Structure and properties of RERhZn (RE = La, Ce, Pr, Nd)
Résumé
The equiatomic intermetallic compounds RERhZn (RE = La, Ce, Pr, Nd) were synthesized from the elements in sealed tantalum ampoules in an induction furnace and investigated by X-ray diffraction on powders and single crystals: LaNiAl type, Pnma, Z = 8, a = 738.5(4), b = 406.5(2), c = 1656.5(6) pm, wR2 = 0.0572, 1217 F2 values for LaRhZn, a = 735.1(2), b = 396.4(1), c = 1632.1(4) pm, wR2 = 0.0900, 1157 F2 values for CeRhZn, a = 727.7(2), b = 401.9(2), c = 1635.3(7) pm, wR2 = 0.0707, 1000 F2 values for PrRhZn, and a = 724.7(2), b = 400.15(9), c = 1635.9(3) pm, wR2 = 0.0596, 1164 F2 values for NdRhZn with 38 variables for each refinement. The structures contain two crystallographically independent rare earth, rhodium, and zinc positions. All rhodium atoms show trigonal prismatic coordination by the rare earth and zinc atoms. Together the rhodium and zinc atoms build up three-dimensional [RhZn] networks with substantial Rh–Zn and Zn–Zn bonding in which the rare earth atoms fill channels. Temperature dependent susceptibility measurements reveal Pauli paramagnetism for LaRhZn and CeRhZn, indicating almost tetravalent cerium in CeRhZn. PrRhZn and NdRhZn are Curie–Weiss paramagnets with experimental magnetic moments of 3.60(2) μB/Pr atom and 3.63(2) μB/Nd atom, repectively. Low-temperature susceptibility and specific heat data point to inhomogeneous magnetism in PrRhZn. Antiferromagnetic ordering is detected at 7.15(2) K for NdRhZn and a metamagnetic transition at around 10 kOe in the magnetically ordered state. Electronic structure calculations for CeRhZn within the density functional theory (DFT) show agreement with experimental findings as to the magnetic valence of cerium. Detailed examination of the chemical bonding features point to dominant Ce–Rh and Rh–Zn interactions.