ritical phenomenon of the single crystal helimagnet MnSi

he critical behavior of the single crystal helimagnet MnSi is investigated by means of bulkdc-magnetization at the boundary between the conical state and paramagnetic phase. We obtainthe critical exponents (ˉ = 0:242 § 0:006, ° = 0:915 § 0:003, and ± = 4:734 § 0:006), where theself-consistency and reliability are veriˉed by the Widom scaling law and the scaling equation.The critical exponents of MnSi belong to the universality class of tricritical mean-ˉeld theory,which unambiguously indicates a tricritical phenomenon at the boundary between the ˉrst-orderphase transition and the second-order one induced by the external magnetic ˉeld. The tricriticalpoint (TCP) is determined as HTCP ? 3200 Oe at the critical temperature, consistent with theprevious report [Phys. Rev. Lett. 110, 177207 (2013)]. The critical behavior suggests a long-rangemagnetic coupling with the exchange distance decaying as J(r) ? r?4:3 in MnSi.