Critical current and magnetoresistance measurements in bulk MgB2

Abstract

Resistance measurements were done on a bulk MgB₂ sample. The observed T_c was approximately 39.4 K with a narrow transition width of 5 K indicative of the good quality ofthe sample. Magnetoresistance measurements show both a shift and broadening of the transition region to lower temperatures with an increase in the applied magnetic field. This suggests that the field dependent critical current decreases significantly even in the low field regime. The rapid linear decrease in the temperature dependent critical current indicates that although bulk MgB₂ has a high current carrying capability, by virtue of the fact that grain boundaries have a minimal effect on supercurrent transport, this is strongly dependent on the temperature.