Coexistence of superconductivity and magnetism in the composite material (La_(1.85)Sr_(0.15)CuO_4)_(1-x)(La_(0.3)Dy_(0.4)Sr_(0.3)MnO_3)_x

摘要

The electrical and magnetic properties of the composites (La_(1.85)Sr_(0.15)CuO_4)_(1-x)(La_(0.3)Dy_(0.4)Sr_(0.3)MnO_3)_x with 0 ≤ x ≤ 0.15 were studied by resistivity, ac susceptibility, and magnetization measurements. The undoped La_(1.85)Sr_(0.15)CuO_4 (LSCO) undergoes a superconducting transition at ～40 K, whereas La_(0.3)Dy_(0.4)Sr_(0.3)MnO_3 (LDSMO) exhibits an insulator-to-metal transition (T_(MI)) ～ 100 K and a spin glass transition (T_f) ～ 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.