Effects of Annealing on the Magnetic Properties of High Bs CoHfTa Materials

We have investigated the magnetic properties of sputtered amorphous Co-Hf-Ta films in order to obtain a high saturation magnetization, low saturation magnetostriction, high crystallization temperature and high permeability. A high permeability of 4800 was obtained after annealing in a rotating magnetic field. The permeability ¿ increases with rising annealing temperature, but decreases by crystallization at higher temperatures. This increase in ¿ is dependent on the applied magnetic field, and saturates above 600 Oe. The magnetic field applied during the cooling process has a great influence on the permeability. The domain structure of amorphous Co-Hf-Ta films with a head core pattern was observed using a colloidal solution. The domain structure nearly changes into a single domain on annealing, but the domain wall perpendicular to the gap width remains at the tip even after annealing. A single domain structure was observed in multilayed Co-Hf-Ta/SiN/Co-Hf-Ta films.