Specific heat of superconducting MgCNi3 single crystals

Abstract

The ac microcalorimetry measurements with light emitting diode used as a heater has been performed on high quality MgCNi3 single crystals with T c of 6.9 K. The measurements have been realized in the temperature range down to 0.7 K and magnetic fields up to 8 T. All the measurements show sharp and well defined specific heat anomaly at the transition. The low-temperature electronic specific heat in superconducting state shows a classical exponential decrease confirming an s-wave pairing. Analysis of the data in the framework of classical BCS theory points to the moderate coupling in this material. The upper critical field Hc2 has also been derived from specific heat measurements in different magnetic fields. The temperature dependence of Hc2 is discussed. © 2009 IOP Publishing Ltd.