Spectrum of dynamic magnetic susceptibility of a randomized f–d magnet with spin–lattice coupling. I. Shift of the magnetic resonance frequencies

In narrow-band ferromagnetic conductors containing local f and quasilocal d magnetic moments the interatomic spin correlations created by the combined effects of the intra-atomic interactions of the quasilocal electrons and their intersite hops are playing a role in the formation of the magnetic resonance spectra. This role is examined, and the transformation of the spectra of the transverse dynamic magnetic susceptibility under conditions of weak spin–lattice coupling and spatial randomization of the g factors of the quasilocal and local spin subsystems is investigated. A calculation done by the method of two-time retarded Green’s functions shows that the interaction of the d and f electrons leads to an effective renormalization of the g factors of both magnetic subsystems, and at zero temperature the spin–lattice coupling lowers the frequency of the inhomogeneous magnetic resonance and causes threshold damping of acoustic and optical magnons.