Tricritical behavior in MnSi at nearly hydrostatic pressure

AC magnetic susceptibility of a single crystal of MnSi was measured along the ferromagnetic phase-transition line up to a pressure of 0.8 GPa created by compressed helium. The results show that the tricritical point is situated at much lower pressure and at significantly higher temperature (Ptr~0.355 GPa, Ttr~25.2 K) than was reported previously (~1.2 GPa,~12 K). These new observations put certain constraints on the origin of the tricritical point in MnSi.