Competition between magnetism and superconductivity in erbium rhodium stannide

To understand the competition between magnetic ordering and superconductivi ty at low temperature in (Sn1-xErx)(1)Er(2)(4) Rh6Sn(2)(18) compounds the v ariation as function x of the a.c. susceptibility and the magnetic structur e, 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 superconducti vity (x approximate to 0.4) and to magnetic ordering only (x approximate to 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 determ ine the variation of the low-temperature magnetic structure as a function o f the mixed (Sn1-xErx)(1) site composition, Our results indicate that the c hanges in the low-temperature physical properties are essentially related t o 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 pr esent, with a correlation length of only a few unit cells large. For the in termediate x = 0.42 sample, superconductivity appears and is suppressed at lower temperature due to magnetic ordering, For x = 0.6, long-range magneti c order is established for one of the two Er sublattices, preventing the ap pearance of superconductivity. This allows the coexistence of superconducti vity and short-range magnetic order. (C) 1999 Academic Press.