Coexistence of superconductivity and magnetism in the composite material (La1.85Sr0.15CuO4)1-x(La0.3Dy0.4Sr0.3MnO3)x

The electrical and magnetic properties of the composites (La1.85Sr0.15CuO4)(1-x)(La0.3Dy0.4Sr0.3MnO3)(x) with 0 <= x <= 0.15 were studied by resistivity, ac susceptibility, and magnetization measurements. The undoped La1.85Sr0.15CuO4 (LSCO) undergoes a superconducting transition at similar to 40 K, whereas La0.3Dy0.4Sr0.3MnO3 (LDSMO) exhibits an insulator-to-metal transition (T-MI)similar to 100 K and a spin glass transition (T-f)similar to 70 K. The saturation magnetization of the composites shows an increase with increase in x. The onset temperature (T-c) of the superconducting transition of LSCO remains almost unaltered upon intercalation with LDSMO, whereas the superconducting volume fraction decreases drastically with increase in x. The normal state resistivity of LSCO changes from the initial metallic behavior to that of an insulator when x is increased. The signature of another magnetic transition is observed in the composites below T-f in the ac susceptibility and magnetization measurements. The nature and frequency dependence of this magnetic transition could not, however, be determined due to the onset of superconducting transition. On the basis of analysis of the resistivity data, it is conjectured that intercalation of LSCO with LDSMO leads to charge localization in LSCO which suggests possible microscopic phase separation of LSCO into hole-rich and hole-poor regions.