Ferromagnetism and spin glass in amorphous FeZr alloys

Abstract

Magnetic properties of the amorphous FeZr alloys have been investigated on the basis of a finite temperature theory of magnetism for amorphous alloys with strong local environment effects. The calculated magnetic phase diagram and magnetization vs. concentration curve explain well those obtained from experimental data, exhibiting a spin-glass ferromagnet transition. It is demonstrated that the spin-glass behaviour near the amorphous pure Fe is mainly caused by the competition between the short-range ferromagnetic interactions and long-range antiferromagnetic interactions via structural disorder, while the formation of ferromagnetism with increasing Zr concentration originates in the band narrowing at the Fe site, which is caused by a reduction in average coordination number of Fe atom due to the difference between Fe and Zr atomic sizes. The re-entrant spin-glass behaviour in Fe-rich amorphous alloys is shown to be realized by the thermal spin fluctuations of amplitude of local magnetic moment. © 1994.