Structure and magnetic properties of nanocrystalline FeCuNbSiB alloys after a thermomechanical treatment

Structure of Nanocrystals in Finemets with Different Silicon Content and Stress-Induced Magnetic Anisotropy

“…If the magnetic moment is perpendicular to the sample plane, i.e., lies along the direction of incidence of γ quanta, then А 2 /А 1 = 0; in the case of an isotropic distribution of the magnetic moment, А 2 /А 1 = 0.67; if the magnetic moments are located in the sample plane, А 2 /А 1 = 1.33. 13 displays the concentration dependence of the coefficient А 2 /А 1 for the alloys studied, which is compared with the magnitudes of the constant of induced anisotropy, K TSA , found from the hysteresis loops measured on the samples subjected to TSA (Serikov et al, 2006). It is seen that in all the curves there is a feature near the Si content X ~ 8.…”

“…As a result of the heat treatments, samples from the alloys in three different states: initial (or immediately after quenching on the wheel), nanocrystalline (after NCA) and subjected to TSA were obtained. The magnetic state of the samples after NCA and TSA was controlled by the shape of hysteresis loops measured by the ballistic method using an F-190 microwebermeter (Serikov et al, 2006). The hysteresis loops of the samples after NCA and TSA treatments measured upon reversal magnetization along the ribbon are compared in Fig.…”

“…This argument is supported by the fact that, in bulk crystalline samples of the Fe 1-x Si x alloy, with increasing concentration of silicon the magnetostriction constant changes its sign from positive to negative at x ~ 0.12 (Bozorth, 1993;Bertotti & Fiorillo, 1994c), and that the silicon concentration in nanoparticles is a few percent higher then the average Si concentration X in the alloy (Serikov et al, 2006). For example, if X is equal to 8 at.% then silicon in nanocrystals is contained in an amount of about 12 at.%.…”

“…For the first time it was assumed that the transverse magnetic anisotropy is due to residual elastic strain in the lattice of nanocrystals having a negative constant of the magnetostriction. It is known that the type of the magnetic anisotropy induced in the Fe 87-X Si X B 9 Nb 3 Cu 1 alloy during tensile stress annealing (TSA) depends on the silicon content X (Serikov et al, 2006). If X ≤ 8, in specimens after TSA the magnetic anisotropy of easy axis type is induced, whose axis is oriented along the tape (i.e.…”

“…If the formation of a state with magnetic anisotropy after annealing and cooling under a tensile load is associated with residual elastic stresses (Glazer et al 1991;Herzer, 1994), − a result of the so-called Villari effect, then the type of magnetic anisotropy can be explained by the nature of magnetoelastic interactions in the nanoparticles (Serikov et al, 2006;Filippov, 2006) mainly consisting of Fe-Si crystals having a bcc lattice. This argument is supported by the fact that, in bulk crystalline samples of the Fe 1-x Si x alloy, with increasing concentration of silicon the magnetostriction constant changes its sign from positive to negative at x ~ 0.12 (Bozorth, 1993;Bertotti & Fiorillo, 1994c), and that the silicon concentration in nanoparticles is a few percent higher then the average Si concentration X in the alloy (Serikov et al, 2006).…”