Structures and magnetic properties in nano-crystalline Fe-rich Fe-Ni and Fe-Co alloys

¹ Department of Mathematics and Physics, Shanghai University of Electric Power, Shanghai 200090, P.R. China
² Department of Physics, Shanghai University, Shanghai 200444, P.R. China

Corresponding author: lysly99313@sohu.com

Received: 24 March 2006
Revised: 24 July 2006
Accepted: 23 October 2006
Published online: 24 January 2007

Abstract

Nano-crystalline magnetic alloys of Fe-Ni and Fe-Co are fabricated by high-energy milling. The coexistence of bcc and fcc lattice structures is observed in some of Fe-Ni alloys, as opposed to Fe-Co ones which exhibit the bcc phase only. The grain sizes increase linearly with the lattice strains for Fe-Co, and exponentially so for Fe-Ni. The cut-off frequency decreases with increasing nickel content in Fe-Ni alloys, but increases with increasing cobalt content in Fe-Co alloys. The larger the cut-off frequency is, the smaller the initial permeability. Resonant behaviour is observed in the pure Fe and Fe-Ni samples, which is replaced by relaxant behaviour in Fe-Co, implying that the Co plays an important role in hindering the resonance. The initial permeability at 10 kHz varies inverse proportionally with the coercivity H_c. It reaches a maximum while H_c goes to a minimum at 7.69 at.% Ni or Co. It is interesting that average atomic moments of nanocrystalline alloys are inconsistent with the Slater-Pauling relation.