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

TL;DR

This study demonstrates that reducing YIG thickness significantly enhances spin-flip scattering efficiency at YIG/Pt interfaces, revealing new insights into magnon generation and control in nanoscale magnetic insulators.

Contribution

It uncovers the dramatic increase in spin conductance with YIG thickness reduction and highlights the impact of device miniaturization on magnonic effects.

Findings

Decreasing YIG thickness from 100 to 10 nm increases spin conductance by a factor of 30.

Magnetic field exponentially suppresses magnon generation efficiency.

Subthermal magnons dominate spin-flip scattering at room temperature.

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.