Observation of the spin-charge thermal isolation of ferromagnetic Ga_{0.94}Mn_{0.06}As by time-resolved magneto-optical measurement

TL;DR

This study uses time-resolved magneto-optical Kerr effect measurements to reveal that in ferromagnetic Ga_{0.94}Mn_{0.06}As, charge and spin systems are thermally isolated, supporting its half-metallic nature due to hole-mediated double exchange.

Contribution

It provides experimental evidence of spin-charge thermal isolation in ferromagnetic GaMnAs, highlighting its half-metallic character from a double exchange mechanism.

Findings

Rapid carrier temperature rise within 1 ps

Slow spin temperature rise over 500 ps

Thermal isolation between charge and spin systems

Abstract

The dynamics of magnetization under femtosecond optical excitation is studied in a ferromagnetic semiconductor Ga_{0.94}Mn_{0.06}As with a time-resolved magneto-optical Kerr effect measurement with two color probe beams. The transient reflectivity change indicates the rapid rise of the carrier temperature and relaxation to a quasi-thermal equilibrium within 1 ps, while a very slow rise of the spin temperature of the order of 500ps is observed. This anomalous behavior originates from the thermal isolation between the charge and spin systems due to the spin polarization of carriers (holes) contributing to ferromagnetism. This constitutes experimental proof of the half-metallic nature of ferromagnetic Ga_{0.94}Mn_{0.06}As arising from double exchange type mechanism originates from the d-band character of holes.