The specific heat of polycrystalline Mg11B2 has been measured with high resolution ac calorimetry from 5 to 45 K at constant magnetic fields. The excess specific heat above Tc is discussed in terms of Gaussian fluctuations and suggests that Mg11B2 is a bulk superconductor with Ginzburg-Landau coherence length ξ0=26 \AA . The transition-width broadening in field is treated in terms of lowest-Landau-level (LLL) fluctuations. That analysis requires that ξ0=20 \AA . The underestimate of the coherence length in field, along with deviations from 3D LLL predictions, suggest that there is an influence from the anisotropy of Bc2 between the c-axis and the a-b plane.
@article{arxiv.cond-mat/0204233,
title = {Fluctuation Study of the Specific Heat of MgB2},
author = {Tuson Park and M. B. Salamon and C. U. Jung and Min-Seok Park and Kyunghee Kim and Sung-Ik Lee},
journal= {arXiv preprint arXiv:cond-mat/0204233},
year = {2009}
}