Conductance anisotropy and linear magnetoresistance inLa2 − xSrxCuO4 thin films

Abstract

We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) ofLa2 − xSrxCuO4 (LSCO)thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features ofthe conductance anisotropy are revealed by measuring the transverse resistanceRxy in zero magnetic field. It is demonstrated that the sign ofRxy depends on the orientation of the LSCO Hall bar with respect to the terrace structure ofthe substrate. Unit-cell-high substrate step edges must therefore be a dominant nucleationsource for antiphase boundaries during film growth. We show that the measurement ofRxy is sensitive enough to detect the cubic–tetragonal phase transition of theSrTiO3(100) (STO) substrate at 105 K. The MR of LSCO thin films shows for0.10 < x < 0.25 a non-monotonic temperature dependence, resulting from the onset of a linear term in theMR above 90 K. We show that the linear MR scales with the Hall resistivity as , with the constant of proportionality independent of temperature. Such scaling suggeststhat the linear MR originates from current distortions induced by structural or electronicinhomogeneities. The possible role of stripes for both the MR and the conductanceanisotropy is discussed throughout the paper.