A novel technique to measure magnetisation hysteresis curves in the peak-effect regime of superconductors

Magnetisation hysteresis of type II superconductors measured using SQUID-based Magnetic Property Measurement System (MPMS) made by Quantum Design is known to be affected by inhomogeneity in the external field. We present a new method, viz., half-scan technique, for measuring magnetisation hysteresis loops using MPMS. This technique circumvents the problems caused by field inhomogeneity. We have used this technique to measure magnetisation hysteresis loops in the peak-effect regime of superconducting CeRu₂ and 2H-NbSe₂. The magnetisation hysteresis obtained using half-scan technique is found to be significantly larger than that obtained by conventional MPMS measurements. At very low fields where the extent of field inhomogeneity is not significant and in the reversible region, the results of the half-scan technique are comparable to those obtained using conventional technique. Moreover, hysteresis measurements are shown to be independent of scan length used in the measurement, thus reaffirming that the results are unaffected by the field inhomogeneity.