Here is a collection of articles on skyrmions in magnets, an increasingly hot topic:
1) Spontaneous skyrmion ground states in magnetic metals.
U. K. Rö
ler, A. N. Bogdanov and C. Pfleiderer
Nature 442, 797 (2006)
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Three chiral modulated structures for noncentrosymmetric ferromagnets and comparison of their energy density.
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2) Spin chirality on a two-dimensional frustrated lattice.
Daniel Grohol, Kittiwit Matan, Jin-Hyung Cho, Seung-Hun Lee, Jeffrey W. Lynn, Daniel G. Nocera and Young S. Lee
Nature Materials 4, 323 (2005)
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| Measurements of the field-induced transition to a state with non-zero scalar chirality. |
3) Skyrmion lattice in a two-dimensional chiral magnet.
Jung Hoon Han, Jiadong Zang, Zhihua Yang, Jin-Hong Park, and Naoto Nagaosa
Phys. Rev. B 82, 094429 (2010)
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| (a) A typical Skyrme-crystal spin configuration given by Eq. 19 with B=D2 /J, with the optimized lattice spacing lH= 3/ 2. (b) Skyrme-crystal spin configuration obtained by Monte Carlo method from the lattice spin model |
4) Skyrmions and anomalous Hall effect in a Dzyaloshinskii-Moriya spiral magnet.
Su Do Yi, Shigeki Onoda, Naoto Nagaosa, and Jung Hoon Han
Phys. Rev. B 80, 054416 (2009)
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A plot of the spin configuration projected on the xy plane Si x ,Si y in the three spin crystal ground states: a SC1 at A2 ,H = 2.0, 0.0 , b SC2 at A2 ,H = 3.0, 0.0 , and cSCh at A2 ,H = 0.0, 2.0 . At the bottom left of each figure are the plots of the Bragg intensity Sk 2 showing two SC1,SC2 and three SCh sets of modulation vectors. Shown at the bottom right
are the plots of the local chirality r. Bright dark regions correspond to Skyrmions anti-Skyrmions |
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5) Condensed-matter physics: Single skyrmions spotted.
Christian Pfleiderer, Achim Rosch
Nature 465, 880 (2010) N&V
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| When an electron moves through a special type of magnetic texture called a skyrmion, its magnetic moment (spin) twists to adjust to the skyrmion's local spin structure (ribbon-like pattern). This twisting changes the electron's direction of travel and pushes the electron and the skyrmion in opposite directions (not shown). |
Real-space observation of a two-dimensional skyrmion crystal.
X. Z. Yu, Y. Onose, N. Kanazawa, J. H. Park, J. H. Han, Y. Matsui, N. Nagaosa, Y. Tokura
Nature 465, 09124 (2010)
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Topological spin textures in the helical magnet Fe0.5Co0.5Si. a, b, Helical (a) and skyrmion (b) structures predicted by Monte Carlo simulation. c, Schematic of the spin configuration in a skyrmion. d–f, The experimentally observed real-space images of the spin texture, represented by the lateral magnetization distribution as obtained by TIE analysis of the Lorentz TEM data: helical structure at zero magnetic field (d), the skyrmion crystal (SkX) structure for a weak magnetic field (50 mT) applied normal to the thin plate (e) and a magnified view of e (f). |
6) Giant Skyrmions Stabilized by Dipole-Dipole Interactions in Thin Ferromagnetic Films.
Motohiko Ezawa
Phys. Rev. Lett. 105, 197202 (2010)
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| (a) Illustration of a giant Skyrmion ( 1 m) in a thin ferromagnetic film. The simplest spin texture has naturally a nontrivial Pontryagin number. It can be created by applying femtosecond optical pulse irradiation focused on a micrometer spot and thus destroying the magnetic order locally. (b) Illustration of magnetic flux lines around a Skyrmion due to magnetic dipoles. When the magnetic order is destroyed locally, a new order is generated which is opposite to that of the environs, so that the magnetic flux closes by itself as short as possible. |
7) Comment to previous article.
N. S. Kiselev, A. N. Bogdanov, R. Schäfer, and U. K. Rößler
Phys. Rev. Lett. 107, 179701 (2011)
8) Spin waves in a skyrmion crystal.
Olga Petrova and Oleg Tchernyshyov
Phys. Rev. B.84. 214433 (2011)
9) Chiral skyrmions in thin magnetic films: new objects for magnetic storage technologies?
N S Kiselev, A N Bogdanov, R Schäfer and U K Rößler
J. Phys. D 44, 392001 (2011)
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| The magnetic phase diagram in reduced variables κ and applied magnetic field H/Ha for fixed values of Q and the reduced layer thickness l indicate the existence region of isolated skyrmions.In the double-hatched area spatially modulated phases (helicoids and skyrmion lattices) correspond to the equilibrium state of the film. |
10) Spontaneous atomic-scale magnetic skyrmion lattice in two dimensions.
Stefan Heinze, Kirsten von Bergmann, Matthias Menzel , Jens Brede , André Kubetzka, Roland Wiesendanger, Gustav Bihlmayer and Stefan Blügel
Nature Physics 7, 2045 (2011)
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| The nanoskyrmion lattice of the Fe ML on Ir(111). a, Sketch of the nanoskyrmion lattice: cones represent atoms of the hexagonal Fe layer and point along their magnetization directions; red and green represent up and down magnetization components, respectively. b, Atomic-resolution STM image of the pseudomorphic hexagonal Fe layer at an Ir step edge. Upper inset: The FT. Lower inset: A side view of the system (tunnel parameters UDC5 mV, ID30 nA). c, SP-STMimage of the Fe ML on Ir(111) with a magnetic tip sensitive to the out-of-plane component of magnetization (Fe-coatedWtip, BDC2 T along the tip axis, UDC50 mV, ID0:5 nA): bright (dark) spots indicate areas with magnetization parallel (antiparallel) to the tip magnetization. Left inset: Simulated SP-STMimage of the nanoskyrmion with out-of-plane magnetic tip. Right inset: FT of the experimental SP-STMimage shown in the two-dimensional Brillouin zone. |
11) ChiralityWaves in Two-Dimensional Magnets.
D. Solenov, D. Mozyrsky, and I. Martin
Phys. Rev. Lett. 108,096403 (2012)
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| (a-e) The optimal magnetic state S(r)=(sinKy cosKx, cosKy, sinKy sinKx) realized at small Kondo coupling, J= 1. Panels (a)-(c) show the spatial dependence of the three magnetization components. (d) Full 3D magnetization pattern. (e) The in-plane magnetization has a ‘‘vortexantivortex’’ structure (vortex points are marked with circles, antivortex points—with squares). The superimposed density plot in e represents scalar chirality. (f ) 1D cut showing the chirality density and the induced charge current density in the lowest energy state,S(r) for J ¼ 0:2 and ¼ 0:5. (g), (h) The 2D periodic magnetization patterns can be naturally mapped onto toroidal surface representing the real-space magnetic unit cell. A simple spiral texture, (g), is unstable with respect to configuration (h) that corresponds to the S(r) texture. |
