Magnetostatic backward waves in low dose ion implanted YIG films

Magnetostatic backward volume wave (MSBVW) delay measurements are reported on a 4.8 µm thick YIG film ion implanted at a low dose (3× 10¹⁵ions/cm²) by a 320 keV beam of single ionized helium atoms ( He+). Nonuniform magnetization and uniaxial anisotropy profiles are used to model the ion implanted film. Calculated results fit the experimental data well. Expressions for the bias permeability tensor elements excluding crystalline (cubic) anisotropy are presented. A method is proposed to better characterize the magnetic properties of ferrimagnetic thin films. This method is applied to separate the uniaxial anisotropy field from the magnetization.