Magnetic Moment, Curie Temperature and Invar Effects in Amorphous Alloys

The magnetic moment, Curie temperature and Invar effects in amorphous alloys are briefly reviewed. The average magnetic moment ¿¿ of binary amorphous alloys of Fe, Co, and Ni with an early transition metal E shows a systematic trend, that is, the value of ¿¿ becomes larger as the valence and size differences between Fe, Co, Ni and E increase. Comparison of the experimental results with Friedel´s model suggests that Co-E alloys exhibit strong ferromagnetism while Fe-E alloys present weak ferromagnetism. The concentration dependence of the Curie temperature Tc is similar to that of ¿¿ above 20% E in Fe-E alloys. However, in the dilute concentration range, Tc decreases very rapidly, resulting in spin glass behavior due to spin frustration. Invar effects such as a large thermal expansion anomaly and a remarkable pressure effect on Tc are common in Fe-based amorphous alloys. The anomalous behavior above Tc is closely related to magnetic inhomogeneity.