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In recent years the spin Hall effect (SHE) and its inverse (ISHE) have become very widely used both in spintronics and in the newly emerging field of thermal spintronics, or spincaloritronics.  In this effect, spin-orbit scattering causes electrons with opposite spin to scatter in different directions, leading to creation of a spin potential.  In the inverse effect a pure spin current is converted to a charge voltage again by spin-orbit scattering.    The somewhat rare ability to generate or detect pure spin current, the flow of angular momentum without associated charge flow that is so promising for future low-power and more rapid nanoelectronic circuits, explains much of the intense interest in the SHE.   However, there are a range of current controversies in the field, with different groups and different experimental techniques frequently disagreeing about the size of the effect in various materials.

We are currently working to better understand the physics and materials science of magnetic film heterostructures often used to study spin currents and other magnetodynamic effects, and continuing to search for efficient spin injectors and detectors.  In our first work along these lines, in collaboration with Sebastian Gonnenwein and Mathias Weiler at TU Munich, and Chris Leighton at the University of Minnesota, we detected the dc voltage on a thin normal metal layer as a result of microwave-driven spin pumping of an underlying ferromagnetic metal for a set of heterostructures where transition-metal oxides are intentionally added between a ferromagnet and spin-orbit coupled material.  Surprisingly, we show efficient spin transport through oxides containing magnetic ions.  We continue to explore this and related phenomenon, which is related to the growing field of antiferromagnetic spintronics.

Spin Pump

Another major effort is focused on using the SHE and ISHE to excite and detect spin transport in a wide range of materials.  This includes work on disordered yttrium iron oxides and other disordered systems, as well as some other non-traditional materials.  These studies use non-local spin transport, which we have been working to understand better in this wider range of materials.