Dresden 2011 – scientific programme
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MA: Fachverband Magnetismus
MA 60: Spin Structures and Magnetic Phase Transitions
MA 60.5: Talk
Thursday, March 17, 2011, 18:30–18:45, HSZ 103
Precursor states and Skyrmion confinement in cubic helimagnets — •Andrey A. Leonov, Anna B. Butenko, Alexei N. Bogdanov, and Ulrich K. Rössler — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
Within the phenomenological Dzyaloshinskii model
we show that precursor effects [1] experimentally observed
in cubic helimagnets with B20 structure
near the ordering temperature can be explained
by the unconventional behavior of ’Skyrmion matter’[2].
Skyrmion states in the form of staggered
half-Skyrmion configurations
and ±π-hexagonal lattices
undergo confinement in the temperature range Δ T=TN−TL
and can exist as bound liquid-like or ordered arrays [2].
Confined Skyrmion textures arise from the disordered state
through a rare case of an instability-type nucleation transition.
Their field-driven transformation is marked by
the interplay of angular and longitudinal order parameters.
The confinement temperature TL separates
the major part of the magnetic phase diagram with
regular chiral modulations [3] from
the precursor regime.
The stabilization of Skyrmionic textures against
the competing helical and conical modulations
near magnetic ordering can be achieved by
small additional interactions such as dipolar couplings,
thermal fluctuations, cubic and uniaxial anisotropies, anisotropic
exchange etc.
[1] C. Pappas et al., Phys. Rev. Lett. 102, 197202 (2009); [2] U. K. Rößler et al., J. Phys., in press; [3] A. Bogdanov, A. Hubert, J. Magn. Magn. Mater. 138, 255 (1994); A.B. Butenko et al., Phys. Rev. B 80, 134410 (2009).