Efficient spin-wave transmission in epitaxial thin films of defect spinel γ-Fe_2−xAl_xO₃

The realization of ultra-low energy consumption spin wave device applications requires a material that can efficiently propagate the spin waves. Spinel-type ferrite is a promising insulator from the perspective of application in magnonic devices owing to its good crystal compatibility. In this study, thin films of spinel γ-Fe_2−xAl_xO₃ (0 ≤ x ≤0.5) are fabricated on single-crystal MgO substrates through pulsed laser deposition. High crystalline quality and room temperature ferrimagnetism are observed in all the films. Spin wave propagation is observed in γ-Fe_2−xAl_xO₃ films, and it is found that the spin-wave transmission properties significantly correlate with the crystallinity and magnetization of the films. The γ-Fe_1.85Al_0.15O₃ thin film represents an excellent compromise between a sufficiently high spin-wave amplitude and long propagation distance. These results indicate that the γ-Fe_2−xAl_xO₃ thin film is a highly promising candidate for application in spin-wave-based computing devices in the future.