How spin currents defy our high-school intuition
Yaroslaw Bazaliy
(University of South Carolina, Columbia, SC, USA)
Spin currents in the diffusive regime are an old story. They came into fashion in 1990s with the discovery of the phenomenon of giant magnetoresistance (GMR) that produced modern hard drive read heads and created a revolution in magnetic data storage, and with the Datta-Das spin transistor proposal that was not as successful. As device sizes continue to shrink, reaching tens of nanometers, ballistic and quantum transport regimes become more and more important. Yet diffusive spin currents are still able to produce examples of unexpected and appealing physical situations. In this tutorial-style talk I will present two of them:
The first example considers pure spin injection into a dangling part of a circuit. Electric currents, upon which much of our intuition about currents is based, never enter dead ends of the wires. The reason for that is electric current conservation. Being non-conserved, spin currents can behave counter-intuitively and produce "counter-intuitive" phenomena.
The second example considers the magnetoresistance of a single interface between a ferromagnet and a normal metal. Usually two interfaces, like in a spin valve, are needed to observe spin-related magnetoresistance. I will show how a combination of magnetic field and alternative current spin injection produces a magnetoresistance pattern on a single boundary.