Critical magnetic properties of the re-entrant amorphous ferromagnet Ni_80-xFe_xB₁₂Si₈

Abstract

The critical magnetic properties of the amorphous Ni-Fe-B-Si system have been studied using AC susceptibility techniques. Alloys of the composition Ni80-xFexB12Si8 with x>or=5 show re-entrant ferromagnetic behaviour. The critical exponents gamma , associated with the magnetic susceptibility, and delta , associated with the critical isotherm, have been determined. Values of the exponents are consistent with those predicted for three-dimensional Heisenberg systems. The critical susceptibility of the alloy with x=4 in the region above the spin-glass transition is found to follow a power law with an exponent gamma '0=1.5.