Growth of high current density MgB2 films using ex-situ precursor approach

Abstract Superconducting MgB 2 films with T c =39.0 K were prepared using an ex-situ precursor approach. Precursor films of boron, ∼0.6 μm thick, were deposited onto Al 2 O 3 (1 0 2) substrates by electron beam evaporation; subsequent post-anneal at 890 °C in the presence of MgB 2 and Mg metal produced highly crystalline MgB 2 films. Detailed X-ray diffraction studies indicate that the film is polycrystalline with some degree of c -axis texture. A transport J c of over 4×10 6 A/cm 2 was obtained on MgB 2 films at 25 K and self-field. The higher irreversibility fields, B irr obtained from the transport measurements on MgB 2 films indicate that there is some improvement in flux pinning at lower temperatures. The details of the film growth and transport property measurements are reported.