Letters to Nature

Nature 411, 558-560 (31 May 2001) | doi:10.1038/35079018; Received 20 March 2001; Accepted 27 April 2001

High critical current density and enhanced irreversibility field in superconducting MgB2 thin films

C. B. Eom1,2, M. K. Lee1, J. H. Choi1,2, L. J. Belenky1, X. Song2, L. D. Cooley2, M. T. Naus2, S. Patnaik2, J. Jiang2, M. Rikel2, A. Polyanskii2, A. Gurevich2, X. Y. Cai2, S. D. Bu1, S. E. Babcock1,2, E. E. Hellstrom1,2, D. C. Larbalestier1,2, N. Rogado3, K. A. Regan3, M. A. Hayward3, T. He3, J. S. Slusky3, K. Inumaru3, M. K. Haas3 & R. J. Cava3

  1. Department of Materials Science and Engineering, 1509 University Avenue; and
  2. Applied Superconductivity Center, 1500 Engineering Drive, University of Wisconsin, Madison, Wisconsin 53706, USA
  3. Department of Chemistry and Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544, USA

Correspondence to: C. B. Eom1,2 Correspondence and requests for materials should be addressed to C.B.E. (e-mail: Email: eom@engr.wisc.edu).

The discovery of superconductivity at 39 K in magnesium diboride1 offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current flow has already been demonstrated2, 3, 4, 5. One possible drawback, however, is that the magnetic field at which superconductivity is destroyed is modest. Furthermore, the field which limits the range of practical applications—the irreversibility field H*(T)—is approximately 7 T at liquid helium temperature (4.2 K), significantly lower than about 10 T for Nb-Ti (ref. 6) and approx20 T for Nb3Sn (ref. 7). Here we show that MgB2 thin films that are alloyed with oxygen can exhibit a much steeper temperature dependence of H*(T) than is observed in bulk materials, yielding an H* value at 4.2 K greater than 14 T. In addition, very high critical current densities at 4.2 K are achieved: 1 MA cm-2 at 1 T and 105 A cm-2 at 10 T. These results demonstrate that MgB2 has potential for high-field superconducting applications.