Phys. Rev. B 76, 134509 (2007) [6 pages]Measurements and analysis of the upper critical field Hc2 of underdoped and overdoped La2−xSrxCuO4 series of compoundsReceived 10 April 2007; revised 21 June 2007; published 19 October 2007 The upper critical field Hc2 is one of the many nonconventional properties of high-Tc cuprates. It is possible that the Hc2(T) anomalies are due to the presence of inhomogeneities in the local charge carrier density ρ of the CuO2 planes. In order to study this point, we have prepared good quality samples of polycrystalline La2−xSrxCuO4 using the wet-chemical method, which has been demonstrated to produce samples with a good cation distribution. In particular, we have studied the temperature dependence of the upper critical field Hc2(T) through magnetization measurements on two samples equidistant from the optimal doping on the phase diagram and nearly equal critical temperatures, namely, ρm=0.08 (underdoped) and ρm=0.25 (overdoped). The results close to Tc do not follow the usual Ginzburg-Landau theory and are interpreted by a theory which takes into account the influence of the inhomogeneities. © 2007 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevB.76.134509
DOI:
10.1103/PhysRevB.76.134509
PACS:
74.72.−h, 74.81.−g, 74.20.De, 02.70.Bf
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