Enhanced magneto-thermoelectric power factor of a 70 nm Ni-nanowire

• Published in: Journal of applied physics 2012-05, Vol.111 (10)
• Main Authors: Mitdank, R., Handwerg, M., Steinweg, C., Töllner, W., Daub, M., Nielsch, K., Fischer, S. F.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4721896

Thermoelectric (TE) properties of a single nanowire (NW) are investigated in a microlab which allows the determination of the Seebeck coefficient S, the electrical conductivity σ, and a full ZT-characterization in the validity limit of the Wiedemann-Franz-law (ZT—figure of merit). A significant influence of the magnetization of a 70 nm diameter ferromagnetic Ni-NW on its power factor S2σ is observed. We detected a strong magnetothermopower effect (MTP) of about 10% and an anisotropic magnetoresistance (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 ± 2) μV/K. The thermopower S increases considerably as a function of B up to 10% at B = 0.5 T, and with a magnetothermopower of ∂S/∂B ≈ −(3.8 ± 0.5) μV/(KT). The AMR and MTP are related by ∂s/∂r ≈ −11 ± 1 (∂s = ∂S/S). Hence, the TE efficiency increases in a transversal magnetic field (B = 0.5 T) due to an enhanced power factor by nearly 20%.