Tuning of Spin Dependent Reflection at Ferromagnet/GaAs Interfaces

Semiconductor spintronics aims to integrate memory and logic functions by utilizing the electron's spin degree of freedom in addition to its charge. The building blocks for semiconductor spintronic devices are the ferromagnet (FM)/semiconductor hybrid structures, where the interface plays the key role in spin injection and detection. My graduate research focuses on exploring spin dependent properties of FM/GaAs hybrid structures by ultrafast optics and possible route for tuning of spin polarization through interface modification. In Fe/MgO/GaAs structures, the ultrathin MgO interlayer at the interface causes an unexpected sign reversal in spin dependent reflection, despite being a nonmagnetic insulator. We find that the interfacial bonding with Mg is responsible for the sign reversal. In the Fe3O4/GaAs system, we observed oscillatory spin polarization and magneto-optic Kerr effect with respect to Fe3O4 film thickness, which we attribute to the formation of spin-polarized quantum well states.