Fluctuation study of the specific heat of Mg11B2 -: art. no. 134515

The specific heat of polycrystalline (MgB2)-B-11 has been measured with high-resolution ac calorimetry from 5 to 45 K at constant magnetic fields. The excess specific heat above T-c is discussed in terms of Gaussian fluctuations and suggests that (MgB2)-B-11 is a bulk superconductor with Ginzburg-Landau coherence length xi(0) = 26 Angstrom. The transition-width broadening in field is treated in terms of lowest-Landau-level (LLL) fluctuations. That analysis requires that xi(0) = 20 Angstrom. The underestimate of the coherence length in field, along with deviations from three-dimensional LLL predictions, suggests that there is an influence from the anisotropy of B-c2 between the c axis and a-b plane.