Definitive evidence of interlayer coupling betweenGa1−xMnxAslayers separated by a nonmagnetic spacer

Abstract

We have used polarized neutron reflectometry to study the structural and magnetic properties of the individual layers in a series of $\mathrm{Al}\mathrm{Ga}\mathrm{As}:\mathrm{Be}∕{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}∕\mathrm{Ga}\mathrm{As}∕{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ multilayer samples. Structurally, we observe that the samples are virtually identical except for the GaAs spacer thickness (which varies from $3\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}12\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$), and confirm that the spacers contain little or no Mn. Magnetically, we observe that for the sample with the thickest spacer layer, the ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ layer adjacent to the Be-doped AlGaAs cap has a temperature dependent magnetization very different from that of the other ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ layer. However, as the spacer layer thickness is reduced, the temperature dependent magnetizations of the two ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ 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 ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ layers can couple across a nonmagnetic spacer and that such coupling depends on spacer thickness.