# Ferromagnetic Resonance Studies of Strain tuned Bi:YIG Films

## TL;DR

This study demonstrates how epitaxial strain tuning in Bi:YIG films can control magnetocrystalline anisotropy, revealing potential for advanced spintronic and photonic applications due to their large magneto-optical activity and low damping.

## Contribution

The paper introduces a growth protocol for high-quality, strain-tuned Bi:YIG films with enhanced magnetocrystalline anisotropy and investigates their magnetization dynamics via ferromagnetic resonance.

## Key findings

- Linear dependence of uniaxial anisotropy on strain-induced lattice distortion
- Magnetoelastic constant is enhanced without increasing damping significantly
- Bi:YIG exhibits large magneto-optical activity and low precessional damping

## Abstract

Bismuth-doped Yttrium iron garnet (Bi:YIG) thin films known for large Magneto-optical activity with low losses still needs to get probed for its magnetization dynamics. We demonstrate a controlled tuning of magnetocrystalline anisotropy in Bi-doped Y_3 Fe_5 O_12 (Bi:YIG) films of high crystalline quality using growth induced epitaxial strain on [111]-oriented Gd_3 Ga_5 O_12 (GGG) substrate. We optimize a growth protocol to get thick highly-strained epitaxial films showing large magneto-crystalline anisotropy, compare to thin films prepared using a different protocol. Ferromagnetic resonance measurements establish a linear dependence of the out-of-plane uniaxial anisotropy on the strain induced rhombohedral distortion of Bi:YIG lattice. Interestingly, the enhancement in the magnetoelastic constant due to an optimum substitution of Bi^(3+) ions with strong spin orbit coupling does not strongly affect the precessional damping (~2x10^(-3) ). Large magneto-optical activity, reasonably low damping, large magnetocrystalline anisotropy and large magnetoelastic coupling in BiYIG are the properties that may help BiYIG emerge as a possible material for photo-magnonics and other spintronics applications.