All computer chips get warm when they are used heavily. Those in supercomputers get very warm so that cooling them is a major consideration in their design. There would be a considerable energy saving if the heat energy extracted from the chips in the cooling mechanism could be used to generate electricity that could be then used to run the computer. The Carnot theorem puts a hard limit on how efficient the energy conversion could be but at present most methods for heat extraction fall far short of this limit. The Spin Seebeck Effect is a promising method for using heat to generate a voltage.
This is a theoretical project to model such a device to find the optimal experimental conditions.
When a magnet is heated its magnetisation falls due to the excitation of spin waves. When a magnet is held in a temperature gradient the spin wave travel from the hot to the cool end thus generating a spin current. The project is to model a novel method to detect the spin current from an insulating magnet. We shall model the boundaries between the insulating magnet, a thin film of normal metal and a ferromagnetic metal including the possibilities of spin and charge accumulation. The continuity of the spin current will cause currents to flow in the ferromagnetic metal but since no charge current flows in the insulator . Hence the two currents are equal and opposite in the metal. The conductivities for the two spin channels are known to be different in ferromagnets so this will generate a voltage. Most methods of observing the Spin Seebeck Effect have used platinum as the detector. The method described here should be more cost effective because it uses cheaper materials. The calculation will follow the procedure used by T. Valet and A. Fert Phys Rev B48, 7099 (1993) to model magnetoresistance. A device that uses the ideas proposed here has been shown to work and the project will be done in collaboration with a group in Oxford who will be building such a device.
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