Non-equilibrium Magnon Engineering Enabling Significant Thermal Transport Modulation

TL;DR

This paper demonstrates that magnonic thermal transport can be artificially modulated in ferromagnetic metals at room temperature, revealing magnons' significant role in heat conduction and offering new active thermal management strategies.

Contribution

It introduces magnonic thermal transport engineering as a novel method to control heat conduction in solids, challenging previous assumptions about magnons' limited role in metals.

Findings

Thermal conductivity varies with spin current distribution.

Magnons significantly contribute to heat conduction at room temperature.

Magnonic engineering enables active thermal management.

Abstract

Thermal conductivity, a fundamental parameter characterizing thermal transport in solids, is typically determined by electron and phonon transport. Although other transport properties including electrical conductivity and thermoelectric conversion coefficients have material-specific values, it is known that thermal conductivity can be modulated artificially via phonon engineering techniques. Here, we demonstrate another way of artificially modulating the heat conduction in solids: magnonic thermal transport engineering. The time-domain thermoreflectance measurements using ferromagnetic metal/insulator junction systems reveal that the thermal conductivity of the ferromagnetic metals and interfacial thermal conductance vary significantly depending on the spatial distribution of nonequilibrium spin currents. Systematic measurements of the thermal transport properties with changing the boundary conditions for spin currents show that the observed thermal transport modulation stems from magnon origin. This observation unveils that magnons significantly contribute to the heat conduction even in ferromagnetic metals at room temperature, upsetting the conventional wisdom that the thermal conductivity mediated by magnons is very small in metals except at low temperatures. The magnonic thermal transport engineering offers a new principle and method for active thermal management.