scholarly journals Observation of domain wall bimerons in chiral magnets

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tomoki Nagase ◽  
Yeong-Gi So ◽  
Hayata Yasui ◽  
Takafumi Ishida ◽  
Hiroyuki K. Yoshida ◽  
...  
Keyword(s):  
Domain Wall ◽  
Magnetic Anisotropy ◽  
Domain Walls ◽  
Topological Defects ◽  
Dipolar Interaction ◽  
Micromagnetic Simulations ◽  
Localized State ◽  
Transmission Electron ◽  
Wide Range ◽  
Lorentz Transmission Electron Microscopy

AbstractTopological defects embedded in or combined with domain walls have been proposed in various systems, some of which are referred to as domain wall skyrmions or domain wall bimerons. However, the experimental observation of such topological defects remains an ongoing challenge. Here, using Lorentz transmission electron microscopy, we report the experimental discovery of domain wall bimerons in chiral magnet Co-Zn-Mn(110) thin films. By applying a magnetic field, multidomain structures develop, and simultaneously, chained or isolated bimerons arise as the localized state between the domains with the opposite in-plane components of net magnetization. The multidomain formation is attributed to magnetic anisotropy and dipolar interaction, and domain wall bimerons are stabilized by the Dzyaloshinskii-Moriya interaction. In addition, micromagnetic simulations show that domain wall bimerons appear for a wide range of conditions in chiral magnets with cubic magnetic anisotropy. Our results promote further study in various fields of physics.

scholarly journals Dipolar-stabilized first and second-order antiskyrmions in ferrimagnetic multilayers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Michael Heigl ◽  
Sabri Koraltan ◽  
Marek Vaňatka ◽  
Robert Kraft ◽  
Claas Abert ◽  
...  
Keyword(s):  
Dipole Interaction ◽  
Dipolar Interaction ◽  
Second Order ◽  
Microscopy Imaging ◽  
Micromagnetic Simulations ◽  
Spintronic Devices ◽  
Transmission Electron ◽  
Wide Range ◽  
Lorentz Transmission Electron Microscopy

AbstractSkyrmions and antiskyrmions are topologically protected spin structures with opposite vorticities. Particularly in coexisting phases, these two types of magnetic quasi-particles may show fascinating physics and potential for spintronic devices. While skyrmions are observed in a wide range of materials, until now antiskyrmions were exclusive to materials with D2d symmetry. In this work, we show first and second-order antiskyrmions stabilized by magnetic dipole–dipole interaction in Fe/Gd-based multilayers. We modify the magnetic properties of the multilayers by Ir insertion layers. Using Lorentz transmission electron microscopy imaging, we observe coexisting antiskyrmions, Bloch skyrmions, and type-2 bubbles and determine the range of material properties and magnetic fields where the different spin objects form and dissipate. We perform micromagnetic simulations to obtain more insight into the studied system and conclude that the reduction of saturation magnetization and uniaxial magnetic anisotropy leads to the existence of this zoo of different spin objects and that they are primarily stabilized by dipolar interaction.

scholarly journals Intrinsic stability of magnetic anti-skyrmions in the tetragonal inverse Heusler compound Mn1.4Pt0.9Pd0.1Sn

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Rana Saha ◽  
Abhay K. Srivastava ◽  
Tianping Ma ◽  
Jagannath Jena ◽  
Peter Werner ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Current Interest ◽  
Heusler Compound ◽  
Micromagnetic Simulations ◽  
Intrinsic Stability ◽  
Transmission Electron ◽  
Wide Range ◽  
Topological Characteristics ◽  
Lorentz Transmission Electron Microscopy

AbstractMagnetic anti-skyrmions are one of several chiral spin textures that are of great current interest both for their topological characteristics and potential spintronic applications. Anti-skyrmions were recently observed in the inverse tetragonal Heusler material Mn1.4Pt0.9Pd0.1Sn. Here we show, using Lorentz transmission electron microscopy, that anti-skyrmions are found over a wide range of temperature and magnetic fields in wedged lamellae formed from single crystals of Mn1.4Pt0.9Pd0.1Sn for thicknesses ranging up to ~250 nm. The temperature-field stability window of the anti-skyrmions varies little with thickness. Using micromagnetic simulations we show that this intrinsic stability of anti-skyrmions can be accounted for by the symmetry of the crystal lattice which is imposed on that of the Dzyaloshinskii-Moriya exchange interaction. These distinctive behaviors of anti-skyrmions makes them particularly attractive for spintronic applications.

scholarly journals Unconventional magnetization textures and domain-wall pinning in Sm–Co magnets

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Leonardo Pierobon ◽  
András Kovács ◽  
Robin E. Schäublin ◽  
Stephan S. A. Gerstl ◽  
Jan Caron ◽  
...  
Keyword(s):  
Domain Wall ◽  
High Performance ◽  
Domain Walls ◽  
Atom Probe ◽  
Electron Holography ◽  
Micromagnetic Simulations ◽  
Transmission Electron ◽  
Domain Wall Pinning ◽  
Weak Points ◽  
Magnetic Hardness

AbstractSome of the best-performing high-temperature magnets are Sm–Co-based alloys with a microstructure that comprises an $$\hbox {Sm}_2\hbox {Co}_{17}$$ Sm 2 Co 17 matrix and magnetically hard $$\hbox {SmCo}_5$$ SmCo 5 cell walls. This generates a dense domain-wall-pinning network that endows the material with remarkable magnetic hardness. A precise understanding of the coupling between magnetism and microstructure is essential for enhancing the performance of Sm–Co magnets, but experiments and theory have not yet converged to a unified model. Here, transmission electron microscopy, atom probe tomography, and nanometer-resolution off-axis electron holography have been combined with micromagnetic simulations to reveal that the magnetization state in Sm–Co magnets results from curling instabilities and domain-wall pinning effects at the intersections of phases with different magnetic hardness. Additionally, this study has found that topologically non-trivial magnetic domains separated by a complex network of domain walls play a key role in the magnetic state by acting as nucleation sites for magnetization reversal. These findings reveal previously hidden aspects of magnetism in Sm–Co magnets and, by identifying weak points in the microstructure, provide guidelines for improving these high-performance magnetic materials.

The direct determination of magnetic domain wall profiles using a split detector STEM

1978 ◽  
Vol 36 (1) ◽  
pp. 466-467
Author(s):  
J.N. Chapman ◽  
P.E. Batson ◽  
E.M. Waddell ◽  
R.P. Ferrier
Keyword(s):  
Electron Microscope ◽  
Domain Wall ◽  
Transmission Electron Microscope ◽  
Domain Walls ◽  
Photographic Plate ◽  
Magnetic Domain ◽  
Direct Determination ◽  
Quantitative Information ◽  
Scanning Transmission Electron Microscope ◽  
Transmission Electron

By far the most commonly used mode of Lorentz microscopy in the examination of ferromagnetic thin films is the Fresnel or defocus mode. Use of this mode in the conventional transmission electron microscope (CTEM) is straightforward and immediately reveals the existence of all domain walls present. However, if such quantitative information as the domain wall profile is required, the technique suffers from several disadvantages. These include the inability to directly observe fine image detail on the viewing screen because of the stringent illumination coherence requirements, the difficulty of accurately translating part of a photographic plate into quantitative electron intensity data, and, perhaps most severe, the difficulty of interpreting this data. One solution to the first-named problem is to use a CTEM equipped with a field emission gun (FEG) (Inoue, Harada and Yamamoto 1977) whilst a second is to use the equivalent mode of image formation in a scanning transmission electron microscope (STEM) (Chapman, Batson, Waddell, Ferrier and Craven 1977), a technique which largely overcomes the second-named problem as well.

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.

MAGNETIC RACE-TRACK — A NOVEL STORAGE CLASS SPINTRONIC MEMORY

2008 ◽  
Vol 22 (01n02) ◽  
pp. 117-118 ◽  
Author(s):  
STUART PARKIN
Keyword(s):  
Domain Wall ◽  
Tunnel Junction ◽  
Domain Walls ◽  
Magnetic Tunnel Junction ◽  
Domain Wall Motion ◽  
Wall Structure ◽  
Micromagnetic Simulations ◽  
Confining Potential ◽  
Current Pulses ◽  
Race Track

A proposal for a novel storage-class memory is described in which magnetic domains are used to store information in a "magnetic race-track".1 The magnetic race-track shift register storage memory promises a solid state memory with storage capacities and cost rivaling that of magnetic disk drives but with much improved performance and reliability. The magnetic race track is comprised of tall columns of magnetic material arranged perpendicularly to the surface of a silicon wafer. The domains are moved up and down the race-track by nanosecond long current pulses using the phenomenon of spin momentum transfer. The domain walls in the magnetic race-track are read using magnetic tunnel junction magnetoresistive sensing devices arranged in the silicon substrate. Recent progress in developing magnetic tunnel junction devices with giant tunneling magnetoresistance exceeding 350% at room temperature will be mentioned.2 Experiments exploring the current induced motion and depinning of domain walls in magnetic nano-wires with artificial pinning sites will be discussed. The domain wall structure, whether vortex or transverse, and the magnitude of the pinning potential is shown to have surprisingly little effect on the current driven dynamics of the domain wall motion.3 By contrast the motion of DWs under nanosecond long current pulses is surprisingly sensitive to their length.4 In particular, we find that the probability of dislodging a DW, confined to a pinning site in a permalloy nanowire, oscillates with the length of the current pulse, with a period of just a few nanoseconds. Using an analytical model and micromagnetic simulations we show that this behaviour is connected to a current induced oscillatory motion of the DW. The period is determined by the DW mass and the curvature of the confining potential. When the current is turned off during phases of the DW motion when the DW has enough momentum, there is a boomerang effect that can drive the DW out of the confining potential in the opposite direction to the flow of spin angular momentum. Note from Publisher: This article contains the abstract only.

scholarly journals Stiffness in vortex—like structures due to chirality-domains within a coupled helical rare-earth superlattice

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Amitesh Paul
Keyword(s):  
Rare Earth ◽  
Domain Walls ◽  
Topological Defects ◽  
Magnetic Ordering ◽  
Direct Consequence ◽  
Magnetic Vortex ◽  
Range Magnetic Order ◽  
Wide Range ◽  
Out Of Plane ◽  
The Stability

Abstract Vortex domain walls poses chirality or ‘handedness’ which can be exploited to act as memory units by changing their polarity with electric field or driving/manupulating the vortex itself by electric currents in multiferroics. Recently, domain walls formed by one dimensional array of vortex—like structures have been theoretically predicted to exist in disordered rare-earth helical magnets with topological defects. Here, in this report, we have used a combination of two rare-earth metals, e.g."Equation missing" superlattice that leads to long range magnetic order despite their competing anisotropies along the out-of-plane (Er) and in-plane (Tb) directions. Probing the vertically correlated magnetic structures by off-specular polarized neutron scattering we confirm the existence of such magnetic vortex—like domains associated with magnetic helical ordering within the Er layers. The vortex—like structures are predicted to have opposite chirality, side—by—side and are fairly unaffected by the introduction of magnetic ordering between the interfacial Tb layers and also with the increase in magnetic field which is a direct consequence of screening of the vorticity in the system due to a helical background. Overall, the stability of these vortices over a wide range of temperatures, fields and interfacial coupling, opens up the opportunity for fundamental chiral spintronics in unconventional systems.

Physical Properties inside Domain Walls

Domain Walls ◽  
2020 ◽  
pp. 1-22
Author(s):  
G. Catalan ◽  
N. Domingo
Keyword(s):  
Domain Wall ◽  
Physical Properties ◽  
Domain Walls ◽  
Mechanical Response ◽  
Bulk Material ◽  
Wall Properties ◽  
Transmission Electron ◽  
Basic Physics ◽  
Recent Developments ◽  
The Individual

This chapter explains that the field of domain wall (DW) nanoelectronics is predicated on the premise that the distinct physical properties of domain walls offer new conceptual possibilities for devices. It first deals with basic physics of domain wall properties, and in particular the cross-coupling that allows domain walls to display properties and order parameters different from those of the parent bulk material. The chapter then turns to scanning probe techniques for measuring some of these domain wall properties, and specifically atomic force microscopy (AFM). Together with transmission electron microscopy, AFM is one of the most important tools currently available to probe and manipulate the individual position and physical properties of domain walls. Finally, the chapter focuses on two recent developments that allow investigating hitherto overlooked properties of domain walls: their magnetotransport and their mechanical response.

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