Anisotropy of the in-plane angular magnetoresistance of electron-doed Sr1-xLaxCuO2 thin films

TL;DR

This study investigates the in-plane angular magnetoresistance of Sr1-xLaxCuO2 thin films, revealing oscillations linked to antiferromagnetic signatures within CuO2 planes and their doping-dependent behavior.

Contribution

It demonstrates that magnetoresistance oscillations are intrinsic to CuO2 planes and uncovers a doping-dependent evolution of these oscillations in electron-doped cuprates.

Findings

Magnetoresistance exhibits fourfold and twofold angular oscillations.

Oscillations increase with magnetic field and decrease with doping.

Fourfold oscillations dominate in underdoped samples, twofold in less underdoped.

Abstract

Signatures of antiferromagnetism (AF) in the underdoped Ln2-xCexCuO4 (Ln = Nd, Pr,...) family are observed even for doping levels for which superconductivity exists. We have looked for a similar property in a different electron-doped cuprate family, Sr1-xLaxCuO2, which consists of CuO2 planes separated by Sr/La atoms, and is exempt of the possible influence of magnetic rare earth ions. We report in-plane magnetoresistance measurements in the normal state of underdoped, superconducting, c-axis oriented, epitaxial Sr1-xLaxCuO2 thin films. This probe is sensitive to spin arrangement and we find that the in-plane magnetoresistance, which is negative and does not saturate for T, exhibits an angular dependence when measured upon rotating a magnetic field within the CuO2 planes. The analysis reveals a superposition of fourfold and twofold angular oscillations. Both of these increase in amplitude with increasing field and decreasing and appear below a temperature, which gets higher with decreasing doping levels. Our results demonstrate that these magnetoresistance oscillations, also observed for the Ln2-xCexCuO4 (Ln = Nd, Pr,...) family and attributed to an AF signature, are, without ambiguity, a property of CuO2 planes. Besides, these oscillations vary with doping in an unusual way compared to previous results: fourfold oscillations are essentially present in the more underdoped samples while only twofold oscillations are visible in the less underdoped ones. This intriguing observation appears to be a consequence of spin dilution with increasing doping level.