CORRELATION BETWEEN MICROSTRUCTURE AND MAGNETIC-PROPERTIES OF AMORPHOUS AND NANOCRYSTALLINE FE73.5CU1NB3SI16.5B6

The correlation between microstructure, saturation magnetostriction co nstant lambda(s), coercive field H-c and remanence of nanocrystallizin g Fe73.5Cu1Nb3Si16.5B6 amorphous alloy after 1 h annealing at 400-800 degrees C was studied. The amorphous ribbons (4 mm wide and 20 mu m th ick) were prepared in air by the single-roller chill-block melt-spinni ng method. The structure of partially crystallized alloys was investig ated using differential scanning calorimetry (DSC), X-ray diffractomet ry (XRD) and transmission electron microscopy (TEM). The saturation ma gnetostriction constant lambda(s) was measured at room temperature usi ng two methods: the three-terminal capacitance (TTC) method and the st rain-modulated ferromagnetic resonance (SMFMR) method. Quasi-static hy steresis loop was measured in order to determine H-c and lambda(s). Ve ry soft magnetic behavior (H-c = 0.7-0.9 A m(-1)) was observed for two -phase nanocrystalline material composed of amorphous matrix and alpha -Fe(Si) crystallites 12-15 nm in diameter obtained after annealing at 480-520 degrees C. The observed effect of the almost constant value of H-c when a substantial decrease of lambda(s) was measured is ascribed to the compensation of the decrease of magnetoelastic anisotropy by t he increase of effective magnetocrystalline anisotropy related to the observed increase of average grain diameter. The observed differences in lambda(c) measured using TTC and SMFMR methods suggest a higher vol ume fraction of crystallites at the surface than inside the ribbon. (C ) 1997 Elsevier Science S.A.