Pressure Effect on the Superconducting and Magnetic Transitions of the Superconducting Ferr.pdf

Pressure Effect on the Superconducting and Magnetic Transitions of the Superconducting Ferromagnet RuSr GdCu O 2 2 8 B. Lorenz 1, R. L. Meng 1, Y. Y. Xue 1, C. W. Chu 1,2,3 1 Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX 77204-5932 2 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 3 Hong Kong University of Science and Technology, Hong Kong, China Abstract The superconducting ferromagnet RuSr GdCu O was investigated at high pressure. The 2 2 8 intra-grain superconducting transition temperature, T , is resolved in ac-susceptibility as c well as resistivity measurements. It is shown that the pressure shift of T is much smaller c than that of other high-Tc compounds in a similar doping state. In contrast, the ferromagnetic transition temperature, Tm, increases with pressure at a relative rate that is about twice as large as that of T . The high-pressure data indicate a possible competition c of the ferromagnetic and superconducting states in RuSr GdCu O . 2 2 8 Keywords: RuSr GdCu O , intra-grain superconductivity, pressure effect 2 2 8 1 1. Introduction The coexistence of ferromagnetism and superconductivity in RuSr LnCu O (Ru-1212) 2 2 8 and RuSr (Ln Ce )Cu O (Ru-1222), where Ln = Gd, Eu, has attrac