Abstract
AbstractAmorphous Co76Mo18Ni6 alloy films are prepared by direct current plating. The devitrification-induced microstructure evolutions and variations of magnetic properties during thermal annealing under hydrogen atmosphere are clarified. The structure is amorphous and paramagnetic if annealing temperature is lower than 200℃. Ferromagnetic nanocrystallites ε-Co precipitate out of amorphous matrix if the temperature is within the range of 300 and 600℃. Hence, the hysteresis loop becomes wider and the film becomes ferromagnetic. At 600℃ amorphous matrix transforms into the supersaturated ε-Co plus some κ-Co3Mo phase. Annealing at temperature higher than 800℃, ε-Co is converted into α-Co. κ-Co3Mo becomes the major phase at this stage. The Curie temperature is about 800℃, which is determined by thermogravimetric analyzer (TGA) under the influence of a static magnetic field. Asymmetrical hysteresis loops show the effect of ferromagnetic–antiferromagnetic exchange coupling, which are measured by alternating gradient field magnetometer (AGFM) and electron spectroscopy for chemical analysis (ESCA). The field-displaced loops result from the anti-ferromagnetic oxide films CoO and NiO, which are produced over the surface of ferromagnetic Co-Mo-Ni film. Besides, when the analysis of diffraction data are difficult because of peaks overlap, the magnetic technique can supply a simple solution through TGA in a magnetic field and hysteresis measurement.