Critical behavior of the single-crystal helimagnet MnSi

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2015-01, Vol.91 (2), Article 024403
• Main Authors: Zhang, Lei, Menzel, Dirk, Jin, Chiming, Du, Haifeng, Ge, Min, Zhang, Changjin, Pi, Li, Tian, Mingliang, Zhang, Yuheng
• Format: Article
• Language: English
• Subjects: Boundaries; Condensed matter; Decay; Exponents; Magnetic fields; Magnetization; Mathematical analysis; Single crystals; TCP (protocol)
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.91.024403

The critical behavior of the single-crystal helimagnet MnSi is investigated by means of bulk dc magnetization at the boundary between the conical state and paramagnetic phase. We obtain the critical exponents ( beta = 0.242 + or - 0.006, gamma = 0.915 + or - 0.003 and delta = 4.734 + or - 0.006), where the self-consistency and reliability are verified by the Widom scaling law and the scaling equation. The critical exponents of MnSi belong to the universality class of tricritical mean-field theory, which unambiguously indicates a tricritical phenomenon at the boundary between the first-order phase transition and the second-order one induced by the external magnetic field. The tricritical point (TCP) is determined as H sub(TCP) approximately 3200 Oe at the critical temperature, consistent with the previous report [A. Bauer, M. Garst, and C. Pfleiderer, Phys. Rev. Lett. 110. 177207 (2013) (http://dx.doi.ora/10.1103/PhysRevLett.110.177207)]. The critical behavior suggests a long-range magnetic coupling with the exchange distance decaying as J (r) approximately r super(-4.3) in MnSi.