Large enhancement of spin-flip scattering efficiency at Y3Fe5O12/Pt interfaces due to vertical confinement

Abstract

Magnons, the quanta of spin angular momentum, can be excited in magnetic insulators by spin-flip scattering processes originated from currents applied to a heavy metal overlayer. The efficiency to generate non-equilibrium magnons across interfaces is parametrized by the spin conductance gs, a phenomenological constant that is considered to be dependent on thermal magnons. Here, we investigate non-linear magnetoresistance phenomena originated in Pt due to current-driven nonequilibrium magnons in Y3Fe5O12 (YIG). Remarkably, we find that spin-flip scattering processes are dominated by subthermal magnons at room temperature, resulting in a large modulation of gs with the magnetic field and YIG thickness. Concretely, we find that decreasing the YIG thickness from 100 to 10 nm increases gs by a factor 30 and observe that the magnetic field exponentially suppresses the magnon generation efficiency. These findings challenge current understanding on gs and indicate that electrically-driven magnonic effects such as damping compensation and magnon condensation can be largely boosted by device miniaturization.