Crystal chemistry and physical properties of the ternary compounds RE5B 4C 5 ( RE=Ce, Pr, Nd)

Abstract

The ternary rare-earth metal boride carbides RE 5B 4C 5 ( RE=Ce, Pr, Nd) were prepared by arc melting the mixtures of the pure elements and subsequent annealing at 1270 K. Their crystal structures were determined from single crystal X-ray diffraction data. They crystallize in the Ce 5B 4C 5 type of structure (space group Pna2 1, Z=8). Two new compounds were found, Pr 5B 4C 5: a=24.592(2) Å, b=8.4563(5) Å, c=8.4918(5) Å, R 1=0.043 ( wR 2=0.076) for 2871 reflections with I o⩾2 σ( I o)); for Nd 5B 4C 5: a=24.301(1) Å, b=8.3126(5) Å, c=8.3545(4) Å, R 1=0.035 ( wR 2=0.069) for 3707 reflections with I o⩾2 σ( I o)). Its structural arrangement consists of a three-dimensional framework of rare-earth atoms resulting from the stacking of slightly corrugated two-dimensional square nets, leading to voids filled with B 4C 4, B 3C 3, BC 2 finite chains and isolated carbon atoms. Ce 5B 4C 5 is an antiferromagnet at 5 K followed by a metamagnetic transition in elevated external fields. Pr 5B 4C 5 and Nd 5B 4C 5 are ferromagnets below T C=12 and 15 K, respectively.