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

The saturation magnetostriction constant, lambda(s), and Delta E-effect of amorphous and nanocrystalline CoxFe93-x-yNb7By alloys (17 less than or equal to x less than or equal to 33, 9 less than or equal to y less than or equal to 15) were studied. Different stages of nanocrystallisation were obtained by field- and conventional annealing at different temperatures. On nanocrystallisation lambda(s) slightly decreases but the minimum lambda(s) always exceeds 18 ppm. The maximum Delta E-effect is observed for annealing temperatures 400 - 450 degrees C, i.e. before or at the early stage of nanocrystallisation. With the development of nanocrystalline phase Delta E 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.