Experimental Evidence for a New Interpretation of Local-Moment Resonances in Metals

The transmission and two reflection spin-resonance signals for single-crystal $\mathrm{Ag}\mathrm{Gd}$ are shown to have the same crystal-field parameter, and hence are attributable to an isolated local moment. This identification illustrates why $S$-state resonance data need re-examination. The ratio of the averages of $J(k, k^{\prime })$ appropriate to the exchange field and relaxation rate of the local moment is ≃ 3 which may be difficult to interpret within the framework of presently accepted models.