The influence of nanocrystalline microstructure on the magnetic properties of a wire shaped ferromagnetic alloy

The magnetic properties of nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 13.5/B/sub 9/ alloy wire are reported. The evolution of the structure and of the magnetic properties of the wire is studied as a function of annealing temperature, T/sub ann/. In the as-cast glassy state, the wires show typical bistable magnetic behavior while, after devitrification to a nanocrystalline structure based on alpha -FeSi grains of mean diameter approximately 10 nm (T/sub ann/=550 degrees C), the coercivity and magnetostriction decrease substantially and bistability is lost. The bistability could be recovered on application of a torsional stress. Treatment at T/sub ann/>600 degrees C leads to grain growth and eventually to precipitation of ultrafine boride, resulting in drastic magnetic hardening.<>