Sub-micrometer yttrium iron garnet LPE films with low ferromagnetic resonance losses

TL;DR

This study reports the growth of ultra-thin, high-quality yttrium iron garnet films with exceptionally low ferromagnetic resonance losses, suitable for advanced spin-wave applications.

Contribution

It demonstrates the successful fabrication of sub-micrometer YIG films via liquid phase epitaxy with minimal losses and near-bulk magnetic properties, advancing spintronic material development.

Findings

Lowest reported FMR linewidth for 100 nm YIG films at 1.4 Oe

Near-bulk saturation magnetization of 1800 Gs

Gilbert damping coefficient close to 1 x 10^-4

Abstract

Using liquid phase epitaxy (LPE) technique (111) yttrium iron garnet (YIG) films with thicknesses of ~100 nm and surface roughnesses as low as 0.3 nm have been grown as a basic material for spin-wave propagation experiments in microstructured waveguides. The continuously strained films exhibit nearly perfect crystallinity without significant mosaicity and with effective lattice misfits of delta a(perpendicular)/a(substrate) ~10-4 and below. The film/substrate interface is extremely sharp without broad interdiffusion layer formation. All LPE films exhibit a nearly bulk-like saturation magnetization of (1800+-20) Gs and an `easy cone' anisotropy type with extremely small in-plane coercive fields <0.2 Oe. There is a rather weak in-plane magnetic anisotropy with a pronounced six-fold symmetry observed for saturation field <1.5 Oe. No significant out-of-plane anisotropy is observed, but a weak dependence of the effective magnetization on the lattice misfit is detected. The narrowest ferromagnetic resonance linewidth is determined to be 1.4 Oe @ 6.5 GHz which is the lowest value reported so far for YIG films of 100 nm thicknesses and below. The Gilbert damping coefficient for investigated LPE films is estimated to be close to 1 x 10-4.