Structural and magnetic properties of the rare-earth–borocarbides, R 5B 2C 6 (R=Y, Ce–Tm)

Abstract

The compounds R 5B 2C 6, R=Y, Ce–Tm, were prepared by arc melting the elements, rare earth ingots, boron and carbon. From X-ray powder analyses these compounds were found to crystallize essentially with tetragonal symmetry, space group P4 (No. 75). The yttrium containing sample is a Pauli type paramagnet below room temperature down to 4.2 K. The magnetic properties of Ce 5B 2C 6 are characterized by an intermediate valence behavior. Gd 5B 2C 6 orders antiferromagnetically at a Neél temperature T N=26 K and reveals a metamagnetic transition above B=0.5 T. All the remaining samples investigated undergo ferromagnetic transitions in the temperature regime below T=40 K. These borocarbides exhibit a magnetic behavior typical for narrow domain wall ferromagnets. Both the Curie temperatures, T C, as well as the paramagnetic Curie temperatures, θ P, scale roughly with the de Gennes factor and hence the indirect exchange interaction via the conduction electrons (RKKY-interacting) is the dominating force of the R–R coupling mechanism.