Temperature-Induced Increase of Spin Spiral Periods

Temperature-Induced Increase of Spin Spiral Periods.
Aurore Finco, Levente Rózsa, Pin-Jui Hsu, André Kubetzka, Elena Vedmedenko, Kirsten von Bergmann, and Roland Wiesendanger
Phys. Rev. Lett. 119, 037202 (2017)

DMI across AFM-FM Interface

Dzyaloshinskii-Moriya Interaction across an Antiferromagnet-Ferromagnet Interface.

Xin Ma, Guoqiang Yu, Seyed A. Razavi, Stephen S. Sasaki, Xiang Li, Kai Hao, Sarah H. Tolbert, Kang L. Wang, and Xiaoqin Li

Phys. Rev. Lett. 119, 027202 (2017)

(a) Schematics of BLS experiment and possible atomic arrangement at the interface. (b) BLS spectra for DE spin waves recorded at a fixed incident angle with $k=16.7\mathrm{rad}/\mu m$ under oppositely oriented external magnetic fields $H$. The solid lines represent fittings with Lorentzian functions.

DM interaction in transition-metal chains

Role of Dzyaloshinskii-Moriya interaction for magnetism in transition-metal chains at Pt step edges.
B. Schweflinghaus, B. Zimmermann, M. Heide, G. Bihlmayer, and S. Blügel
Phys. Rev. B 94, 024403 (2016)

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).

High-topological-number magnetic skyrmions

High-topological-number magnetic skyrmions and topologically protected dissipative structure.

Xichao Zhang, Yan Zhou, and Motohiko Ezawa
Phys. Rev. B 93, 024415 (2016)

Time evolution of the high-Q skyrmion (Q=2). (a) Time evolution of the total energy Etotal, the DMI energy EDMI, the topological number Q, the in-plane (mx,my) and out-of-plane mz components of magnetization averaged over the simulation area, and the dissipation functions W. A high-Q skyrmion with Q=2 is created nearly at t=0.38 ns. The DMI constant D=2 mJ m−2. The spin current density j=3×1012 A m−2. The external magnetic field Bz=250 mT. (b) Top views of the magnetization distributions mx,my, and mz of the FM nanodisk, the corresponding topological charge density distribution q, and the Rayleigh dissipation function W at selected times. The green circle indicates the spin current injection region. The nucleation of a high-Q skyrmion with Q=2 occurs nearly at t=0.38 ns, where the dissipation function spreads all over the FM nanodisk, implying that the spin wave propagates. The DMI is turned off at t=10 ns. It is remarkable that the high-Q skyrmion remains stable even if the DMI is switched off, which demonstrates the topological protection against the change of a variable, that is, the DMI.

DM anisotropy in nanomagnets with in-plane magnetization

Dzyaloshinskii-Moriya anisotropy in nanomagnets with in-plane magnetization.
M. Cubukcu, J. Sampaio, K. Bouzehouane, D. Apalkov, A. V. Khvalkovskiy, V. Cros, and N. Reyren
Phys. Rev. B 93, 020401(R) (2016)

DMI-induced anisotropy orthogonal to the shape anisotropy as observed by MFM and simulations. All scale bars are 200 nm long. The arrows indicate the mean magnetization. (a) Experimental MFM phase images are displayed. The actual topographical shape is indicated by a dotted line. The MFM phase is coded in the same way as in Fig. 1. The approximate sizes are 730×260,250×100, and 160×50 nm2. (b) Corresponding simulations for different D values (all the other micromagnetic parameters fixed), using an ideal dipolar MFM tip 30 nm above the magnetic layer. The observations of the magnetization direction in ellipses of different shapes (but same materials) allow constraining the Dzyaloshinskii-Moriya interaction strength D: The shadings indicate the D values compatible with observations. In the intermediate case, the magnetization does not align along one of the axes, reflecting the minute energy difference between the states with different magnetization directions. (c) Map of the DMI and exchange energy densities (darker means lower energy density) for the case D=2.1 mJ/m2. The energy gain concentrates close to the edges.

 

Guiding Spin Spirals by Strain

Guiding Spin Spirals by Local Uniaxial Strain Relief.

Pin-Jui Hsu, Aurore Finco, Lorenz Schmidt, André Kubetzka, Kirsten von Bergmann, and Roland Wiesendanger

Phys. Rev. Lett. 116, 017201 (2016)

(a) Overview SP-STM topography image of the spin spiral in the Fe DL and the nanoskyrmion lattice in the Fe ML; the zigzag shape of the spin spiral wave fronts with an angle of θ∼154° is indicated (measurement parameters: U=+1.0  V, I=1  nA, T=4.8  K). (b) Sketch of the magnetic state of the reconstructed Fe DL, as deduced from the SP-STM measurements. (c),(d) SP-STM topography images of the zigzag spin spiral measured with an out-of-plane and in-plane spin-sensitive tip, respectively. The corresponding SP-STM simulations are in the insets

Magnetic order induced by torsion in magnetic nanowires

Torsion-induced effects in magnetic nanowires.
Denis D. Sheka, Volodymyr P. Kravchuk, Kostiantyn V. Yershov, and Yuri Gaididei

Phys. Rev. B 92, 054417 (2015)

Magnetization distributions in the helix wire with easy-tangential anisotropy and C=+1 obtained from numerical simulations

Equilibrium magnetization distribution in the quasitangential state of the helix wire with C=+1

Spins on a Möbius ring

Coupling of Chiralities in Spin and Physical Spaces: The Möbius Ring as a Case Study.
Oleksandr V. Pylypovskyi, Volodymyr P. Kravchuk, Denis D. Sheka, Denys Makarov, Oliver G. Schmidt, and Yuri Gaididei
Phys. Rev. Lett. 114, 197204 (2015)

Diagram of ground states of magnetic Möbius rings with fixed radius R=100  nm and width w=80, see (a). The magnetization distributions of possible ground states are shown in the middle part in a large scale: (b) vortex state (marked by disks on the diagram), (c) state with single transversal Bloch domain wall (open squares), (d) state with three transversal Bloch walls (filled triangles), (e) states with longitudinal domain wall (filled squares). The detailed structures of the transverse and longitudinal domain walls are shown in (c′) and (e′), respectively.

Magnon driven DW motion by DM

Magnon-Driven Domain-Wall Motion with the Dzyaloshinskii-Moriya Interaction.
Weiwei Wang, Maximilian Albert, Marijan Beg, Marc-Antonio Bisotti, Dmitri Chernyshenko, David Cortés-Ortuño, Ian Hawke, and Hans Fangohr
Phys. Rev. Lett. 114, 087203 (2015)

(a) Illustration of the head-to-head DW in the nanowire using red-blue opaque arrows. The translucent purple arrows represent a spin wave excitation. The DMI exerts a torque to change the DW tilt angle when spin waves pass through the DW. (b) DW profile using Eq. (5) with parameters A=8.78×10-12  J/m, K=1×105  J/m3, D=1.58×10-3  J/m2, K⊥=0 and Φ=0. The red dashed line shows the simulation data for mz with K⊥2=6×105  J/m3: the easy-plane anisotropy favors a reduced mz. (c) The dispersion relations inside and outside the DW

Spin Spirals in Mn

Thermal properties of a spin spiral: Manganese on tungsten (110)
G. Hasselberg, R. Yanes, D. Hinzke, P. Sessi, M. Bode, L. Szunyogh, and U. Nowak

Phys. Rev. B 91, 064402 (2015)

Sketch of the calculated DM vectors Dij up to the fifth NN shell of the 2D lattice formed by the Mn atoms. The DM vectors (grey arrows) are placed at the center of the line connecting the center atom (red sphere) and its corresponding neighbor (green sphere). The length of the DM vector is proportional to its magnitude and also reflects the orientation in space. Note the rapid decay in the magnitude of DM vectors with distance; see also Fig. 1. Green arrows represent the magnetic moment.

Information transfer by spin chirality

Information transfer by vector spin chirality in finite magnetic chains.
Matthias Menzel, Yuriy Mokrousov, Robert Wieser, Jessica E. Bickel, Elena Vedmedenko, Stefan Blügel, Stefan Heinze, Kirsten von Bergmann, André Kubetzka, and Roland Wiesendanger
ArXiv 1204.2650 (2012)

SP-STM measurements of Fe chains on Ir(001). (a) and (b) Typical sample area of 30 x 30 nm2 measured with an Fe-coated
W tip without and with an applied external magnetic field of B = +2 T perpendicular to the sample surface, respectively (constant current images colorized with simultaneously acquired dI/dU maps, measurement parameters: U = +500mV, I = 5 nA, T = 8 K).(c) Topographic line profiles of the same Fe chain at B = 0 T and B = 2 T measured with a Cr-coated tip. The insets show schematically the tip magnetization and how a 120 deg spin-spiral, which is inverting in opposite fields, could explain the experimental results.

Skyrmion lattice generated by DM interaction

Effect of anisotropy and dipole interaction on long-range order magnetic structures generated by Dzyaloshinskii–Moriya interaction
H.Y. Kwon, K.M. Bu,Y.Z Wu, C. Won
J. Magn. Magn. Mater. 324, 2171 (2012)

(a) Magnetic structure of the stripe domain and (b) skyrmion lattice domain. The black-and-white scales show the out-of-plane part of the magnetization and the arrows show the in-plane part of the magnetization of a grid at the location of the arrows. (c) Change of magnetic structure with increasing external field. The field strength is 0.0, 0.2, 0.4, 0.6, and 0.9J/ς² from left to right.

Dynamics of a magnetic dimer

Dynamics of a magnetic dimer with exchange, dipolar, and Dzyalozhinski-Moriya interaction.
A. F. Franco, J. M. Martinez, J. L. Déjardin, and H. Kachkachi
Phys. Rev. B 84, 134423 (2011)

Evolution of the energy potential surface of a DDI-MD with longitudinal anisotropy configuration as ξ increases,
with σ = 1.5.