Vertical spin transport in MnAs/GaMnAs heterostructures

We have studied the effect of barrier strength on the tunneling magnetoresistance of MnAs/GaMnAs heterostructures with double AlAs barriers. The epitaxial structures were grown by low-temperature molecular beam epitaxy. The vertical magnetotransport properties were studied for various GaAs spacer thicknesses. We find that the junction resistivities of double barrier samples increase exponentially as the barrier strength increases, implying that direct tunneling process governs the transport properties. In contrast, the tunneling magnetoresistance depends primarily on the number of interfaces rather than on the barrier strength.