Magnetic and Dielectric Excitations in the W-Band in Aluminum Substituted Barium and Strontium Hexaferrites

Single crystal strontium and barium hexaferrites in which Al is substituted for Fe have uniaxial anisotropy fields on the order of 20-30 kOe and have magnetic excitations at 75-110 GHz. Here, we discuss results of investigations on magnetostatic forward volume waves and dielectric resonances in such ferrites. Data on the mode frequencies were utilized to characterize the ferrites in terms of saturation magnetization, anisotropy field, gyromagnetic ratio, dielectric permittivity, and dielectric and magnetic losses. A refined theory of magnetostatic forward volume waves with explicit characteristic equation for the dominant mode is presented. The estimates on the mode characteristics are in very good agreement with the data.