Optimization of soft magnetic properties in nanoperm type alloys

In the present paper, it was shown that soft magnetic properties of the group of amorphous alloys Fe–X2–B22 (X=Cr, Zr and Nb) can be optimized (magnetic permeability increases about five times) by applying 1-h annealing at temperatures: 600, 600, 650 and 700 K for the Fe78B22, Fe76Cr2B22, Fe76Zr2B22 and Fe76Nb2B22 alloys, respectively. This effect is attributed to annealing out of free volumes formed into material during fabrication and for the Fe76Zr2B22 alloy also to a formation of a nanocrystalline phase. Using isothermal measurements of magnetization (magnetic balance), it was shown that the process of formation of nanocrysalline phase can be described by Johnson–Mhel–Avrami kinetic. Activation enthalpy of this process was deduced as 3.2 eV and the power law exponent 3.4.