Simple Theory of the ?Negative Residual Linewidth? in Reflection Spectroscopy of Magnetically Concentrated Local Moment Systems

Abstract

A mathematically improved analytical approximation is obtained to the solutions of the phenomenological equations of H. Hasegawa that describe the electron spin resonance of local moments in metals and the bottleneck effect that frequently occurs. The approximation shows that at all temperatures above the Curie point () the Iinewidth is proportional to T -- () for any degree of bottlenecking, and not to temperature T. The solution also reveals that the g shift remains explicitly independent of temperature down to the Curie point. The expressions obtained take into account explicitly the direct local moment spin lattice relaxation rate and show that it is effective in breaking the bottleneck.