Measurements of the Hall coefficient in metallic materials are challenging because besides the small Hall voltage signal, one is measuring a potentially significantly larger voltage contribution originating from the resistance of the sample and the asymmetrical placement of the measurement contacts. This unwanted contribution can greatly impair or even prevent the accurate determination of the Hall coefficient.
The aim of the final project was to develop and test an external electronic circuit that enables us to perform Hall coefficient with balancing or in other words a five-terminal Hall measurement. The central part of the circuit is a precise voltage divider, which the user uses to compensate or "balance" the voltage offset before starting the measurement, at zero magnetic field. This process sufficiently isolates the signal that depends on the magnetic field, enabling reliable determination of a more accurate Hall voltage value.
We tested the operation of the manufactured adapter with measurements on a reference copper sample in the PPMS physical property measurement system. The results obtained with our circuit in combination with two measurement options (ACT, Resistivity option) were compared with reference measurements performed with the factory-installed balancing option.
We have demonstrated that the interface works successfully and enables five-point measurement on standard four-point resistance meters. Although measurements with the developed circuit show slightly higher noise compared to the reference method, the interface represents a working and cost-effective solution. Its usefulness is particularly important because dedicated measurement options with built-in balancing are no longer manufactured, which means that our circuit ensures that such measurements can continue to be performed in the future.
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