Study On Superconductivity And Magnetism In Correlated Electron Materials

In correlated materials, the many body interaction among electrons can induce rich quantum phenomena, such as unconventional superconductivity and quantum phase transitions, which have been the focus of condensed matter physics in the past decades. In this dissertation, we tune the magnetism in Ce2Ni11.5Pd0.5As7 by measuring the electrical resistivity under pressure, and study the superconducting order parameter of Yb3Rh4Sn13, the interplay of superconductivity and magnetic in EuFe2(As0.81P0.19)2 by measuring the magnetic penetration depth at low temperature.This dissertation consists of five chapters. The first chapter presents a brief introduction on superconductivity and its relation with magnetism. The second chapter describes the experimental setups, and the experimental principles. The third chapter is devoted to the magnetism of Ce2Ni11.5Pd0.5As7 tuned by pressure. Measurements of the electrical resistivity under pressure show that the magnetic transition shifts to higher temperature with increasing pressure in the pressure region of 0Gpa<p<1.0Gpa. In the fourth chapter, we measured the upper critical field and the penetration depth for Yb3Rh4Sn13, these results indicate that this compound is a weak coupling superconductor. Measurements of the penetration depth at various field is presented for EuFe2(As0.81Po0.19)2 in the last chapter. We find that magnetism coexists with superconductivity in this compound and the magnetic transition shows anisotropic behavior in a magnetic field.