MAGNETIC-PROPERTIES OF FE-TA-(B)-N FILMS

In-plane magnetic anisotropy and thickness dependence of soft magnetic properties for Fe-Ta-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-mu-m have good soft magnetic properties. For those with thicknesses less than around 1-mu-m, 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 (mu' greater-than-or-equal-to 5000 at 1 MHz) and a low anisotropy field (H(K) congruent-to 50 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-Ta-B-N films was investigated. By adding B to Fe-Ta-N system, the thermal stability of soft magnetic properties is improved, because the growth of alpha-Fe and Ta-(N, B) grains is suppressed during annealing at higher temperatures.