铁磁体中缺陷对自旋波的影响

本文提出了一个处理磁性杂质或其他缺陷在磁性晶体中对自旋波频谱的影响的一般理论方法,并特别着重讨论了局域模自旋波。以一维线性格子为例进行计算的结果显示出:一个代位磁性杂质,可能产生不只一个高于连续带顶的局域模。其产生的条件和其能级位置均通过J′S′/JS和J′/J表达出来,这里S′和S各为杂质原子和基质原子的自旋量子数,J′和J各为杂质与近邻之间和一般近邻之间的交换作用系数。高度集中的应变和间隙原子如致使邻近处的交换作用增大,也导致局域模的出现。我们也考虑了磁偶极矩相互作用的影响,证明其并不破坏这些局域模的

EFFECT OF IMPERFECTIONS ON SPIN WAVES IN FERROMAGNETS

A general theoretical approach is developed to treat the effect of point imperfections on the spin waves in a ferromagnetic crystal. Special attention is paid to the formation of localized modes. As an example, the calculations have been carried out for a one-dimensional linear lattice. The main results obtained indicate the following features. A substitutional magnetic impurity atom may introduce more than one localized mode of spin waves. The conditions for the localized modes to appear and the positions of their energy levels are given in terms of J′S′/JS and J′/J. Here S′ and S are respectively the spin quantum number of the impurity and that of the normal atoms. J′ and J are respectively the exchange integral between an impurity and its neighbors and that between the normal neighboring atoms. Highly concentrated strains and interstitial atoms which cause the exchange interaction between the atoms in their neighborhood to increase lead also to the formation of localized modes. Furthermore, the dipole-dipole interaction has been taken into consideration with the conclusion reached that it should not destroy the existence of these localized modes. Discussions have been given to the discrete energy levels which appear below the continuous spectrum in case of J′<0. It is pointed out that the Holstein-Primakoff approximation adopted in the present work is not quite legitimate for certain cases in which on one or more atoms the spin deviation becomes not very much smaller than 2S or 2S′.