Boron isotope effect in superconducting MgB2

We report the preparation method of and boron isotope effect for MgB2, a new binary intermetallic superconductor with a remarkably high superconducting transition temperature T-c(B-10) = 40.2 K. Measurements of both temperature dependent magnetization and specific heat reveal a 1.0 K shift in T-c between (MgB2)-B-11 and (MgB2)-B-10. Whereas such a high transition temperature might imply exotic coupling mechanisms, the boron isotope effect in MgB2 is consistent with the material being a phonon-mediated BCS superconductor.