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arXiv 1206.2776cond-mat.supr-con
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La1.85 Sr 0.15 CuO 4单晶的上临界场各向异性及顺磁迈斯纳效应

Anisotropy of the upper critical fields and the paramagnetic Meissner effect in La1.85Sr0.15CuO4 single Crystals

I. Felner, M. I. Tsindlekht, G. Drachuck, A. Keren

摘要:

采用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,长针轴平行于晶体学c轴(c-晶体)或平行于基面(a-晶体)。在这两种晶体中,上临界场(HC 2)和表面临界场(HC 3)的温度依赖性进行了测量。给出了H-T相图。在TC =35 K附近,c-晶体的γc = 1.80(2),而a-晶体的γa =4.0(2),比理论值1.69高得多。在较低的直流电场作用下,可以观察到被称为“顺磁迈斯纳效应“(PME)的正向场冷分支,其大小与H成反比。在a-和c-晶体中观察到各向异性的PME,只有当施加的场是沿着基面。推测高γa与PME相互联系。

英文摘要:

Optimally-doped La1.85Sr0.15CuO4 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 (HC2) and the surface critical field (HC3) were measured. The H-T phase diagram is presented. Close to TC =35 K, for the c-crystal, γc = / = 1.80(2), whereas for the a-crystal the γa = / =4.0(2) obtained, is much higher than the theoretical value 1.69. 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 γa and the PME are connected to each other.

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