Low-Temperature Magnetic Properties of LuBaCuFeO5+delta and TmBaCuFeO5 +delta

The compounds CeMIn5 (M=Co, Rh, Ir) have been shown to exhibit heavy fermion behavior. In order to better understand this effect and the nature of the observed superconductivity, we have synthesized and characterized the non-magnetic analogs, LaMIn5 (M=Co, Rh, Ir). The structures of LaCoIn5, LaRhIn5, and LaIrIn5 were determined by single-crystal X-ray diffraction. CeMIn5 and LaMIn5 compounds are isostructural and adopt a tetragonal structure with space group P4/mmm, Z=1. Lattice parameters are a=4.6399(4) and c=7.6151(6) ? for LaCoIn5, a=4.6768(3) and c=7.5988(7) ? for LaRhIn5, and a=4.6897(6) and c=7.5788(12) ? for LaIrIn5. We compare these experimental data with band structure computations and examine structural trends that affect the magnetic and transport properties of these compounds.