Magnetic properties and millimeter wave loss of highly oriented scandium substituted barium hexaferrite thin films for millimeter wave applications

Scandium substituted barium hexaferrite (BaFe12-xScxO19, BaM) were grown on platinum-coated Si substrates using sol-gel method. It is found that scandium pay an important role in the structure, magnetic and millimeter wave properties of BaM system. The number of hexagonal grains decreased with increasing the substituted contents x of Sc. XRD results confirmed that BaM films have crystal texture of c-axis grains perpendicular to film plane, and the degree of texture for all the films are as high as 92%. The anisotropy field decreased from 16.2 kOe (x = 0) to 2.5 kOe (x = 2), meanwhile, the saturated magnetization decreased from 4.1 to 1.8 kG. The millimeter wave loss was studied by ferromagnetic resonance (FMR) system from 35 to 60 GHz, it is found that it has lowest FMR linewith of 129 Oe at 45 GHz for x = 0 sample, and the FMR field shift to higher for substituted thin films, together with the FMR linewith became broader. These results mean that the anisotropy field and FMR of BaM thin films were tunable and these thin films can be used in millimeter wave devices.