Dragging of domains by a temperature gradient in ferromagnetic metals

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Abstract
A temperature gradient normal to domain walls generates an eddy current running around each wall. The magnetic fields of the various eddy‐current loops have the right direction and sense to exert forces pushing all walls in the direction of the gradient. If the gradient exceeds a certain value, all walls will start moving in that direction. This ’’thermal domain drag’’ is similar to the domain‐drag effect recently predicted and observed in ferromagnets traversed by an electric current, except that the eddy currents are caused by the Nernst‐Ettingshausen effect rather than by the Hall effect. When the walls move, the observed thermoelectric voltage will not be proportional to the temperature gradient anymore. This is similar to the failure of Ohm’s law predicted and observed in ferromagnets traversed by a current. While a uniaxial magnetic anisotropy is required for domain drag, thermal domain drag can be achieved even in isotropic or cubic materials. Numerical estimates suggest that the proposed experiment should be possible in low‐coercivity materials at room temperature or above, as well as at low temperature. The inverse effect exists too: moving walls generate a heat flux parallel to their direction of motion.