Magnon Transport in Insulating Magnetic Thin Films

Abstract

Magnon-mediated spin flow in magnetically ordered insulators enables long-distance spin-based information transport with low dissipation. MAFO (MgAl0.5Fe1.5O4) is a spinel ferrite that has been recently stabilized in epitaxial thin-film form and has a substantial in-plane four-fold magnetic anisotropy. Employing nonlocal transport measurements, we studied magnon diffusion in MAFO along different crystallographic axes in both the uniformly magnetized state under applied magnetic field and multi-domain state near zero field. In the uniformly magnetized state, we observed a significant anisotropy (30%) in the spin diffusion length between the easy and hard axes. No such anisotropy has been observed in other materials studied till date. This finding provides a new knob for controlling high frequency magnon transport. Meanwhile, in the multi-domain state, where the size of the domains is much smaller than the magnon decay length, we demonstrated magnon transport without losing angular momentum compared to its transport in the single domain state. This opens up the possibility of transportation of magnons in the low energy multi-domain state without the need for external magnetic fields.