Anisotropy and Field-Sensing Bandwidth in Self-Biased Bismuth-Substituted Rare-Earth Iron Garnet Films: Measurement by Ferromagnetic Resonance Spectroscopy

The high-frequency response of magneto-optic ferrites for field-sensing applications is dictated by the ferromagnetic resonance (FMR) frequency. The FMR frequency can be increased by applying an external biasing field or by tuning the internal anisotropies of the material to provide a self-bias. We report the angular dependence of FMR spectra of bismuth-substituted rare-earth iron garnet thin films to extract their uniaxial and cubic anisotropies. These measurements allow us to estimate the characteristic resonant frequency in the self-bias regime, which is equivalent to the high-frequency limit for magnetic field-sensing in these materials when no external field is applied. We find that the frequency limit estimated by FMR agrees with the measured frequency limit of a magneto-optic field sensor utilizing the same garnet composition.