Magnetization dynamics in the inertial regime: nutation predicted at short time scales

TL;DR

This paper extends the magnetization dynamics model to include inertial effects, predicting nutation at short time scales and enabling ultrafast magnetic switching in devices.

Contribution

It introduces a generalized Landau-Lifshitz-Gilbert equation with inertial terms derived from mesoscopic thermodynamics, revealing inertial effects at short time scales.

Findings

Inertial effects lead to nutation at short timescales.

The model recovers the Gilbert equation at longer times.

Inertial dynamics enable ultrafast magnetization switching.

Abstract

The dynamical equation of the magnetization has been reconsidered with enlarging the phase space of the ferromagnetic degrees of freedom to the angular momentum. The generalized Landau-Lifshitz-Gilbert equation that includes inertial terms, and the corresponding Fokker-Planck equation, are then derived in the framework of mesoscopic non-equilibrium thermodynamics theory. A typical relaxation time $\tau$ is introduced describing the relaxation of the magnetization acceleration from the inertial regime towards the precession regime defined by a constant Larmor frequency. For time scales larger than $\tau$, the usual Gilbert equation is recovered. For time scales below $\tau$, nutation and related inertial effects are predicted. The inertial regime offers new opportunities for the implementation of ultrafast magnetization switching in magnetic devices.