Spin-valve effect by ballistic transport in ferromagnetic metal (MnAs)/semiconductor (GaAs) hybrid heterostructures

We demonstrate the spin-valve effect by ballistic transport in fully epitaxial MnAs ferromagnetic metal/GaAs semiconductor/GaAs:MnAs granular hybrid heterostructures. The GaAs:MnAs material contains ferromagnetic NiAs-type hexagonal MnAs nanoparticles in a GaAs matrix, and acts as a spin injector and a spin detector. Although the barrier height of the GaAs/MnAs interface was found to be very small, relatively large magnetoresistance was observed. This result shows that by using ballistic transport, we can realize a large spin-valve effect without inserting a high tunnel barrier at the ferromagnetic metal/semiconductor interface.