Magnetization reversal of Ga1−xMnxAs layers separated by a nonmagnetic spacer

Abstract

We have used polarized neutron reflectometry to individually examine the magnetization reversals of ferromagnetic Ga1−xMnxAs layers separated by a nonmagnetic GaAs spacer layer of varying thickness. For each of the samples studied, the top Ga1−xMnxAs layer is adjacent to a Be-doped Al0.25Ga0.75As capping layer on one side and the GaAs spacer on the other, while the bottom Ga1−xMnxAs layer is surrounded by GaAs on either side. For samples with spacer thicknesses of 12 and 6nm, antiparallel alignment of the two Ga1−xMnxAs layer magnetizations was observed at multiple fields, implying that hole doping from the capping layer strongly affects the coercivity of the top Ga1−xMnxAs layer but has a weaker effect on the coercivity of the bottom Ga1−xMnxAs layer. However, for a spacer thickness of 3nm, both top and bottom Ga1−xMnxAs layers appear to be equally influenced by the capping layer, as virtually identical coercivities were observed. This behavior is evidence of coupling between the Ga1−xMnxAs layers across the 3nm GaAs spacer.