The preparation of, and B isotope effect in, MgB2 with TC(10B) = 40.2K were described. Measurements of the temperature-dependent magnetization and specific heat revealed a 1.0K shift in TC between Mg11B2 and Mg10B2. Although such a high transition temperature could imply the occurrence of exotic coupling mechanisms, the B isotope effect was here consistent with the material being a phonon-mediated BCS superconductor.

Boron Isotope Effect in Superconducting MgB2. S.L.Budko, G.Lapertot, C.Petrovic, C.E.Cunningham, N.Anderson, P.C.Canfield: Physical Review Letters, 2001, 86[9], 1877-80