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Bethe-Weiss方法是Bethe对合金有序现象所创建的近似理论被移植于铁磁性海森堡模型的统计理论的结果。在这方法中,我们选出由一个中心原子与它所有的最近邻原子所组成的集团作为处理的对象,它们之间的交换作用得到精确的对待,而集团以外的原子的作用就近似地用一有效场代替,后者由自洽条件来推。我们应用这一方法来计算由磁性原子(自旋为1/2)与非磁性原子组成的代换固溶体在较高温度段内的铁磁性,得出简单立方和体心立方晶格居里点Tc随非磁性原子浓度f的增加而下降的曲线,居里点以上的磁化率与磁矩的短程有序能与温度的关系。由后者看出,当f增加时,在有较高的短程有序的情况下才出现铁磁性。从居里点的计算中发现:这一方法只能应用在非磁性原子的浓度较低的情况,我们讨论了这一事实出现的原因。The Bethe-Weiss method in the statistical theory of Heisenberg ferromagnetism is generalized and applied to the case of subtitutional solid solutions of random distribution. Calculations are carried out for binary solutions containing magnetic atoms of spin 1/2 and nonmagnetic ones. The Curie temperature v.s. composition and the paramagnetic susceptibility v.s. temperature curves are obtained for simple and body-centered cubic lattices. The degree of magnetic short-range order at the Curie point becomes higher as the concentration of non-magnetic atoms increases. The results are qualitatively applicable to solutions of two different kinds of magnetic atoms. It is also concluded that the method gives an useful approximation only for higher concentrations of magnetic atoms.
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