Phonon-induced spin inertia in ferromagnets

Abstract

Spintronics has been gaining attention due to its possible technical applications. A central topic in spintronics is magnetization dynamics, often described by the Landau-Lifshitz-Gilbert equation. This equation accurately describes the dynamics of many spin systems, and has been experimentally confirmed. However, there have been theoretical predictions that this equation is not complete, and should be expanded with inertial terms. Recently, this prediction has been confirmed by the observation of nutation on top of the precessional magnetization dynamics by various experimental studies, which suggest that more investigation into spin inertia is needed. In this thesis, we demonstrate that spin inertia is an effect due to the environment of the spins. Moreover, we consider an explicit example of a phonon bath as the environment. Our results demonstrate that there is indeed spin inertia, and we provide a calculation of the inertial constant in the case of a ferromagnetic thin film in contact with a bulk phonon bath. To experimentally validate our results we propose investigating an Yttrium Iron Garnet film in contact with a bulk Gadolinium Gallium Garnet substrate.