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

morphous FeCu73.5Cu1Ta3Si13.5B9 alloy was transformed, during annealin g for 1 h at T-a = 480-580 degrees C, to nanocrystalline material comp osed of an amorphous matrix and alpha-Fe(Si) crystallites with bcc str ucture and diameters of similar to 15 nm. The temperature dependence o f the magnetic properties of the nanocrystalline samples with differen t 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 comp uterized 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 incr ease in H-c at temperatures around the Curie point of the amorphous ma trix. The superparamagnetic behavior of the crystallites and the decre ase in their magnetocrystalline anisotropy are the origins of the decr ease in H-c at high temperatures.