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Two-step magnetization in a spin-chain system on the triangular lattice: Wang-Landau simulation

Physical Review B

The Wang-Landau algorithm is used to study the thermodynamic and magnetic properties of triangular spin-chain system based on two-dimensional Ising model in order to understand the magnetic-order dynamics in Ca(3)Co(2)O(6) compound. The calculated results demonstrate that the equilibrium state of the rigid spins produces the two-step magnetization curve at low temperature even when the random-exchange term is considered. This work indicates that the four-step magnetization behavior observed experimentally must be due to the nonequilibrium magnetization.

关键词: calcium compounds;exchange interactions (electron);Ising model;magnetisation;thermodynamics;one-dimensional ca3co2o6;density-of-states;compound ca3co2o6;phase-diagram;proteins;crystal

Investigations of the g factors of Fe+ in MgO and CaO

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The g factors of Fe+ in MgO and CaO are theoretically investigated by the perturbation formula of the g factor of a V ion in cubic octahedral symmetry based on the cluster approach. By considering the partial quenching of the spin-orbit coupling interaction and the effective Lande factor due to the dynamic Jahn-Teller effect (DJTE), the experimental g factors of the studied systems are reasonably interpreted. It can be suggested that the small g factors of the Fe+ centers in MgO and CaO can be likely attributed to the DJTE, rather than the covalency effect within the scheme of the static crystal-field model.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Fe+;MgO;CaO;atomic screening constants;electron spin resonance;paramagnetic-resonance;orbit interaction;scf functions;crystals;spectra;oxide;co2+

Investigations of the g factors for Co2+ in fluoroperovskites

Physica B-Condensed Matter

The perturbation formula of g factor for 3d(7) ion in cubic octahedral crystals has been obtained from a cluster approach. In the formula, the parameters related to the configuration interaction and the covalency reduction effect can be obtained from the optical spectra of the crystal under study and so no adjustable parameters are applied. From the formula, the g factors for Co2+ in fluoroperovskites LiBaF3, KMBF3, KZnF3 and CsCdF3 are calculated. The calculated results are in agreement with the observed values. The g factor following the order of LiBaF3 : Co2+ < KMgF3 : Co2+ < KZnF3: Co2+ < CsCdF3 : Co2+ is also explained. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Co2+;LiBaF3;KMgF3;KZnF3;CsCdF3;perovskite;transition;impurities;crystals

利用(G’/G)展开法求解广义变系数Burgers方程

庞晶 , 靳玲花 , 应孝梅

量子电子学报 doi:10.3969/j.issn.1007-5461.2011.06.005

近年来,变系数非线性发展方程受到越来越多的关注. 2008年王明亮等提出了一种新的方法,即(G’/G)展开法.将(G’/G)展开法首次尝试应用到变系数非线性发展方程中,并以广义变系数Burgers方程为例,成功得到了在系数满足一定条件时新的精确解;又尝试将该展开法进行新的扩展,再一次对广义变系数Burgers方程求解,又成功得到了一些新解.实践证明,该展开法不仅易于求解常系数非线性发展方程,而且对变系数非线性发展方程仍很高效、简洁、实用,并且具有广泛的应用前景.

关键词: 非线性发展方程 , 精确解 , (G’/G)展开法 , 广义变系数Burgers方程

应用改进的G/G'展开法求ZS方程的精确解

冯庆江 , 杨世玲

量子电子学报 doi:10.3969/j.issn.1007-5461.2013.06.007

应用改进的G/G'展开法构造出Zhiber-Shabat(ZS)方程的20组精确解,这些解的类型主要包含双曲函数通解、三角函数通解和有理函数通解三种形式.对解的性质进行了相应分析,当对双曲函数通解中的参数取特殊值时,可以得到孤立波解.当对三角函数通解中的参数取特殊值时,可以得到对应的周期波函数解.实践证明,应用改进的G/G'展开法能够得到方程一些新的精确解,扩大了解的范围.

关键词: 非线性方程 , 改进的G/G'展开法 , ZS方程 , 孤立波解 , 周期波解

应用改进的G'/G2展开法求Zakharov方程的精确解

冯庆江 , 肖绍菊

连铸 doi:10.3969/j.issn.1007-5461.2015.01.006

应用改进的G'/G2展开法构造出Zakharov方程的18组精确解,这些解主要包括双曲函数通解、三角函数通解和有理函数通解三种形式.当对双曲函数通解中的参数取特殊值时,可以得到孤立波解.对三角函数通解中的参数取特殊值时,可以得到对应的周期波函数解.实践证明,应用改进的G'/G2展开法能够得到Zakharov方程一些新的精确解,扩大了解的范围,这种方法对于研究非线性光学和量子光学具有非常广泛的应用意义.

关键词: 非线性方程 , 改进的G'/G2展开法 , Zakharov方程 , 孤立波解

Investigations of the EPR g factors for Er3+ in CaMoO4

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The electron paramagnetic resonance (EPR) g factors g(parallel to) and g(perpendicular to) for Er3+ in CaMoO4 are theo retically investigated by using the perturbation formulas of the g factors for a 4f(11) ion in tetragonal symmetry. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various states are considered. The crystal-field parameters for the tetragonally distorted tetrahedra are determined by using the superposition model and the structural data of the impurity Er3+ on the host Ca2+ site in CaMoO4. The calculated g factors agree with the. observed values. The validity of the results is discussed.

关键词: electron paramagnetic resonance (EPR);crystal- and spin Hamiltonians;Er3+;CaMoO4;electron-paramagnetic-resonance;superposition-model;molybdate;crystals;calcium molybdate;ion;spectroscopy;parameters;tungstate;liyf4

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