Fluctuation Study of the Specific Heat of MgB2

Abstract

The specific heat of polycrystalline Mg${}^{11}$B${}_2$ 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 Mg${}^{11}$B${}_2$ is a bulk superconductor with Ginzburg-Landau coherence length ${\xi }_0=26$ Å. The transition-width broadening in field is treated in terms of lowest-Landau-level (LLL) fluctuations. That analysis requires that ${\xi }_0=20$ Å. 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 B${}_{c2}$ between the c-axis and the a-b plane.

Phys. Rev. B 66, 134515 (2002)

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• Specific Heat Study of the Magnetic Superconductor HoNi2B2C
• Pressure and isotope effect on the anisotropy of MgB${}_2$
• Fluctuations in two-band superconductors in a strong magnetic field
• Wide critical fluctuations of the field-induced phase transition in graphite
• Probing superconductivity in MgB2 confined to magnetic field tuned cylinders by means of critical fluctuations
• Differential-thermal analysis around and below the critical temperature Tc of various low-Tc superconductors: A comparative study