Thermoelectric power factor of a 70 nm Ni-nanowire in a magnetic field

TL;DR

This study investigates how a magnetic field influences the thermoelectric properties of a 70 nm Ni nanowire, revealing significant magneto thermopower effects and increased thermoelectric efficiency under magnetic influence.

Contribution

It demonstrates the magnetic field's impact on the thermoelectric power factor and thermopower in ferromagnetic Ni nanowires, highlighting a nearly 20% efficiency increase.

Findings

Magneto thermopower effect of about 10% observed.

Thermoelectric efficiency increases by nearly 20% in a magnetic field.

Thermopower increases up to 10% at B = 0.5 T.

Abstract

Thermoelectric (TE) properties of a single nanowire (NW) are investigated in a microlab which allows the determination of the Seebeck coefficient S and the conductivity {\sigma}. A significiant influence of the magnetization of a 70 nm ferromagnetic Ni-NW on its power factor S^{2}{\sigma} is observed. We detected a strong magneto thermopower effect (MTP) of about 10% and an anisotropic magneto resistance (AMR) as a function of an external magnetic field B in the order of 1%. At T = 295 K and B = 0 T we determined the absolute value of S = - (19 \pm 2) {\mu}V/K. At zero field the figure of merit ZT \approx 0.02 was calculated using the Wiedemann-Franz-law for the thermal conductivity. The thermopower S increases considerably as a function of B up to 10% at B = 0.5 T, and with a magneto thermopower of \partialS/\partialB \approx - (3.8 \pm 0,5) {\mu}V/(K.T). The AMR and MTP are related by \partials/\partialr \approx -11 \pm 1 (\partials = \partialS/S). The TE efficiency increases in a transversal magnetic field (B =0.5T) due to an enhanced power factor by nearly 20%.