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Magnetic Devices Research Lab., Matsushita E l e c t r i c I nd. Co., L td.Abstract--I n-plane magnetic anisotropy and thickness dependence of soft magnetic properties for Fe-T a -N films near the eutectic composition, annealed either in a rotating magnetic field, in a static field or with no magnetic field were investigated in detail. The soft magnetic films were prepared by r. f. reactive sputtering. The films with thicknesses greater than around 2 pm have good soft magnetic properties. For those with thicknesses less than around 1 pm, the soft magnetic properties deteriorate and the domain structure changes with decreasing thickness. The films annealed without magnetic field or in a rotating field have an isotropic high permeability ( p ' 85000 at 1 M H z ) and a low anisotropy field ( H r z 5 0 A/m), whereas for the films annealed in a static field, uniaxial anisotropy is induced. This anisotropy increases with increasing N concentration. Moreover, B was added to Fe-Ta-N system, and the relation between the structures and soft magnetic properties of Fe-To-B-N films was investigated. By adding B to F e -T a -N system, the thermal stability of soft magnetic properties is improved, because the growth of a -F e and Ta-(N, B ) grains is suppressed during annealing at higher temperatures.

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For the practical application of nano-crystalline Fe-based nitride (Fe-Ta-N) films to magnetic heads, a new production of the films in mind. The anisotropy direction of the films with low N concentration (11.5 at%) annealed without magnetic field changes with the substrate position, but the anisotropy of the films with high N concentration is in the same direction at all substrate positions. With increasing N concentration, anisotropy field increases and permeability is improved at high frequencies.The direction of the in-plane magnetic anisotropy of the films fabricated with an RF bias applied to the bias method makes possible mass production of FeTaN/SiO2 multilayer films having isotropic high permeability at high frequencies.