MAGNETIC-PROPERTIES OF 2-PHASE NANOCRYSTALLINE ALLOY DETERMINED BY ANISOTROPY AND EXCHANGE INTERACTIONS THROUGH AMORPHOUS MATRIX

morphous FeCu73.5Cu1Ta3Si13.5B9 alloy was transformed, during annealing for 1 h at T-a = 480-580 degrees C, to nanocrystalline material composed of an amorphous matrix and alpha-Fe(Si) crystallites with bcc structure and diameters of similar to 15 nm. The temperature dependence of the magnetic properties of the nanocrystalline samples with different volume fractions of crystallites was studied. The coercive field and saturation magnetization were determined from quasi-static hysteresis loops measured from room temperature up to 580 degrees C using a computerized hysteresis loop tracer. A peak of the coercive field H-c was found for all the samples studied. The peak temperature and intensity depend strongly on the material microstructure. Reduction of exchange interactions between crystallites is responsible for the observed increase in H-c at temperatures around the Curie point of the amorphous matrix. The superparamagnetic behavior of the crystallites and the decrease in their magnetocrystalline anisotropy are the origins of the decrease in H-c at high temperatures.