Correlation between the orthorhombicity and the transition temperatures of the "123" rare earth series superconductors

Abstract

The influence of the tetragonal-to-orthorhombic phase transition on the normal-to-superconducting phase transition in REBa2Cu3O7-y(RE = rare earth element) is studied within the framework of a Ginzburg-Landau (GL) approach. Through a minimization of the GL free energy, an expression for the superconducting critical temperature is obtained which predicts that Tcshould vary as the square of the orthorhombicity. It is found that the correlation between the observed Tcs and orthorhombicities of the "123" RE series superconductors require the two phase transitions to be competitive. This is unlike the case for the "124" RE series superconductors, where the two phase transitions enhance each other. © 1997 Elsevier Science Ltd.