Coexistence of various Nd-rich and Fe-rich Fe-Nd short range orderings in bulk glassy Nd60Fe30Al10 hard magnets

Abstract

Bulk Nd60Fe30Al10 metallic glasses are found to exhibit a complex magnetic behavior at very low temperatures related to the coexistence of various Nd-rich and Fe-rich magnetic short range orderings, as evidenced by AC-susceptibility studies in combination with hysteretic loops at fields up to 30 T. Above 80 K the magnetic behavior is shown to correlate with Stoner-Wohlfarth hysteresis loops with pronounced thermal activation effects. These observation suggest the existence of an Fe-rich Fe-Nd hard magnetic 'phase' formed by an ensemble of randomly oriented uniaxial magnetic nanoentities embedded in a Nd-rich matrix. The exchange coupling and development of a large axial crystal field anisotropy at very low temperatures and the uncoupling above 70 K of the Fe-rich Fe-Nd hard magnetic phase to the Nd-rich matrix appears to be at the origin of the observed overall magnetic behavior.