# Magnetic control of flexible thermoelectric devices based on macroscopic 3D interconnected nanowire networks

## TL;DR

This paper demonstrates the fabrication of large-area 3D interconnected Co/Cu nanowire networks that enable magnetic control of thermoelectric effects, leading to efficient, flexible thermoelectric cooling devices with high power factors at room temperature.

## Contribution

It introduces a novel method to create macroscopic, flexible nanowire networks with significant spin-dependent thermoelectric properties for heat management applications.

## Key findings

- Large spin-dependent Seebeck coefficient of -9.4 μV/K at room temperature.
- High power factor of ~7.5 mW/K^2·m surpassing state-of-the-art thermoelectric materials.
- Magneto-power factor ratio reaches about 100% over a wide temperature range.

## Abstract

Spin-related effects in thermoelectricity can be used to design more efficient refrigerators and offer novel 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. Here, 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 inherent limitations of nanoscale magnetic structures due to insufficient power generation capability that limits the heat management applications. From properly designed experiments, large spin-dependent Seebeck and Peltier coefficients of $-9.4$ $\mu$V/K and $-2.8$ mV at room temperature, respectively. The resulting power factor of Co/Cu nanowire networks at room temperature ($\sim7.5$ mW/K$^2$m) is larger than those of state of the art thermoelectric materials, such as BiTe alloys and the magneto-power 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 lay the groundwork to design shapeable thermoelectric coolers exploiting the spin degree of freedom.