Magnetization reversal and anisotropy at the Fe/AlGaAs (001) interface

We distinguish the magnetic reversal process of an Fe interface layer from that of the bulk in Fe/AlGaAs heterostuctures using magnetization induced second harmonic generation (MSHG) and the magneto-optical Kerr effect (MOKE). We find that the switching characteristics are distinctly different -- single step switching occurs at the interface layer, while two jump switching occurs in the bulk for the magnetic field orientations employed. This indicates a larger contribution from uniaxial versus cubic anisotropy at the interface layer, causing the absence of an intermediate single domain state during reversal. The general assumption that spins within a ferromagnetic metal films are strictly parallel due to strong exchange coupling is therefore incorrect at the interface. Our results show that MSHG is a powerful technique to probe interface magnetic properties in non-centrosymmetric hybrid structures.