Thermomagnetic annealing of soft amorphous metallic alloys monitored by in situ resistance and magnetoresistance measurements

Abstract

This study concerns structural relaxation in sputtered Co-metal amorphous films (here, Co8.15Zr8.5Pt10) taking place during isochronal and isothermal thermomagnetic treatment. The aim is to improve the stability of the films and to reduce their induced magnetic anisotropy. In these materials, the topological short-range ordering (TSRO) directly connected to the amorphous film stability is irreversible, whereas the chemical short-range ordering (CSRO), which has to do with magnetic anisotropy, is reversible. With a view to maintaining strict control over both TSRO and CSRO and to treat them separately, equipment was constructed to perform thermomagnetic anneals up to 900 K combined with quenches with initial rates of 500 K s−1. In the course of these treatments, resistance and magnetoresistance measurements were used to follow accurately, with a sensitivity better than 10−5, the evolution of TSRO and of induced anisotropic field HK without resorting to any other characterization than those made with this apparatus. Under these conditions several isochronal and isothermal anneals were carried out which show that: (1) TSRO and CSRO can easily be differentiated, and (2) HK can be reversibly changed or controlled at will.