Ultra-low damping insulating magnetic thin films get perpendicular

TL;DR

This paper reports the growth of ultrathin BiYIG films with low damping and tunable perpendicular magnetic anisotropy, demonstrating high-quality magnetic properties suitable for spintronic applications.

Contribution

It introduces a method to produce ultrathin BiYIG films with low damping and controllable PMA using epitaxial strain and growth anisotropies, advancing magnetic thin film technology.

Findings

Achieved Gilbert damping as low as 3×10^{-4} in ultrathin BiYIG films.

Demonstrated high FMR linewidth of 0.3 mT at 8 GHz.

Confirmed spin current transparency via ISHE measurements on Pt/BiYIG stacks.

Abstract

A magnetic material combining low losses and large Perpendicular Magnetic Anisotropy (PMA) is still a missing brick in the magnonic and spintronic fields. We report here on the growth of ultrathin Bismuth doped Y$_{3}$Fe$_{5}$O$_{12}$ (BiYIG) films on Gd$_{3}$Ga$_{5}$O$_{12}$ (GGG) and substituted GGG (sGGG) (111) oriented substrates. A fine tuning of the PMA is obtained using both epitaxial strain and growth induced anisotropies. Both spontaneously in-plane and out-of-plane magnetized thin films can be elaborated. Ferromagnetic Resonance (FMR) measurements demonstrate the high dynamic quality of these BiYIG ultrathin films, PMA films with Gilbert damping values as low as 3 10$^{-4}$ and FMR linewidth of 0.3 mT at 8 GHz are achieved even for films that do not exceed 30 nm in thickness. Moreover, we measure Inverse Spin Hall Effect (ISHE) on Pt/BiYIG stacks showing that the magnetic insulator$'$s surface is transparent to spin current making it appealing for spintronic applications.