Racah Institute of Physics, The Hebrew University, Jerusalem, Israel.
J Phys Condens Matter. 2013 Feb 13;25(6):065702. doi: 10.1088/0953-8984/25/6/065702. Epub 2013 Jan 11.
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.
通过直流和交流磁测量研究了最佳掺杂的 La(1.85)Sr(0.15)CuO(4) 单晶。这些晶体具有矩形针状形状，长针轴与晶体学 c 轴平行（c 晶体）或与基面平行（a 晶体）。在两种晶体中，都测量了上临界场（H(C2)) 和表面临界场（H(C3)) 的温度依赖性。给出了 H-T 相图。在接近 T(C) = 35 K 时，对于 c 晶体，γ(C) = H(C3)(c)/H(C2)(c) = 1.80(2)，而对于 a 晶体，γ(a) = H(C3)(a)/H(C2)(a) = 4.0(2)，远高于理想数学模型预测的 1.69。在较低的直流应用场下，观察到称为“顺磁迈斯纳效应”（PME）的正磁场冷却分支；它们的大小与 H 成反比。在 a 晶体和 c 晶体中都观察到各向异性的 PME，只有当施加的磁场沿基面时才会出现。有人推测，高 γ(a) 和 PME 是相互关联的。
