Properties of Fe-Zr-N Thin Films
Gases emerging from Fe-Zr-N films with various compositions during heating were analyzed by thermal desorption spectroscopy. The structures and magnetic properties of films were also investigated. H2, N2 and Ar were detected at 300-400°C, 500°C and 650°C, respectively. Larger amounts of N2 were emitted by films which contained larger amounts of N2. The changes in composition of films due to the emerging N2 is as follows. The composition changed for N/Zr ratios ranging from N/Zr≫1 to N/Zr~1, but was unchanged when N/Zr1. A (100) preferred orientation occurred in films in which the composition was N~Zr≫8 at% in the as-deposited state, while either a (100) orientation or random orientation occurred in all other cases. Under the former conditions, Fe-Zr-N films showed excellent soft magnetic properties and thermal stability up to 700°C.
Fe-(Ta, Nb, Zr)-N系合金薄膜の組織と磁気持性
Microstructures and magnetic properties of Fe- (Ta, Nb, Zr)-N alloy films near the eutectic composition were studied. These new soft magnetic alloy films were prepared by N2 reactive sputtering. The structures and magnetic properties were changed by annealing or adjusting N2 partial pressure ratio. The film structures were investigated with X-ray diffraction and TEM, and the following results were obtained. (i) the as prepared films; amorphous like phase, (ii) the annealed films; homogeneous mixture of fine-grained α-Fe and (Ta, Nb, Zr) nitrides, (iii) the films annealed at higher temperatures; composite of grown grains of α-Fe and (Ta, Nb, Zr) nitrides. Among these films, the films (ii) exhibit good soft magnetic properties, small magnetostriction and high saturation magnetization up to 1.6 T. Furthermore, Fe-Ta-Zr-N alloy films show higher thermal stability of the soft magnetic properties.
Ni-F-Nb (50Ni-Fe組成) 合金薄膜の軟磁気特性
The relation between soft magnetic properties and local anisotropy fluctuation, which is strongly connected with the microstructure of the films, was systematically examined for Ni-Fe-Nb alloy films with nearly 50 wt%Ni. According to the micromagnetic ripple theory by Hoffmann, effective magnetic anisotropy Ueff in each of the grains decreases drastically with increases in the number of grains N within the coupling volume. Experimental results show local anisotropy fluctuation for Ni-Fe-Nb alloy films strongly depends on Ueff/Ku, and it decreases with decreasing Ueff/Ku. Therefore, to realize high initial permeability in these films, it is necessary to increase N within the coupling volume by decreasing the size of the grains. In the case of Ni-Fe-Nb alloy films, decreasing the size of the grains less than 200A to obtain high initial permeability more than 2000 is needed.