Observation of Pure-Spin-Current Diodelike Effect at the Au/Pt Interface

Asymmetric charge transport at the interface of two materials with dissimilar electrical properties, such as metal-semiconductor and p-n junctions, is the fundamental feature behind modern diode and transistor technology. Spin pumping from a ferromagnet into an adjacent nonmagnetic material is a powerful technique to generate pure-spin currents, wherein spin transport is unaccompanied by net charge transport. It is therefore interesting to study pure-spin transport at the interface of two materials with different spin transport properties. Here we demonstrate asymmetric transport of pure-spin currents across an interface of dissimilar nonmagnetic materials Au/Pt. We exploit Py/Au/Pt/Co structures where spin pumping can generate pure-spin current from either Py or Co independently. We find that the transmission of pure-spin current from Au into Pt is twice as efficient as transmission from Pt into Au. Experimental results are interpreted by extending conventional spin-pumping, spin-diffusion theory to include boundary conditions of reflected and transmitted spin current at the Au/Pt interface that are proportional to the established spin chemical potentials on either side of the interface.