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Center for Nonlinear Studies |
The fundamental mechanism for the formation of chiral skyrmions in certain acentric (ferro)magnets is beautifully simple [1], and the basic solution for the localized two-dimensional skyrmion is now known for more than 25 years [2]. Since experimental evidence for such states and microscopic pictures have emerged in a small class of magnetic non-centrosymmetric materials, there now is great scientific interest and even ideas to employ these solitonic states in spintronics applications. The frustrated nature of the magnetic order in systems with the so-called 'inhomogeneous Dzyaloshinskii-Moriya' coupling [3] makes the skyrmion itself, and the condensed mesophases of skyrmions, susceptible to distortions and competing other phases.
Notably the usual ground-states are either collinear conventional or one-dimensionally modulated `Dzyaloshinskii spirals' depending on secondary magnetic couplings like anisotropies [4]. In the technologically important thin films, surface effects of these low-symmetry materials strongly affect the properties of skyrmions and their existence range in the magnetic phase diagram. Therefore, the question of materials and their specific magnetic properties need to be addressed to create the arena for the new research field of 'skyrmionics' in magnetism. To illustrate problems and chances, I discuss our theoretical understanding and experimental results for real materials like surfaces of the cubic chiral helimagnet FeGe, Cu2OSeO3 [5], and acentric tetragonal Heusler-alloys [6].
[1] A. Bogdanov, Pis'ma Zh. Ekps. Teor.Fiz. 62 (1995) 231 [JETP Letter 62 (1995), 247].
[2] A.N. Bogdanov, D. A. Yablonskii, Zh.Eksp.Teor.Fiz 95 (1989) 182 [Sov. Phys. JETP 66 (1989) 101].
[3] A.N. Bogdanov, U.K. Rößler, M.Wolf, K.-H. Müller, Phys.Rev.B 66 (2002) 214410.
[4] A.B. Butenko, A.A. Leonov, UKR, A. Bogdanov, Phys. Rev. B 85 (2010) 052403.
[5] O. Janson et al., Nature Comm. 5 (2014) 5376.
[6] O. Meshcheriakova et al., Phys.Rev. Lett. 113 (2014) 087203.
Host: Avadh Saxena, 7-5227