Relation between cuprate superconductivity and magnetism: A Raman study of (CaLa)1(BaLa)2Cu3 Oy

Abstract

We present an investigation of charge-compensated antiferromagnetic (CaxLa1.x)(Ba1.75.xLa0.25+x)Cu3Oy single crystals using Raman scattering as well as muon spin rotation. In this system the parameter x controls the Cu-O-Cu superexchange interaction via bond distances and buckling angles. The oxygen content y controls the charge doping. In the absence of doping the two-magnon peak position is directly proportional to the superexchange strength J .We find that both x and y affect the peak position considerably. The N´eel temperature determined from muon spin rotation on the same samples independently confirms the strong dependence of the magnetic interaction on x and y. We find a considerable increase in the maximum superconducting transition temperature T max c with J . This is strong evidence of the importance of orbital overlap to superconductivity in this family of cuprates.