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.

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.

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.

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.

Initial Magnetization Behavior of Rapidly Quenched Neodymium-Iron-Boron Magnets

1987 ◽  
Vol 96 ◽  
Author(s):  
F. E. Pinkerton
Keyword(s):  
Grain Size ◽  
Domain Wall ◽  
Domain Walls ◽  
Initial Permeability ◽  
Single Domain ◽  
Initial Magnetization ◽  
Domain Wall Pinning ◽  
Rapidly Solidified ◽  
Coercivity Mechanism ◽  
Magnetization Behavior

ABSTRACTInitial magnetization and demagnetization data are reported for three forms of rapidly solidified Nd-Fe-B permanent magnet materials: melt-spun ribbons, hot pressed magnets, and die upset magnets. In all three materials the results are consistent with domain wall pinning at grain boundary phases as the coercivity mechanism. Optimally quenched ribbons are comprised of randomly oriented single domain Nd2Fe14B grains, and both initial magnetization and demagnetization are controlled by strong domain wall pinning at grain boundaries. Maximum coercivity is accompanied by a low initial permeability. Coercivity is reduced in overquenched ribbons by partial retention of a magnetically soft amorphous or very finely crystalline microstructure. Coercivity decreases in underquenched ribbons because wall pinning weakens as the grain size increases above optimum. Correlation of magnetization and demagnetization behaviors suggests that maximum coercivity in ribbons is largely determined by the resistance to domain wall formation in grains smaller than the single domain particle limit. Grain size is much less important in the aligned die upset magnets. Domain walls are initially free to move until they become strongly pinned at grain edges, and complete magnetization requires an applied field greater than the coercive field. Hot pressed magnets show a mixture of ribbon and die upset behavior.

Application of electron holography to ferroelectric study

1993 ◽  
Vol 51 ◽  
pp. 1092-1093
Author(s):  
X. Zhang ◽  
D. C. Joy ◽  
L. F. Allard ◽  
T. A. Nolan
Keyword(s):  
Domain Wall ◽  
Domain Walls ◽  
Ferroelectric Domain ◽  
Electron Holography ◽  
Local Domain ◽  
Holographic Method ◽  
Wall Area ◽  
Weak Phase ◽  
Wall Structures ◽  
Essential Input

With the development of FE TEM, electron holography becomes a reality to materials scientists, which opens a new window for materials study. Weak phase objects, such as a thin transparent specimen or an electric or a magnetic field, which have little or no effect on the intensity of the transmitted wave, can readily be observed via holography because of the phase shift that they produce. Application of the electron holographic method has been extended to the study of ferroelectric domain wall structures. This work presents the most recent results in this area.Polarization gradients within domain walls are extremely important for the understanding of the extrinsic elastio-dielectric properties of ferroelectrics. Electron holographic studies of the local domain wall profiles provide essential input parameters for phenomenological theories of domain structure and of the macroscopic properties derived from the theories. Figure 1(a) is an electron hologram of the ferroelectric (BaTiO3) 90° domain wall area.

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.

NANO CHARACTERIZATION OF MATERIALS

2008 ◽  
Vol 18 (04) ◽  
pp. 861-878 ◽  
Author(s):  
DIETER K. SCHRODER
Keyword(s):  
Atom Probe ◽  
Electron Holography ◽  
Magnetic Exchange ◽  
Force Microscopy ◽  
Transmission Electron ◽  
Long Time ◽  
Ion Microscopy ◽  
Characterization Of Materials ◽  
User Friendly

Material characterization is challenged by continuously decreasing device dimensions placing significant demands on characterization instruments and measurement interpretation. Numerous techniques exist and a few are highlighted here. Some of these have existed for a long time, while others have only emerged from the laboratory recently. Generally they are more user-friendly and have reasonable turn-around times. The trend in many techniques is clearly toward characterization of smaller dimensions. Among the myriad of characterization techniques in use today, I will discuss recent advances in transmission electron microscopy (TEM), electron holography, magnetic exchange force microscopy (MExFM), atom probe ion field ion microscopy, and X-ray tomography. They have made significant advances in the last few years and in some cases have produced very impressive results. For example, TEM is now able to generate images with 0.05 nm resolution, allowing display of individual atoms. MExFM in conjunction with magnetic fields has demonstrated vertical resolution of 0.0015 nm. Helium ion microscopy is also highlighted because it contributes a new application of ion beams, which had been largely the domain of Rutherford backscattering. Progress in developing further advances in nm dimensional characterization will, no doubt, continue to satisfy the demand for such measurements in the future.

scholarly journals In-Situ Electrical Biasing of Electrically Connected TEM Lamellae with Embedded Nanodevices

2021 ◽  
Author(s):  
Maria Brodovoi ◽  
Kilian Gruel ◽  
Lucas Chapuis ◽  
Aurélien Masseboeuf ◽  
Cécile Marcelot ◽  
...  
Keyword(s):  
Electric Fields ◽  
High Performance ◽  
Low Cost ◽  
Electron Holography ◽  
Device Architecture ◽  
Quantitative Studies ◽  
Transmission Electron ◽  
Microelectronics Industry

Abstract In response to a continually rising demand for high performance and low-cost devices, and equally driven by competitivity, the microelectronics industry excels in meeting innovation challenges and further miniaturizing products. However, device shrinkage and the increasing complexity of device architecture require local quantitative studies. In this paper, we demonstrate with a case study on a nanocapacitor, the capability of transmission electron microscopy in electron holography mode to be a unique in-situ technique for mapping electric fields and charge distributions on a single device.

Mechanisms of Pinning of Domain Walls in Nanowires

2010 ◽  
Vol 168-169 ◽  
pp. 230-233 ◽  
Author(s):  
A.A. Ivanov ◽  
V.A. Orlov ◽  
N.N. Podolsky
Keyword(s):  
Numerical Methods ◽  
Domain Wall ◽  
Coercive Force ◽  
Magnetization Curve ◽  
Domain Walls ◽  
Magnetostatic Interaction ◽  
Crystallographic Anisotropy ◽  
Domain Wall Pinning ◽  
Force Profile ◽  
Pinning Of Domain Walls

Analytical and numerical methods are used to study the process of motion of domain walls in an individual nanowire consisting of ferromagnetic crystallites with a chaotic crystallographic anisotropy. The influence of magnetostatic interaction on the motion is considered. The force profile of the domain wall pinning, caused by stochastic crystallographic anisotropy, is examined. The magnetization curve is analytically constructed and the coercive force is calculated. The Barkhausen jumps of domain walls are investigated. The result is verified by numerically modeling.

scholarly journals FEI Helios NanoLab 460F1 FIB-SEM

2016 ◽  
Vol 2 ◽  
Author(s):  
Max Kruth ◽  
Doris Meertens ◽  
Karsten Tillmann
Keyword(s):  
High Performance ◽  
Process Development ◽  
Atom Probe ◽  
Inert Gas ◽  
Gas Transfer ◽  
Contrast Imaging ◽  
Dual Beam ◽  
Transmission Electron ◽  
Material Contrast ◽  
Technical Specifications

The FEI Helios NanoLab 460F1 is a highly advanced dual beam FIB-SEM platform for imaging and analytical measurements, transmission electron microscopy (TEM) sample and atom probe (AP) needle preparation, process development and process control. For these purposes, the FEI Helios NanoLab 460F1 combines an ElstarTM UC technology electron column for high-resolution and high material contrast imaging with the high-performance TomahawkTM ion column for fast and precise sample preparation. The FEI Helios NanoLab 460F1 is additionally equipped with the MultiChemTM gas delivery system, an EasyLiftTM nanomanipulator, a cooling trap, an inert gas transfer (IGT) holder loadlock, a quick loader, a FlipStage 3TM, an EDX-System and an STEM III detector. This instrument is one of the few dual beam systems which combine an IGT holder loadlock with a FlipStage 3+TM EasyLiftTM nanomanipulator. Typical examples of use and technical specifications for the instrument are given below.

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