Transverse voltages and reciprocity theorem in magnetic fields for high T_c superconductors

TL;DR

This study investigates the Hall effect measurement methods and the validity of the reciprocity theorem in high-temperature superconductors, revealing discrepancies in resistance calculations and violations of the theorem.

Contribution

It demonstrates that different measurement combinations yield varying Hall resistance values and shows the magnetic field form of the reciprocity theorem does not hold in these materials.

Findings

Different resistance determination methods produce varying Hall resistance values.

The odd part of the resistance, related to the Hall effect, remains consistent across methods.

The magnetic field form of the reciprocity theorem is invalid in the tested superconductor.

Abstract

We have tested four-point methods of the Hall effect measurement on BiSrCaCuO (2223) polycrystal and also the validity of the magnetic field form of the reciprocity theorem. We found that different types of determination of the Hall resistance using various combination of measured resistances provide different value of it. We have separated two parts of the resistance combinations, which are even and odd in magnetic field, respectively. The odd part, which is equivalent to the Hall effect, is equal for all formulae used. The even part of transverse resistance varies in different formulae. The magnetic field form of the reciprocity theorem is not valid. Models for explanation of this violation are also discussed.