Spin diode effect in extended magnetic insulating films

This paper provides a comprehensive study of the nonlinear transport properties of magnons, which are electrically emitted or absorbed inside extended YIG films by spin transfer effects at a YIG|Pt interface. Our purpose is to experimentally elucidate the pertinent picture behind the asymmetric electrical variation of the magnon transconductance analogous to an electric diode. The feature is rooted in the variation of the density of low-lying spin excitations via an electrical shift of the magnon chemical potential. As the intensity of the spin transfer increases in the forward direction (regime of magnon emission), the transport properties of low-energy magnon go through 3 distinct regimes: i) at low currents, where the spin current is a linear function of the electrical current, the spin transport is ballistic and set by the film thickness; ii) for amplitudes of the order of the damping compensation threshold, it switches to a highly correlated regime limited by magnon-magnon relaxation process and marked by a saturation of the magnon transconductance. Here the main bias, that controls the magnon density, is thermal fluctuations beneath the emitter. iii) As the temperature under the emitter approaches the Curie temperature, scattering with high-energy magnons dominates, leading to diffusive transport.