2021 Volume 45 Issue 2 Pages 37-40
We investigated both the Seebeck and anomalous Nernst effects in NiCo2O4(001) epitaxial films with a preferential magnetization direction normal to the film plane. Since the thermoelectric signals were extremely small, we custom-built a measurement system to detect the weak voltage signals. To suppress spurious voltage signals originating from the electrical contacts in the measurement circuit, we employed the following measures. We reduced the number of electrical contacts between the output of a commercial cryostat with a superconducting magnet and the nano-voltmeters. We employed silver soldering while making the electrical contacts to reduce the thermal electromotive force voltages at the remaining contacts. By adopting these measures, we have succeeded in detecting thermoelectric voltages as small as 5 nV. The observed thermoelectric efficiency of NiCo2O4 is quite small compared to conventional ferromagnetic metals.