SQUID-detected broadband ferrimagnetic resonance in bulk poly- and single-crystalline Y3Fe5O12

Ferromagnetic resonance (FMR) and strongly gyrotropic magnetic materials have been at the heart of applied magnetism and microwave engineering for many decades. Here we demonstrate two new techniques for the detection of broadband ferromagnetic resonance in bulk materials, which rely on SQUID-based gradiometry detection of small changes in the magnetisation. In the first method, we detect small changes in the largest projection of coupled magnetic moment (Δmz) as the material is driven into resonance. The second method measures the change in Δm_z caused by the resonance induced thermal heating.