Writing and Deleting Single Magnetic Skyrmions

Writing and Deleting Single Magnetic Skyrmions.
Niklas Romming, Christian Hanneken, Matthias Menzel, Jessica E. Bickel, Boris Wolter,

Kirsten von Bergmann, André Kubetzka, Roland Wiesendanger

Science 341, 636 (2015)

Magnetic field dependence of the PdFe bilayer on the Ir(111) surface at T = 8 K. (A to C) Perspective sketches of the magnetic phases. (D) Overview SP-STM image, perspective view of constant-current image colorized with its derivative. (E to G) PdFe bilayer at different magnetic fields (U = +50 mV, I = 0.2 nA, magnetically out-of-plane sensitive tip). (E) Coexistence of spin spiral and skyrmion phase. (F) Pure skyrmion phase. (G) Ferromagnetic phase. A remaining skyrmion is marked by the white circle.

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.

Vortex dynamics in arrays of nanomagnets

Observation of vortex dynamics in arrays of nanomagnets.
W. Yu, P. S. Keatley, P. Gangmei, M. K. Marcham, T. H. J. Loughran, R. J. Hicken, S. A. Cavill, G. van der Laan, J. R. Childress, and J. A. Katine
Phys. Rev. B 91, 174425 (2015)

TRSKM images, XPEEM images, and SEM images of arrays of 250-nm squares with separation of 500 nm in (a) and (b), and 50 nm in (c). After acquisition of the TRSKM images in (a), the equilibrium state was reinitialized before acquiring the TRSKM images in (b). In all TRSKM images the horizontal white bar has length of 1 μm. In (c) the white arrows in the TRSKM images denote regions of contrast with size comparable to, or larger than, that of a single element, while the dashed white rectangle in the XPEEM image highlights a cluster of elements with vortex equilibrium states. (d) Enlarged view of (c), in which the black grid position is a guide to the eye to show where the individual elements lie, and the white boxes highlight regions of contrast

Dipolar Kagome lattice

Classical dipoles on the kagome lattice.
Mykola Maksymenko, V. Ravi Chandra, and Roderich Moessner

Phys. Rev. B 91, 184407 (2015)

The kagome lattice (left) and the ground-state phase diagram of the model consisting of nearest-neighbor exchange J=sinθ and dipolar interactions of strength D=cosθ (right). A1 and A2 are the basis vectors of the triangular Bravais lattice, and a dark green triangle denotes the unit cell of three sites labeled by r0=(0,0),r1=(1/2,0), and r2=(0,1/2) in this basis. The system exhibits long-range 120∘ order for π/2≥θ>θ1 with θ1=10.01∘ and ferrimagnetic order for −π/2<θ<θ2 where θ2=1.03∘. The latter has two spins inclined with respect to one of the unit-cell edges by angle ±ϕ(θ). The area between two phases possibly contains an incommensurate intermediate regime.

Quantitative simulation of temperature-dependent magnetization dynamics

Quantitative simulation of temperature-dependent magnetization dynamics and equilibrium properties of elemental ferromagnets.
R. F. L. Evans, U. Atxitia, and R. W. Chantrell

Phys. Rev. B 91, 144425 (2015)

Temperature-dependent magnetization for the elemental ferromagnets (a) Co, (b) Fe, (c) Ni, and (d) Gd. Circles give the simulated mean magnetization, and dark solid lines show the corresponding fit according to Eq. (4) for the classical case α=1. Light solid lines give the experimentally measured temperature-dependent magnetization as fitted by Kuz'min's equation. Triangles give the simulated data after the temperature rescaling has been applied, showing excellent agreement with the experimentally measured magnetizations for all studied materials.

Single Magnetic Skyrmions

Field-Dependent Size and Shape of Single Magnetic Skyrmions.
Niklas Romming, André Kubetzka, Christian Hanneken, Kirsten von Bergmann, and Roland Wiesendanger
Phys. Rev. Lett. 114, 177203 (2015)

Spin structure of individual Skyrmion in PdFe/Ir(111). (a) Sketch of the experimental setup of a spin-polarized STM tip probing a magnetic Skyrmion. (b) Topographic constant-current SP-STM image measured with out-of-plane sensitive magnetic tip; each blue circular entity is a Skyrmion (U=+200  mV, I=1  nA, T=2.2  K, B=-1.5  T). (c) Magnetic signal (methods [22]) of two Skyrmions measured with an in-plane magnetization of the tip, m→T, revealing a two-lobe structure (U=+250  mV, I=1  nA, T=4.2  K). (d) Same area as in (c) with inverted magnetic field; due to the preserved rotational sense, the contrast is inverted. (e),(f) Line profiles across a Skyrmion along the rectangles in (c) and (d), respectively, and fits with Eq. (1) [(e) c=(0.90±0.01)  nm, w=(1.18±0.02)  nm; (f) c=(0.91±0.01)  nm, w=(1.17±0.01)  nm] and corresponding calculated out-of-plane magnetization mz. The sketches show spins with atomic distance, colorized according to the SP-STM contrast.