We have found that the domain structure of a 40% cobalt-nickel single crystal is very small-scaled and complicated in the annealed state as compared with that of ordinary ferromagnetic substances but it becomes simpler and larger after quenching from above the Curie temperature, indicating that the domain structure of a cubic solid solution can be affected by the induced uniaxial anisotropy. It is shown that these findings, together with the results of considerations reported previously, lead us to the conclusion that the Perminvar-type magnetic properties are due to the stabilization of domain walls by the induced uniaxial anisotropy in face-centered cubic solid solutions and in body-centered cubic solid solutions with negative cubic anisotropy constants. R ECENTLY we 1 and, independently, Neel 2 have interpreted the uniaxial ferromagnetic anisotropy induced by magnetic annealing in cubic solid solutions as being due to an anisotropic distribution of atoms. According to this idea, when a ferromagnetic solid solution is cooled slowly from above its Curie temperature in the absence of an externally applied magnetic field, the uniaxial anisotropy may be induced along the directions of magnetization vectors distributed in compliance with the domain structure, and thus domain walls may be stabilized since the rotation of a magnetization vector from its original stabilized direction accompanies an increase in induced uniaxial anisotropy.We have calculated 3 the restoring force acting on such a stabilized domain wall as a function of its displacement, using the theoretical results of our previous paper 1 and a method of calculation similar to that employed by Neel 4 in his theory of the magnetic after-effect due to the diffusion of Interstitial atoms in a body-centered cubic lattice. Our calculation shows that, in a face-centered cubic (f.c.c.) solid solution with a cubic anisotropy constant, K, of any sign and in a body-centered cubic (b.c.c.) solid solution with a negative K, each of the substitutional type, the restoring force for the non-180 0 wall displacement increases almost linearly at first and eventually reaches a finite value, while that for the 180° wall displacement also increases almost linearly at first but finally tends to zero. Accordingly, for these solid solutions in which the induced uniaxial anisotropy is so large 5 that the displacements of domain walls in low fields may be 1 S. Taniguchi and M. Yamamoto, Sci. Repts. Research Inst.

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Anisotropy constants of K 1 of single crystals of Mo x Fe21-x Ni79(x=0∼8) were determined by torque method between 77° and 300°K. The sign of K 1 at room temperature changes from negative to positive as the Mo content is increased. The Mo content at which K 1 becomes zero increased as the rate of cooling from 600°C is reduced. These behaviors have a good correspondence to the variation of the initial permeability µ0 with the rate of cooling. Temperature dependence of K 1 of these alloys were also influenced by the rate of cooling and showed an unusual behavior. These results are discussed in terms of the relation between magnetic crystalline anisotropy energy and atomic ordering.