Rare earth-rhodium-plumbides RE 2Rh2Pb with RE = La–Nd, Sm, Gd and Tb

Abstract

Abstract The plumbides RE 2Rh2Pb (RE = La–Nd, Sm, Gd, Tb) were synthesized in sealed niobium ampoules by induction melting of the pure elements or directly via arc-melting. The characterization of the samples by X-ray powder diffraction confirmed their Mo2B2Fe-type structure (space group P4/mbm) at room temperature. The Sm2Rh1.924Pb structure was refined from single-crystal X-ray diffractometer data: a=760.02(5), c=378.20(3) pm, wR=0.0387, 292 F 2 values, 13 variables. The rhodium site shows small defects. The RE 2Rh2Pb plumbides are simple 1:1 intergrowth structures of AlB2 and CsCl related slabs of compositions RERh2 and REPb. The Rh2 dumbbell in the SmRh2 slab of Sm2Rh2Pb shows a Rh–Rh distance of 281 pm. Temperature-dependent magnetic susceptibility measurements of La2Rh2Pb, Pr2Rh2Pb and Nd2Rh2Pb showed that the rhodium atoms carry no localized magnetic moments. La2Rh2Pb exhibits Pauli-paramagnetic behavior induced by the conduction electrons. The ground state of the praseodymium compound is ferromagnetic below T C=3.3 K while the neodymium compound shows a transition to an antiferromagnetic state at T N=6.1 K and a metamagnetic transition at a critical field of ca. 1000 Oe.