Tricritical behavior in MnSi at nearly hydrostatic pressure

Abstract

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 (P tr ∼ = 0.355 GPa, T tr ∼ = 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. PACS numbers: 62.50.+p, 64.60.Kw, 75.30.Kz Recently, there has been a considerable interest in studying the magnetic phase transition in the intermetallic compound MnSi [1,2,3,4,5,6,7,8,9,10,11], which reveals weak ferromagnetic properties slightly below 30 K with spins having been ordered into a long wavelength helical structure [12,13]

Magnetic phase transition in the itinerant helimagnetMnSi: Thermodynamic and transport properties

“…Using the Clausius-Clapeyron equation and taking the slope of the transition line from Ref. 11, we get for the corresponding entropy change 5 ϫ 10 −4 R ͑R is the gas constant͒. 22 This value agrees with the direct estimate from the entropy variation through the phase transition, calculated by integration of the heat capacity.…”

High Pressure Helium Gas Technique for Low Temperature Applications

“…10, where some results on measuring the AC susceptibility χ AC of MnSi along the ferromagnetic phase transition line is shown . 7) As seen from Fig. 9, 10 under the hydrostatic conditions used in the present experiments, a λ-type singularity of χ AC at the phase transition in MnSi remains essentially independent on pressure to 0.355 GPa (Fig.…”

High-pressure study of the magnetic phase transition in MnSi

“…A slightly different behavior of ac observed in Ref. 15 is most probably connected with a smaller size of the sample used in the old measurements compared to the present ones. So the nonhydrostatic stress amplitude could reach a critical value only at some distance from the melting point inside the solid helium domain.…”

“…15 But one could notice subtle differences between present data and the data in Ref. 15 ͑see Fig. 2͒.…”

“…1 and 2, the sharp maximum of ac magnetic susceptibility ac does not change much up to a pressure of about 0.3 GPa and then starts to decrease rapidly at higher pressures, as observed before. 15 But one could notice subtle differences between present data and the data in Ref. 15 ͑see Fig.…”