1203.0483 (Eva Rozkotova et al.)

Investigation of Optical Spin Transfer Torque in Ferromagnetic
Semiconductor GaMnAs by Magneto-Optical Pump-and-Probe Method    [PDF]

Eva Rozkotova, Petr Nemec, Nada Tesarova, Frantisek Trojanek, Petr Maly, Vit Novak, Tomas Jungwirth

We report on magnetization precession induced in (Ga,Mn)As by an optical spin transfer torque (OSTT). This phenomenon, which corresponds to a transfer of angular momentum from optically-injected spin-polarized electrons to magnetization, was predicted theoretically in 2004 and observed experimentally by our group in 2012. In this paper we provide experimental details about the observation of OSTT by a time-resolved pump-and-probe magneto-optical technique. In particular, we show that the precession of magnetization due to OSTT can be experimentally separated from that induced by the well known magnetic-anisotropy-related mechanism in a hybrid structure piezo-stressor/(Ga,Mn)As with an in situ electrical control of the magnetic anisotropy. We also illustrate that OSTT is clearly apparent in the measured dynamical magneto-optical signal in a large variety of (Ga,Mn)As samples with a Mn concentration from 3% to 9%.

View original: http://arxiv.org/abs/1203.0483