Helicity control in magnetic nanotubes

Tailoring dual reversal modes by helicity control in ferromagnetic nanotubes.
H. D. Salinas, J. Restrepo, and Òscar Iglesias

Phys. Rev. B 101, 054419 (2020)

Magnetic configurations along the hysteresis loops for the different reversal modes displayed in Fig. 4 (left and right columns correspond to panels (a) and (c) of that figure). Upper panels represent the height profiles of the quantities ⟨θ⟩, ⟨mz⟩, and <mϕ⟩  averaged per layer for the tube (8,15) and γ= 0.035, whereas lower ones present snapshots of the spin configurations taken at points labeled in Fig. 4.

Magnetic Möbius stripe

Magnetic Möbius stripe without frustration: Noncollinear metastable states.
S. Castillo-Sepúlveda, R. A. Escobar, D. Altbir, M. Krizanac, and E. Y. Vedmedenko
Phys. Rev. B 96, 024426 (2017)

Equilibrium MC configuration of a chain consisting of 100 moments for $D=1,K=0.4$ meV, $J=-40$ meV: (a) closed KB configuration and (b) the same shown with open ends for clarity.

Chirality-Dependent Transmission of SW through DW

Chirality-Dependent Transmission of Spin Waves through Domain Walls.
F. J. Buijnsters, Y. Ferreiros, A. Fasolino, and M. I. Katsnelson
Phys. Rev. Lett. 116, 147204 (2016)

Effect of the interfacial DMI on the magnetization profile $m\left(x\right)$ of a DW in a thin film with perpendicular anisotropy. (a) Away from the DW, magnetization points out of the film ($\hat{z}$ or $-\hat{z}$). Near the DW, the DMI creates an effective field $H_{\mathrm{DMI}}$ in the $-\hat{x}$ direction. Depending on the competition between the dipolar and DMI interactions, the equilibrium configurations circle, circle prime, star, star prime, and square, shown in (b)–(d), are possible. (b) Without DMI, the minimum-energy configurations (flux closure) are two equivalent Bloch DWs (circle, in dark colors, and circle prime, in light colors), whose in-plane orientations differ by 180°. (c) For intermediate DMI, the minimum-energy configurations are intermediate between Bloch and Néel. There are two equivalent minimum-energy states (star and star prime), whose in-plane orientations differ by approximately 90° for an appropriately tuned DMI strength $D$. (d) For strong DMI, a single minimum-energy configuration (square) exists: a Néel DW with magnetization in the center pointing in the $-\hat{x}$ direction.

Chiral magnetic interaction between two individual atoms

Tailoring the chiral magnetic interaction between two individual atoms
A. A. Khajetoorians, M. Steinbrecher, M. Ternes, M. Bouhassoune, M. dos Santos Dias, S. Lounis, J. Wiebe & R. Wiesendanger
Nature Communications 7, 10620 (2016)

The interaction between two magnetic atoms (red/green) is mediated by scattering of conduction electrons at a substrate atom (grey) with strong spin-orbit coupling (SOC)2,15,16. The shown scattering process leads to a contribution to the Heisenberg-like exchange (J) and DM vector (D), which is oriented perpendicular to the indicated triangle constituted by the two magnetic atoms and the substrate atom. The overall J and D are given by the contributions of all substrate atoms resulting in a nonzero D=(D||, D⊥, Dz) (orientation of the components as indicated) because of broken inversion symmetry at the surface18. The orientation of the spins S1 and S2 of the coupled pair is determined by the interplay between the single ion magnetic anisotropy of each atom (Ki), J, D, and the applied magnetic field (Bz).

Tunable exchange bias in dilute magnetic alloys – chiral spin glasses

Tunable exchange bias in dilute magnetic alloys – chiral spin glasses

Matthias Hudl, Roland Mathieu and Per Nordblad

Scientific Reports 6, 19964 (2016)

(a) The central part of M vs. H loops after cooling the sample in H_FC to 5 K, and measure the hysteresis loop on decreasing the field to – H_FC and back to +H_FC. The insets show the field dependence of the parameter H_sw1, H_sw2, (right) and ΔM (left) in the H_FC range 1 to 9 T. (b) Full hysteresis loops measured at 5 K from 0 to 14, 14 to −14 and then back +14 T. The inset shows the central part of the loop and the fields H_sw1 and H_sw2 are marked. The jump and definition of the excess magnetization, ΔM, is indicated in the main frame. (c,d) The central part of the hysteresis loops measured after field cooling (c) and zero field cooling (d) in fields up to 5 T at 5 K. The arrows indicate the initial field sweep direction. (Red loops- positive initial fields, blue loops - negative initial fields).

Chiral damping of DWs

Chiral damping of magnetic domain walls.

Emilie Jué, C. K. Safeer, Marc Drouard, Alexandre Lopez, Paul Balint, Liliana Buda-Prejbeanu, Olivier Boulle, Stephane Auffret, Alain Schuhl, Aurelien Manchon, Ioan Mihai Miron & Gilles Gaudin

Nature Materials AOL (2015)

Graphic illustration of the asymmetric DW dynamics in PMA materials.

Universal helimagnon and skyrmion excitations

Universal helimagnon and skyrmion excitations in metallic, semiconducting and insulating chiral magnets.

T. Schwarze, J.Waizner, M. Garst, A. Bauer, I. Stasinopoulos, H. Berger, C. Pfleiderer and D. Grundler

Nature Materials 14, 478 (2015)

Spin textures of cubic chiral helimagnets and their collective excitations.

Skyrmions in magnets

Here is a collection of articles on skyrmions in magnets, an increasingly hot topic:

1) Spontaneous skyrmion ground states in magnetic metals.
U. K. Röler, A. N. Bogdanov and C. Pfleiderer
Nature 442, 797 (2006)

Three chiral modulated structures for noncentrosymmetric ferromagnets and comparison of their energy density.

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)

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)

(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)

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

.
5) Condensed-matter physics: Single skyrmions spotted.
Christian Pfleiderer, Achim Rosch
 Nature 465, 880 (2010) N&V

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)

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)

(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)

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)

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)

(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.