FINE-PARTICLE MAGNETIC-PROPERTIES AND MICROSTRUCTURES OF NANOCRYSTALLINE FE-CU-NB-SI-B ALLOY AT ELEVATED-TEMPERATURES

Magnetic behavior in nanocrystalline Fe(72)Cu(1)Nb(4.5)Si(13.5)E(9) al loy is investigated by measurements of low and high field magnetizatio n and coercivity over the temperature range from 300 K to 800 K. When the measuring temperatures approach the Curie temperature of intergran ular amorphous phase T-c(amorphous), the nanocrystalline materials con sist of ferromagnetic Fe-rich nanocrystals embedded in a weakly magnet ic or non-magnetic matrix. Samples with different volume fractions of crystalline phase are prepared to investigate the nature and strength of inter-particle interactions between the nanocrystallites. It is sho wn that at temperatures above T-c(amorphous), the specimens with low f raction of nanocrystalline particles exhibit superparamagnetic behavio r. In the case of specimens with increasing volume fraction of crystal line phase, the magnetic interaction between particles suppresses supe rparamagnetic fluctuations and superferromagnetic ordering of the part icle magnetic moments above T-c(amorphous) is observed. Copyright (C) 1996 Elsevier Science S.A.