Ferrimagnetism of the Rare-Earth-Cobalt Intermetallic Compounds R2Co17

Abstract

Saturation moments, Curie temperatures, and supporting crystallographic data are reported for a series of ferrimagnetic intermetallic compounds of the stoichiometry R2Co17, where R is any of the rare-earth elements Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The saturation moment of Y2Co17 is 27.2, that of Lu2Co17 is 27.6 Bohr magnetons per formula unit, indicating a cobalt moment of 1.61 μB in this series. Substitution of Pr and Nd for R raises the saturation to 32.8 μB/F.U. for Pr2Co17; all other lanthanides lower it (minimum: 5.7 μB/F.U. for Ho2Co17). Except for Sm2Co17, the values agree well with the concept that the Co moments couple antiparallel with the rare-earth spin sublattice. For Ce and Pr, a valence>3 and electron transfer from R to Co must be assumed. The Curie temperatures lie between 795° and 940°C. The variation of Tc with the atomic number suggests that two coupling mechanisms are active: direct Co-Co exchange interaction and indirect exchange between R and Co via polarized conduction electrons.