Magnetoresistance, voltage-current characteristics, and Hall effect measurements of bulk MgB₂ superconductors

Abstract

Bulk MgB2 samples were prepared from the commercially available powder (Alfa-Aesar). One of the samples was used in measuring the transport properties by the DC four-probe technique while the other was used in measuring Hall effect using the van-der-Pauw configuration. From the transport measurements, we noticed that the R-T curves shift to lower temperatures under applied magnetic field without any observed enlargement of the transition width. T-c gradually decreases from 37 K at zero field to 32 K at B = 1.4 T. Our V-I data were found to obey a power law expression V proportional to I-beta(T,I- B). The change of beta with temperature and magnetic field was shown and discussed. R-H is positive under positive applied magnetic field. The 1/R-H linear dependency on T, usually observed in high temperature superconductors, could not be observed in our case. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.