Generalized CPA approach to the disordered Heisenberg ferromagnet
Generalized CPA approach to the disordered Heisenberg ferromagnet
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无序海森堡铁磁体的广义 CPA 方法
DOI：
10.1088/0022-3719/7/13/013
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发表时间：
1974
期刊：
影响因子：
--
通讯作者：
A. Theumann
中科院分区：
文献类型：
--
作者：
A. Theumann
考虑一种铁磁二元合金，其中各组分的自旋分别为SA， SB，浓度分别为XA， XB=1-XA。相互作用由海森堡哈密顿量给出，在最近的自旋Salpha， Sbeta （α, β =A或B）之间具有交换常数Jalpha beta。结果表明，忽略自旋SA （SB）在静态场中的波动，对于具有分量的构型平均矩阵Gij，可以写出广义CPA方程。该形式在两个分量中都是对称的，并且对交换常数和自旋的任意值都有效。在一般情况下，预计它只适用于浓度的中间值，因为它无法在稀释极限Xalpha <<1（alpha =A或B）中重现已知的精确结果，因为局部场的近似处理抑制了p和d模式并改变了s模式的能量。然而，当杂质自旋和主自旋的值受到条件(Salpha Jalpha alpha /Salpha Jalpha alpha)=1的限制时，如果α =B或A，则α =A或B，则该理论再现了精确的结果。
A ferromagnetic binary alloy is considered where each component has spin SA, SB and concentration XA, XB=1-XA, respectively. The interaction is given by the Heisenberg hamiltonian with exchange constants Jalpha beta between nearest-neighbour spins Salpha , Sbeta ( alpha , beta =A or B). It is shown that neglecting fluctuations in the static field seen by a spin SA (SB), generalized CPA equations can be written for the configurational average matrix Gij, with components Gijalpha beta . The formalism is symmetric in both components and valid for arbitrary values of the exchange constants and spins. In the general case it is expected to be good only for intermediate values of the concentrations, because it fails to reproduce the known exact results in the dilute limit Xalpha <<1( alpha =A or B) due to the approximate treatment of the local field that suppresses the p and d modes and modifies the energy of the s modes. However, it is shown that the theory reproduces the exact results when the values of the impurity and host spins are restricted by the condition (Salpha Jalpha alpha /Salpha Jalpha alpha )=1, where alpha =A or B if alpha =B or A.