Transport properties of MgB2 films grown on Hastelloy tape: Substrate temperature effect

Abstract

We report on the transport properties of MgB2 films that were directly grown on Hastelloy tapes by using a hybrid physical chemical deposition method. The substrate temperatures was varied from 480 A degrees C to 540 A degrees C in 20 A degrees C increment while the deposition time and the gas mixing ratio were kept constant at 10 min and H-2:B2H6 = 70:30, respectively. Within this window of substrate temperature, all the samples except the one grown at 480 A degrees C exhibited critical current densities, J (c) , much higher than those observed in MgB2 wires and tapes that were made by using the powder method. For instance, the film grown at 500 A degrees C exhibited a value of J (c) exceeding 3 x 10(5) A/cm(2) at 4 T and 5 K measured in magnetic fields applied perpendicular to the substrate. In the samples grown at temperatures above 500 A degrees C, a resistance dip was observed in the same field orientation, which can be regarded as evidence for strong flux pinning.