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 0.80.3em0exGPa created by compressed helium. The results show that the tricritical point is situated at much lower pressure and at significantly higher temperature (Pₜᵣ0.3550.3em0exGPa, Tₜᵣ25.20.3em0exK) than was reported previously (~1.20.3em0exGPa, ~120.3em0exK). These observations put certain constraints on the origin of the tricritical point in MnSi.