Spin wave dynamics in epitaxial antiferromagnetic α-Fe₂O₃ thin film prepared by pulsed laser deposition method

Abstract

Spin wave dynamics in antiferromagnetic materials, which has large group velocity (over 20 km/s) and long diffusion length (up to 10 μm), is getting more attention in many fields. [1-2] Especially, the α-Fe2O3, which has high bulk Dzyaloshinskii-Moriya interaction (DMI), low Gilbert damping constant (~10-5) and relatively low resonance frequency (tens to hundreds of GHz frequency) than other antiferromagnetic materials (over THz frequency), is emerging as a promising material recently. [3-5] However, the relevant spin wave dynamics studies are mostly dealing with the bulk single crystal structure, which shows considerably different characteristics in epitaxial thin film structure.In this study, we investigate the unique characteristics of spin wave dynamics in the α-Fe2O3 thin film at room temperature. The sample is deposited by using pulsed laser deposition (PLD) system with 85 nm of epitaxial Fe2O3 on the c-plane Al2O3 substrate. We confirm the crystallinity by X-ray diffractometer (XRD) and check the magnetic properties using SQUID-VSM. To measure the special features of spin wave dynamics in the α-Fe2O3 thin film, we used ferromagnetic resonance (FMR) and micro-Brillouin light scattering (μBLS). We detect the unexpected low frequency mode (f-) and multiple peaks of BLS signal which could be the clue of the new properties. Our results can widen the insight of the spin wave dynamics in the thin film α-Fe2O3 and the usage in the antiferromagnetic spintronics applications.