High field magnetoresistivity of epitaxial La2−xSrxCuO4 thin films

A large positive magnetoresistivity (up to tens of percents) is observed in both underdoped and overdoped superconducting La2−xSrxCuO4 epitaxial thin films at temperatures far above the superconducting critical temperature Tc. For the underdoped samples, this magnetoresistance cannot be described by the Kohler rule and we believe it is to be attributed to the influence of superconducting fluctuations. In the underdoped samples (0.05 ⩽ x ⩽ 0.15), the large magnetoresistance is only present when at low temperatures superconductivity occurs. The strong magnetoresistivity, which persists even at temperatures substantially above Tc, can be related to the pairs forming eventually the superconducting state below Tc. Our observations support the idea of a close relation between the pseudogap and the superconducting gap and provide new indications for the presence of pairs above Tc.