Laser‐Induced Rashba Spin‐Orbit Torques in Multiferroic Semiconductor (Ge,Mn)Te
Zeynab Sadeghi, Tomáš Ostatnický, Eva Schmoranzerová, Jozef Kimák, Dominik Kriegner, Helena Reichlová, Lukáš Nádvorník, Gunther Springholz, J. Hugo Dil, Juraj Krempasky, Petr NěmecABSTRACT
The multiferroic semiconductor (Ge,Mn)Te exhibits ferroelectricity, strong Rashba spin‐orbit coupling, and carrier‐mediated magnetic order, making it a unique platform for exploring the interplay between electronic, structural, and magnetic degrees of freedom. In this study, we investigate the ultrafast magnetization dynamics of Ge 0.85 Mn 0.15 Te using time‐resolved magneto‐optical spectroscopy. By separating magnetic and nonmagnetic contributions in the transient response, we identify two distinct laser‐induced magnetic phenomena, both arising from a photoinduced effective spin‐orbit torque. Coherent magnetization precession is driven by a laser‐induced increase in hole concentration, which modifies the occupation of Rashba‐split, spin‐locked valence band states, and shifts the position of the magnetic easy axis. The transient change in magnetic properties, observed as variations in the amplitude and coercive field of the pump‐induced change in ellipticity hysteresis loops, is attributed to laser‐induced modifications of the ferroelectric sublattice displacement, which affect the ferroelectric polarization and the associated Rashba spin‐orbit interaction. While the first type of optical spin‐orbit torque has already been observed in the diluted magnetic semiconductor (Ga,Mn)As, the second effect is unique to the multiferroic Rashba semiconductor (Ge,Mn)Te, opening new opportunities for all‐optical manipulation of magnetic order and spin‐orbit torque generation in spin‐orbitronic devices.