The Study Of Coexistance Of Superconductivity And Ferromagnetism In Y1−Xprxba2cu3o7−Δ

Abstract

In this thesis, coexistence of superconductivity and ferromagnetism states in cuprate based superconductor Y1−xPrxBa2Cu3O7−δ was investigated theoretically. A model Hamiltonian which represents the competing energies in the system was developed. This model Hamiltonian was solved employing the equation of motion approach of the retarded Green’s function. From the Green’s functions of the Hamiltonian, we obtained the mathematical expressions for superconducting transition temperature (Tc), magnetic order transition temperature (Tm), superconducting order parameter (∆SC) and magnetic order parameter η. The suppression of superconductivity by Praseodymium, including hole filling by charge transfer from Pr to the CuO2 planes, hole localizations, magnetic pair breaking. Using the experimental and theoretical values and by considering plausible approximations of the parameters in the obtained expressions, the phase diagrams of superconducting transition temperature versus Pr concentration and magnetic ordering temperature versus magnetic ordering parameter are plotted. By merging the two graphs, we have got a region in which both superconductivity and ferromagnetism coexist in Y1−xPrxBa2Cu3O7−δ system. Superconductivity appears together with ferromagnetism continue only until the ferromagnetic effect is not sufficiently large .