scholarly journals Deriving the skyrmion Hall angle from skyrmion lattice dynamics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
R. Brearton ◽  
L. A. Turnbull ◽  
J. A. T. Verezhak ◽  
G. Balakrishnan ◽  
P. D. Hatton ◽  
...  
Keyword(s):  
High Efficiency ◽  
Magnetic Field Gradient ◽  
Real Space ◽  
Magnetic Multilayer ◽  
Multilayer Systems ◽  
Space Technique ◽  
Hall Angle ◽  
Lattice State ◽  
The Many ◽  
Magnetic Skyrmions

AbstractMagnetic skyrmions are topologically non-trivial, swirling magnetization textures that form lattices in helimagnetic materials. These magnetic nanoparticles show promise as high efficiency next-generation information carriers, with dynamics that are governed by their topology. Among the many unusual properties of skyrmions is the tendency of their direction of motion to deviate from that of a driving force; the angle by which they diverge is a materials constant, known as the skyrmion Hall angle. In magnetic multilayer systems, where skyrmions often appear individually, not arranging themselves in a lattice, this deflection angle can be easily measured by tracing the real space motion of individual skyrmions. Here we describe a reciprocal space technique which can be used to determine the skyrmion Hall angle in the skyrmion lattice state, leveraging the properties of the skyrmion lattice under a shear drive. We demonstrate this procedure to yield a quantitative measurement of the skyrmion Hall angle in the room-temperature skyrmion system FeGe, shearing the skyrmion lattice with the magnetic field gradient generated by a single turn Oersted wire.

scholarly journals Creation and observation of Hopfions in magnetic multilayer systems

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Noah Kent ◽  
Neal Reynolds ◽  
David Raftrey ◽  
Ian T. G. Campbell ◽  
Selven Virasawmy ◽  
...  
Keyword(s):  
Magnetic Circular Dichroism ◽  
Three Dimensional ◽  
Perpendicular Magnetic Anisotropy ◽  
Theoretical Models ◽  
Magnetic Multilayer ◽  
Multilayer Systems ◽  
Transmission Microscopy ◽  
X Ray ◽  
Three Dimensional Objects ◽  
Magnetic Skyrmions

AbstractAmong topological solitons, magnetic skyrmions are two-dimensional particle-like objects with a continuous winding of the magnetization, and magnetic Hopfions are three-dimensional objects that can be formed from a closed loop of twisted skyrmion strings. Theoretical models suggest that magnetic Hopfions can be stabilized in frustrated or chiral magnetic systems, and target skymions can be transformed into Hopfions by adapting their perpendicular magnetic anisotropy, but their experimental verification has been elusive so far. Here, we present an experimental study of magnetic Hopfions that are created in Ir/Co/Pt multilayers shaped into nanoscale disks, known to host target skyrmions. To characterize three-dimensional spin textures that distinguish Hopfions from target skyrmions magnetic images are recorded with surface-sensitive X-ray photoemission electron microscopy and bulk-sensitive soft X-ray transmission microscopy using element-specific X-ray magnetic circular dichroism effects as magnetic contrast. These results could stimulate further investigations of Hopfions and their potential application in three-dimensional spintronics devices.

A Simple Real-Space Channelling Theory for Electron Diffraction and HREM

1990 ◽  
Vol 48 (1) ◽  
pp. 64-65
Author(s):  
D. Van Dyck
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Direct Method ◽  
Real Space ◽  
Zone Axis ◽  
Phase Object ◽  
High Resolution Images ◽  
The Many ◽  
Analytical Expressions ◽  
Electron Wavefunction

The computation of the many beam dynamical electron diffraction amplitudes or high resolution images can only be done numerically by using rather sophisticated computer programs so that the physical insight in the diffraction progress is often lost. Furthermore, it is not likely that in this way the inverse problem can be solved exactly, i.e. to reconstruct the structure of the object from the knowledge of the wavefunction at its exit face, as is needed for a direct method [1]. For this purpose, analytical expressions for the electron wavefunction in real or reciprocal space are much more useful. However, the analytical expressions available at present are relatively poor approximations of the dynamical scattering which are only valid either for thin objects ((weak) phase object approximation, thick phase object approximation, kinematical theory) or when the number of beams is very limited (2 or 3). Both requirements are usually invalid for HREM of crystals. There is a need for an analytical expression of the dynamical electron wavefunction which applies for many beam diffraction in thicker crystals. It is well known that, when a crystal is viewed along a zone axis, i.e. parallel to the atom columns, the high resolution images often show a one-to-one correspondence with the configuration of columns provided the distance between the columns is large enough and the resolution of the instrument is sufficient. This is for instance the case in ordered alloys with a column structure [2,3]. From this, it can be suggested that, for a crystal viewed along a zone axis with sufficient separation between the columns, the wave function at the exit face does mainly depend on the projected structure, i.e. on the type of atom columns. Hence, the classical picture of electrons traversing the crystal as plane-like waves in the directions of the Bragg beams which historically stems from the X-ray diffraction picture, is in fact misleading.

scholarly journals High-density Néel-type magnetic skyrmion phase stabilized at high temperature

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Hee Young Kwon ◽  
Kyung Mee Song ◽  
Juyoung Jeong ◽  
Ah-Yeon Lee ◽  
Seung-Young Park ◽  
...  
Keyword(s):  
High Temperature ◽  
High Density ◽  
Low Density ◽  
Memory Devices ◽  
Magnetic Multilayer ◽  
Multilayer Systems ◽  
Micromagnetic Simulations ◽  
Transmission Electron ◽  
Ultrahigh Density ◽  
Lorentz Transmission Electron Microscopy

AbstractThe discovery of a thermally stable, high-density magnetic skyrmion phase is a key prerequisite for realizing practical skyrmionic memory devices. In contrast to the typical low-density Néel-type skyrmions observed in technologically viable multilayer systems, with Lorentz transmission electron microscopy, we report the discovery of a high-density homochiral Néel-type skyrmion phase in magnetic multilayer structures that is stable at high temperatures up to 733 K (≈460 °C). Micromagnetic simulations reveal that a high-density skyrmion phase can be stabilized at high temperature by deliberately tuning the magnetic anisotropy, magnetic field, and temperature. The existence of the high-density skyrmion phase in a magnetic multilayer system raises the possibility of incorporating chiral Néel-type skyrmions in ultrahigh-density spin memory devices. Moreover, the existence of this phase at high temperature shows its thermal stability, demonstrating the potential for skyrmion devices operating in thermally challenging modern electronic chips.

AB INITIO CALCULATIONS OF THE MAGNETO-OPTICAL RESPONSE OF LAYERED SYSTEMS

2002 ◽  
Vol 09 (02) ◽  
pp. 1135-1142
Author(s):  
HUBERT EBERT ◽  
ALEXANDER PERLOV ◽  
TILMANN HUHNE
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Optical Conductivity ◽  
Atomic Layer ◽  
Magnetic Multilayer ◽  
Layered Systems ◽  
Layer System ◽  
Multilayer Systems

The concept of the layer-resolved optical conductivity [Formula: see text] applied by means of a conventional band structure method is introduced. It is demonstrated that it allows a detailed discussion of the magneto-optical properties of magnetic multilayer systems. In particular it is found that the layer-projected optical conductivity [Formula: see text] of an atomic layer is influenced by only very few neighboring layers. This property can be exploited within the Baukasten principle, which aims to predict the magneto-optical properties of a complex layer system from the properties calculated for a closely related but simpler one.

Microstructure of periodic metallic magnetic multilayer systems

2017 ◽  
Vol 632 ◽  
pp. 79-87 ◽  
Author(s):  
Yu.M. Chesnokov ◽  
A.L. Vasiliev ◽  
G.V. Prutskov ◽  
E.M. Pashaev ◽  
I.A. Subbotin ◽  
...  
Keyword(s):  
Magnetic Multilayer ◽  
Multilayer Systems

scholarly journals Skyrmions in anisotropic magnetic fields: strain and defect driven dynamics

MRS Advances ◽  
2019 ◽  
Vol 4 (11-12) ◽  
pp. 643-650 ◽  
Author(s):  
Richard Brearton ◽  
Maciej W. Olszewski ◽  
Shilei Zhang ◽  
Morten R. Eskildsen ◽  
Charles Reichhardt ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Magnetic Field Gradient ◽  
Particle Model ◽  
Shear Forces ◽  
Magnetic Field Profile ◽  
Peak Broadening ◽  
Diffraction Patterns ◽  
The Stability ◽  
Magnetic Skyrmions

ABSTRACTMagnetic skyrmions are particle-like, topologically protected magnetization entities that are promising candidates for information carriers in racetrack-memory schemes. The transport of skyrmions in a shift-register-like fashion is crucial for their embodiment in practical devices. Recently, we demonstrated experimentally that chiral skyrmions in Cu2OSeO3 can be effectively manipulated by a magnetic field gradient, leading to a collective rotation of the skyrmion lattice with well-defined dynamics in a radial field gradient. Here, we employ a skyrmion particle model to numerically study the effects of resultant shear forces on the structure of the skyrmion lattice. We demonstrate that anisotropic peak broadening in experimentally observed diffraction patterns can be attributed to extended linear regions in the magnetic field profile. We show that topological (5-7) defects emerge to protect the six-fold symmetry of the lattice under the application of local shear forces, further enhancing the stability of proposed magnetic field driven devices.

Real-space technique applied to crystal structure determination from powder data

2002 ◽  
Vol 35 (2) ◽  
pp. 182-184 ◽  
Author(s):  
Angela Altomare ◽  
Corrado Cuocci ◽  
Carmelo Giacovazzo ◽  
Antonietta Guagliardi ◽  
Anna Grazia Giuseppina Moliterni ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structural Model ◽  
Real Space ◽  
Structure Parameters ◽  
Powder Diffraction Data ◽  
Structure Solution ◽  
Phase Extension ◽  
Space Technique ◽  
New Process

Real-space techniques used for phase extension and refinement in the modern direct procedures forab initiocrystal structure solution of proteins have been optimized for application to powder diffraction data. The new process has been implemented in a modified version ofEXPO[Altomareet al.(1999).J.Appl.Cryst.32, 339–340]. The method is able to supply a structural model that is more complete than that provided by the standardEXPOprogram. The model is then refinedviaa diagonal least-squares procedure, but only when the ratio of the number of observations to the number of structure parameters to be refined is larger than a given threshold.

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