Nonequilibrium Magnetization Dynamics of Nickel

TL;DR

This study investigates ultrafast magnetization changes in nickel induced by laser pulses, revealing that magnetization dynamics can be tracked before electrons and lattice reach thermal equilibrium, with transient effects occurring within 50 fs.

Contribution

It demonstrates that magnetization dynamics in nickel can be observed on sub-thermalization timescales using pump-probe SHG, providing new insights into nonequilibrium magnetic processes.

Findings

Magnetization reaches a minimum approximately 50 fs before electron thermalization.

Classical M(T)-curve is reproducible for delay times >280 fs.

Transient magnetization dynamics occur during the initial 50 fs after excitation.

Abstract

Ultrafast magnetization dynamics of nickel has been studied for different degrees of electronic excitation, using pump-probe second-harmonic generation with 150 fs/800 nm laser pulses of various fluences. Information about the electronic and magnetic response to laser irradiation is obtained from sums and differences of the SHG intensity for opposite magnetization directions. The classical M(T)-curve can be reproduced for delay times larger than the electron thermalization time of about 280 fs, even when electrons and lattice have not reached thermal equilibrium. Further we show that the transient magnetization reaches its minimum approx. 50 fs before electron thermalization is completed.