Long-Wavelength Helimagnetic Order and Skyrmion Lattice Phase inCu2OSeO3

Abstract

We report a long-wavelength helimagnetic superstructure in bulk samples of the ferrimagnetic insulator Cu2OSeO3. The magnetic phase diagram associated with the helimagnetic modulation inferred from small-angle neutron scattering and magnetization measurements includes a skyrmion lattice phase and is strongly reminiscent of MnSi, FeGe, and Fe(1-x)Co(x)Si, i.e., binary isostructural siblings of Cu2OSeO3 that order helimagnetically. The temperature dependence of the specific heat of Cu2OSeO3 is characteristic of nearly critical spin fluctuations at the helimagnetic transition. This provides putative evidence for effective spin currents as the origin of enhancements of the magnetodielectric response instead of atomic displacements considered so far.

The quantum nature of skyrmions and half-skyrmions in Cu2OSeO3

“…First, the double-twisted core of skyrmions is energetically favourable and is stabilized at T ¼ T 0 C þ DT=2, while the helical ground state sets in only at T 0 C þ DT=4, and second, the chiral twisting is accompanied by strong longitudinal modulations of the magnetization M. Hence, anomalous skyrmionic spin-textures can be expected within this temperature range. The model parameters yield an estimate DTC1.04 K, in good agreement with the interval of about 2 K in which the so-called 'A-phases' appear under magnetic field in Cu 2 OSeO 3 crystals 28,29 . Given the crude representation of the thermodynamic potential term in the continuum theory by the Landau expansion, this value gives only the order or magnitude of the expected effects.…”

A Centrosymmetric Hexagonal Magnet with Superstable Biskyrmion Magnetic Nanodomains in a Wide Temperature Range of 100–340 K

“…including Refs. [1][2][3][4][5][6][7][8][9][10][11][12], [22], [29][30][31], [33]. The red solid squares indicate the experimental data based on the in-situ Lorentz TEM observations.…”

“…Such unique mangetic naondomains have been recently discovered in bulk chiral magnetic materials, such as MnSi [1][2][3][4] , FeGe [5,6] , FeCoSi [7] , Cu 2 OSeO 3 [8][9][10] , -Mn-type Co-Zn-Mn [11] , and also GaV 4 S 8[12] a polar magnet. The crystal structure of these materials is cubic and lack of centrosymmetry, leading to the existence of Dzyaloshinskii-Moriya (DM) interactions.…”

Incommensurate Magnetic Structure in the Cubic Noncentrosymmetric Ternary Compound Pr5Ru3Al2

“…Instead, magnetic ordering was observed in the DC magnetic susceptibility at T N ≃ 3.8 K. Neutron powder diffraction further indicates that an incommensurate magnetic structure is established below T N , with the magnetic modulation vector q ≃ (0.066, 0.066, 0.066) (r.l.u.). A candidate for the magnetic structure is proposed using the representation analysis.Non-colinear incommensurate magnetic structures, such as a helical magnetic structure, have attracted renewed interests because of the recent discovery of novel topological spin textures, for instance magnetic skyrmion [1][2][3][4][5][6] and chiral magnetic soliton lattice. 7-9) A helical magnetic structure is stabilized by the magnetic frustration 10, 11) and/or DzyaloshinskyMoriya (DM) interaction.…”

“…Non-colinear incommensurate magnetic structures, such as a helical magnetic structure, have attracted renewed interests because of the recent discovery of novel topological spin textures, for instance magnetic skyrmion [1][2][3][4][5][6] and chiral magnetic soliton lattice. 7-9) A helical magnetic structure is stabilized by the magnetic frustration 10, 11) and/or DzyaloshinskyMoriya (DM) interaction.…”