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arXiv · 2510.07465

Ultrathin bismuth-yttrium iron garnet films with tunable magnetic anisotropy

Hanchen Wang·William Legrand·Davit Petrosyan·Min-Gu Kang·Emir Karadža·Hiroki Matsumoto·Richard Schlitz·Michaela Lammel·Myriam H. Aguirre·Pietro Gambardella
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Abstract

We report on the epitaxial growth of nm-thick films of bismuth-substituted yttrium iron garnet (BiYIG) by high-temperature off-axis radio-frequency magnetron sputtering. We demonstrate accurate control of the magnetic properties by tuning of the sputtering parameters and epitaxial strain on various (111)-oriented garnet substrates. BiYIG films with up to -0.80\% lattice mismatch with the substrate remain fully strained up to 60~nm-thick, maintaining a high crystalline quality. Transmission electron microscopy and energy-dispersive X-ray spectroscopy confirm coherent epitaxial growth, the absence of defects, and limited interdiffusion at the BiYIG/substrate interface. Varying the tensile or compressive strain between -0.80\% and +0.56\% in BiYIG allows for accurate compensation of the total magnetic anisotropy through magneto-elastic coupling. The effective magnetic anisotropy of sputtered BiYIG films can be further tuned via the off-axis deposition angle and the oxygen flow during growth, which determine the cation stoichiometry. Under optimized growth conditions, a ferromagnetic resonance (FMR) linewidth of 1~mT at 10~GHz is reliably obtained even for thicknesses as low as 10~nm. We also report small FMR linewidths in ultrathin (2-5~nm) BiYIG films grown on diamagnetic substrate yttrium scandium gallium garnet. These findings highlight the promise of low-damping, strain-engineered nm-thick BiYIG films for implementing advanced functionalities in spin-orbitronic and magnonic devices. Specifically, the magnetic-anisotropy compensation and low damping enable large cone-angle magnetization dynamics immune to magnon-magnon nonlinear scattering.

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Hanchen Wang, William Legrand, Davit Petrosyan, Min-Gu Kang, Emir Karadža, Hiroki Matsumoto, Richard Schlitz, Michaela Lammel, Myriam H. Aguirre, Pietro Gambardella. 2025-10-08. Ultrathin bismuth-yttrium iron garnet films with tunable magnetic anisotropy. https://doi.org/10.1103/8l57-yqsx

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