Conductance anisotropy and linear magnetoresistance in La2-xSrxCuO4 thin films

TL;DR

This study investigates conductance anisotropy and magnetoresistance in La2-xSrxCuO4 thin films, revealing substrate effects, phase transitions, and a linear MR component linked to inhomogeneities, with implications for stripe detection.

Contribution

It demonstrates the sensitivity of transverse resistance measurements to substrate structure and phase transitions, and uncovers a linear magnetoresistance scaling with Hall resistivity in LSCO films.

Findings

Rxy sign depends on substrate terrace orientation

Linear MR scales with Hall resistivity independent of temperature

Substrate step edges influence nucleation and anisotropy

Abstract

We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La2-xSrxCuO4 (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 Rxy in zero magnetic field. It is demonstrated that the sign of Rxy 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 Rxy 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 absolute Hall resistivity, 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.