title: Anisotropy of the upper critical fields and the paramagnetic Meissner effect in La1.85Sr0.15CuO4 single crystals.
abstract: Optimally doped La(1.85)Sr(0.15)CuO(4) single crystals have been investigated by dc and ac magnetic measurements. These crystals have rectangular needle-like shapes with the long needle axis parallel to the crystallographic c axis (c-crystal) or parallel to the basal planes (a-crystal). In both crystals, the temperature dependence of the upper critical fields (H(C2)) and the surface critical field (H(C3)) were measured. The H-T phase diagram is presented. Close to T(C) = 35 K, for the c-crystal, γ(C) = H(C3)(c)/H(C2)(c) = 1.80(2), whereas for the a-crystal the γ(a) = H(C3)(a)/H(C2)(a) = 4.0(2) obtained is much higher than 1.69, predicted by the ideal mathematical model. At low applied dc fields, positive field-cooled branches known as the 'paramagnetic Meissner effect' (PME) are observed; their magnitude is inversely proportional to H. The anisotropic PME is observed in both a- and c-crystals, only when the applied field is along the basal planes. It is speculated that the high γ(a) and the PME are connected to each other.
authors: Racah Institute of Physics, The Hebrew University, Jerusalem, Israel. israela@mail.huji.ac.il
authors: I
authors: I
authors: Felner
authors: M I
authors: MI
authors: Tsindlekht
authors: G
authors: G
authors: Drachuck
authors: A
authors: A
authors: Keren
mesh_terms: D016880:Anisotropy; D003300:Copper / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D007811:Lanthanum / Q000737:chemistry*; D008280:Magnetics; D008962:Models, Theoretical; D010087:Oxides / Q000737:chemistry*; D044367:Phase Transition; D013324:Strontium / Q000737:chemistry*
chemical_list: D010087:Oxides; D007811:Lanthanum; D003300:Copper; D013324:Strontium