B2 and D0 3 clusters in soft magnetic single crystal Fe 1−xSi x alloys with induced magnetic anisotropy

Abstract

The atomic structure of α-Fe 1− x Si x single crystals with x = 0.05 , 0.06, and 0.08 was studied by means of X-ray diffraction to clarify the origin of the magnetic anisotropy induced under thermomagnetic or thermomechanical treatment. The B2-type short-range order is observed only at x = 0.05 and 0.06. B2 clusters, about 8 Å in size, are extended in the direction of induced magnetic anisotropy by ∼2 Å more than in a direction transverse to it. When the sequential junction of B2 unit cells—two or more in number—is realized along the easy magnetization axes 〈1 0 0〉, the B2 clusters are inevitably anisotropic. The probability of the orientation of B2 clusters along any of the axes 〈1 0 0〉 is the same. The appeared preferable orientation of B2 clusters upon annealing in a dc saturating magnetic field or under stress loading has emerged via the Si-atom diffusion. After cooling, this anisotropic B2-cluster distribution becomes “frozen” and is the origin of the appearance and stability of the uniaxial anisotropy of magnetic properties. In Fe 0.92Si 0.08, the B2 clusters coexist with D0 3 clusters, the latter being isotropic. With increasing x, the increase in a D0 3-phase amount progressively suppresses the magnetic anisotropy caused by anisotropic distribution of B2 clusters, and, to be exact, completely, at x ∼ 0.14 .