COOLING-INDUCED PHASE-TRANSITION IN AMORPHOUS COCRZR ALLOY

In amorphous Co77Cr11.7Zr11.3 ribbons, produced by melt spinning, irre versible changes of hysteresis magnetic properties and Curie temperatu re were observed after thermal cycling (TC) (300 K-78 K-300 K). After TC the coercive force H(c) increased by 35%, magnetization B(s) at the magnetic field 4.5 Oe by 6%, and remanent magnetization B(r) by 3%. M aturing of thermal-cycled samples at 300 K during 10 h led to the furt her increasing of H(c), B(s), and B(r) by 60%, 16%, and 10%, respectiv ely, as compared with the as-cast state. Subsequent TC changed neither H(c) nor B(s) and B(r) After maturing of as-cast ribbons at 300 K for 4 weeks H(c) became larger by 55%. The observed dependencies are expl ained as a sequence of phase transitions in the amorphous state connec ted with metastable high-temperature modification of Co-based local or der after quenching.