Effect of the annealing conditions and grain size on the soft magnetic character of FeCu(Nb/Ta)SiB nanocrystalline alloys

Melt spun amorphous Fe73.5Si13.5B9Cu1(Ta/Nb)(3) ribbons have been submitted to thermal treatments carried out both in a conventional furnace and by us ing the Joule heating technique. These treatments resulted in a partial dev itrification to a nanocrystalline structure of the samples. The effect of t he treatment parameters both on the magnetization work, W, and on the coerc ive force, H-c has also been investigated. Our conclusions correlate the de pendence of W on the annealing parameters with the occurrence of structural relaxation in the amorphous phase and of domain wall pinning at the precip itated nanocrystals. In addition, the obtained coercive force dependence on the average grain size, D is discussed in the framework of an extended ran dom anisotropy model. Discrepancies with the theoretical H-c proportional t o D-6 law were found which could be assigned to the role of inhomogeneous m agnetic anisotropy induced by the Joule heating on the averaged magneto-cry stalline anisotropy. (C) 2000 Elsevier Science B.V. All rights reserved.