1. Department of Physics, Aoyama-Gakuin University, Chitosedai, Setagaya-ku, Tokyo 157-8572, Japan
2. CREST, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012, Japan

Correspondence to: Jun Akimitsu^1,2 Correspondence and requests for materials should be addressed to J.A. (e-mail: Email: jun@soliton.phys.aoyama.ac.jp).

Abstract

In the light of the tremendous progress that has been made in raising the transition temperature of the copper oxide superconductors (for a review, see ref. 1), it is natural to wonder how high the transition temperature, T_c, can be pushed in other classes of materials. At present, the highest reported values of T_c for non-copper-oxide bulk superconductivity are 33 K in electron-doped Cs_xRb_yC₆₀ (ref. 2), and 30 K in Ba_1-xK_xBiO₃ (ref. 3). (Hole-doped C₆₀ was recently found⁴ to be superconducting with a T_c as high as 52 K, although the nature of the experiment meant that the supercurrents were confined to the surface of the C₆₀ crystal, rather than probing the bulk.) Here we report the discovery of bulk superconductivity in magnesium diboride, MgB₂. Magnetization and resistivity measurements establish a transition temperature of 39 K, which we believe to be the highest yet determined for a non-copper-oxide bulk superconductor.

1. Department of Physics, Aoyama-Gakuin University, Chitosedai, Setagaya-ku, Tokyo 157-8572, Japan
2. CREST, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012, Japan

Correspondence to: Jun Akimitsu^1,2 Correspondence and requests for materials should be addressed to J.A. (e-mail: Email: jun@soliton.phys.aoyama.ac.jp).