Anisotropy-assisted magnon condensation in ferromagnetic thin films

TL;DR

This paper theoretically shows that easy-axis magnetic anisotropy can facilitate room-temperature magnon condensation in ferromagnetic thin films like YIG, with potential applications in quantum spintronics.

Contribution

It introduces the concept that magnetic anisotropy can assist magnon condensation, supported by analytical and micromagnetic simulation results.

Findings

Easy-axis anisotropy stabilizes magnon condensation at room temperature.

Dipolar interactions in YIG support quasi-equilibrium magnon states.

Anisotropy can enhance electrically generated magnon condensates.

Abstract

We theoretically demonstrate that adding an easy-axis magnetic anisotropy facilitates magnon condensation in thin yttrium iron garnet (YIG) films. Dipolar interactions in a quasi-equilibrium state stabilize room-temperature magnon condensation in YIG. Even though the out-of-plane easy-axis anisotropy generally competes with the dipolar interactions, we show that adding such magnetic anisotropy may even assist the generation of the magnon condensate electrically via the spin transfer torque mechanism. We use analytical calculations and micromagnetic simulations to illustrate this effect. Our results may explain the recent experiment on Bi-doped YIG and open a pathway toward applying current-driven magnon condensation in quantum spintronics.