Abstract
The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devices.
Highlights
Thermoelectric (TE) effects, the conversion of thermal energy to electric signal, have gained increasing attention because of their potentials for harvesting electric energy from various sources including waste heat[1,2,3,4,5]
In a given magnetization direction and temperature gradient, the total spin thermoelectrics (STE) voltage is composed of the spin Seebeck effect (SSE) and the anomalous Nernst effect (ANE) which can be either additive or subtractive depending on the relative sign of the SS and the CANE
The exact ANE signal of the CFB cannot be separately quantified from the total measured TE voltages due to the same symmetry with SSE, as the σ is determined by the Ms, and Js is induced by the temperature difference between the FM and NM layer[16,17]
Summary
Thermoelectric (TE) effects, the conversion of thermal energy to electric signal, have gained increasing attention because of their potentials for harvesting electric energy from various sources including waste heat[1,2,3,4,5]. Detectable voltage[10,11,12,13] Because this TE effect is based on the spin current, it is called spin thermoelectrics (STE) or spin caloritronics. In such system, at least two materials are necessary, so that the electrical and thermal conductivities are not limited to the Wiedemann-Franz law, but permitted to be independently modulated. The second is to introduce a FM/NM multilayer structure where the injection of the thermally induced spin current can be multiplied This demonstrates that the material engineering in STE devices would enhance the TE signal as well as modulate the device resistance simultaneously
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