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

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 ${\sigma }_{xy}(\epsilon )$ 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 ${\partial }_{\epsilon }{\sigma }_{xy}(\epsilon ){|}_{E_{\mathrm{F}}}$ 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.

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