Ferromagnetic resonance linewidth and magnetic properties of highly c-axis oriented barium ferrite thin films by magnetron sputtering

BaM thin films with narrow ferromagnetic resonance were successfully deposited on Pt/TiO₂/SiO₂/Si substrate by magnetron sputtering. It is found that higher substrate temperature lead to lower FMR linewidth and higher remanent magnetization. X-ray diffraction (XRD) results revealed that it has highly c-axis textured, perpendicular to film plane and the Lotgering factor is as high as 96%. Atomic force microscope showed that it has nice hexagonal grain, with both the grain size and domain size about 500 nm. Hysteresis loops indicated high remanent magnetization (Mr/4πM_S = 95%), and the 4πM_S is 3.9 kG. Ferromagnetic resonance spectroscopy (FMR) revealed the FMR peak can be tuned by external field, and gyromagnetic ratio is 2.81 GHz kOe⁻¹, FMR linewidth can be maintained to be 162 Oe at 55 GHz, while the anisotropy field calculated to be 16.37 kOe. These results mean that these BaM thin films are suitable for possible use in self-biased millimeter wave devices (40–60 GHz) such as circulators and isolators. (paper)