Precession dynamics of a small magnet with non-Markovian damping: Theoretical proposal for an experiment to determine the correlation time

TL;DR

This paper develops a theoretical framework to understand the precession dynamics of small magnets with non-Markovian damping and proposes an experiment to measure the bath correlation time using ultrafast magnetization measurements.

Contribution

It extends previous theoretical analysis to derive analytical expressions for precession velocity and damping, and suggests an experimental method to determine correlation time.

Findings

Analytical expressions for precession angular velocity and damping constant.

Dependence of magnetization dynamics on bath correlation time.

Proposal for an experimental measurement of correlation time.

Abstract

Recent advances in experimental techniques have made it possible to manipulate and measure the magnetization dynamics on the femtosecond time scale which is the same order as the correlation time of the bath degrees of freedom. In the equations of motion of magnetization, the correlation of the bath is represented by the non-Markovian damping. For development of the science and technologies based on the ultrafast magnetization dynamics it is important to understand how the magnetization dynamics depend on the correlation time. It is also important to determine the correlation time experimentally. Here we study the precession dynamics of a small magnet with the non-Markovian damping. Extending the theoretical analysis of Miyazaki and Seki [J. Chem. Phys. 108, 7052 (1998)] we obtain analytical expressions of the precession angular velocity and the effective damping constant for any values of the correlation time under assumption of small Gilbert damping constant. We also propose a possible experiment for determination of the correlation time.