Magnetic and structural features of glass-coated Cu-based (Co,Fe,Ni,Mn-Cu)alloy microwires

The various factors (compositional and geometrical) which determine the mic rostructural and magnetic behaviour of glass-coated microwires are describe d. The discussion is based on results performed on microwires at several co mpositions (Co,Fe,Ni,Mn-Cu, Cu-based). The structural changes (experimental ly determined by XRD diffraction) due to variations of the chemical composi tion, geometry (ratio, rho, of the metallic core to the total diameter of t he microwire) and heat treatment can be correlated with the evolution of th e hysteresis behaviour. A significant change of the magnetization curve is observed in Fe30Cu70 microwire,which is ascribed to the presence of two dif ferent magnetic phases depending on rho. Enhanced magnetic hardness (up to 800 Oe) is obtained for Co29Ni25Cu4.5Mn1 microwire after annealing at 700 d egreesC for 1 h, which could be correlated with phase separation during hea t treatment. Variations of the coercivity evidence a certain correlation wi th the grain size and rho parameter, which could be ascribed to the effect of the internal stresses on the grain size. (C) 2000 Elsevier Science B.V. All rights reserved.