杂质散射引起的亚铁磁体的共振线宽

本文得到了具有二个等价次点阵的椭球亚铁磁体的二支自旋波频谱,它们的频率对波矢的依赖关系与椭球铁磁体的相类似。基于此频谱和交换作用涨落引起的自旋波散射机制,计算了一致共振和交换共振的线宽。对一致共振,用等效铁磁模型得到的结论仍然成立:非磁性杂质离子和自旋等于同一次点阵上基质离子自旋的杂质离子,对一致共振线宽没有贡献。但这二类杂质离子对交换共振线宽有贡献。用我们的简化亚铁磁模型对各种铁氧体算得的一致共振线宽差别很大。对许多尖晶石型铁氧体,交换作用涨落可能是引起一致共振线宽的主要机制。对于铁氧体,由此机制引起的交换共振线宽其数量级为几十奥。

ON THE RESONANCE LINE WIDTH OF FERRIMAGNETICS CAUSED BY IMPURITY SCATTERING

In this work, it has been found for an ellipsoid of a ferrimagnetic with two equivalent sublattices of unlike ions that the frequency spectrum of spin waves consists of two branches and in each of them the dependence of frequency on the wave vector is similar to the spin wave spectrum of a ferromagnetic ellipsoid. Based on this spectrum and the scattering mechanism of spin waves due to the fluctuation of exchange interactions, calculations have been made for the line width of the uniform resonance and that of the exchange resonance. For the former the conclusions obtained by using the model of an equivalent ferromagnetic are still valid; i.e. nonmagnetic impurity ions and the impurity ions whose spins equal to that of the matrix ion on the same sublattice have no effect on the line width of uniform resonance. However, the impurity ions of both these kinds should give rise to the line width of exchange resonance. There exists a large difference in the line width of uniform resonance estimated for various ferrites by making use of our simplified model of ferrimagnetism. Quite probably the fluctuation of the exchange interactions is the main cause of the line width of uniform resonance in a number of ferrites. The exchange resonance line width caused by this mechanism are estimated for ferrites generally of the order of several tens in the oersted.