Magnetic properties of novel compounds R 3(Fe,Cr) 29X y (R=Nd, Sm and X=N, C)

Abstract

The novel ternary rare-earth iron-rich interstitial compounds R 3(Fe,Cr) 29X y (R=Nd, Sm and X=N, C) with the monoclinic Nd 3(Fe,Ti) 29 structure have been successfully synthesized. Introduction of the interstitial nitrogen and carbon atoms led to a relative volume expansion ΔV/ V of about 6% and an enhancement of Curie temperatures T c about 268 K for the nitride and about 139 K for the carbide, respectively. The Nd 3Fe 24.5Cr 4.5X y compounds have a planar anisotropy at room temperature. A first-order magnetization process (FOMP) with critical field B cr=4.4 T and 3.1 T at room temperature were observed for the Nd-nitride and carbide compounds, respectively. The Sm 3Fe 24Cr 5X y compounds were found to have a large uniaxial anisotropy of about 18 T at 4.2 K and about 11 T at 293 K. A FOMP with B cr=2.3 T was also observed in the Sm-nitride compounds at 4.2 K. Magnets with coercivity of μ Oj H c∼0.8 T at 293 K has been successfully developed from the Sm 3Fe 24Cr 5X y (XN and C) phases.