Influence of Ni on the structural and magnetic properties of NixFe73.5−xSi13.5B9Nb3Cu1 (⩽x⩽25) alloys

Abstract

A systematic investigation about the influence of Ni content on structure and magnetic properties of melt-spun NixFe73.5−xSi13.5B9Nb3Cu1 (0⩽x⩽25) alloys has been performed. The study has been done in amorphous ribbons as well as after thermal treatments leading to structure relaxation, to partial devitrification into nanocrystalline state, and finally to full structural crystallization. Different characterization techniques have been employed. Structure has been investigated by x-ray diffraction, differential scanning calorimetry, and Mössbauer technique, while magnetic properties as coercivity, saturation magnetostriction constant, or Curie temperature have been studied by induction methods. Two main behaviors have been distinguished depending on the Ni content of the alloys: (i) Low Ni content (up to x=15), when Ni atoms diffuse towards Fe sites in the disordered bcc (Fe,Ni)3Si structure originating reduced structural distortion and small changes in magnetic properties as coercivity and (ii) High Ni content (x=20,25) for which drastic changes are observed in structure (appearance of a tetragonal Fe3NiSi1.5 phase) and magnetic properties (coercivity increases up to two orders of magnitude) particularly after annealing at those temperatures for which optimum nanocrystalline structure is achieved for x=0.