交换作用涨落所引起的铁磁共振线宽

本文同时考虑自旋矩和交换积分的室间涨落,计算了在一个次点阵上有二类阳离子无规分布的铁氧体的铁磁共振线宽。这种不均匀性使由微波场所激发的一致进动散射为与之简併的自旋波。Clogston等用来解释此线宽的赝偶极作用涨落是估计过高了,它与我们现在所考虑的交换作用涨落相比实际上可以略去。我们计算的结果不仅给出了足够大的线宽,它在数量级上与许多反型尖晶石型铁氧体的实验结果相同,并且自然地解释了镁锰铁氧体和无序锂铁氧体的线宽非常小的原因。

ON THE FERROMAGNETIC RESONANCE LINE WIDTH CAUSED BY THE FLUCTUATION OF THE EXCHANGE INTERACTIONS

In this work, the ferromagnetic resonance line width of a ferrite with two kinds of cations randomly distributed on a sublattice is calculated by taking into account the spatial fluctuation of both the spins and the exchange integrals. The uniform precession excited by the microwave field is scattered into degenerate spin waves by this inhomo-geneity. It is explained that the fluctuation of the pseudo-dipole forces considered by Clogston et al. was overestimated and is actually negligible in the present problem as comparing with the fluctuation of the exchange interactions. The result of our calculation not only gives rise to a large line width in the same order of magnitude as that observed with a number of inverted spinels, but also leads very naturally to an explanation of the noticeably small line width observed with the magnesium-manganese ferrite and the disordered lithium ferrite.