Neutron diffraction study of superconducting RESr(2)Cu(3-x)M(x)O(z) (M=Re,W)

Abstract

Superconductivity has recently been reported in RESr(2)CU(2.85)Re(0.15)O(x) (RE = Y,Tb,Dy,Ho,Er and Tm) and RESr(2)Cu(2.80)W(0.20)O(x) (RE = Y, Dy, Ho and Er) with T-c ranging from 22 to 41 K. Room temperature powder neutron diffraction studies have been carried out for obtaining structural parameters and their relation with superconductivity in these materials. Reitveld refinements were carried out adopting the space groups P4/mmm (tetragonal). Occupancy of the rare earths is less than 1 indicating vacancy at the rare earth sites. Cu(2)-O distance in RESr(2)Cu(3-x)M(x)O(z) (M = Re and W) is smaller than that of REBa(2)Cu(3)O(7-delta) which is consistent with the smaller ionic radius of Sr2+. Our studies show that the M-cations (Re or W) occupy the Cu(1) chain site.