Bottlenecking of indirect g shifts of local moments in metals

The indirect g shift in the electron spin resonance of local moments in metals is examined using the Bloch-Hasegawa equations. The g shift is found to have three components. First the usual Hasegawa term that decreases as the bottleneck increases, and second, a temperature dependent indirect shift that is unaffected by the bottleneck. The third term becomes unobservable in the unbottlenecked limit; it is proportional to the ratio of the non S-state local moment susceptibility to the S-state local moment susceptibility. The width of the resonance is found to be proportional to T — θ, where θ is the ordering temperature, and not to temperature T, thereby providing an explanation for the “negative” residual linewidth frequently observed in magnetically concentrated systems.