Anomalous behavior of the electrical resistivity of MnSi near the ferromagnetic phase transition

The results of measuring the electrical resistivity of a MnSi single crystal near the ferromagnetic phase transition at atmospheric and high pressures are reported. In contrast to the previous works, compressed helium is used as a pressure-transferring medium. It is shown that the temperature derivative of the electrical resistivity has the form of sharp maximum on the phase-transition line over the entire its length. Moreover, the observed maxima have a fine structure exhibiting a pronounced shoulder at temperatures slightly higher (by approximately 0.5 K) than the peak temperature, which indicates the existence of nontrivial fluctuations in the paramagnetic phase of MnSi. This feature disappears at a pressure of about 0.35 GPa, which corresponds to the tricritical-point coordinate.