Role of critical fluctuations in the formation of a skyrmion lattice in MnSi

• Published in: Journal of experimental and theoretical physics 2017-11, Vol.125 (5), p.789-797
• Main Authors: Chubova, N. M., Moskvin, E. V., Dyad’kin, V. A., Dewhurst, Ch, Maleev, S. V., Grigor’ev, S. V.
• Format: Article
• Language: English
• Subjects: Classical and Quantum Gravitation; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CRITICAL TEMPERATURE; Defects; Disorder; Elementary Particles; FLUCTUATIONS; MAGNETIC FIELDS; MAGNETS; MANGANESE SILICIDES; NEUTRON DIFFRACTION; Order; Particle and Nuclear Physics; PHASE DIAGRAMS; Phase Transition in Condensed System; Physics; Physics and Astronomy; Quantum Field Theory; Relativity Theory; SKYRME POTENTIAL; Solid State Physics; SOLITONS; Transition temperature; Variation
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776117100119

The region in the H – T phase diagram near the critical temperature ( T c ) of the cubic helicoidal MnSi magnet is comprehensively studied by small-angle neutron diffraction. Magnetic field H is applied along the [111] axis. The experimental geometry is chosen to simultaneously observe the following three different magnetic states of the system: (a) critical fluctuations of a spin spiral with randomly orientated wavevector k f , (b) conical structure with k c ǁ H , and (c) hexagonal skyrmion lattice with k sk ⊥ H . Both states (conical structure, and skyrmion lattice) are shown to exist above critical temperature T c = 29 K against the background of the critical fluctuations of a spin spiral. The conical lattice is present up to the temperatures where fluctuation correlation length ξ becomes comparable with pitch of spiral d s . The skyrmion lattice is localized near T c and is related to the fluctuations of a spiral with correlation length ξ ≈ 2 d s , and the propagation vector is normal to the field ( k sk ⊥ H ). These spiral fluctuations are assumed to be the defects that stabilize the skyrmion lattice and promote its formation.