Contact resistance as a probe of near-interface ferromagnetism in GaMnAs/Cu bilayers

We used contact resistance measurements as a sensitive probe of near-surface magnetism in GaMnAs by studying the temperature dependence of the contact resistance at Cu/GaMnAs interfaces. The specific contact resistance (ARC) has a peak that is clearly shifted towards lower temperature than that seen in GaMnAs resistivity. This shift suggests that the magnetization in the GaMnAs film is suppressed near the Cu interface. Furthermore, we show that when a native oxide layer is present between GaMnAs and Cu, the behavior of ARC is dramatically different, due to the thicker tunnel barrier at the interface.

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