The formation, structure and physical properties of M(2)Pd(14+x)B(5-y) compounds, with M = La, Ce, Pr, Nd, Sm, Eu, Gd, Lu and Th

J Phys Condens Matter. 2009 Jul 29;21(30):305401. doi: 10.1088/0953-8984/21/30/305401. Epub 2009 Jul 6.

Abstract

Novel ternary compounds, M(2)Pd(14+x)B(5-y) (M = La, Ce, Pr, Nd, Sm, Eu, Gd, Lu, Th; x∼0.9, y∼0.1), have been synthesized by arc melting. The crystal structures of Nd(2)Pd(14+x)B(5-y) and Th(2)Pd(14+x)B(5-y) were determined from x-ray single-crystal data and both are closely related to the structure type of Sc(4)Ni(29)B(10). All compounds were characterized by Rietveld analyses and found to be isotypic with the Nd(2)Pd(14+x)B(5-y) type. Measurements of the temperature dependent susceptibility and specific heat as well as the temperature and field dependent resistivity were employed to derive basic information on bulk properties of these compounds. The electrical resistivity of M(2)Pd(14+x)B(5-y), in general, is characterized by small RRR (residual resistance ratio) values originating from defects inherent to the crystal structure. Whereas the compounds based on Ce, Nd, Sm and Gd exhibit magnetic order, those based on Pr and Eu seem to be non-magnetic, at least down to 400 mK. While the non-magnetic ground state of the Pr based compound is a consequence of crystalline electric field effects in the context of the non-Kramers ion Pr, the lack of magnetic order in the case of the Eu based compound results from an intermediate valence state of the Eu ion.