Preparation of Low Microwave Loss YIG Thin Films by Pulsed Laser Deposition

Abstract

Y3Fe5O12 thin films with thickness 10 $10~{\rm nm} \le t \le 1440$ nm were grown on Gd3Ga5O12 (111) substrates by pulsed laser deposition. The X-ray diffraction experiments confirmed the films are pure yttrium iron garnet (YIG) phase with preferred (111) orientation. The magnetic and microwave properties were studied as a function of film thickness by the dc magnetization and ferromagnetic resonance (FMR) measurements. The FMR linewidth ( $\Delta H$ ) was found to decrease with the increase in film thickness $10~{\rm nm} \le t \le 45$ nm), attaining a minimum value of $\Delta H_{\bot }=5$ Oe and $\Delta H_{\mathrm {\vert \vert }}=6$ Oe, for perpendicular and parallel resonance, and then rising with further increase in thickness. Acid etching experiments were performed to understand the mechanism contributing to $\Delta H$ . The increase in $\Delta H$ with thickness ( $t > 45$ nm) may be explained in terms of extrinsic mechanisms, such as inhomogeneities present at the surface of the films. However, the decrease in $\Delta H$ with thickness ( $t nm) is believed to be due to the surface anisotropy effect. The films showed low coercivity values in the range of $\sim 1.5$ –7 Oe, which is an indicator of good quality YIG films.