CHANGES IN MAGNETIC-ANISOTROPY DISTRIBUTION DURING STRUCTURAL EVOLUTION OF FE76SI10.5B9.5CU1NB3

Magnetic properties of Fe76Si10.5B9.5Cu1Nb3 have been correlated to th e structural evolution of this alloy upon heat treatment. The influenc e of isochronal annealing on the hysteresis loop has been analysed. Th e very beginnings of nanocrystallization causes a slight magnetic hard ening in the samples which will be overcome by the enhancement of the volume fraction of the Fe,Si crystallites. For further beat treatment, the appearance of boride-type phases provokes an abrupt magnetic hard ening, whilst final recrystallization phenomena can hardly decrease co ercivity. The evolution of the magnetic anisotropy distribution upon h eat treatment has been explained. in the light of the generalized rand om anisotropy model. The appearance of new origins of anisotropy (magn etocrystalline) and the development of new stresses in the sample by t he emerging crystallites makes the magnetic anisotropy distribution sh ift to higher values and unfold in various maxima. In the range of cry stallized volume fraction and grain size where Herzer's model is appli cable, the distribution folds again and certainly resembles that of th e relaxed amorphous due to the effective averaging of macroscopic magn etic anisotropy. (C) 1998 Elsevier Science B.V. All rights reserved.