Competition between Magnetism and Superconductivity in Erbium Rhodium Stannide

To understand the competition between magnetic ordering and superconductivity at low temperature in (Sn1−xErx)(1)Er(2)4Rh6Sn(2)18 compounds the variation as function x of the a.c. susceptibility and the magnetic structure, as determined by single-crystal neutron diffraction, were investigated. For increasing x, the low temperature properties change from coexistence of magnetic ordering and superconductivity (x=0) to reentrant superconductivity (x≈0.4) and to magnetic ordering only (x≈0.6). The neutron diffraction experiments at low temperatures carried out for three samples of compositions x=0, 0.42, and 0.6 allowed us to determine the variation of the low-temperature magnetic structure as a function of the mixed (Sn1−xErx)(1) site composition. Our results indicate that the changes in the low-temperature physical properties are essentially related to the increase in coherence length of the magnetic ordering for increasing x. For x=0, only short-range magnetic order of the Er(2) sublattice is present, with a correlation length of only a few unit cells large. For the intermediate x=0.42 sample, superconductivity appears and is suppressed at lower temperature due to magnetic ordering. For x=0.6, long-range magnetic order is established for one of the two Er sublattices, preventing the appearance of superconductivity. This allows the coexistence of superconductivity and short-range magnetic order.