Relaxation Annealing Influence on the Magnetic Properties and Magnetic Impedance of Amorphous Co-Based Wires

Abstract

Abstract—The results of a study of the influence of the 2 hours relaxation annealing at a temperature of 620 K on the magnetoimpedance effect (MI) in amorphous Co66Fe4Nb2.5Si12.5B15 wires are presented. It was found that MI at low ac frequencies after heat treatment increases noticeably, while it changes slightly at high frequencies. Using magneto-impedance tomography, it is shown that this is due to the fact that the changes in magnetic properties caused by heat treatment are not the same in different regions of the wire. Thus, in the surface region with a thickness of about 2.5 μm, the magnetic permeability remains almost unchanged, but in the internal regions it increases significantly after annealing.