The spin-Seebeck effect in a GaMnAs/MnAs bilayer

The spin-Seebeck effect, recently discovered in ferromagnetic metals such as permalloy, semiconductors such as GaMnAs and insulators such as YIG, consists of a thermally generated spin redistribution. This effect is measured by detecting an inverse spin Hall voltage that varies spatially across a sample due to the thermally generated local spin currents. Here, we describe measurements of the spin-Seebeck effect in metallic ferromagnetic MnAs thin films grown on GaMnAs. The difference in H$_{c}$ and T$_{c}$ of each layer allows independent measurement of spin-Seebeck signals arising from MnAs from that of GaMnAs. We discuss the effect of the exchange bias between these layers on the spin-Seebeck effect above and below the magnetic phase transition. Work support in parts by NSF, NSF-CBET-0754023, ONR, and DMR-0820414.