Domain wall pinning and domain wall resistivity in notched La_0.7Sr_0.3MnO₃ nanostructures

Creation and manipulation of magnetic domain walls (DWs) are a core subject of research in developing prototype devices for spintronic applications. DWs can be created artificially and moved by applying either a magnetic field or an electric current, as has been extensively investigated. Here, we study the DW pinning and depinning in half-metallic ferromagnetic La_0.7Sr_0.3MnO₃ nanostructures with a notch that is about 90% of the width of the wire. By measuring the magnetoresistance of the notched wires while sweeping the magnetic field, we unambiguously observe DW pinning and depinning from 10 to 300 K. Analysis of the temperature dependence reveals that both ΔR (the DW resistance) and ΔR/R₀ (R₀ is the resistance at zero field) are proportional to the temperature. The DW resistivity is calculated to be of the order of 10⁻¹⁷Ωm² at 10 K and 10⁻¹⁵Ωm² at 300 K. The latter value agrees with the reported intrinsic DW resistivity in films. In addition, we find approximately constant ΔR and ΔR/R₀ for widths from 1.8µm and a pronounced increase in both quantities when the width goes down to 755 nm. With the extracted magnetocrystalline anisotropy parameters from the measurements of the remanent magnetization and the magnetic torque as function of angle of the magnetic field with respect to the substrate normal, we further perform micromagnetic simulations and obtain results consistent with the experimental data. Our work may promote designing relevant prototypes and may constitute a platform to explore the effect of spin torque transfer on DWs.