Magneto-Optic Effects In Spin-Injection Devices

The magneto-optic properties of semi-transparent ferromagnetic films are presented in the context of ferromagnet/GaAs spin-injection devices. We have measured the polarization-dependent photoresponse and magneto-optic properties of Co/n-GaAs, Co/p-GaAs and NiFe/n-GaAs Schottky diodes and NiFe/SiO2 and Co/SiO2 structures as a function of ferromagnetic film thickness, ranging from 8 to 100 nm. Our results show that magneto-optic effects intrinsic to the ferromagnetic films (2%-3%) are sufficient to account for the majority of the polarization-dependent photoresponse of the ferromagnet/GaAs systems studied. These effects are well described by a simple thin-film transmission model, which gives an upper limit of 0.4% for spin-transmission effects. (C) 2003 American Institute of Physics.