Carrier-mediated antiferromagnetic interlayer exchange coupling in diluted magnetic semiconductor multilayers Ga$_{1-x}$Mn$_x$As/GaAs:Be

摘要

We use neutron reflectometry to investigate the interlayer exchange couplingbetween Ga$_{0.97}$Mn$_{0.03}$As ferromagnetic semiconductor layers separatedby non-magnetic Be-doped GaAs spacers. Polarized neutron reflectivity measuredbelow the Curie temperature of Ga$_{0.97}$Mn$_{0.03}$As reveals acharacteristic splitting at the wave vector corresponding to twice themultilayer period, indicating that the coupling between the ferromagneticlayers are antiferromagnetic (AFM). When the applied field is increased toabove the saturation field, this AFM coupling is suppressed. This behavior isnot observed when the spacers are undoped, suggesting that the observed AFMcoupling is mediated by charge carriers introduced via Be doping. The behaviorof magnetization of the multilayers measured by DC magnetometry is consistentwith the neutron reflectometry results.