STRUCTURAL RELAXATION IN AN AMORPHOUS RAPIDLY QUENCHED COBALT-BASED ALLOY

An amorphous melt-spun Co-based alloy (Metglas 2705 MN) is investigate d by Doppler Broadening and Positron Lifetime techniques in order to f ollow the microstructural changes yielded by isochronal annealings bef ore crystallization. The results are correlated with those of Differen tial Scanning Calorimetry and Coercive Field measurements. The quenche d empty spaces underlined by Lifetime measurements are less than one a tomic volume in size and migrate without clustering in larger voids. B oth Positron Annihilation and Coercive Field investigations suggest th at the overall decrease of free volume related to structural relaxatio n in this amorphous material, proceeds mainly via compositional short- range ordering. These local chemical rearrangements which lead to a pa rtial disorientation of the magnetic moments act as strong pinning poi nts for Bloch Walls.