Magnetic and microwave magnetic properties of barium hexaferrite permanent magnet films having the c-axis in the film plane

Thick (1-14 mum) films of ferrimagnetic barium hexaferrite (BaFe12O19 or BaM) having the c-axis ([0001]) in the film plane were deposited by pulsed laser deposition onto a-plane (11 (2) under bar0) sapphire (Al2O3) substrates, and were found to have a (10 (1) under bar0) orientation. Torque and magnetization measurements show these films are permanent magnets with easy magnetization direction in the plane of the film. Ferrimagnetic resonance (FMR) spectra exhibited linewidths of 1.00-1.40 kOe, where low-field FMR measurements do not show uniform mode broadening due to the formation of multiple domains. All film parameters were affected by the large stress present in these films due to crystallographic and thermal mismatches. These films have dual functionality as gyrotropic media and permanent magnets, and are usable as either nonreciprocal microwave devices or biasing magnets. (C) 2003 American Institute of Physics.