Large magneto-crystalline anisotropy in strain-tuned epitaxial BiYIG thick films*

Bi-doped Yttrium Iron Garnet (Bi:YIG) with large Magneto-optical (MO) activity and low optical losses still needs to get probed for its magnetization dynamics. The fact that the ablation laser fluence strongly affects the lattice constant of the films, was used to grow two sets of BiYIG/GGG(111) samples with different strain states. The set-A films with lower thicknesses (10.2, 37.0, and, 92.5 nm), grown using ∼ 1 J/cm² laser fluence, show large magnetocrystalline anisotropy (MCA) due to larger rhombohedral distortion induced strain. The set-B films with larger thicknesses (120 and 150 nm) grown using higher laser fluence of ∼ 2 J/cm² show large strain irrespective of film thicknesses and large magnitude of MCA, comparable to the value of a film as-thin-as ∼ 37 nm from Set-A. Interestingly, the substitution of strong spin orbit coupling Bi³⁺ ions enhances the magnetoelastic coupling (MEC) but weakly affects the precessional damping (∼ 9.7×10^-4). Coexistence of two mutually exclusive parameters i.e., low precessional damping and strong MEC, combined with large MO activity and large MCA in BiYIG films may provide a possible material platform for light dependent magnonics and other spintronics applications.