Sensor free, self regulating thermal switching via anomalous Ettingshausen effect and spin reorientation in DyCo5

TL;DR

This paper introduces a novel, sensor-free thermal switch leveraging the anomalous Ettingshausen effect and spin reorientation in DyCo5, enabling self-regulating thermal control through material properties and magnetic orientation.

Contribution

It demonstrates a new approach to thermal switching using intrinsic material effects and spin reorientation, eliminating the need for external sensors or feedback systems.

Findings

Significant contrast in anomalous Nernst conductivity across the spin reorientation transition.

Robust orientation-controlled thermal switching demonstrated in DyCo5.

Theoretical calculations link Berry curvature hot spots to the observed effects.

Abstract

We propose a sensor free, self regulating thermal switch that combines the anomalous Ettingshausen effect (AEE) with a temperature driven spin reorientation transition (SRT) in the rare earth cobalt compound DyCo$_5$. Using density functional theory and the Kubo linear-response formalism, we compute the anomalous Hall conductivity $\sigma_{xy}(\varepsilon)$ and the finite temperature anomalous Nernst conductivity $\alpha_{xy}(T)$ for two magnetization directions, magnetization parallel and perpendicular to the crystallographic c axis. While the intrinsic $\sigma_{xy}$ at the Fermi level remains sizable for both orientations, $\alpha_{xy}$ exhibits an about two orders of magnitude contrast in the SRT temperature window. This contrast is consistent with the low temperature Mott relation through the energy slope $\partial_\varepsilon \sigma_{xy}(\varepsilon)\rvert_{E_{\mathrm F}}$ and is traced to strongly peaked Berry curvature hot spots generated by spin orbit coupling induced avoided crossings of Co $3d$ bands. Combining $\alpha_{xy}$ with longitudinal transport coefficients, we estimate device level metrics, namely the anomalous Nernst thermopower $S_{\mathrm{ANE}}$ and the Ettingshausen coefficient $\Pi_{\mathrm{AEE}}=T S_{\mathrm{ANE}}$, and demonstrate robust orientation controlled switching under a fixed in plane bias current. These results establish a materials based route to compact thermal control without external sensors or feedback electronics and provide a concrete example that the proposed principle can be realized in an existing ferromagnet.