scholarly journals Visibility and Apparent Size of Néel-Type Magnetic Skyrmions in Fresnel Defocus Images of Multilayer Films

2021 ◽  
pp. 1-10
Author(s):  
Thibaud Denneulin ◽  
Jan Caron ◽  
Knut Müller-Caspary ◽  
Olivier Boulle ◽  
András Kovács ◽  
...  
Keyword(s):  
Multilayer Structure ◽  
Room Temperature ◽  
Signal To Noise Ratio ◽  
Apparent Size ◽  
Magnetic Signal ◽  
Small Component ◽  
Transmission Electron ◽  
Out Of Plane ◽  
Lorentz Transmission Electron Microscopy ◽  
Magnetic Skyrmions

Multilayers that comprise thin films of heavy metals and ferromagnets have been shown to host Néel-type magnetic skyrmions at room temperature. Fresnel defocus imaging in Lorentz transmission electron microscopy is a widely used technique for recording magnetic information about skyrmions. However, the visibility of Néel-type skyrmions in Fresnel defocus images is typically low, both because only a small component of their magnetic field contributes to the signal and because of the presence of diffraction contrast from the polycrystalline multilayer structure. Here, we take advantage of the out-of-plane hysteresis in such samples to record background-subtracted Fresnel defocus images. We demonstrate an improvement in magnetic signal-to-noise ratio and spatial resolution by a factor of 3 for a (Pt/Co/NiFe)×5 multilayer. We also use simulated Fresnel defocus images of Néel-type magnetic skyrmions to understand the influence of defocus on apparent skyrmion size.

scholarly journals Dynamic transition of current-driven single-skyrmion motion in a room-temperature chiral-lattice magnet

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Licong Peng ◽  
Kosuke Karube ◽  
Yasujiro Taguchi ◽  
Naoto Nagaosa ◽  
Yoshinori Tokura ◽  
...  
Keyword(s):  
Electric Current ◽  
Motion Tracking ◽  
Room Temperature ◽  
Dynamic Transition ◽  
Spintronic Devices ◽  
Transmission Electron ◽  
Flow Motion ◽  
Lorentz Transmission Electron Microscopy ◽  
And Control

AbstractDriving and controlling single-skyrmion motion promises skyrmion-based spintronic applications. Recently progress has been made in moving skyrmionic bubbles in thin-film heterostructures and low-temperature chiral skyrmions in the FeGe helimagnet by electric current. Here, we report the motion tracking and control of a single skyrmion at room temperature in the chiral-lattice magnet Co9Zn9Mn2 using nanosecond current pulses. We have directly observed that the skyrmion Hall motion reverses its direction upon the reversal of skyrmion topological number using Lorentz transmission electron microscopy. Systematic measurements of the single-skyrmion trace as a function of electric current reveal a dynamic transition from the static pinned state to the linear flow motion via a creep event, in agreement with the theoretical prediction. We have clarified the role of skyrmion pinning and evaluated the intrinsic skyrmion Hall angle and the skyrmion velocity in the course of the dynamic transition. Our results pave a way to skyrmion applications in spintronic devices.

Lorentz transmission electron microscopy for magnetic skyrmions imaging

2019 ◽  
Vol 28 (8) ◽  
pp. 087503 ◽  
Author(s):  
Jin Tang ◽  
Lingyao Kong ◽  
Weiwei Wang ◽  
Haifeng Du ◽  
Mingliang Tian
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Lorentz Transmission Electron Microscopy ◽  
Magnetic Skyrmions

Characteristics of nanophase TiAl produced by inert gas condensation

1992 ◽  
Vol 7 (11) ◽  
pp. 2962-2970 ◽  
Author(s):  
H. Chang ◽  
C.J. Altstetter ◽  
R.S. Averback
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Large Fraction ◽  
Inert Gas ◽  
Full Density ◽  
Indentation Creep ◽  
Small Component ◽  
Grain Sizes ◽  
Transmission Electron ◽  
20 Nm

Nanophase TiAl, with grain sizes in the range of 10–20 nm, was synthesized by magnetron sputtering in an inert gas atmosphere and consolidated, in situ, under vacuum. The properties of the powders and sintered compacts were studied by transmission electron microscopy, scanning electron microscopy, calorimetry, Rutherford backscattering, and x-ray diffraction. Samples compacted at 1.0 GPa at room temperature had a large fraction of amorphous phase, while samples compacted at the same pressure and 250 °C were predominantly the equilibrium γ phase. An enthalpy change of 22 kJ/g-atom was measured during a DSC scan over the temperature range 125–450 °C, which is approximately the range over which crystallization occurs. Nearly full density could be achieved by sintering at 450 °C without significant, concomitant grain growth. The Vickers microhardness of these samples at room temperature and at −30 °C revealed an inverse Hall–Petch relationship at small grain sizes, 10–30 nm, and the usual Hall–Petch behavior at larger grain sizes. A small component of indentation creep was also observed. The maximum hardness is 4 times larger than that of a cast TiAl specimen of the same composition. The Vickers hardness was also observed to decrease rapidly with temperature above 200 °C.

scholarly journals Creation of skyrmions in van der Waals ferromagnet Fe3GeTe2 on (Co/Pd)n superlattice

2020 ◽  
Vol 6 (36) ◽  
pp. eabb5157
Author(s):  
M. Yang ◽  
Q. Li ◽  
R. V. Chopdekar ◽  
R. Dhall ◽  
J. Turner ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Van Der Waals ◽  
Magnetic Coupling ◽  
Transmission Electron ◽  
Host Materials ◽  
Lorentz Transmission Electron Microscopy ◽  
Magnetic Skyrmions ◽  
Nanoscale Features ◽  
Photoemission Electron ◽  
Moriya Interaction

Magnetic skyrmions are topological spin textures, which usually exist in noncentrosymmetric materials where the crystal inversion symmetry breaking generates the so-called Dzyaloshinskii-Moriya interaction. This requirement unfortunately excludes many important magnetic material classes, including the recently found two-dimensional van der Waals (vdW) magnetic materials, which offer unprecedented opportunities for spintronic technology. Using photoemission electron microscopy and Lorentz transmission electron microscopy, we investigated and stabilized Néel-type magnetic skyrmion in vdW ferromagnetic Fe3GeTe2 on top of (Co/Pd)n in which the Fe3GeTe2 has a centrosymmetric crystal structure. We demonstrate that the magnetic coupling between the Fe3GeTe2 and the (Co/Pd)n could create skyrmions in Fe3GeTe2 without the need of an external magnetic field. Our results open exciting opportunities in spintronic research and the engineering of topologically protected nanoscale features by expanding the group of skyrmion host materials to include these previously unknown vdW magnets.

Off-Axis Electron Holography of Self-Assembled Co Nanoparticle Rings

2007 ◽  
Vol 1026 ◽  
Author(s):  
Takeshi Kasama ◽  
Rafal E. Dunin-Borkowski ◽  
Michael R. Scheinfein ◽  
Steven L. Tripp ◽  
Jie Liu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Phase Image ◽  
Objective Lens ◽  
Electron Holography ◽  
Zero Field ◽  
Transmission Electron ◽  
Out Of Plane ◽  
Self Assembled ◽  
Magnetic States

AbstractWe use off-axis electron holography in the transmission electron microscope (TEM) to study magnetic flux closure (FC) states in self-assembled nanoparticle rings that each contain between five and eleven 25-nm-diameter Co crystals. Electron holograms are acquired at room temperature in zero-field conditions after applying chosen magnetic fields to the samples in situ in the TEM by partially exciting the conventional microscope objective lens. Mean inner potential contributions to the phase shift are determined by turning the samples over, and subsequently subtracted from each recorded phase image to obtain magnetic induction maps. Our results show that most nanoparticle rings form FC remanent magnetic states, and occasionally onion-like states. Although the chiralities (the directions of magnetization) of the FC states are determined by the shapes, sizes and positions of the constituent nanoparticles, reproducible magnetization reversal of each ring can be achieved by using an out-of-plane magnetic field of between 1600 and 2500 Oe.

Indentation of AlN/CrN Multilayers from Room Temperature to 400 °C

2005 ◽  
Vol 492-493 ◽  
pp. 335-340 ◽  
Author(s):  
F. Giuliani ◽  
A. Goruppa ◽  
S.J. Lloyd ◽  
Dennis Teer ◽  
W.J. Clegg
Keyword(s):  
Multilayer Structure ◽  
Room Temperature ◽  
Deformation Behaviour ◽  
Dislocation Motion ◽  
Effect Of Temperature ◽  
Columnar Microstructure ◽  
Cross Sectional ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

Observations elsewhere have shown that multilayer structures with layers ~10 nm thick can be harder than monolithic ones. Here we see whether these effects can be observed at high temperatures and investigate the effect of temperature on the manner of deformation. The hardness of an AlN/CrN multilayer structure with a range of wavelengths from 6-200 nm has been measured at temperatures from room temperature to 400 oC. The changes in hardness have been related to the deformation behaviour observed by cross-sectional transmission electron microscopy and atomic force microscopy. These observations suggest that the mechanical properties of the coatings are dominated by the refinement in the columnar microstructure rather than directly by an effect of the layer interfaces on dislocation motion.

scholarly journals Evolution and competition between chiral spin textures in nanostripes with D2d symmetry

2020 ◽  
Vol 6 (49) ◽  
pp. eabc0723
Author(s):  
Jagannath Jena ◽  
Börge Göbel ◽  
Vivek Kumar ◽  
Ingrid Mertig ◽  
Claudia Felser ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Applied Magnetic Field ◽  
Room Temperature ◽  
Memory Storage ◽  
Heusler Compound ◽  
Storage Devices ◽  
Transmission Electron ◽  
Lorentz Transmission Electron Microscopy

Chiral spin textures are of considerable interest for applications in spintronics. It has recently been shown that magnetic materials with D2d symmetry can sustain several distinct spin textures. Here, we show, using Lorentz transmission electron microscopy, that single and double chains of antiskyrmions can be generated at room temperature in nanostripes less than 0.5 μm in width formed from the D2d Heusler compound Mn1.4Pt0.9Pd0.1Sn. Typically, truncated helical spin textures are formed in low magnetic fields, whose edges are terminated by half antiskyrmions. These evolve into chains of antiskyrmions with increasing magnetic field. Single chains of these objects are located in the middle of the nanostripes even when the stripes are much wider than the antiskyrmions. Moreover, the chains can even include elliptical Bloch skyrmions depending on details of the applied magnetic field history. These findings make D2d materials special and highly interesting for applications such as magnetic racetrack memory storage devices.

Structural Characterisation of Fe-Cu Multilayers of Differing Fe Thicknesses Using Transmission Electron Microscopy

1995 ◽  
Vol 382 ◽  
Author(s):  
S. J. Lloyd ◽  
R. E. Somekh ◽  
W. M. Stobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Elasticity Theory ◽  
Multilayer Structure ◽  
High Resolution Electron Microscopy ◽  
Structural Characterisation ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Out Of Plane

ABSTRACTIn-plane and out-of-plane lattice parameters were measured in a series of coherent Fe-Cu multilayers using non-axial high resolution electron microscopy (HREM). The results indicate that the multilayers are tetragonally distorted with the magnitude of the distortion varying with the thickness of the Fe component. These distortions preclude an understanding of the multilayer structure in terms of conventional elasticity theory. The breakdown of epitaxy for thicker Fe layers was also investigated and it was found that the b.c.c. Fe grew with [110] parallel to [001] of the coherent f.c.c. multilayer.

scholarly journals Microwave resonances of magnetic skyrmions in thin film multilayers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Bhartendu Satywali ◽  
Volodymyr P. Kravchuk ◽  
Liqing Pan ◽  
M. Raju ◽  
Shikun He ◽  
...  
Keyword(s):  
Room Temperature ◽  
Dipolar Coupling ◽  
Dynamic Properties ◽  
Ferromagnetic Layer ◽  
Layer Spacing ◽  
Micromagnetic Simulations ◽  
Out Of Plane ◽  
New Material ◽  
Magnetic Skyrmions ◽  
Spin Resonances

AbstractNon-collinear magnets exhibit a rich array of dynamic properties at microwave frequencies. They can host nanometre-scale topological textures known as skyrmions, whose spin resonances are expected to be highly sensitive to their local magnetic environment. Here, we report a magnetic resonance study of an [Ir/Fe/Co/Pt] multilayer hosting Néel skyrmions at room temperature. Experiments reveal two distinct resonances of the skyrmion phase during in-plane ac excitation, with frequencies between 6–12 GHz. Complementary micromagnetic simulations indicate that the net magnetic dipole moment rotates counterclockwise (CCW) during both resonances. The magnon probability distribution for the lower-frequency resonance is localised within isolated skyrmions, unlike the higher-frequency mode which principally originates from areas between skyrmions. However, the properties of both modes depend sensitively on the out-of-plane dipolar coupling, which is controlled via the ferromagnetic layer spacing in our heterostructures. The gyrations of stable isolated skyrmions reported in this room temperature study encourage the development of new material platforms and applications based on skyrmion resonances. Moreover, our material architecture enables the resonance spectra to be tuned, thus extending the functionality of such applications over a broadband frequency range.

scholarly journals Filming the formation and fluctuation of skyrmion domains by cryo-Lorentz transmission electron microscopy

2015 ◽  
Vol 112 (46) ◽  
pp. 14212-14217 ◽  
Author(s):  
Jayaraman Rajeswari ◽  
Ping Huang ◽  
Giulia Fulvia Mancini ◽  
Yoshie Murooka ◽  
Tatiana Latychevskaia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Long Range ◽  
Temporal Fluctuation ◽  
Storage Devices ◽  
Transmission Electron ◽  
Lorentz Transmission Electron Microscopy ◽  
Magnetic Skyrmions ◽  
External Stimuli ◽  
Nanometric Size

Magnetic skyrmions are promising candidates as information carriers in logic or storage devices thanks to their robustness, guaranteed by the topological protection, and their nanometric size. Currently, little is known about the influence of parameters such as disorder, defects, or external stimuli on the long-range spatial distribution and temporal evolution of the skyrmion lattice. Here, using a large (7.3×7.3 μm2) single-crystal nanoslice (150 nm thick) of Cu2OSeO3, we image up to 70,000 skyrmions by means of cryo-Lorentz transmission electron microscopy as a function of the applied magnetic field. The emergence of the skyrmion lattice from the helimagnetic phase is monitored, revealing the existence of a glassy skyrmion phase at the phase transition field, where patches of an octagonally distorted skyrmion lattice are also discovered. In the skyrmion phase, dislocations are shown to cause the emergence and switching between domains with different lattice orientations, and the temporal fluctuation of these domains is filmed. These results demonstrate the importance of direct-space and real-time imaging of skyrmion domains for addressing both their long-range topology and stability.

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