Coexistence and competition between superconductivity and magnetism in La2−xSrxCu0.94M0.06O4 (M=Mn and Ru)

Abstract

The infrared (IR) transmission, Raman Scattering, magnetic measurement, and electronic resistance measurement have been carried out in La2−xSrxCu0.94Mn0.06O4 and La2−xSrxCu0.94Ru0.06O4 systems. The superconductivity that is suppressed by impurity reappears as Sr content increases and forms a new relationship of the Meissner volume and Tconset versus Sr doping content. The Mn4+ doping system exhibits twice superconductive phase transitions while Ru4+ doping system exhibits only one superconductive phase transition. Coexistence and competition between superconductivity and magnetism are observed. We suggest that these surprising phenomena should be attributed to the compensation effect that is the electrons on high valence impurities are compensated by holes introduced through Sr doping. This compensation effect is confirmed by our IR spectra results. We also find that the compensation effect is strong for the localized 3d electrons of Mn4+ while very weak for the itinerant 4d electrons of Ru4+.

Coexistence of superconductivity and ferromagnetism in La1.85Sr0.15CuO4–La2/3Sr1/3MnO3 matrix composites

“…One is that the high superconducting transition temperature (T sc ) superconductivity can be obtained by appropriate substitution of Sr for La in the form of La 1.85 Sr 0.15 CuO 4 due to some hole-carries introduced by Sr in CuO 2 planes [8]. Another is that the superconductivity in La 1.85 Sr 0.15 CuO 4 can be significantly suppressed by both the magnetic and nonmagnetic impurities doping on the Cu sites [1,2,[9][10][11][12][13][14][15][16][17][18]. Here, to avoid the destruction of CuO 2 planes in La 1.85 Sr 0.15 CuO 4 with intercalation of ferromagnets, we have studied the influence of La 2/3 Sr 1/3 MnO 3 (LSMO) on the superconductivity of La 1.85 Sr 0.15 CuO 4 (LSCO) below the T sc .…”

“…In the recent years, interface properties of ferromagnets and superconductors have been one of the most interesting topics due to potential device applications in superconducting electronics [1][2][3][4][5][6]. In conventional s-wave superconductors, local magnetic moments break up spin-singlet Cooper pairs and hence strongly suppress the superconductivity (SC).…”

Phase separation in a lattice model of a superconductor with pair hopping

“…The phase separations involving superconducting states have been evidenced in a broad range of currently intensely investigated materials including iron pnictides, cuprates and organic conductors (see for example [2][3][4][5][6][7][8][9][10][11][12] and references therein).…”

Phase Separation of Superconducting Phases in the Penson–Kolb–Hubbard Model

“…In particular, there are experimental evidences of phase separation between superconducting and (anti-)ferromagnetic [4,5] or magnetic and non-magnetic (superconducting) order [6][7][8][9] in iron-based superconductors. Moreover, the coexistence of superconductivity and magnetic order [10][11][12] as well as charge-order [13] has been reported in cuprates. Organic compounds also exhibit the superconductor-insulator phase separations as a result of the external pressure (e.g.…”

“…Moreover, the phase separations phenomenon involving superconducting states (SS) is a very current topic after it has been evidenced in a broad range of intensely investigated materials including iron pnictides, cuprates and organic conductors (discussed below, also see for examples in Refs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and references therein). The phase separation is a coexistence of two (homogeneous) phases.…”