Nonequilibrium Noise Measurement of a spin current induced by the spin Seebeck effect

In one implementation of the spin seebeck effect, a net angular momentum current is driven from a ferrimagnetic insulator into a nonmagnetic metal due to an applied temperature gradient. This phenomenon has shown its significance for studies of fundamental spintronic physics and potential thermoelectric applications. Nonequilibrium charge noise (or charge “shot”) noise is the inherent fluctuations in the charge current in a driven conductor due to the discreteness of charge carriers. An analogous spin shot noise is predicted to be an outstanding experimental probe for physics in spin transport in which angular momentum is carried by discrete magnons. Here we report initial results in attempting to measure the nonequilibrium spin current noise in a junction comprising a ferrimagnetic insulator Y₃Fe₅O₁₂ (YIG) and the strong spin-orbit coupling paramagnetic metal Pt, with the spin current driven by the spin Seebeck effect.