Optimizing Deposition Parameters for High-Quality Thulium Iron Garnet Thin Films

Abstract

The development of energy-efficient spintronic and magnonic devices relies critically on high-quality magnetic insulator thin films with well-controlled magnetic anisotropy. Among these, thulium iron garnet (TmIG, Tm3Fe5O12) has emerged as a promising material due to its low magnetic damping and potential for perpendicular magnetic anisotropy (PMA) when grown epitaxially on gadolinium gallium garnet (GGG) substrates. However, the fabrication of ultrathin TmIG films that preserve bulk-like magnetic properties remains a significant challenge. In this thesis, we investigate the growth and magnetic characteristics of ultrathin TmIG films with thicknesses down to 17 nm, deposited using pulsed laser deposition (PLD) on (111)-oriented GGG substrates. A systematic study was conducted by varying key deposition parameters, including laser energy, oxygen pressure, and film thickness, to optimize film quality. The magnetic properties of the films were characterized using a broadband ferromagnetic resonance spectroscopy. Our results reveal the critical role of deposition conditions in tuning the crystallinity, surface morphology, and magnetic anisotropy of the films. Under optimized conditions, the TmIG films exhibit strong out-of-plane anisotropy and low Gilbert damping, making them suitable candidates for spintronic applications such as spin-orbit torque-driven magnetization switching. Moreover, the analysis of Perpendicular Standing Spin Wave (PSSW) modes observed in the films, allowed us to determine the exchange stiffness constant in these films. These findings contribute to a deeper understanding of the growth–property relationship in TmIG thin films and open new avenues for the design of high-performance magnetic insulator-based devices.