Magnetoelastic properties of amorphous and nanocrystalline Co-Fe-Nb-B alloys

Abstract
The saturation magnetostriction constant, λs, and ΔE of amorphous and nanocrystalline Co_xFe_93-x-yNb₇B_y alloys (17 ≤ x ≤ 33.9 ≤ y ≤ 15) were studied. Different stages of nanocrystallisation were obtained by field- and conventional annealing at different temperatures. On nanocrystallisation αs slightly decreases but the minimum αs always exceeds 18 ppm. The maximum ΔE is observed for annealing temperatures 400 - 450°C, i.e. before or at the early stage of nanocrystallisation. With the development of nanocrystalline phase ΔE decreases. In the field-annealed samples quite a large in-plane anisotropy transversal to the ribbon axis was observed. On the other hand, some conventionally annealed ribbons exhibit magnetic anisotropy perpendicular to the ribbon surface. The results are discussed in terms of the phenomenological model developed by Squire.