Magnon Hall effect and anisotropic thermal transport in NiFe and YIG ferromagnets

TL;DR

This paper reports experimental evidence of magnon Hall and planar Righi-Leduc effects in ferromagnets, revealing universal thermokinetic phenomena linked to anisotropic ferromagnetic properties in both conducting and insulating materials.

Contribution

It provides the first experimental demonstration of thermal Hall effects in ferromagnets, highlighting their universal nature and relation to magnetic anisotropy.

Findings

Observation of magnon Hall effect in NiFe and YIG

Detection of planar Righi-Leduc effect in ferromagnets

Effects are linked to intrinsic chirality of ferromagnetic anisotropy

Abstract

The Righi-Leduc effect refers to the thermal analogue of the Hall effect, for which the electric current is replaced by the heat current and the electric field by the temperature gradient. In both cases, the magnetic field generates a transverse force that deviates the carriers (electron, phonon, magnon) in the direction perpendicular to the current. In a ferromagnet, the magnetization plays the role of the magnetic field, and the corresponding effect is called anomalous Hall effect. Furthermore, a second transverse contribution due to the anisotropy, the planar Hall effect, is superimposed to the anomalous Hall effect. We report experimental evidence of the thermal counterpart of the Hall effects in ferromagnets, namely the magnon Hall effect (or equivalently the anomalous Righi-Leduc effect) and the planar Righi-Leduc effect, measured on ferromagnets that are either electrical conductor (NiFe) or insulator (YIG). The study shows the universal character of these new thermokinetic effects, related to the intrinsic chirality of the anisotropic ferromagnetic degrees of freedom.