Nanoscale magnetic and charge anisotropies at manganite interfaces

TL;DR

This study investigates how local Sr-doping gradients in manganite bilayers influence charge and magnetic anisotropies at the nanoscale, revealing critical thicknesses and doping effects on orbital and spin configurations.

Contribution

It provides detailed insights into the thickness-dependent charge and spin anisotropies in manganite bilayers, highlighting the impact of Sr-doping gradients on magnetic and orbital properties.

Findings

Antiferromagnetic spin axis prefers out-of-plane orientation.

Doping level affects critical thickness for anisotropy stability.

Subtle domain reorientation linked to anisotropy modifications.

Abstract

Strong correlated manganites are still under intense research owing to their complex phase diagrams in terms of the Sr-doping and their sensitivity to intrinsic and extrinsic structural deformations. Here, we performed x-ray absorption spectroscopy measurements of manganites bilayers to explore the effects that a local Sr-doping gradient produce on the charge and antiferromagnetic anisotropies. In order to gradually tune the Sr-doping level along the axis perpendicular to the samples we have grown a series of bilayers with different thicknesses of low-doped manganites (from 0 nm to 6 nm) deposited over a La0.7Sr0.3MnO3 metallic layer. This strategy permitted us to resolve with high accuracy the thickness region where the charge and spin anisotropies vary and the critical thickness tc over which the out of plane orbital asymmetry does not have any further modifications. We found that the antiferromagnetic spin axis points preferentially out of the sample plane regardless the capping layer thickness. However, it tilts partially into the sample plane far from this critical thickness, owing to the jointed contributions of the external structural strain and electron doping. Furthermore, we found that the doping level of the capping layer sensibly affects the critical thickness, giving clear evidence of the influence exerted by the electron doping on the orbital and magnetic configurations. These anisotropy changes induce subtle modifications on the domain reorientation of the La0.7Sr0.3MnO3, as evidenced from the magnetic hysteresis cycles.