Specific heat fluctuations in the vicinity of the spin-Peierls transition of CuGeO3

We present an analysis of experimental specific heat data measured in the v icinity of the spin-Peierls transition of a CuGeO3 single crystal. The aim of the investigation was to analyse the type of the transition, including t he character of the fluctuations, and to give a proper determination of the critical temperature. We used and successively compared the Gaussian and c ritical fluctuations models to fit the experimental points detected in magn etic fields up to 21 T. Our results present new information about the influ ence of a magnetic held on fluctuations in the CuGeO3 compound. Within the framework of the Gaussian fluctuations model, there is no significant magne tic field dependence of the fluctuations. Using this model, the critical re gion is estimated to be as small as 10 mK in zero field, which excludes the possibility of observation of critical fluctuations in the present experim ents. In spite of this, a critical fluctuations type of analysis can also b e carried out, with a critical exponent value lying between the three-dimen sional XY and the Heisenberg universality classes. We also note the absence of broadening of the fluctuations regime under magnetic field. Taking into account the scatter of the data, the two models are equally suitable in th e fitting process.