Definitive evidence of interlayer coupling between Ga1-xMnxAs layers separated by a nonmagnetic spacer

We have used polarized neutron reflectometry to study the structural and magnetic properties of the individual layers in a series of AlGaAs:Be/Ga1-xMnxAs/GaAs/Ga1-xMnxAs multilayer samples. Structurally, we observe that the samples are virtually identical except for the GaAs spacer thickness (which varies from 3 to 12 nm), and confirm that the spacers contain little or no Mn. Magnetically, we observe that for the sample with the thickest spacer layer, the Ga1-xMnxAs layer adjacent to the Be-doped AlGaAs cap has a temperature dependent magnetization very different from that of the other Ga1-xMnxAs layer. However, as the spacer layer thickness is reduced, the temperature dependent magnetizations of the two Ga1-xMnxAs layers become progressively more similar--a trend we find to be independent of the crystallographic direction along which spins are magnetized. These results definitively show that Ga1-xMnxAs layers can couple across a nonmagnetic spacer and that such coupling depends on spacer thickness