Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 27: Spin Structures and Magnetic Phase Transitions

MA 27.6: Vortrag

Donnerstag, 25. März 2010, 18:30–18:45, H10

Skyrmion textures in noncentrosymmetric cubic helimagnets — •Andrey A. Leonov, Alexei N. Bogdanov, and Ulrich K. Rößler — IFW Dresden, P.O.B. 270116, D-01171 Dresden

In noncentrosymmetric magnetic systems, chiral Dzyaloshinskii-Moriya (DM) interactions give rise to one-dimensional (cycloids and conical helices), two-dimensional (baby-Skyrmions), and three-dimensional (Hopfions) modulated and localized structures with a fixed sense of rotation. Within the standard phenomenological (Dzyaloshinskii) theory [1], which includes only basic isotropic interactions the conical phase is a global minimum. Other modulated textures exist only as metastable states. Detailed numerical analysis on two dimensional models shows that bound Skyrmion states arise as hexagonal lattices of ±π-Skyrmions or square staggered lattices of π/2-Skyrmions. In real materials additional magnetic couplings (for example, uniaxial or exchange anisotropy) can render Skyrmionic states into thermodynamically stable phases. The transitions between different Skyrmionic and other modulated phases is generally first order, which should be discernible as hysteresis of magnetization processes. The model results show that diverse Skyrmionic textures may underlie the exotic magnetic phenomena of “partial order” or the field-driven “A-phase” observed in MnSi and other cubic helimagnets.
[1] U.K.Rößler, A.N.Bogdanov, C.Pfleiderer, Nature (London) 442, 797 (2006); U. K. Rößler, A. A. Leonov, A. N. Bogdanov, J. Phys., in press; arXiv: 0907.3651v2 (2009).