Definitive Evidence of Interlayer Coupling Between (Ga,Mn)As Layers Separated by a Nonmagnetic Spacer

TL;DR

This study provides definitive evidence that (Ga,Mn)As magnetic layers can interact across a nonmagnetic spacer, with the strength of coupling depending on the spacer's thickness, as shown by polarized neutron reflectometry.

Contribution

The paper demonstrates interlayer magnetic coupling in (Ga,Mn)As multilayers separated by nonmagnetic spacers, revealing thickness-dependent magnetic interactions.

Findings

Magnetic coupling decreases as spacer thickness increases.

Magnetizations of layers become more similar with thinner spacers.

Coupling occurs regardless of crystallographic spin orientation.

Abstract

We have used polarized neutron reflectometry to study the structural and magnetic properties of the individual layers in a series of (Al,Be,Ga)As/(Ga,Mn)As/GaAs/(Ga,Mn)As multilayer samples. Structurally, we observe that the samples are virtually identical except for the GaAs spacer thickness (which varies from 3-12 nm), and confirm that the spacers contain little or no Mn. Magnetically, we observe that for the sample with the thickest spacer layer, modulation doping by the(Al,Be,Ga)As results in (Ga,Mn)As layers with very different temperature dependent magnetizations. However, as the spacer layer thickness is reduced, the temperature dependent magnetizations of the top an bottom (Ga,Mn)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 (Ga,Mn)As layers can couple across a non-magnetic spacer, and that such coupling depends on spacer thickness.