Theory of Resolved and Unresolved Crystal Field Structure of ESR Spectra in Dilute Magnetic Alloys

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Abstract
The influence of crystal fields on the dynamic transverse susceptibility of localized spin moments coupled to the conduction electrons in a metal is investigated. In Liouville‐space, the projector onto the subspace is introduced which is spanned by the transverse component of the conduction electron magnetization and the transition operators of the crystal field energy levels. Within the framework of projector formalism, the susceptibility is expressed in terms of a transition matrix which is then calculated in lowest order perturbation theory. The found explicit expression of the susceptibility is valid for the isothermal case as well as for the bottleneck one. The theoretical predicted resolved and unresolved ESR spectra are discussed for high and low temperature. For the bottleneck and the isothermal case, a resolved spectrum is expected when crystal field splittings are greater than the Korringa relaxation rate.