Anomalous Nernst effect based near field imaging of magnetic nanostructures

TL;DR

This paper demonstrates a nanoscale imaging method using the anomalous Nernst effect to map magnetic textures and temperature gradients in magnetic nanostructures with approximately 80 nm resolution, advancing thermo-electric imaging techniques.

Contribution

The study introduces a reliable ANE-based imaging technique for nanoscale magnetic textures and reveals the presence of significant in-plane temperature gradients, extending the method's application.

Findings

Achieved ~80 nm spatial resolution in magnetic domain imaging.

Identified larger in-plane temperature gradients than out-of-plane.

Extended ANE imaging to out-of-plane magnetization in nanowires.

Abstract

The anomalous Nernst effect (ANE) gives rise to an electrical response transverse to the magnetization and an applied temperature gradient in a magnetic metal. A nanoscale temperature gradient can be generated by the use of a laser beam applied to the apex of an atomic force microscope tip, thereby allowing for spatially-resolved ANE measurements beyond the optical diffraction limit. Such a method has been used previously to map in-plane magnetized magnetic textures. However, the spatial distribution of the out-of-plane temperature gradient, which is needed to fully interpret such an ANE-based imaging, was not studied. We therefore use a well-known magnetic texture, a magnetic vortex core, to demonstrate the reliability of the ANE method for the imaging of magnetic domains with nanoscale resolution. Moreover, since the ANE signal is directly proportional to the temperature gradient, we can also consider the inverse problem and deduce information about the nanoscale temperature distribution. Our results together with finite element modeling indicate that besides the out-of-plane temperature gradients, there are even larger in-plane temperature gradients. Thus we extend the ANE imaging to study out-of-plane magnetization in a racetrack nano-wire by detecting the ANE signal generated by in-plane temperature gradients. In all cases, a spatial resolution of about 80 nm is obtained. These results are significant for the rapidly growing field of thermo-electric imaging of antiferromagnetic spintronic device structures.