Contactless Conductivity Measurement

Introduction

In our Spintronics Lab, when we want to analyze a sample, conductivity or resistivity as a electrical property is almost always necessary. Normally, we use a Voltmeter or standard four probes method to take a measurement. However, surface preparation and contamination have great effects on the electrical properties of the samples. Thus, a contactless technic would be a better way to carry out the conductivity measurement. When we were doing the ac magnetic susceptibility measurement, we learn from literature that there is connection between the electrical conductivity and the ac magnetic susceptibility. We would like to build the set up from the literature, take a measurement on the conductivity of our metal sample and compare it with the result from standard four probes measurement.

Theory

The mechanism for the contactless conductivity measurement is identical to the effective magnetic susceptibility measurement. Basically, the sample is inserted into a primary coil and a secondary coil. An ac current passes through the primary windings will induce magnetic field. The sample responds to the magnetic field and eddy current will be induced within the coil. As a result, the secondary coil responds to the eddy current and EMF will be induced. We take measurement on the EMF from secondary coil and due to phase difference, the real part and imaginary part of the voltage will be separately related to the ac magnetic susceptibility and the conductivity. When calculating the conductivity from voltage, there are two different papers use different approaches which appear to make sense and can be applied to our metal samples.

To do list

Prepare the samples

Prepare the coils

Build the experimental set up

Measure

Graph and Report

Team Members

Chen Guohao, Jiang Luwen

Lab Location

Spintronics and Magnetic Materials Lab

References

Bean, C. P., DeBlois, R. W., & Nesbitt, L. B. (1959). Eddy‐Current method for measuring the resistivity of metals. Journal of Applied Physics, 30(12), 1976-1980. https://doi.org/10.1063/1.1735100​

Crowley, J. D., & Rabson, T. A. (1976). Contactless method of measuring resistivity. Review of Scientific Instruments, 47(6), 712-715. https://doi.org/10.1063/1.1134714​

Oike, H., Miyagawa, K., Kanoda, K., Taniguchi, H., & Murata, K. (2009). Contactless conductivity measurements on the organic conductor, κ-(ET)4Hg2.89Br8, under pressure. Physica. B, Condensed Matter, 404(3-4), 376-378. https://doi.org/10.1016/j.physb.2008.11.023

Kraftmakher, Y. A. (1991). Measurement of electrical resistivity via the effective magnetic susceptibility. Measurement Science & Technology, 2(3), 253-256. https://doi.org/10.1088/0957-0233/2/3/011

Bauhofer, W. (1977). Continuous, contactless measurement of the temperature-dependent electrical resistivity of metals. Journal of Physics. E, Scientific Instruments, 10(12), 1212-1214. https://doi.org/10.1088/0022-3735/10/12/003