  The high-frequency shear modulus of five Zr-, Pd-, Cu-based conventional and
two high-entropy bulk metallic glasses was measured in a wide temperature range
up to the beginning of crystallization. Using these data and general
thermodynamic relations, the "fluctuation" heat capacity $\Delta C_f$
determined by local structural fluctuations in the defect regions is introduced
and calculated. It is found that $\Delta C_f$ temperature dependence for all
metallic glasses has a large peak located slightly below or above the glass
transition temperature but clearly lower than the crystallization onset
temperature. The form of this peak resembles the characteristic $\lambda$-peak
typical for order-disorder phase transitions. It is suggested that this $\Delta
C_f$-peak reflects certain underlying critical phenomenon. The critical
temperature $T_0$ (peak temperature) and corresponding critical index $\alpha$
are determined. Averaged over all seven metallic glasses under investigation in
the initial and relaxed states, the critical index $\alpha=0.26$. The results
obtained indicate that the fluctuations of thermal energy near the glass
transition bear the marks of a continuous phase transition. However, the
derived critical index is between those corresponding to a second-order phase
transition ($\alpha\approx 0.1$) and a critical transition characterized by a
tricritical point ($\alpha \approx 0.5$).
