On the absence of magnetism in quasi-two dimensional ternary rare earth intermetallics.

摘要

The non-magnetic limit of the coupling constant in ternary rare earth intermetallics has been investigated in several ternary quasi-2D structures: (1) A new class of rare earth intermetallics RIr₂Ga (R = rare earth) of the Na₃As structure. (2) CeCu₂Si ₂ of the ThCr₂Si₂ structure. (3) A New class of heavy fermion materials, CeMIn₅ and Ce₂MIn₈ (M = Rh, Ir, Co), which crystallize in the HoCoGa₅ and Ho ₂CoGa₈ structures.; The RIr₂Ga series has been found as a new environment for the rare earth ions. Its layered structure gives rise to the spatial inhomogeniety of the magnetic interactions, which contributes to anomalous magnetic order in the members of the series that order magnetically. It has been proposed that CeIr₂Ga and YbIr₂Ga are new mixed valence materials. Experimental results for the magnetization and electrical resistivity are presented.; The resistivity and AC susceptibility measurements were performed on different CeCu₂Si₂ samples and the distinction was made between a magnetically ordered sample (Cu deficient) and a superconducting sample (made with excess Cu). Subsequent investigation showed signs of lattice inhomogeniety in the latter sample. A possible cause of the absence of magnetic order and appearance of superconductivity in CeCu₂Si₂ has been indicated.; Magnetic susceptibility and resistivity measurements were performed on the various members of CeMIn₅ (M = Rh, Ir, Co) and Ce₂MIn ₈ (M = Ir, Rh) compounds at different pressures and magnetic fields. Bulk superconductivity was observed and resistive superconductivity was confirmed in CeRhIn₅. Superconductivity has been observed in CeIrIn ₅ and the superconducting ground state has been perturbed by pressure and Rh doping. The CeCoIn₅ member of the series has been made and the bulk superconductivity was observed. These results have been discussed in the framework of the spin fluctuations theory of superconductivity for heavy fermion superconductors.; The comments are given for all compounds used in the study on the relation between the quasi 2D structure and electronic properties.