Advanced Electronic Materials

Thermoelectric Power Factor Enhancement by Spin-Polarized Currents—A Nanowire Case Study

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Thermoelectric (TE) measurements have been performed on the workhorses of today's data storage devices, exhibiting either the giant or the anisotropic magnetoresistance effect (GMR and AMR). The temperature-dependent (50–300 K) and magnetic field-dependent (up to 1 T) TE power factor (PF) has been determined for several CoNi alloy nanowires with varying Co:Ni ratios as well as for CoNi/Cu multilayered nanowires with various Cu layer thicknesses, which are all synthesized via a template-assisted electrodeposition process. A systematic investigation of the resistivity, as well as the Seebeck coefficient, is performed for CoNi alloy nanowires and CoNi/Cu multilayered nanowires. At room temperature, measured values of TE PFs up to 3.6 mW K−2 m−1 for AMR samples and 2.0 mW K−2 m−1 for GMR nanowires are obtained. Furthermore, the TE PF is found to increase by up to 13.1% for AMR CoNi alloy nanowires and by up to 52% for GMR CoNi/Cu samples in an external applied magnetic field. The magnetic nanowires exhibit TE PFs that are of the same order of magnitude as TE PFs of BiSbSeTe based thermoelectric materials and, additionally, give the opportunity to adjust the TE power output to changing loads and hotspots through external magnetic fields.