Control of magnetization dynamics by substrate orientation in YIG thin films

Yttrium Iron Garnet (YIG) and bismuth (Bi) substituted YIG (Bi_0.1Y_2.9Fe₅O₁₂, BYG) films are grown in-situ on single crystalline Gadolinium Gallium Garnet (GGG) substrates [with (100) and (111) orientations] using pulsed laser deposition (PLD) technique. As the orientation of the Bi-YIG film changes from (100) to (111), the lattice constant is enhanced from 12.384 Å to 12.401 Å due to orientation dependent distribution of Bi³⁺ ions at dodecahedral sites in the lattice cell. Atomic force microscopy (AFM) images show smooth film surfaces with roughness 0.308 nm in Bi-YIG (111). The change in substrate orientation leads to the modification of Gilbert damping which, in turn, gives rise to the enhancement of ferromagnetic resonance (FMR) line width. The best values of Gilbert damping are found to be (0.54 ± 0.06) × 10⁻⁴, for YIG (100) and (6.27 ± 0.33) × 10⁻⁴, for Bi-YIG (111) oriented films. Angle variation (ϕ) measurements of the H_r are also performed, that shows a four-fold symmetry for the resonance field in the (100) grown film. In addition, the value of effective magnetization (4πM_eff) and extrinsic linewidth (ΔH₀) are observed to be dependent on substrate orientation. Hence PLD growth can assist single-crystalline YIG and BYG films with a perfect interface that can be used for spintronics and related device applications. (paper)