Magnetic and crystallographic properties of ternary rare earth compounds of the type R 2Co 14B

Abstract

Compounds of the type R 2Co 14B having the tetragonal Nd 2Fe 14B structure were found to exist for R = Y, La, Pr, Nd, Sm, Gd and Tb. The lattice constants of all these compounds were determined. Differential scanning calorimetry was used to determine the Curie temperatures of these materials, ranging from T c=955 K for La 2Co 14B to T c = 1050 K for Gd 2Co 14B. The saturation moment and anisotropy fields were studied at 4.2 K on magnetically aligned powder samples in magnetic fields up to 35 T. Estimated values of the anisotropy fields range from 6 T for La 2Co 14B to 75 T for Pr 2Co 14 B. The 3d sublattice anisotropy favours an easy magnetization direction perpendicular to the c axis whereas the crystal field induced anisotropy of the 4f sublattice corresponds to the second-order Stevens factor α J of the R component. As in R 2Fe 14B, the 3d sublattice moment couples antiparallel with the spin moment of the 4f sublattice.