Magnetic AC Impedance Analysis Method Using High-Tc SQUID Based Magnetic Measurement System

A new ac impedance analysis method that uses magnetic measurements was demonstrated. The magnetic field generated from the current flowing in the sample was detected by changing the frequency of the applied voltage. To detect the generated small magnetic field, a high-temperature superconductor superconducting quantum interference device (HTS-SQUID) based magnetic measurement system was developed. The developed system could detect the magnetic field without a change in the intensity and phase in the frequency range of 1 Hz to 10 kHz. In this frequency range, the spectrum correlated with the ac impedance of the electric circuit was obtained by measuring the magnetic field from the current in the circuit. Moreover, dye-sensitized solar cells with counter electrodes of different catalysis materials were prepared, and the magnetic field from the solar cell was measured. The Cole-Cole plot of the magnetic field correlated with the ac impedance measured by a conventional method, and the difference in the shape of Cole-Cole plot was explained using the equivalent circuit analysis of the dye-sensitized solar cell. Therefore, it was clarified that is possible to obtain the spectrum correlated with ac impedance using magnetic measurements.