Conductance anisotropy and linear magnetoresistance in La_2-xSr_xCuO₄ thin films

We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La_2-xSr_xCuO₄ (LSCO) thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features of the conductance anisotropy are revealed by measuring the transverse resistance R_xy in zero magnetic field. It is demonstrated that the sign of R_xy depends on the orientation of the LSCO Hall bar with respect to the terrace structure of the substrate. Unit-cell-high substrate step edges must therefore be a dominant nucleation source for antiphase boundaries during film growth. We show that the measurement of R_xy is sensitive enough to detect the cubic–tetragonal phase transition of the SrTiO₃(100) (STO) substrate at 105 K. The MR of LSCO thin films shows for 0.10 < x < 0.25 a non-monotonic temperature dependence, resulting from the onset of a linear term in the MR above 90 K. We show that the linear MR scales with the Hall resistivity as Δp/p₀ α Ιp_xy(B)Ι, with the constant of proportionality independent of temperature. Such scaling suggests that the linear MR originates from current distortions induced by structural or electronic inhomogeneities. The possible role of stripes for both the MR and the conductance anisotropy is discussed throughout the paper.