Ultrafast Photoinduced Softening in a III-V Ferromagnetic Semiconductor for Non-thermal Magneto-Optical Recording

TL;DR

This study demonstrates that ultrafast photoexcitation can transiently soften the coercivity of a ferromagnetic semiconductor, enabling nonthermal magnetization control on picosecond timescales.

Contribution

It introduces a nonthermal, ultrafast method to manipulate magnetization in a ferromagnetic semiconductor using transient carrier-induced effects.

Findings

Transient coercivity decrease lasts about 2 ps

Carrier recombination restores original coercivity

Proposes carrier-enhanced exchange as the softening mechanism

Abstract

Through time-resolved two-color magneto-optical Kerr spectroscopy we have demonstrated that photogenerated transient carriers decrease the coercivity of ferromagnetic InMnAs at low temperatures. This transient ``softening'' persists only during the carrier lifetime ($\sim$ 2 ps) and returns to its original value as soon as the carriers recombine to disappear. We discuss the origin of this unusual phenomenon in terms of carrier-enhanced ferromagnetic exchange interactions between Mn ions and propose an entirely nonthermal scheme for magnetization reversal.