High-Field Susceptibility of Fe-La Amorphous Alloys

In Fe-La amorphous alloys, composition does not have a great effect on the Curie temperature (Tc) at high concentrations, but there was a significant drop at low concentrations which is believed due to a strong antiferromagnetic interaction. The magnetization of alloys with a higher La concentration saturated more easily, but for low concentration alloys, there was a more pronounced curve and no saturation in the magnetization curves. This is thought to be related to the spin frustration and spin glass characteristics. The Fe-La alloys have a high-field susceptibility that is much larger than Co-base alloys, and is similar to Invar alloys. The thermal expansion curves have a remarkable anomaly with some contraction above Tc in low Fe concentrations. This is thought due to cluster formation.