vienna, Vienna 1090 (Austria); Hachemian, Nilouparak [Department of Obstetrics and Gynecology, Medical University of Vienna, Vienna 1090 (Austria); Prayer, Daniela; Trattnig, Siegfried; Weber, Michael; Ba-Ssalamah, Ahmed [Department of Radiology, Medical University of Vienna, Vienna 1090 (Austria)

    2013-07-01

    An ex vivo study found a copper-containing intrauterine device (IUD) to be safe for women undergoing an MRI examination at a 3.0-T field. No significant artifacts caused by the metallic implant were detected. However, there are still no in vivo data about these concerns. The aim of this study was to evaluate 3.0-T magnetic field interactions of copper-containing IUDs in vivo. Magnetic field interactions and potential adverse events were evaluated in 33 women using a questionnaire-based telephone survey. Two experienced radiologists performed artifact evaluation on MR images of the pelvis. Eighteen patients were eligible for the survey. One patient reported a dislocation of the IUD after the MR examination. All other patients had no signs of field interactions. No IUD-related artifacts were found. MRI at 3.0-T is possible for women with copper-containing IUDs. However, consulting a gynecologist to check the correct position of the IUD and exclude complications after an MR examination is highly recommended. High-quality clinical imaging of the female pelvis can be performed without a loss in image quality.

  1. Magnetic Field Interactions of Copper-Containing Intrauterine Devices in 3.0-Tesla Magnetic Resonance Imaging: In Vivo Study

    International Nuclear Information System (INIS)

    Berger-Kulemann, Vanessa; Einspieler, Henrik; Hachemian, Nilouparak; Prayer, Daniela; Trattnig, Siegfried; Weber, Michael; Ba-Ssalamah, Ahmed

    2013-01-01

    An ex vivo study found a copper-containing intrauterine device (IUD) to be safe for women undergoing an MRI examination at a 3.0-T field. No significant artifacts caused by the metallic implant were detected. However, there are still no in vivo data about these concerns. The aim of this study was to evaluate 3.0-T magnetic field interactions of copper-containing IUDs in vivo. Magnetic field interactions and potential adverse events were evaluated in 33 women using a questionnaire-based telephone survey. Two experienced radiologists performed artifact evaluation on MR images of the pelvis. Eighteen patients were eligible for the survey. One patient reported a dislocation of the IUD after the MR examination. All other patients had no signs of field interactions. No IUD-related artifacts were found. MRI at 3.0-T is possible for women with copper-containing IUDs. However, consulting a gynecologist to check the correct position of the IUD and exclude complications after an MR examination is highly recommended. High-quality clinical imaging of the female pelvis can be performed without a loss in image quality

  2. Magnetic response to applied electrostatic field in external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, T.C. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); University of Florida, Department of Physics, Gainesville, FL (United States); Gitman, D.M. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Shabad, A.E. [P. N. Lebedev Physics Institute, Moscow (Russian Federation)

    2014-04-15

    We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics. (orig.)

  3. High magnetic field magnetization of a new triangular lattice antiferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, H. D. [Univ. of Tennessee, Knoxville, TN (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Stritzinger, Laurel Elaine Winter [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrison, Neil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-23

    In CsV(MoO4)2, the magnetic V3+ ions with octahedral oxygen-coordination form a geometrically frustrated triangular lattice. So fare, there is no magnetic properties reported on it. Recently, we successfully grew single crystals of CsV(MoO4)2 by using flux method. The susceptibility shows a sharp drop around 24 K, representing a long range magnetic ordering. To understand the physical properties of this new triangular lattice antiferromagnet (TLAF), we pursued high field magnetization measurements to answer two questions: (i) what is the saturation field, which will be very useful to calculate the exchange interaction of the system? (ii) Will it exhibit spin state transition, such as the up up down phase with 1/3-saturation moment as other TLAFs? Recently, we performed VSM measurements in Cell 8, Tallahassee, NHMFL, the results show that the magnetization reaches 0.38 MuB at 34 T, which is just 19% of the full moment of 2 MuB for V3+ (3d2) ions. Apparently we need higher field to reach 1/3 value or full moment.

  4. Omnigenous magnetic fields

    International Nuclear Information System (INIS)

    Stupakov, G.V.

    1982-01-01

    In omnigenous magnetic fields particles' drift surfaces coincide with plasma magnetic surfaces. In this paper we formulate equations of omnigenous magnetic fields in natural curvilinear coordinates. An analysis of fields which are omnigenous only in the paraxial approximation is presented. (author)

  5. High heat generation ability in AC magnetic field for nano-sized magnetic Y3Fe5O12 powder prepared by bead milling

    International Nuclear Information System (INIS)

    Aono, Hiromichi; Ebara, Hiroki; Senba, Ryota; Naohara, Takashi; Maehara, Tsunehiro; Hirazawa, Hideyuki; Watanabe, Yuji

    2012-01-01

    Nano-sized magnetic Y 3 Fe 5 O 12 ferrite having a high heat generation ability in an AC magnetic field was prepared by bead milling. A commercial powder sample (non-milled sample) of ca. 2.9 μm in particle size did not show any temperature enhancement in the AC magnetic field. The heat generation ability in the AC magnetic field improved with a decrease in the average crystallite size for the bead-milled Y 3 Fe 5 O 12 ferrites. The highest heat ability in the AC magnetic field was for the fine Y 3 Fe 5 O 12 powder with a 15-nm crystallite size (the samples were milled for 4 h using 0.1 mmφ beads). The heat generation ability of the excessively milled Y 3 Fe 5 O 12 samples decreased. The main reason for the high heat generation property of the milled samples was ascribed to an increase in the Néel relaxation of the superparamagnetic material. The heat generation ability was not influenced by the concentration of the ferrite powder. For the samples milled for 4 h using 0.1 mmφ beads, the heat generation ability (W g −1 ) was estimated using a 3.58×10 −4 fH 2 frequency (f/kHz) and the magnetic field (H/kA m −1 ), which is the highest reported value of superparamagnetic materials. - Highlights: ► The nano-sized Y 3 Fe 5 O 12 powder prepared by bead-milling has the highest heat generation ability in an AC magnetic field. ► The heat generation properties are ascribed to an increase in the Néel relaxation of the superparamagnetic material. ► The heat ability (W g −1 ) can be estimated using 3.58×10 −4 fH 2 (f=kHz, H=kA m −1 ). ► This is an expectable material for use in a drug delivery system for the thermal coagulation therapy of cancer tumors.

  6. Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe1.64Ga0.36O3 oxide

    Directory of Open Access Journals (Sweden)

    R. N. Bhowmik

    2015-06-01

    Full Text Available We have studied current-voltage (I-V characteristics of α-Fe1.64Ga0.36O3, a typical canted ferromagnetic semiconductor. The sample showed a transformation of the I-V curves from linear to non-linear character with the increase of bias voltage. The I-V curves showed irreversible features with hysteresis loop and bi-stable electronic states for up and down modes of voltage sweep. We report positive magnetoresistance and magnetic field induced negative differential resistance as the first time observed phenomena in metal doped hematite system. The magnitudes of critical voltage at which I-V curve showed peak and corresponding peak current are affected by magnetic field cycling. The shift of the peak voltage with magnetic field showed a step-wise jump between two discrete voltage levels with least gap (ΔVP 0.345(± 0.001 V. The magnetic spin dependent electronic charge transport in this new class of magnetic semiconductor opens a wide scope for tuning large electroresistance (∼500-700%, magnetoresistance (70-135 % and charge-spin dependent conductivity under suitable control of electric and magnetic fields. The electric and magnetic field controlled charge-spin transport is interesting for applications of the magnetic materials in spintronics, e.g., magnetic sensor, memory devices and digital switching.

  7. Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe1.64Ga0.36O3 oxide

    Science.gov (United States)

    Bhowmik, R. N.; Vijayasri, G.

    2015-06-01

    We have studied current-voltage (I-V) characteristics of α-Fe1.64Ga0.36O3, a typical canted ferromagnetic semiconductor. The sample showed a transformation of the I-V curves from linear to non-linear character with the increase of bias voltage. The I-V curves showed irreversible features with hysteresis loop and bi-stable electronic states for up and down modes of voltage sweep. We report positive magnetoresistance and magnetic field induced negative differential resistance as the first time observed phenomena in metal doped hematite system. The magnitudes of critical voltage at which I-V curve showed peak and corresponding peak current are affected by magnetic field cycling. The shift of the peak voltage with magnetic field showed a step-wise jump between two discrete voltage levels with least gap (ΔVP) 0.345(± 0.001) V. The magnetic spin dependent electronic charge transport in this new class of magnetic semiconductor opens a wide scope for tuning large electroresistance (˜500-700%), magnetoresistance (70-135 %) and charge-spin dependent conductivity under suitable control of electric and magnetic fields. The electric and magnetic field controlled charge-spin transport is interesting for applications of the magnetic materials in spintronics, e.g., magnetic sensor, memory devices and digital switching.

  8. Magnetic field of Mercury

    International Nuclear Information System (INIS)

    Jackson, D.J.; Beard, D.B.

    1977-01-01

    The geomagnetic field, suitably scaled down and parameterized, is shown to give a very good fit to the magnetic field measurements taken on the first and third passes of the Mariner 10 space probe past Mercury. The excellence of the fit to a reliable planetary magnetospheric model is good evidence that the Mercury magnetosphere is formed by a simple, permanent, intrinsic planetary magnetic field distorted by the effects of the solar wind. The parameters used for a best fit to all the data are (depending slightly on the choice of data) 2.44--2.55 for the ratio of Mercury's magnetic field strength at the subsolar point to that of the earth's subsolar point field (this results in a dipole moment of 170 γR/sub M/ 3 (R/sub M/ is Mercury Radius), i.e., 2.41 x 10 22 G cm 3 in the same direction as the earth's dipole), approx.-113 γR/sub M/ 4 for the planetary quadrupole moment parallel to the dipole moment, 10degree--17degree for the tilt of the planet dipole toward the sun, 4.5degree for the tilt of the dipole toward dawn, and 2.5degree--7.6degree aberration angle for the shift in the tail axis from the planet-sun direction because of the planet's orbital velocity. The rms deviation overall for the entire data set compared with the theoretical fitted model for the magnetic field strength was 17 γ (approx.4% of the maximum field measured). If the data from the first pass that show presumed strong time variations are excluded, the overall rms deviation for the field magnitude is only 10 γ

  9. Nuclear magnetic resonance and earth magnetic field

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Nuclear magnetic resonance concerns nuclei whose spin is different from 0. These nuclei exposed to a magnetic field is comparable to a peg top spinning around its axis while being moved by a precession movement called Larmor precession. This article presents an experiment whose aim is to reveal nuclear magnetism of nuclei by observing Larmor precession phenomena due to the earth magnetic field. The earth magnetic field being too weak, it is necessary to increase the magnetization of the sample during a polarization phase. First the sample is submitted to a magnetic field B perpendicular to the earth magnetic field B 0 , then B is cut off and the nuclei move back to their equilibrium position by executing a precession movement due to B 0 field. (A.C.)

  10. Non-Abelian anyons: when Ising meets Fibonacci

    NARCIS (Netherlands)

    Grosfeld, E.; Schoutens, K.

    2009-01-01

    We consider an interface between two non-Abelian quantum Hall states: the Moore-Read state, supporting Ising anyons, and the k=2 non-Abelian spin-singlet state, supporting Fibonacci anyons. It is shown that the interface supports neutral excitations described by a (1+1)-dimensional conformal field

  11. Analysis of magnetic field measurement results for the AGS Booster magnets

    International Nuclear Information System (INIS)

    Bleser, E.; Thern, R.

    1991-01-01

    Magnetic field measurements have been made on nearly 200 conventional magnets that have been installed in the AGS Booster and its associated transfer lines. The measurements were intended to monitor the quality of the magnets being produced and to check the performance of each magnet before installation. The magnetic measurements effort led to certain improvements in the manufacturing process, which ten subsequently produced very good, very uniform magnets. The integrated dipole fields of the 36 booster dipoles are uniform to 1.5 parts in ten thousand. The magnetic measurements indicate that the quadrupoles were manufactured to an accuracy of 3 ten thousandths of an inch, which is better than we can physically measure. 3 refs., 2 figs., 4 tabs

  12. Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Canko, Osman

    2005-01-01

    The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a 'flatness' property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems

  13. Indoor localization using magnetic fields

    Science.gov (United States)

    Pathapati Subbu, Kalyan Sasidhar

    Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth's magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth's magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth's field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing

  14. Magnetic fields in an expanding universe

    International Nuclear Information System (INIS)

    Kastor, David; Traschen, Jennie

    2014-01-01

    We find a solution to 4D Einstein–Maxwell theory coupled to a massless dilaton field, for all values of the dilaton coupling, describing a Melvin magnetic field in an expanding universe with ‘stiff matter’ equation of state parameter w = +1. As the universe expands, magnetic flux becomes more concentrated around the symmetry axis for dilaton coupling a<1/√3 and more dispersed for a>1/√3. An electric field circulates around the symmetry axis in the direction determined by Lenz's law. For a = 0 the magnetic flux through a disc of fixed comoving radius is proportional to the proper area of the disc. This result disagrees with the usual expectation based on a test magnetic field that this flux should be constant, and we show why this difference arises. We also find a Melvin solution in an accelerating universe with w = −7/9 for a dilaton field with a certain exponential potential. (paper)

  15. Permanent magnet assembly producing a strong tilted homogeneous magnetic field: towards magic angle field spinning NMR and MRI.

    Science.gov (United States)

    Sakellariou, Dimitris; Hugon, Cédric; Guiga, Angelo; Aubert, Guy; Cazaux, Sandrine; Hardy, Philippe

    2010-12-01

    We introduce a cylindrical permanent magnet design that generates a homogeneous and strong magnetic field having an arbitrary inclination with respect to the axis of the cylinder. The analytical theory of 3 D magnetostatics has been applied to this problem, and a hybrid magnet structure has been designed. This structure contains two magnets producing a longitudinal and transverse component for the magnetic field, whose amplitudes and homogeneities can be fully controlled by design. A simple prototype has been constructed using inexpensive small cube magnets, and its magnetic field has been mapped using Hall and NMR probe sensors. This magnet can, in principle, be used for magic angle field spinning NMR and MRI experiments allowing for metabolic chemical shift profiling in small living animals. Copyright © 2010 John Wiley & Sons, Ltd.

  16. Annealed central limit theorems for the ising model on random graphs

    NARCIS (Netherlands)

    Giardinà, C.; Giberti, C.; van der Hofstad, R.W.; Prioriello, M.L.

    2016-01-01

    The aim of this paper is to prove central limit theorems with respect to the annealed measure for the magnetization rescaled by √N of Ising models on random graphs. More precisely, we consider the general rank-1 inhomogeneous random graph (or generalized random graph), the 2-regular configuration

  17. ISR Radial Field Magnet

    CERN Multimedia

    1983-01-01

    There were 37 (normal) + 3 (special) Radial Field magnets in the ISR to adjust vertically the closed orbit. Gap heights and strengths were 200 mm and .12 Tm in the normal magnets, 220 mm and .18 Tm in the special ones. The core length was 430 mm in both types. Due to their small length as compared to the gap heights the end fringe field errors were very important and had to be compensated by suitably shaping the poles. In order to save on cables, as these magnets were located very far from their power supplies, the coils of the normal type magnets were formed by many turns of solid cpper conductor with some interleaved layers of hollow conductor directly cooled by circulating water

  18. Magnetic field induced low temperature upturn of magnetization in highly Ca-doped La{sub 0.1875}Ca{sub 0.8125}MnO{sub 3} polycrystalline compound

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kalipada, E-mail: kalipadadasphysics@gmail.com [Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032 (India); Dasgupta, P.; Poddar, A. [CMP Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064 (India)

    2017-06-15

    Highlights: • Magnetic field induced super paramagnetic nanoclusters formation. • Magnetic field dependent change of the curvature of the magnetization. • We report the training effect in polycrystalline La{sub 0.1875}Ca{sub 0.8125}MnO{sub 3} compound. - Abstract: In our present study we have reported the magnetic properties of highly Ca-doped polycrystalline compound La{sub 0.1875}Ca{sub 0.8125}MnO{sub 3}. Along with the conventional charge ordered antiferromagnetic ground state, a small ferromagnetic phase fraction is present at the low temperature. The effect of the external magnetic field markedly modifies the ground state of the compound. Our experimental results indicate that in addition to the ferromagnetic phase fraction, another field induced super paramagnetic phase grow at low temperature (T < 50 K) above H = 10 kOe magnetic field within the charge ordered antiferromagnetic matrix. The nature of the temperature dependent magnetization curves influenced by the external applied magnetic field was observed and analyzed using Langevin theory of super paramagnetism.

  19. Measurements of Solar Vector Magnetic Fields

    Science.gov (United States)

    Hagyard, M. J. (Editor)

    1985-01-01

    Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display.

  20. Measurements of Solar Vector Magnetic Fields

    International Nuclear Information System (INIS)

    Hagyard, M.J.

    1985-05-01

    Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display

  1. Compact magnetic-field sensor based on optical microfiber Michelson interferometer and Fe3O4 nanofluid.

    Science.gov (United States)

    Deng, Ming; Sun, Xiaokang; Han, Meng; Li, Decai

    2013-02-01

    We report a magnetic-field sensor by merging the advantages of optical fiber Michelson interferometers with that of magnetic fluid. Compact and low-cost optical fiber Michelson interferometers were first fabricated by a high-frequency CO(2) laser, and then they were inserted into glass capillaries with water-based Fe(3)O(4) magnetic fluid as sensing elements. The sensing characteristics have been investigated and the experimental results show that the reflective spectrum of the fiber-magnetic sensor linearly shifted with the change of the magnetic-field strength that is perpendicular to the axial of the devices. The fiber-magnetic sensor with interference arm's diameter of 50 μm is most sensitive to the external magnetic field, and the sensitivity is up to 64.9 pm/mT, which is 20 times higher than that of 125 μm diameter.

  2. Photonic crystal fiber injected with Fe{sub 3}O{sub 4} nanofluid for magnetic field detection

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Harneet V.; Nalawade, Sandipan M.; Gupta, Swati [Photonics Group, Department of Applied Physics, Defence Institute of Advanced Technology, Girinagar, Pune 411 025 (India); Kitture, Rohini [Department of Electronic-Science, Fergusson College, Pune 411 004 (India); Kale, S. N. [Nanotechnology Group, Department of Applied Physics, Defence Institute of Advanced Technology, Girinagar, Pune 411 025 (India)

    2011-10-17

    We report a magnetic field sensor having advantages of both photonic crystal fiber and optofluidics, combining them on a single platform by infiltrating small amount of Fe{sub 3}O{sub 4} magnetic optofluid/nanofluid in cladding holes of polarization-maintaining photonic crystal fiber. We demonstrated that magnetic field of few mT can be easily and very well detected with higher sensitivity of 242 pm/mT. The change in the birefringence values has been correlated to the response of nanofluid to applied field.

  3. Entanglement and quantum state geometry of a spin system with all-range Ising-type interaction

    Science.gov (United States)

    Kuzmak, A. R.

    2018-04-01

    The evolution of an N spin-1/2 system with all-range Ising-type interaction is considered. For this system we study the entanglement of one spin with the rest spins. It is shown that the entanglement depends on the number of spins and the initial state. Also, the geometry of the manifold, which contains entangled states, is obtained. For this case we find the dependence of entanglement on the scalar curvature of the manifold and examine it for different numbers of spins in the system. Finally we show that the transverse magnetic field leads to a change in the manifold topology.

  4. Disorder Identification in Hysteresis Data: Recognition Analysis of the Random-Bond-Random-Field Ising Model

    International Nuclear Information System (INIS)

    Ovchinnikov, O. S.; Jesse, S.; Kalinin, S. V.; Bintacchit, P.; Trolier-McKinstry, S.

    2009-01-01

    An approach for the direct identification of disorder type and strength in physical systems based on recognition analysis of hysteresis loop shape is developed. A large number of theoretical examples uniformly distributed in the parameter space of the system is generated and is decorrelated using principal component analysis (PCA). The PCA components are used to train a feed-forward neural network using the model parameters as targets. The trained network is used to analyze hysteresis loops for the investigated system. The approach is demonstrated using a 2D random-bond-random-field Ising model, and polarization switching in polycrystalline ferroelectric capacitors.

  5. Magnetic Field Measurements In Magnetized Plasmas Using Zeeman Broadening Diagnostics

    Science.gov (United States)

    Haque, Showera; Wallace, Matthew; Presura, Radu; Neill, Paul

    2017-10-01

    The Zeeman effect has been used to measure the magnetic field in high energy density plasmas. This method is limited when plasma conditions are such that the line broadening due to the high plasma density and temperature surpasses the Zeeman splitting. We have measured magnetic fields in magnetized laser plasmas under conditions where the Zeeman splitting was not spectrally resolved. The magnetic field strength was determined from the difference in widths of two doublet components, using an idea proposed by Tessarin et al. (2011). Time-gated spectra with one-dimensional space-resolution were obtained at the Nevada Terawatt Facility for laser plasmas created by 20 J, 1 ns Leopard laser pulses, and expanding in the azimuthal magnetic field produced by the 0.6 MA Zebra pulsed power generator. We explore the response of the Al III 4s 2S1/2 - 4p 2P1 / 2 , 3 / 2 doublet components to the external magnetic field spatially along the plasma. Radial magnetic field and electron density profiles were measured within the plasma plume. This work was supported by the DOE/OFES Grant DE-SC0008829 and DOE/NNSA contract DE-FC52-06NA27616.

  6. ISE System Development Methodology Manual

    Energy Technology Data Exchange (ETDEWEB)

    Hayhoe, G.F.

    1992-02-17

    The Information Systems Engineering (ISE) System Development Methodology Manual (SDM) is a framework of life cycle management guidelines that provide ISE personnel with direction, organization, consistency, and improved communication when developing and maintaining systems. These guide-lines were designed to allow ISE to build and deliver Total Quality products, and to meet the goals and requirements of the US Department of Energy (DOE), Westinghouse Savannah River Company, and Westinghouse Electric Corporation.

  7. Novel Electrochemical Phenomena in Magnetic Fields(Research in High Magnetic Fields)

    OpenAIRE

    Mogi, Iwao; Kamiko, Masao

    1996-01-01

    Recent two topics are given of electrochemical studies in steady magnetic fields at the High Field Laboratory of Tohoku University. One is the magnetic-field-induced diffusion-limited-aggregation in the pattern formation of silver electrodeposits . The other is the magnetic field effect on the learning effect in a dopant-exchange process of an organic conducting polymer polypyrrole.

  8. Observing Interstellar and Intergalactic Magnetic Fields

    Science.gov (United States)

    Han, J. L.

    2017-08-01

    Observational results of interstellar and intergalactic magnetic fields are reviewed, including the fields in supernova remnants and loops, interstellar filaments and clouds, Hii regions and bubbles, the Milky Way and nearby galaxies, galaxy clusters, and the cosmic web. A variety of approaches are used to investigate these fields. The orientations of magnetic fields in interstellar filaments and molecular clouds are traced by polarized thermal dust emission and starlight polarization. The field strengths and directions along the line of sight in dense clouds and cores are measured by Zeeman splitting of emission or absorption lines. The large-scale magnetic fields in the Milky Way have been best probed by Faraday rotation measures of a large number of pulsars and extragalactic radio sources. The coherent Galactic magnetic fields are found to follow the spiral arms and have their direction reversals in arms and interarm regions in the disk. The azimuthal fields in the halo reverse their directions below and above the Galactic plane. The orientations of organized magnetic fields in nearby galaxies have been observed through polarized synchrotron emission. Magnetic fields in the intracluster medium have been indicated by diffuse radio halos, polarized radio relics, and Faraday rotations of embedded radio galaxies and background sources. Sparse evidence for very weak magnetic fields in the cosmic web is the detection of the faint radio bridge between the Coma cluster and A1367. Future observations should aim at the 3D tomography of the large-scale coherent magnetic fields in our Galaxy and nearby galaxies, a better description of intracluster field properties, and firm detections of intergalactic magnetic fields in the cosmic web.

  9. From tricritical Ising to critical Ising by thermodynamic Bethe ansatz

    International Nuclear Information System (INIS)

    Zamolodchikov, A.B.

    1991-01-01

    A simple factorized scattering theory is suggested for the massless Goldstone fermions of the trajectory flowing from the tricritical Ising fixed point to the critical Ising one. The thermodynamic Bethe ansatz approach is applied to this scattering theory to support its interpretation both analytically and numerically. As a generalization a sequence of massless TBA systems is proposed which seems relevant for the trajectories interpolating between two successive minimal CFT models M p and M p-1 . (orig.)

  10. Magnetic anisotropy study of UGe2in a static high magnetic field

    International Nuclear Information System (INIS)

    Sakon, T; Saito, S; Koyama, K; Awaji, S; Sato, I; Nojima, T; Watanabe, K; Motokawa, M; Sato, N K

    2006-01-01

    UGe 2 has orthorhombic C mmm crystalline symmetry and shows ferromagnetic Heavy-Fermion (HF) Superconductor, which provides superconductivity under pressure in the range from 1.0 GPa to 1.5 GPa. Magnetic field dependence of magnetization shows strong magnetic anisotropy. When a magnetic field is applied parallel to easy axis (a-axis), magnetization presents ferromagnetic behavior. At 4.2 K, which is much lower than the Curie temperature T c = 54 K. Spontaneous magnetization is 1.4 μ B /U, and the magnetization gradually increase with increasing field. On the contrary, when a field is applied parallel to hard axis (b-axis or c-axis), magnetization increases linearly with increasing magnetic field. As for H//b-axis, magnetization is 0.23 μ B /U even at 27 T. Magnetocrystalline anisotropy constant is obtained as 230 [T μ B ] 3.4[kJ/kg] at 4.2 K. This value is comparable with rare-earth magnet Nd 2 Fe 17 , which is typical strongly correlated ferromagnet

  11. Giant crystal-electric-field effect and complex magnetic behavior in single-crystalline CeRh3Si2

    Science.gov (United States)

    Pikul, A. P.; Kaczorowski, D.; Gajek, Z.; Stȩpień-Damm, J.; Ślebarski, A.; Werwiński, M.; Szajek, A.

    2010-05-01

    Single-crystalline CeRh3Si2 was investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, electrical resistivity, and specific-heat measurements carried out in wide temperature and magnetic field ranges. Moreover, the electronic structure of the compound was studied at room temperature by cerium core-level x-ray photoemission spectroscopy (XPS). The physical properties were analyzed in terms of crystalline electric field and compared with results of ab initio band-structure calculations performed within the density-functional theory approach. The compound was found to crystallize in the orthorhombic unit cell of the ErRh3Si2 type (space group Imma No.74, Pearson symbol: oI24 ) with the lattice parameters a=7.1330(14)Å , b=9.7340(19)Å , and c=5.6040(11)Å . Analysis of the magnetic and XPS data revealed the presence of well-localized magnetic moments of trivalent cerium ions. All the physical properties were found to be highly anisotropic over the whole temperature range studied and influenced by exceptionally strong crystalline electric field with the overall splitting of the 4f1 ground multiplet exceeding 5700 K. Antiferromagnetic order of the cerium magnetic moments at TN=4.70(1)K and their subsequent spin rearrangement at Tt=4.48(1)K manifest themselves as distinct anomalies in the temperature characteristic of all the physical properties investigated and exhibit complex evolution in an external magnetic field. A tentative magnetic B-T phase diagram, constructed for B parallel to the b axis being the easy magnetization direction, shows very complex magnetic behavior of CeRh3Si2 , similar to that recently reported for an isostructural compound CeIr3Si2 . The electronic band-structure calculations corroborated the antiferromagnetic ordering of the cerium magnetic moments and well-reproduced the experimental XPS valence-band spectrum.

  12. Isostructural magnetic phase transition and magnetocaloric effect in Ising antiferromagnet

    International Nuclear Information System (INIS)

    Lavanov, G.Yu; Kalita, V.M.; Loktev, V.M.

    2014-01-01

    It is shown that the external magnetic field induced isostructural I st order magnetic phase transition between antiferromagnetic phases with different antiferromagnetic vector values is associated with entropy. It is found, that depending on temperature the entropy jump and the related heat release change their sign at this transition point. In the low-temperature region of metamagnetic I st order phase tensition the entropy jump is positive, and in the triple point region this jump for isostructural magnetic transition is negative

  13. Assembly and Test of HD2, a 36 mm bore high field Nb3Sn Dipole Magnet

    International Nuclear Information System (INIS)

    Ferracin, P.; Bingham, B.; Caspi, S.; Cheng, D.W.; Dietderich, D.R.; Felice, H.; Godeke, A.; Hafalia, A.R.; Hannaford, C.R.; Joseph, J.; Lietzke, A.F.; Lizarazo, J.; Sabbi, G.; Trillaud, F.; Wang, X.

    2008-01-01

    We report on the fabrication, assembly, and test of the Nb 3 Sn dipole magnet HD2. The magnet, aimed at demonstrating the application of Nb 3 Sn superconductor in high field accelerator-type dipoles, features a 36 mm clear bore surrounded by block-type coils with tilted ends. The coil design is optimized to minimize geometric harmonics in the aperture and the magnetic peak field on the conductor in the coil ends. The target bore field of 15 T at 4.3 K is consistent with critical current measurements of extracted strands. The coils are horizontally pre-stressed during assembly using an external aluminum shell pre-tensioned with water-pressurized bladders. Axial pre-loading of the coil ends is accomplished through two end plates and four aluminum tension rods. The strain in coil, shell, and rods is monitored with strain gauges during assembly, cool-down and magnet excitation, and compared with 3D finite element computations. Magnet's training performance, quench locations, and ramp-rate dependence are then analyzed and discussed.

  14. The effects of Earth's magnetic field on 3-inch diameter photomultipliers used in KM3NeT neutrino telescope

    Directory of Open Access Journals (Sweden)

    Giordano V.

    2016-01-01

    Full Text Available The KM3NeT neutrino telescope will be the largest underwater neutrino telescope and will be located in the abyss of the Mediterranean Sea. In neutrino telescopes the key element of the detector is the optical module and for KM3NeT it consists of 31 PMTs stored inside a transparent pressure-resistant glass sphere of 17-inch that serves as mechanical protection while ensuring good light transmission. Since the PMTs installed into an underwater neutrino telescope can change their orientation because of movements of the detector structure due to sea currents, the influence of Earth's magnetic field has been investigated. Magnetic shielding by means of a mu-metal cage is used to reduce magnetic effects and to make the response of the PMT sufficiently orientation independent. In order to quantify the effect on magnetic field, we compared measurements on variation of gain, transit time spread and detection efficiency for a 3-inch PMT in shielded and unshielded condition at 3 PMT inclinations. Data shows that variations are sufficiently low especially for timing properties.

  15. The Strongest Magnetic Field in Sunspots

    Science.gov (United States)

    Okamoto, J.; Sakurai, T.

    2017-12-01

    Sunspots are concentrations of magnetic fields on the solar surface. Generally, the strongest magnetic field in each sunspot is located in the dark umbra in most cases. A typical field strength in sunspots is around 3,000 G. On the other hand, some exceptions also have been found in complex sunspots with bright regions such as light bridges that separate opposite polarity umbrae, for instance with a strength of 4,300 G. However, the formation mechanism of such strong fields outside umbrae is still puzzling. Here we report an extremely strong magnetic field in a sunspot, which was located in a bright region sandwiched by two opposite-polarity umbrae. The strength is 6,250 G, which is the largest ever observed since the discovery of magnetic field on the Sun in 1908 by Hale. We obtained 31 scanned maps of the active region observed by Hinode/SOT/SP with a cadence of 3 hours over 5 days (February 1-6, 2014). Considering the spatial and temporal evolution of the vector magnetic field and the Doppler velocity in the bright region, we suggested that this strong field region was generated as a result of compression of one umbra pushed by the outward flow from the other umbra (Evershed flow), like the subduction of the Earth's crust in plate tectonics.

  16. Pulsed magnetic field generation suited for low-field unilateral nuclear magnetic resonance systems

    Science.gov (United States)

    Gaunkar, Neelam Prabhu; Selvaraj, Jayaprakash; Theh, Wei-Shen; Weber, Robert; Mina, Mani

    2018-05-01

    Pulsed magnetic fields can be used to provide instantaneous localized magnetic field variations. In presence of static fields, pulsed field variations are often used to apply torques and in-effect to measure behavior of magnetic moments in different states. In this work, the design and experimental performance of a pulsed magnetic field generator suited for low static field nuclear magnetic resonance (NMR) applications is presented. One of the challenges of low bias field NMR measurements is low signal to noise ratio due to the comparable nature of the bias field and the pulsed field. Therefore, a circuit is designed to apply pulsed currents through an inductive load, leading to generation of pulsed magnetic fields which can temporarily overpower the effect of the bias field on magnetic moments. The designed circuit will be tuned to operate at the precession frequency of 1H (protons) placed in a bias field produced by permanent magnets. The designed circuit parameters may be tuned to operate under different bias conditions. Therefore, low field NMR measurements can be performed for different bias fields. Circuit simulations were used to determine design parameters, corresponding experimental measurements will be presented in this work.

  17. Inverse Ising inference with correlated samples

    International Nuclear Information System (INIS)

    Obermayer, Benedikt; Levine, Erel

    2014-01-01

    Correlations between two variables of a high-dimensional system can be indicative of an underlying interaction, but can also result from indirect effects. Inverse Ising inference is a method to distinguish one from the other. Essentially, the parameters of the least constrained statistical model are learned from the observed correlations such that direct interactions can be separated from indirect correlations. Among many other applications, this approach has been helpful for protein structure prediction, because residues which interact in the 3D structure often show correlated substitutions in a multiple sequence alignment. In this context, samples used for inference are not independent but share an evolutionary history on a phylogenetic tree. Here, we discuss the effects of correlations between samples on global inference. Such correlations could arise due to phylogeny but also via other slow dynamical processes. We present a simple analytical model to address the resulting inference biases, and develop an exact method accounting for background correlations in alignment data by combining phylogenetic modeling with an adaptive cluster expansion algorithm. We find that popular reweighting schemes are only marginally effective at removing phylogenetic bias, suggest a rescaling strategy that yields better results, and provide evidence that our conclusions carry over to the frequently used mean-field approach to the inverse Ising problem. (paper)

  18. Interaction of Mutually Perpendicular Magnetic Fields in HTSC

    Directory of Open Access Journals (Sweden)

    Vasilyev Aleksandr Fedorovich

    2015-11-01

    Full Text Available In this article a problem of interaction of the crossed magnetic fields in superconductors is considered. Superconducting materials have nonlinear magnetic properties. It allows using a non-linear magnetic susceptibility for measurement of feeble magnetic fields. We place a wire of superconducting material in a constant parallel uniform magnetic field. Then we let through a wire the alternating current leak. Interaction of mutual and perpendicular variation magnetic fields, with adequate accuracy is described by Ginzburg-Landau's equations. Approximate solution of the written equations is received. The component of a magnetic field parallel to a wire contains a variable component. Frequency of a variable component of the magnetic field is equal to the doubled current frequency. Amplitude of the variable component of the magnetic field is proportional to strength of the constant magnetic field. The experimental installation for research of interaction of mutually perpendicular magnetic fields is created. The cylinder from HTSC of ceramics of the YBa2Cu3O7-x was used as a sensor. Dependence of amplitude of the second harmonica of a variation magnetic field on strength of a constant magnetic field is received.

  19. Determination of the saturation magnetization, anisotropy field, mean field interaction, and switching field distribution for nanocrystalline hard magnets

    International Nuclear Information System (INIS)

    McCallum, R. William

    2005-01-01

    For a uniaxial nanocrystalline magnetic material, the determination of the saturation magnetization, M s , requires measurements of the magnetization at fields which exceed the anisotropy field. For a typical RE-Tm compound, where RE=rare earth and Tm=transition metal, this may require fields above 7 T if the approach to saturation law is used. However for an isotropic material composed of a random distribution of non-interacting uniaxial grains, both M s and the anisotropy filed, H a , may be determined by fitting the Stoner-Wohlfarth (SW) model (Philos. Trans. Roy. Soc. 240 (1948) 599) to the reversible part of the demagnetization curve in the first quadrant. Furthermore, using the mean field interaction model of Callen, Liu and Cullen [2], a quantitative measure of the interaction strength for interacting particles may be determined. In conjunction with an analytical fit to the first quadrant demagnetization curve of the SW model, this allows M s , H a and the mean field interaction constant of a nanocrystalline magnet to be determined from measurements below 5 T. Furthermore, comparison of the model solution for the reversible magnetization with experimental data in the 2nd and 3rd quadrants allows the accurate determination of the switching field distribution. In many cases the hysteresis loop may be accurately described by a normal distribution of switching fields

  20. Magnetic Fields in the Solar Convection Zone

    Directory of Open Access Journals (Sweden)

    Fan Yuhong

    2004-07-01

    Full Text Available Recent studies of the dynamic evolution of magnetic flux tubes in the solar convection zone are reviewed with focus on emerging flux tubes responsible for the formation of solar active regions. The current prevailing picture is that active regions on the solar surface originate from strong toroidal magnetic fields generated by the solar dynamo mechanism at the thin tachocline layer at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. This review discusses results with regard to the following major topics: 1. the equilibrium properties of the toroidal magnetic fields stored in the stable overshoot region at the base of the convection zone, 2. the buoyancy instability associated with the toroidal magnetic fields and the formation of buoyant magnetic flux tubes, 3. the rise of emerging flux loops through the solar convective envelope as modeled by the thin flux tube calculations which infer that the field strength of the toroidal magnetic fields at the base of the solar convection zone is significantly higher than the value in equipartition with convection, 4. the minimum twist needed for maintaining cohesion of the rising flux tubes, 5. the rise of highly twisted kink unstable flux tubes as a possible origin of d -sunspots, 6. the evolution of buoyant magnetic flux tubes in 3D stratified convection, 7. turbulent pumping of magnetic flux by penetrative compressible convection, 8. an alternative mechanism for intensifying toroidal magnetic fields to significantly super-equipartition field strengths by conversion of the potential energy associated with the superadiabatic stratification of the solar convection zone, and finally 9. a brief overview of our current understanding of flux emergence at the surface and post-emergence evolution of the subsurface magnetic fields.

  1. Temperature and exchange field dependences of the magnetic and magnetooptical properties of Y3Fe5O12 under low and intense magnetic field

    International Nuclear Information System (INIS)

    Guillot, M.; Le Gall, H.

    1976-01-01

    Faraday rotation (phi/sub F/) measurements are reported in YIG at 1.15 and 0.6328 microns wavelengths under low and very intense magnetic fields (up to 4 mega-Oersteds). These results are discussed from the applied field and temperature dependences of the magnetooptical (M.O.) coefficients induced by the light beam in both the octahedral (a) and tetrahedral (d) sites. It is shown that under very intense magnetic field and in the visible range the M.O. coefficients A/sub m/ and D/sub m/ induced by the magnetic dipole transitions are independent on the applied field and phi/sup m/ follows the usual evolution of the magnetic structure which shows a first-order transition (ferri → non colinear structure) near H/sub a/ = 1.7 mega-Oersteds. On the other hand in the near infrared A/sub m/ and D/sub m/ have a strong magnetic field dependence in the mega-Oersteds range with increasing the dc field. It is shown that the magnetic and electric parts of phi/sub F/ are increasing and decreasing respectively when increasing the dc field and the experimental data are in agreement with a molecular field model where the magnetic intra-sublattices interactions J/sub aa/ and J/sub dd/ are vanishing

  2. Zeros of the partition function for some generalized Ising models

    International Nuclear Information System (INIS)

    Dunlop, F.

    1981-01-01

    The author considers generalized Ising Models with two and four body interactions in a complex external field h such that Re h>=mod(Im h) + C, where C is an explicit function of the interaction parameters. The partition function Z(h) is then shown to satisfy mod(Z(h))>=Z(c), so that the pressure is analytic in h inside the given region. The method is applied to specific examples: the gauge invariant Ising Model, and the Widom Rowlinson model on the lattice. (Auth.)

  3. Magnetic hysteresis of an artificial square ice studied by in-plane Bragg x-ray resonant magnetic scattering

    Directory of Open Access Journals (Sweden)

    J. P. Morgan

    2012-06-01

    Full Text Available We report X-ray resonant magnetic scattering studies of a Permalloy artificial square ice nanomagnet array, focussing on the field-driven evolution of the sum Σ and difference Δ signals of left and right handed circularly polarized synchrotron X-rays at different lateral positions in reciprocal space Qx. We used X-rays tuned to the Fe L3 resonance energy, with the scattering plane aligned along a principal symmetry axis of the array. Details of the specular Δ hysteresis curve are discussed, following the system magnetization from an initial demagnetized state. The periodic structure gives rise to distinct peaks at in-plane reciprocal Bragg positions, as shown by fitting Σ(Qx to a model based on a simple unit cell structure. Diffraction order-dependent hysteresis in Δ is observed, indicative of the reordering of magnetization on the system's two interpenetrating sublattices, which markedly deviates from an ideal Ising picture under strong applied fields.

  4. Magnetic field-assisted synthesis of wire-like Co3O4 nanostructures: Electrochemical and photocatalytic studies

    International Nuclear Information System (INIS)

    Zhao, Xiubin; Pang, Zhanwen; Wu, Mingzai; Liu, Xiansong; Zhang, Hui; Ma, Yongqing; Sun, Zhaoqi; Zhang, Lide; Chen, Xiaoshuang

    2013-01-01

    Graphical abstract: Schematic illustration for the magnetic field-assisted growth of wire-like Co 3 O 4 nanostructure. Display Omitted Highlights: ► Co 3 O 4 nanowires are prepared by magnetic field hydrothermal reduction and annealing. ► These Co 3 O 4 nanowires possess enhanced capacitance. ► The Co 3 O 4 nanowires have a good photocatalytic activity for methyl orange. -- Abstract: Wire-like Co 3 O 4 nanostructures were prepared by the combination of magnetic field-assisted hydrothermal reduction of cobalt ions and the subsequent ambient annealing at 500 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphological evolution of the products. The results show that the wire-like nanostructures possess diameters about 250 nm and lengths over 10 μm. The possible formation mechanism of the wire-like Co 3 O 4 nanostructures is also proposed based on the SEM results. Galvanostatic methods were used to characterize the electrochemical properties. The measurements indicate that the wire-like Co 3 O 4 nanostructures show larger discharge and charge capacities than that of spherical Co 3 O 4 nanoparticles prepared in the absence of magnetic field. In addition, the photocatalytic activity of the products was investigated by measuring the photodegradation of methyl orange solution under ultraviolet radiation, which shows that both the wire-like and spherical products have a good photocatalytic activity.

  5. Evidence for single-chain magnet behavior in a Mn(III)-Ni(II) chain designed with high spin magnetic units: a route to high temperature metastable magnets.

    Science.gov (United States)

    Clérac, Rodolphe; Miyasaka, Hitoshi; Yamashita, Masahiro; Coulon, Claude

    2002-10-30

    We herein present the synthesis, crystal structure, and magnetic properties of a new heterometallic chain of MnIII and NiII ions, [Mn2(saltmen)2Ni(pao)2(py)2](ClO4)2 (1) (saltmen2- = N,N'-(1,1,2,2-tetramethylethylene) bis(salicylideneiminate) and pao- = pyridine-2-aldoximate). The crystal structure of 1 was investigated by X-ray crystallographic analysis: compound 1 crystallized in monoclinic, space group C2/c (No. 15) with a = 21.140(3) A, b = 15.975(1) A, c = 18.6212(4) A, beta = 98.0586(4) degrees , V = 6226.5(7) A3, and Z = 4. This compound consists of two fragments, the out-of-plane dimer [Mn2(saltmen)2]2+ as a coordination acceptor building block and the neutral mononuclear unit [Ni(pao)2(py)2] as a coordination donor building block, forming an alternating chain having the repeating unit [-Mn-(O)2-Mn-ON-Ni-NO-]n. In the crystal structure, each chain is well separated with a minimum intermetallic distance between Mn and Ni ions of 10.39 A and with the absence of interchain pi overlaps between organic ligands. These features ensure a good magnetic isolation of the chains. The dc and ac magnetic measurements were performed on both the polycrystalline sample and the aligned single crystals of 1. Above 30 K, the magnetic susceptibility of this one-dimensional compound was successfully described in a mean field approximation as an assembly of trimers (Mn...Ni...Mn) with a NiII...MnIII antiferromagnetic interaction (J = -21 K) connected through a ferromagnetic MnIII...MnIII interaction (J'). However, the mean field theory fails to describe the magnetic behavior below 30 K emphasizing the one-dimensional magnetic character of the title compound. Between 5 and 15 K, the susceptibility in the chain direction was fitted to a one-dimensional Ising model leading to the same value of J'. Hysteresis loops are observed below 3.5 K, indicating a magnet-type behavior. In the same range of temperature, combined ac and dc measurements show a slow relaxation of the magnetization

  6. Magnetic Grüneisen parameter and magnetocaloric properties of a coupled spin–electron double-tetrahedral chain

    International Nuclear Information System (INIS)

    Gálisová, Lucia; Strečka, Jozef

    2015-01-01

    Magnetocaloric effect in a double-tetrahedral chain, in which nodal lattice sites occupied by the localized Ising spins regularly alternate with three equivalent lattice sites available for mobile electrons, is exactly investigated by considering the one-third electron filling and the ferromagnetic Ising exchange interaction between the mobile electrons and their nearest Ising neighbours. The entropy and the magnetic Grüneisen parameter, which closely relate to the magnetocaloric effect, are exactly calculated in order to investigate the relation between the ground-state degeneracy and the cooling efficiency of the hybrid spin–electron system during the adiabatic demagnetization. - Highlights: • A double-tetrahedral chain of mobile electrons and localized Ising spins is studied. • Magnetic Grüneisen parameter for the system is exactly derived. • Macroscopically degenerate phases FRU and FM constitute the ground state. • MCE is three times higher nearby FRU–FM transition than in FRU phase at small fields

  7. Planetary science. Low-altitude magnetic field measurements by MESSENGER reveal Mercury's ancient crustal field.

    Science.gov (United States)

    Johnson, Catherine L; Phillips, Roger J; Purucker, Michael E; Anderson, Brian J; Byrne, Paul K; Denevi, Brett W; Feinberg, Joshua M; Hauck, Steven A; Head, James W; Korth, Haje; James, Peter B; Mazarico, Erwan; Neumann, Gregory A; Philpott, Lydia C; Siegler, Matthew A; Tsyganenko, Nikolai A; Solomon, Sean C

    2015-05-22

    Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury's crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury's history. Ancient field strengths that range from those similar to Mercury's present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury's crust inferred from MESSENGER elemental composition data. Copyright © 2015, American Association for the Advancement of Science.

  8. A wheel-shaped single-molecule magnet of [MnII 3MnIII 4]: quantum tunneling of magnetization under static and pulse magnetic fields.

    Science.gov (United States)

    Koizumi, Satoshi; Nihei, Masayuki; Shiga, Takuya; Nakano, Motohiro; Nojiri, Hiroyuki; Bircher, Roland; Waldmann, Oliver; Ochsenbein, Stefan T; Güdel, Hans U; Fernandez-Alonso, Felix; Oshio, Hiroki

    2007-01-01

    The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (=H3(5-NO2-hbide)) with Mn(OAc)2* 4 H2O in methanol, followed by recrystallization from 1,2-dichloroethane, yielded a wheel-shaped single-molecule magnet (SMM) of [MnII 3MnIII 4(5-NO2-hbide)6].5 C2H4Cl2 (1). In 1, seven manganese ions are linked by six tri-anionic ligands and form the wheel in which the two manganese ions on the rim and the one in the center are MnII and the other four manganese ions are MnIII ions. Powder magnetic susceptibility measurements showed a gradual increase with chimT values as the temperature was lowered, reaching a maximum value of 53.9 emu mol(-1) K. Analyses of magnetic susceptibility data suggested a spin ground state of S=19/2. The zero-field splitting parameters of D and B 0 4 were estimated to be -0.283(1) K and -1.64(1)x10(-5) K, respectively, by high-field EPR measurements (HF-EPR). The anisotropic parameters agreed with those estimated from magnetization and inelastic neutron scattering experiments. AC magnetic susceptibility measurements showed frequency-dependent in- and out-of-phase signals, characteristic data for an SMM, and an Arrhenius plot of the relaxation time gave a re-orientation energy barrier (DeltaE) of 18.1 K and a pre-exponential factor of 1.63x10(-7) s. Magnetization experiments on aligned single crystals below 0.7 K showed a stepped hysteresis loop, confirming the occurrence of quantum tunneling of the on magnetization (QTM). QTM was, on the other hand, suppressed by rapid sweeps of the magnetic field even at 0.5 K. The sweep-rate dependence of the spin flips can be understood by considering the Landau-Zener-Stückelberg (LZS) model.

  9. Electric-field switchable magnetization via the Dzyaloshinskii-Moriya interaction: FeTiO3 versus BiFeO3

    International Nuclear Information System (INIS)

    Ederer, Claude; Fennie, Craig J

    2008-01-01

    In this paper we review and discuss a mechanism for coupling between electric polarization and magnetization that can ultimately lead to electric-field switchable magnetization. The basic idea is that a ferroelectric distortion in an antiferromagnetic material can 'switch on' the Dzyaloshinskii-Moriya interaction which leads to a canting of the antiferromagnetic sublattice magnetizations, and thus to a net magnetization. This magnetization M-vector is coupled to the polarization P-vector via a trilinear free energy contribution of the form P-vector·(M-vectorxxL-vector), where L-vector is the antiferromagnetic order parameter. In particular, we discuss why such an invariant is present in R3c FeTiO 3 but not in the isostructural multiferroic BiFeO 3 . Finally, we construct symmetry groups that in general allow for this kind of ferroelectrically-induced weak ferromagnetism.

  10. Low-field anomalous magnetic phase in the kagome-lattice shandite C o3S n2S2

    Science.gov (United States)

    Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

    2017-07-01

    The magnetization process of single crystals of the metallic kagome ferromagnet C o3S n2S2 was carefully measured via magnetization and ac susceptibility. Field-dependent anomalous transitions observed in low fields indicate the presence of an unconventional magnetic phase just below the Curie temperature, TC. The magnetic phase diagrams in low magnetic fields along different crystallographic directions were determined for the first time. The magnetic relaxation measurements at various frequencies covering five orders of magnitude from 0.01 to 1000 Hz indicate markedly slow spin dynamics only in the anomalous phase with characteristic relaxation times longer than 10 s.

  11. 3-D magnetic field calculations for wiggglers using MAGNUS-3D

    International Nuclear Information System (INIS)

    Pissanetzky, S.; Tompkins, P.

    1988-01-01

    The recent but steady trend toward increased magnetic and geometric complexity in the design of wigglers and undulators, of which tapered wigglers, hybrid structures, laced electromagnetic wigglers, magnetic cladding, twisters and magic structures are examples, has caused a need for reliable 3-D computer models and a better understanding of the behavior of magnetic systems in three dimensions. The capabilities of the MAGNUS-3D Group of Programs are ideally suited to solve this class of problems and provide insight into 3-D effects. MAGNUS-3D can solve any problem of Magnetostatics involving permanent magnets, linear or nonlinear ferromagnetic materials and electric conductors of any shape in space. The magnetic properties of permanent magnets are described by the complete nonlinear demagnetization curve as provided by the manufacturer, or, at the user's choice, by a simpler approximation involving the coercive force, the residual induction and the direction of magnetization. The ferromagnetic materials are described by a magnetization table and an accurate interpolation relation. An internal library with properties of common industrial steels is available. The conductors are independent of the mesh and are described in terms of conductor elements from an internal library

  12. Magnetic-flux dynamics of high-Tc superconductors in weak magnetic fields

    DEFF Research Database (Denmark)

    Il’ichev, E. V.; Jacobsen, Claus Schelde

    1994-01-01

    Aspects of magnetic-flux dynamics in different types of samples of the high-temperature superconductor YBa2Cu3Ox have been investigated in magnetic fields below 1 Oe and at 77 K. The experiments were carried out in an arrangement including a field coil, a flat sample perpendicular to the field...

  13. 3D accelerator magnet calculations using MAGNUS-3D

    International Nuclear Information System (INIS)

    Pissanetzky, S.; Miao, Y.

    1989-01-01

    The steady trend towards increased magnetic and geometric complexity in the design of accelerator magnets has caused a need for reliable 3D computer models and a better understanding of the behavior of magnetic system in three dimensions. The capabilities of the MAGNUS-3D family of programs are ideally suited to solve this class of problems and provide insight into 3D effects. MAGNUS-3D can solve any problem of magnetostatics involving permanent magnets, nonlinear ferromagnetic materials and electric conductors. MAGNUS-3D uses the finite element method and the two-scalar-potentials formulation of Maxwell's equations to obtain the solution, which can then be used interactively to obtain tables of field components at specific points or lines, plots of field lines, function graphs representing a field component plotted against a coordinate along any line in space (such as the beam line), and views of the conductors, the mesh and the magnetic bodies. The magnetic quantities that can be calculated include the force or torque on conductors or magnetic parts, the energy, the flux through a specified surface, line integrals of any field component along any line in space, and the average field or potential harmonic coefficients. We describe the programs with emphasis placed on their use for accelerator magnet design, and present an advanced example of actual calculations. (orig.)

  14. Initial magnetic field decay of the superconducting magnet in persistent current mode

    International Nuclear Information System (INIS)

    Yamamoto, S.; Yanada, T.

    1988-01-01

    The initial magnetic field decay in the persistent current mode of a magnetic resonance imaging magnet has been studied experimentally. The field decay is greater than the steady field decay due to joint resistances of conductors. Imaging experiments cannot be carried out during the periods, which last ten or more hours. The current distribution in the multifilamentory conductor is non-uniform just after the energization. It is suggested that the change of the current distribution causes the initial magnetic field decay. A 6th order superconducting magnet was prepared for experiments (central field = 0.35 T, inner diameters = 1 m, length = 1.86 m). The steady state magnetic field decay was 7*10/sup -8//hr. The initial magnetic field decay was 3*10/sup -6//hr. Overshoot currents (101 and 105 percent of the rated current) were applied to the magnet and the current reduced to the rated current to improve the initial decay. The energizing and de-energizing rate of the field was 1.8 gauss/second. No initial decay was observed when 105 percent current pattern was applied to the magnet

  15. A Comprehensive Model of the Near-Earth Magnetic Field. Phase 3

    Science.gov (United States)

    Sabaka, Terence J.; Olsen, Nils; Langel, Robert A.

    2000-01-01

    The near-Earth magnetic field is due to sources in Earth's core, ionosphere, magnetosphere, lithosphere, and from coupling currents between ionosphere and magnetosphere and between hemispheres. Traditionally, the main field (low degree internal field) and magnetospheric field have been modeled simultaneously, and fields from other sources modeled separately. Such a scheme, however, can introduce spurious features. A new model, designated CMP3 (Comprehensive Model: Phase 3), has been derived from quiet-time Magsat and POGO satellite measurements and observatory hourly and annual means measurements as part of an effort to coestimate fields from all of these sources. This model represents a significant advancement in the treatment of the aforementioned field sources over previous attempts, and includes an accounting for main field influences on the magnetosphere, main field and solar activity influences on the ionosphere, seasonal influences on the coupling currents, a priori characterization of ionospheric and magnetospheric influence on Earth-induced fields, and an explicit parameterization and estimation of the lithospheric field. The result of this effort is a model whose fits to the data are generally superior to previous models and whose parameter states for the various constituent sources are very reasonable.

  16. The magnetic field dependent dynamic properties of magnetorheological elastomers based on hard magnetic particles

    Science.gov (United States)

    Wen, Qianqian; Wang, Yu; Gong, Xinglong

    2017-07-01

    In this study, novel magnetorheological elastomers based on hard magnetic particles (H-MREs) were developed and the magnetic field dependent dynamic properties of the H-MREs were further investigated. The storage modulus of H-MREs could not only be increased by increasing magnetic field but also be decreased by the increasing magnetic field of opposite orientation. For the anisotropic H-MREs with 80 wt% NdFeB particles, the field-induced increasing and decreasing modulus was 426 kPa and 118 kPa respectively. Moreover, the dynamic performances of H-MREs significantly depended on the pre-structure magnetic field, magnetizing field and test magnetic field. The H-MREs were initially magnetized and formed the chain-like microstructure by the pre-structure magnetic field. The field-induced increasing and decreasing modulus of H-MREs both raised with increasing of the magnetizing field. When the magnetizing field increased from 400 to 1200 kA m-1, the field induced decreasing modulus of the 80 wt% isotropic H-MREs raised from 3 to 47 kPa. The magnetic field dependent curves of H-MREs’ storage modulus were asymmetric if the magnetizing field was higher than the test magnetic field. Based on the dipolar model of MREs and magnetic properties of hard magnetic material, a reasonable explanation was proposed to understand the H-MREs’ field dependent mechanical behaviors.

  17. Two dimensional kicked quantum Ising model: dynamical phase transitions

    International Nuclear Information System (INIS)

    Pineda, C; Prosen, T; Villaseñor, E

    2014-01-01

    Using an efficient one and two qubit gate simulator operating on graphical processing units, we investigate ergodic properties of a quantum Ising spin 1/2 model on a two-dimensional lattice, which is periodically driven by a δ-pulsed transverse magnetic field. We consider three different dynamical properties: (i) level density, (ii) level spacing distribution of the Floquet quasienergy spectrum, and (iii) time-averaged autocorrelation function of magnetization components. Varying the parameters of the model, we found transitions between ordered (non-ergodic) and quantum chaotic (ergodic) phases, but the transitions between flat and non-flat spectral density do not correspond to transitions between ergodic and non-ergodic local observables. Even more surprisingly, we found good agreement of level spacing distribution with the Wigner surmise of random matrix theory for almost all values of parameters except where the model is essentially non-interacting, even in regions where local observables are not ergodic or where spectral density is non-flat. These findings question the versatility of the interpretation of level spacing distribution in many-body systems and stress the importance of the concept of locality. (paper)

  18. Magnetic fringe field interference between the quadrupole and corrector magnets in the CSNS/RCS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Mei, E-mail: yangmei@ihep.ac.cn [Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); China Spallation Neutron Source, Institute of High Energy Physics, Chinese Academy of Sciences, Dongguan 523803,China (China); Dongguan Neutron Science Center, Dongguan 523808,China (China); Kang, Wen; Deng, Changdong [Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); China Spallation Neutron Source, Institute of High Energy Physics, Chinese Academy of Sciences, Dongguan 523803,China (China); Dongguan Neutron Science Center, Dongguan 523808,China (China); Sun, Xianjing [Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Li, Li; Wu, Xi [Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); China Spallation Neutron Source, Institute of High Energy Physics, Chinese Academy of Sciences, Dongguan 523803,China (China); Dongguan Neutron Science Center, Dongguan 523808,China (China); Gong, Lingling; Cheng, Da [Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhu, Yingshun; Chen, Fusan [Key Laboratory of Particle Acceleration Physics and Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2017-03-01

    The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) employs large aperture quadrupole and corrector magnets with small aspect ratios and relatively short iron to iron separations; so the fringe field interference becomes serious which results in integral field strength reduction and extra field harmonics. We have performed 3D magnetic field simulations to investigate the magnetic field interference in the magnet assemblies and made some adjustments on the magnet arrangement. The Fourier analysis is used to quantify the integral gradient reduction and field harmonic changes of the quadrupole magnets. Some magnetic field measurements are undertaken to verify the simulation results. The simulation details and the major results are presented in this paper.

  19. The spin S quantum Ising model at T=0

    International Nuclear Information System (INIS)

    Kamieniarz, G.; Kowalewski, L.; Piechocki, W.

    1982-09-01

    The Ising model with a transverse field for a general spin S is investigated within the framework of the Green-function method in the paramagnetic region at T=0. The analysis of selfconsistent equations gives a description of softmode phase transition as well as extrapolated values of critical fields and critical energy gap exponents. (author)

  20. Magnetic Fields Versus Gravity

    Science.gov (United States)

    Hensley, Kerry

    2018-04-01

    Deep within giant molecular clouds, hidden by dense gas and dust, stars form. Unprecedented data from the Atacama Large Millimeter/submillimeter Array (ALMA) reveal the intricate magnetic structureswoven throughout one of the most massive star-forming regions in the Milky Way.How Stars Are BornThe Horsehead Nebulasdense column of gas and dust is opaque to visible light, but this infrared image reveals the young stars hidden in the dust. [NASA/ESA/Hubble Heritage Team]Simple theory dictates that when a dense clump of molecular gas becomes massive enough that its self-gravity overwhelms the thermal pressure of the cloud, the gas collapses and forms a star. In reality, however, star formation is more complicated than a simple give and take between gravity and pressure. Thedusty molecular gas in stellar nurseries is permeated with magnetic fields, which are thought to impede the inward pull of gravity and slow the rate of star formation.How can we learn about the magnetic fields of distant objects? One way is by measuring dust polarization. An elongated dust grain will tend to align itself with its short axis parallel to the direction of the magnetic field. This systematic alignment of the dust grains along the magnetic field lines polarizes the dust grains emission perpendicular to the local magnetic field. This allows us to infer the direction of the magnetic field from the direction of polarization.Magnetic field orientations for protostars e2 and e8 derived from Submillimeter Array observations (panels a through c) and ALMA observations (panels d and e). Click to enlarge. [Adapted from Koch et al. 2018]Tracing Magnetic FieldsPatrick Koch (Academia Sinica, Taiwan) and collaborators used high-sensitivity ALMA observations of dust polarization to learn more about the magnetic field morphology of Milky Way star-forming region W51. W51 is one of the largest star-forming regions in our galaxy, home to high-mass protostars e2, e8, and North.The ALMA observations reveal