Exploring the thermoelectric properties of normal/ferromagnetic interfaces using current heating techniques

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In this project we propose to study in detail the nature of thermoelectric phenomena at normal/ferromagnetic interface using current heating techniques to locally apply the heat gradient. Our material of choice for this work will be the ferromagnetic semiconductor (Ga,Mn)As for two reasons. First, an all semiconductor device is much more appropriate for the current heating techniques needed to measure the diffusive thermopower (distinct from the phonon drag) than would be metallic junctions, and second, as our preliminary work already shows, the strong spin orbit coupling in this material, which couples the magnetic properties to the density of states, leads to a rich phenomenology of thermopower. Our preliminary studies have, for example, already revealed a strong tunneling anisotropic magneto-thermopower in the thermoelectric Seebeck effect. We expect to find and explore in detail anomalous and anisotropic contributions in all the thermoelectric and thermomagnetic effects such as Nernst, Ettinghausen and Righi-Leduc. It should be emphasized that while (Ga,Mn)As is the ideal material for our investigations, the effects studied here are by no means confined to the realm of semiconductors, and indeed will be important in all magnetic materials, but in particular those with strong spin orbit coupling, such as for example, CoPt multilayers.