Magnetic and structural features of RNi2B2C and RNiBC (R=Er, Ho, Dy, Tb, Gd) superconducting compounds

Abstract

Temperature dependent Mössbauer spectroscopy on 57Fe doped (1 at % of Ni) RNi2B2C and RNiBC provided clear evidence of a pair-breaking field at the Ni site for non-superconducting compounds. This field is not present in the superconducting collinear AF DyNi2B2C, however it appears when this compound is diluted with non-magnetic Lu (Dy1-xLuxNi2B2C). Important local information on the spin structure of the R magnetic moments is obtained for both systems. The local symmetries of RNi2B2C and RNiBC compounds, measured through the ΔEQ, were found to be linearly correlated with the c'/a ratio (c' is the distance of the R-C layers between which the Ni2-B2 layers are sandwiched). A scaling of Tc with the local symmetry (c'/a) was found to be the same for all the RNi2B2C and RNiBC (except for Y) compounds.