Ultrafast Quenching of Ferromagnetism in InMnAs Induced by Intense Laser Irradiation

TL;DR

This paper demonstrates that intense laser irradiation can rapidly quench ferromagnetism in InMnAs within sub-picoseconds, revealing two distinct demagnetization processes driven by spin heating and spin-lattice relaxation.

Contribution

It provides the first detailed time-resolved analysis of ultrafast ferromagnetic quenching in InMnAs, identifying two separate demagnetization mechanisms and their dependence on laser power and temperature.

Findings

Fast demagnetization (<1 ps) saturates at high laser fluence.

Complete quenching of ferromagnetism occurs on a sub-picosecond scale.

Two demagnetization processes are identified: spin heating and spin-lattice relaxation.

Abstract

Time-resolved magneto-optical Kerr spectroscopy of ferromagnetic InMnAs reveals two distinct {\em demagnetization} processes -- fast ($<1$ ps) and slow ($\sim$100 ps). Both components diminish with increasing temperature and are absent above the Curie temperature. The fast component rapidly grows with pump power and saturates at high fluences ($>10$ mJ/cm$^2$); the saturation value indicates a {\em complete quenching} of ferromagnetism on a sub-picosecond time scale. We attribute this fast dynamics to spin heating through $p$-$d$ exchange interaction between photo-carriers and Mn ions while the $\sim$100 ps component is interpreted as spin-lattice relaxation.