共查询到20条相似文献,搜索用时 765 毫秒
1.
Thermodynamic properties of the spin-1/2 ferromagnetic Heisenberg chain with long-range interactions
The one-dimensional spin-1/2 XYZ ferromagnetic model in a transverse field and uniform long-range interactions among the z components of the spins is studied using the mean-field Jordan–Wigner transformation. The thermodynamic quantities results like Helmholtz free energy, the internal energy, the specific heat and the isothermal susceptibility are obtained both analytically and numerically. The phase transition of the system at a finite temperature is also discussed. Our results agree with numerical results of the XYZ spin chain by others. 相似文献
2.
A. M. Khamzin R. R. Nigmatullin 《Journal of Experimental and Theoretical Physics》2010,111(6):1028-1038
A simple model is proposed for describing magnetic properties of magnetoactive nanoclusters, which permits exact analytic
solution. Exact expressions are obtained for thermodynamic characteristics of the model, which hold in the entire range of
temperatures, magnetic fields, and interaction parameters. It is found that in the case of easy-axis anisotropy, the field
dependence of magnetization of a nanocluster consisting of N particles with a spin of 1/2 has [N/2] fractional plateaus ([…] is the integer part) corresponding to polarized phases with ruptures singlet pairs. A nonmonotonic
behavior observed for the magnetic susceptibility of an easy-plane cluster is typical of gap magnets. The spin gap between
the ground state and excited states is proportional to the anisotropy parameter. 相似文献
3.
Based on the effective mass approximation, the magnetic and thermal properties of parabolic GaAs quantum dot have been investigated in the presence of Rashba Spin-Orbit interaction (RSOI), donor impurity and applied magnetic and electric fields. The exact diagonalization method has been used to solve the Hamiltonian of an electron confined in a quantum dot (QD) and obtain the eigenenergies and the binding energy of the donor impurity as a function of various QD physical parameters. We have shown the dependence of the average statistical energy, magnetization, magnetic susceptibility and heat capacity of the donor impurity in the QD on: the Rashba interaction parameter, the magnetic and electric fields, confining frequency, and temperature. The results reveal that these parameters can tune the magnetic properties of the GaAs quantum dot and flip the sign of magnetic susceptibility from negative (diamagnetic) to positive (paramagnetic) type material. 相似文献
4.
F. Mancini F. P. Mancini 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(3):341-351
Within the Green’s function and equations of motion formalism it is possible to exactly solve a large class of models useful
for the study of strongly correlated systems. Here, we present the exact solution of the one-dimensional extended Hubbard
model with on-site U and first nearest neighbor repulsive V interactions in the presence of an external magnetic field h,
in the narrow band limit. At zero temperature our results establish the existence of four phases in the three-dimensional
space (U, n, h) – n is the filling – with relative phase transitions, as well as different types of charge ordering. The magnetic
field may dramatically affect the behavior of thermodynamic quantities, inducing, for instance, magnetization plateaus in
the magnetization curves, and a change from a single to a double-peak tructure in the specific heat. According to the value
of the particle density, we find one or two critical fields, marking the beginning of full or partial polarization. A detailed
study of several thermodynamic quantities is also presented at finite temperature. 相似文献
5.
The magnetization fluctuations are considered in thin films treated as a set of monoatomic layers parallel to the film surfaces. The correlation functions have been determined and their forms are discussed. The influence of inhomogeneity of magnetization on the equation of state for a magnetic system described by Valenta's model is studied. The behaviour of the spontaneous magnetization as well as the magnetic susceptibility near the Curie point is described.This work is partially supported by the Institute of Physics of the P.A.S. 相似文献
6.
利用有效场理论研究了纳米管上外磁场中Blume-Capel模型格点的磁化强度、磁化率、内能、比热和自由能,得到了系统格点的磁化强度、磁化率、内能、比热和自由能与外磁场和晶场的关系.结果表明:外磁场强度、交换相互作用和晶场强度等诸多因素相互竞争,使系统表现出比没有外磁场作用的Blume-Capel模型更为丰富的磁学特性;外磁场能够增大系统格点的磁化强度,导致系统的二级相变消失;负晶场作用系统时,系统会发生一级相变;晶场强度、外磁场强度不同时,系统的磁化率、内能、比热和自由能也呈现出复杂性. 相似文献
7.
The emergence of a finite staggered magnetization in quantum Heisenberg antiferromagnets subject to a uniform magnetic field can be viewed as Bose-Einstein condensation of magnons. Using nonperturbative results for the infrared behavior of the interacting Bose gas, we present exact results for the staggered spin-spin correlation functions of quantum antiferromagnets in a magnetic field at zero temperature. In particular, we show that in dimensions 1相似文献
8.
Experimental observation of the 1/3 magnetization plateau in the diamond-chain compound Cu3(CO3)2(OH)2 总被引:1,自引:0,他引:1
Kikuchi H Fujii Y Chiba M Mitsudo S Idehara T Tonegawa T Okamoto K Sakai T Kuwai T Ohta H 《Physical review letters》2005,94(22):227201
The magnetic susceptibility, high field magnetization, and specific heat measurements of Cu3(CO3)2(OH)2, which is a model substance for the frustrating diamond spin chain model, have been performed using single crystals. Two broad peaks are observed at around 20 and 5 K in both magnetic susceptibility and specific heat results. The magnetization curve has a clear plateau at one third of the saturation magnetization. The experimental results are examined in terms of theoretical expectations based on exact diagonalization and density matrix renormalization group methods. An origin of magnetic anisotropy is also discussed. 相似文献
9.
高分辨核磁共振(Nuclear Magnetic Resonance,NMR)谱的获得通常需要高度稳定且均匀的强静磁场. 阻抗磁体或阻抗-超导混合磁体可获得比超导磁体高得多的磁场, 但它们的磁场的稳定性与均匀性比较差;另一方面, 在活体定域波谱研究中,样品内部组分的磁化率差异,运动或生理活动等作用将不可避免地导致磁场的不均匀不稳定,并且这些不稳定不均匀性无法通过锁场匀场等传统的方法消除. 基于分子间零量子相干的方法、空间编码单扫描快速方法、反卷积技术等日渐成为在不均匀不稳定磁场下获取高分辨率的NMR谱的研究热点. 相似文献
10.
A. F. Deutz H. B. Brom H. Deelen L. J. de Jongh W. J. Huiskamp
K. H. J. Buschow
《Solid State Communications》1986,60(12):917-921We present measurements of the magnetization in very high fields, the low temperature specific heat and the AC susceptibility, both in zero and nonzero magnetic field, of the intermetallic cubic Laves phase compound TmNi2. This material appears to be a singlet-singlet system with an inter-ionic exchange which just exceeds the critical value for magnetic ordering. The absence of a clear anomaly in the specific heat near the ferromagnetic transition temperature Tc = 1.1 K is discussed in a molecular field approximation including crystal field effects. The results of the experiments can qualitatively be described in terms of a set of crystal field parameters corresponding to a Hamiltonian for a system with a distortion from cubic symmetry. 相似文献
11.
Self-Consistent Spin-Wave Analysis of the 1/3 Magnetization Plateau in the Kagome Antiferromagnet 下载免费PDF全文
《中国物理快报》2016,(7)
We propose a modified spin-wave theory to study the 1/3 magnetization plateau of the antiferromagnetic Heisenberg model on the kagome lattice.By the self-consistent inclusion of quantum corrections,the 1/3 plateau is stabilized over a broad range of magnetic fields for all spin quantum numbers S.The values of the critical magnetic fields and the widths of the magnetization plateaus are fully consistent with the recent numerical results from exact diagonalization and infinite projected entangled paired states. 相似文献
12.
YANG Guo-Hui GAO Wen-Bin ZHOU Ling SONG He-Shan 《理论物理通讯》2007,48(3):453-456
The thermal entanglement of a two-qubit anisotropic Heisenberg XYZ chain under an inhomogeneous magnetic field b is studied. It is shown that when inhomogeneity is increased to a certain value, the entanglement can exhibit a larger revival than that of less values of b. The property is both true for zero temperature and a finite temperature. The results also show that the entanglement and threshold temperature can be increased by increasing inhomogeneous external magnetic field. 相似文献
13.
Blume–Emery–Griffiths纳米管的热力学与相变性质 总被引:1,自引:0,他引:1
利用有效场理论研究了圆柱形纳米管上Blume-Emery-Griffiths系统的热力学与相变性质,得到了系统的磁化强度、磁化率、比热和相图.讨论了四次交换作用与二次交换作用的比值 与晶格场对系统热力学量和相图的影响.研究发现:系统存在三临界点,且三临界点由参数 和晶格场共同决定,即若确定了参数 ,则三临界点所对应的晶格场也能确定.随着参数 的增加,系统出现三临界点时所对应的温度和晶格场也相应增大. 相似文献
14.
The thermal entanglement of a two-qubit anisotropic Heisenberg XYZ chain under an inhomogeneous magnetic field b is studied. It is shown that when inhomogeneity is increased to a certain value, the entanglement can exhibit a larger revival than that of less values of b. The property is both true for zero temperature and a finite temperature. The results also show that the entanglement and threshold temperature can be increased by increasing inhomogeneous external magnetic field. 相似文献
15.
MM Altarawneh GW Chern N Harrison CD Batista A Uchida M Jaime DG Rickel SA Crooker CH Mielke JB Betts JF Mitchell MJ Hoch 《Physical review letters》2012,109(3):037201
We present magnetization and magnetostriction studies of LaCoO_{3} in magnetic fields approaching 100?T. In contrast with expectations from single-ion models, the data reveal two distinct first-order transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co^{3+} ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co^{3+} ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data. 相似文献
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17.
The magnetization behavior of q-periodic antiferromagnetic spin- 1/2 Heisenberg chains under uniform magnetic fields is investigated in a background of disorder exchange distributions. By means of both real space decimation procedures and numerical diagonalizations in XX chains, it is found that for binary disorder the magnetization exhibits wide plateaus at values of 1+2(p-1)/q, where p is the disorder strength. In contrast, no spin gaps are observed in the presence of continuous exchange distributions. We also study the magnetic susceptibility at low magnetic fields. 相似文献
18.
J. Stre?ka M. Jaš?ur Y. Narumi S. Kimura 《Journal of Physics and Chemistry of Solids》2005,66(10):1828-1837
Magnetic behavior of a spin-1 Heisenberg dimer is analysed in dependence on the both uniaxial single-ion anisotropy and XXZ exchange anisotropy in a zero- as well as non-zero longitudinal magnetic field. A complete set of eigenfunctions and eigenvalues of the total Hamiltonian is presented together with an exact analytical expression for the Gibbs free energy, longitudinal magnetization, longitudinal and transverse susceptibility. The obtained theoretical results are compared with the relevant experimental data of [Ni2(Medpt)2(μ-ox)(H2O)2](ClO4)2·2H2O (Medpt=methyl-bis(3-aminopropyl)amine). 相似文献
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20.
R. Z. Sadykhov M. A. Aldzhanov E. M. Kerimova M. D. Nadzhafzade 《Physics of the Solid State》2012,54(9):1827-1828
The specific heat, magnetization, and magnetic susceptibility of TlErSe2 have been studied in the temperature range 77?C300 K. The main thermodynamic functions of TlErSe2, namely, the changes of entropy and enthalpy, have been determined from the temperature dependence of the specific heat. 相似文献