MAGNETIC-BEHAVIOR OF NANOSTRUCTURED GLASS COVERED METALLIC WIRES

We present a study of the evolution of the magnetic properties and beh avior of Fe73.5CU1Nb3Si13.5B9 glass covered wires and wires after glas s removal with the annealing temperature up to 600 degrees C starting from the amorphous state. The changes induced in the magnetic properti es of these wires are determined by the stress relief process occurrin g at temperatures below 550 degrees C, and by the appearance of the na nosized alpha-FeSi crystalline grains after annealing for 1 h at 550 d egrees C. The nanocrystalline phase formation leads to an improvement of the soft magnetic properties of these wires-increase of permeabilit y and decrease of the coercive force-but also determines the disappear ance of the large Barkhausen effect presented by these wires in the am orphous state. Annealing at temperatures over 550 degrees C determines a depreciation of the soft magnetic properties of both glass covered wires and wires after glass removal. The magnetic behavior of such wir es can be fully explained by taking into account the relaxation of the internal stresses with increasing the annealing temperature as well a s the changes in the magnetostriction constant due to the appearance o f the nanocrystalline grains. (C) 1997 American Institute of Physics.