Electrical Seebeck-Contrast Observation of Magnon Hall Effect in Topological Ferromagnet Lu$_2$V$_2$O$_7$/Heavy Metal Heterostructures

TL;DR

This paper introduces a sensitive electrical Seebeck-contrast method to observe the magnon Hall effect in Lu$_2$V$_2$O$_7$/heavy metal heterostructures, enabling clearer detection and exploration of MHE in new materials.

Contribution

It presents a novel electrical measurement technique that isolates the magnon Hall effect from other thermoelectric effects in heterostructures, improving detection sensitivity.

Findings

The method effectively separates MHE from ANE and SSE signals.

Heavy metal overlayers can suppress non-MHE signals.

Discovered longitudinal MHE under out-of-plane temperature gradient.

Abstract

The observation of the magnon Hall effect (MHE) has relied solely on the challenging measurement of the thermal Hall conductivity. Here, we report a highly sensitive electrical Seebeck-contrast method for the observation of MHE in Lu$_2$V$_2$O$_7$/heavy metal heterostructures, that is highly desirable for the exploration of new MHE materials and their applications. Using measuring wires with very different Seebeck coefficients, we established a general method that can separate contributions (e.g., MHE) that generates a lateral temperature drop, from those [e.g., anomalous Nernst effect (ANE) and spin Seebeck effect (SSE)] that generate a lateral electric field. We show that a suitable heavy metal overlayer can eliminate the inherent ANE and SSE signals from the semiconducting Lu$_2$V$_2$O$_7$. The MHE in Lu$_2$V$_2$O$_7$ is quasi-isotropic among crystals with different orientations. In addition to the previously reported transverse MHE under an in-plane temperature gradient, we have uncovered longitudinal MHE under an out-of-plane temperature gradient.