Magnetic Control of Flexible Thermoelectric Devices Based on Macroscopic 3D Interconnected Nanowire Networks

Spin-related effects in thermoelectricity can be used to design more efficient refrigerators and offer promising applications for the harvesting of thermal energy. The key challenge is to design structural and compositional magnetic material systems with sufficiently high efficiency and power output for transforming thermal energy into electric energy and vice versa. The fabrication of large-area 3D interconnected Co/Cu nanowire networks is demonstrated, thereby enabling the controlled Peltier cooling of macroscopic electronic components with an external magnetic field. The flexible, macroscopic devices overcome the inherent limitations of nanoscale magnetic structures that are caused by insufficient power generation capability limiting the heat management applications. From properly designed experiments, large spin-dependent Seebeck and Peltier coefficients of -9.4 mu V K-1 and -2.8 mV at room temperature, respectively, are found. The resulting power factor of Co/Cu nanowire networks at room temperature (approximate to 7.5 mW K-2 m(-1)) is larger than those of state-of-the-art thermoelectric materials, such as BiTe alloys, and the magnetopower factor ratio reaches about 100% over a wide temperature range. Validation of magnetic control of heat flow achieved by taking advantage of the spin-dependent thermoelectric properties of flexible macroscopic nanowire networks lays the groundwork to design shapeable thermoelectric coolers exploiting the spin degree of freedom.