AC transport data query (using a PPMS system)

In summary: If you have access to a spectrometer, please perform an impedance spectrum and post the results here. If you are not able to do this, please get in touch with the manufacturer of the PPMS system in order to inquire about this possibility.
  • #1
Dr Eve Wildman
2
1
Hello and thanks for looking at this question.

I have a semi-conducting sample which has been run on a PPMS system - measuring it's resistivity as a function of temperature.
I switched to AC transport mode in order to measure the resistivity again while applying frequencies between 1Hz - 1000Hz. The data looks correct when plotted and shows a shift in the insulating transition with increasing frequency at the correct temperature - but it reports negative resistivity values (- ohm.cm) compared to before. I am assuming this isn't right? In the data file - the voltage is negative and current positive therefore giving a negative resistivity value.

To anyone familiar - do you think I can trust this data? Or is the negative value possibly the reactive part of impedance which needs to be converted to the 'real'/resistive part?

Any help from a fellow scientist would be appreciated!

Eve Wildman
 
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  • #2
When employing AC transport measurements, the data should be provided as an impedance vector as a function of frequency, i.e., a real part (resistance) and an imaginary part (reactance). By this, one can fit the data to some equivalent circuit model in order to interpret the data and to draw conclusions regarding the sample’s behavior. I am not sure, whether the PPMS systems have such an option.
 
  • #3
Lord Jestocost said:
When employing AC transport measurements, the data should be provided as an impedance vector as a function of frequency, i.e., a real part (resistance) and an imaginary part (reactance). By this, one can fit the data to some equivalent circuit model in order to interpret the data and to draw conclusions regarding the sample’s behavior. I am not sure, whether the PPMS systems have such an option.

Thank you for your reply. I am familiar with impedance spectroscopy where you retrieve the real and imaginary part and can plot it in a complex plane.
The PPMS uses a 4 probe measurement and the measurement I have done does not have this option. The data obtained contains the voltage, current and resistivity of the sample while applying fixed frequencies over a given temperature range. I am concerned as to why the resistivity values are negative! Although the overall trend and values are reasonable.
 
  • #4
In case the absolute resistivity values look reasonable, there might be a simple software bug.
 

1. What is an AC transport data query?

An AC transport data query is a process of retrieving and analyzing data related to the electrical conductivity of a material under the influence of an AC (alternating current) electric field. It involves collecting data using a PPMS (Physical Property Measurement System) and using software to analyze the results.

2. How does a PPMS system work?

A PPMS system uses a variety of measurement techniques to collect data on the physical properties of a material, such as electrical conductivity, magnetic susceptibility, and thermal conductivity. It uses a superconducting magnet to generate a high magnetic field, and sensitive detectors to measure the properties of the sample.

3. What types of materials can be tested using AC transport data query?

AC transport data query can be used to test a wide range of materials, such as metals, semiconductors, and superconductors. It is particularly useful for studying materials with unique electronic properties, such as high-temperature superconductors or materials with strong electron-electron interactions.

4. What are the advantages of using a PPMS system for AC transport data query?

A PPMS system offers several advantages for AC transport data query, including high precision measurements, a wide range of measurement capabilities, and the ability to control and vary experimental parameters such as temperature, magnetic field, and frequency. It also allows for automated data collection and analysis, making it a highly efficient and reliable tool for researchers.

5. How can AC transport data query using a PPMS system benefit scientific research?

AC transport data query using a PPMS system can provide valuable insights into the electronic properties of materials, helping researchers to better understand their behavior and potential applications. It can also assist in the development of new materials with desired properties, and aid in the optimization of existing materials for specific applications.

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