Ultrafast Magnetization Dynamics in Diluted Magnetic Semiconductors

TL;DR

This paper introduces a dynamical model for ultrafast magnetization changes in diluted magnetic semiconductors, capturing both rapid demagnetization and slower recovery processes, aligning well with experimental observations.

Contribution

It develops a beyond-mean-field theoretical approach using pseudo-fermion formalism and many-particle expansion to explain magnetization dynamics after laser excitation.

Findings

Model reproduces sub-picosecond demagnetization.

Predicts magnetization enhancement depending on initial temperature.

Aligns with experimental ultrafast magnetization observations.

Abstract

We present a dynamical model that successfully explains the observed time evolution of the magnetization in diluted magnetic semiconductor quantum wells after weak laser excitation. Based on the pseudo-fermion formalism and a second order many-particle expansion of the exact p-d exchange interaction, our approach goes beyond the usual mean-field approximation. It includes both the sub-picosecond demagnetization dynamics and the slower relaxation processes which restore the initial ferromagnetic order in a nanosecond time scale. In agreement with experimental results, our numerical simulations show that, depending on the value of the initial lattice temperature, a subsequent enhancement of the total magnetization may be observed within a time scale of few hundreds of picoseconds.