Semiclassical Magnetization Dynamics with Combined Landau–Lifshitz and Gilbert Relaxation and Electron Paramagnetic Resonance

Abstract

A semiclassical model of magnetization dynamics with a combined relaxation term, including Landau–Lifshitz and Gilbert contributions, is considered and applied for the computation of the electron paramagnetic resonance (EPR) spectra. It is shown that when both contributions have comparable amplitudes, varying the relaxation parameter leads to a restructuring of the EPR spectrum, emulating a magnetic transition with an abrupt change in the resonance field and splitting of the absorption line into several spectral components. These effects occur in a system describing single magnetic oscillator with a constant gyromagnetic ratio and are caused exclusively by the peculiarities of magnetic relaxation in systems with significant damping, i.e., with broad EPR absorption lines. Such lines are characteristic of various strongly correlated electron systems, where magnetic fluctuations additionally contribute to line broadening. The simulation results show that the complex structure of EPR spectra in strongly correlated electron systems may be due to magnetic relaxation processes and, in general, may not be associated with the presence of several types of oscillating magnetic dipoles.