Direct Imaging of Chiral Domain Walls and Néel‐Type Skyrmionium in Ferrimagnetic Alloys

Seng, Boris; Schönke, Daniel; Yeste, Javier; Reeve, Robert M.; Kerber, Nico; Lacour, Daniel; Bello, Jean-Loïs; Bergeard, Nicolas; Kammerbauer, Fabian; Bhukta, Mona Minakshee Manjaree; Ferté, Tom; Boeglin, C.; Radu, F.; Abrudan, R.; Kachel, T.; Mangin, Stéphane; Hehn, Michel; Kläui, Mathias

doi:10.1002/adfm.202102307

Cited by 23 publications

(20 citation statements)

References 52 publications

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“…(see Figure S4, Supporting Information.) Figure 1b exhibits an example of a skyrmionium state [26,59] (corresponding LTEM images of skyrmionium states in Figure S3, Supporting Information). These states have previously proved challenging to isolate, and have often been observed in confined geometries where they have been termed target skyrmions.…”

Section: Composite Skyrmion Observationmentioning

confidence: 99%

Seeding and Emergence of Composite Skyrmions in a van der Waals Magnet

et al. 2023

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Topological charge plays a significant role in a range of physical systems. In particular, observations of real‐space topological objects in magnetic materials have been largely limited to skyrmions – states with a unitary topological charge. Recently, more exotic states with varying topology, such as antiskyrmions, merons, or bimerons and 3D states such as skyrmion strings, chiral bobbers, and hopfions, have been experimentally reported. Along these lines, the realization of states with higher‐order topology has the potential to open new avenues of research in topological magnetism and its spintronic applications. Here, real‐space imaging of such spin textures, including skyrmion, skyrmionium, skyrmion bag, and skyrmion sack states, observed in exfoliated flakes of the van der Waals magnet Fe3−xGeTe2 (FGT) is reported. These composite skyrmions may emerge from seeded, loop‐like states condensed into the stripe domain structure, demonstrating the possibility to realize spin textures with arbitrary integer topological charge within exfoliated flakes of 2D magnets. The general nature of the formation mechanism motivates the search for composite skyrmion states in both well‐known and new magnetic materials, which may yet reveal an even richer spectrum of higher‐order topological objects.

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Section: Composite Skyrmion Observationmentioning

confidence: 99%

Seeding and Emergence of Composite Skyrmions in a van der Waals Magnet

et al. 2023

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“…This shows the complexity of the magneto-ionic mechanisms and that interface engineering can play a key role in the design of optimised materials and devices for magneto-ionics. The insertion of dusting layers in nanostructured magnetic stacks is an efficient strategy used in spintronics materials development to fine tune properties such as tunneling magnetoresistance (TMR), perpendicular magnetic anisotropy (PMA) and DMI [12][13][14] . On the other hand, devices containing CoFeB/MgO interfaces are of great technological relevance, since MgO allows for high tunneling magneto-resistance and PMA 15 .…”

mentioning

confidence: 99%

Controlling interface anisotropy in CoFeB/MgO/HfO2 using dusting layers and magneto-ionic gating

Bhatnagar-Schöffmann

Kovács

Pachat

et al. 2023

Applied Physics Letters

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In this work, we present the magneto-ionic response to ionic liquid gating in Ta/CoFeB/MgO/HfO2 stacks, where heavy metal dusting layers of Ta, W, and Pt are inserted at the Ta/CoFeB and CoFeB/MgO interfaces. Dusting layers of W inserted at the Ta/CoFeB interface increase perpendicular magnetic anisotropy (PMA) by more than 50%, while no significant changes are seen for Pt. In these samples, gating cannot break the PMA seeded at the CoFeB/MgO interface, only relatively small changes in the coercivity can be induced, about 20% for Ta and Pt and 6% for W. At the CoFeB/MgO interface, a significant quenching of the magnetization is seen when W and Ta dusting layers are inserted, which remains unchanged after gating, suggesting a critical deterioration of the CoFeB. In contrast, Pt dusting layers result in an in-plane anisotropy that can be reversibly converted to PMA through magneto-ionic gating while preserving the polycrystalline structure of the MgO layer. This shows that dusting layers can be effectively used not only to engineer magnetic properties in multilayers but also to strongly modify their magneto-ionic performance.

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“…When a skyrmion moves along the nanotrack driven by the electric current, the Magnus force stemming from the spin precession causes its movement along a trajectory at an angle to the direction of the applied current, which is the well-known skyrmion Hall effect (SkHE). , As for other types of magnetic quasiparticles, a similar deflection angle related to their topological charge can also be obtained. , The SkHE is usually deemed harmful to skyrmionic devices because it affects the device performance and robustness, leading to the annihilation of skyrmions at the boundaries . Several strategies are thus proposed to suppress the SkHE, such as stabilizing skyrmions in ferrimagnetic material systems − and synthetic antiferromagnets (SAF) structures, adding high- K materials at boundaries, , modifying the racetrack structure, and moderating the spin Hall angle . However, in this work, we take a different approach to exploit the SkHE rather than circumvent it, to enable device implementation with multiple information carriers.…”

Section: Resultsmentioning

confidence: 99%

Voltage-Controlled Skyrmionic Interconnect with Multiple Magnetic Information Carriers

Chen

Liu

2022

ACS Appl. Mater. Interfaces

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Magnetic skyrmions have been in the spotlight since they were observed in technologically relevant systems at room temperature. More recently, there has been increasing interest in additional quasiparticles that may exist as stable/metastable spin textures in magnets, such as the skyrmionium and the antiskyrmionite (i.e., a skyrmion bag with two skyrmions inside) that have distinct topological characteristics. The next challenge and opportunity, at the same time, is to investigate the use of multiple magnetic quasiparticles as information carriers in a single device for next-generation nanocomputing. In this paper, we propose a spintronic interconnect device where multiple sequences of information signals are encoded and transmitted simultaneously by skyrmions, skyrmioniums, and antiskyrmionites. The proposed spintronic interconnect device can be pipelined via voltage-controlled magnetic anisotropy (VCMA) gated synchronizers that behave as intermediate registers. We demonstrate theoretically that the interconnect throughput and transmission energy can be effectively tuned by the VCMA gate voltage and appropriate electric current pulses. By carefully adjusting the device structure characteristics, our spintronic interconnect device exhibits comparable energy efficiency with copper interconnects in mainstream CMOS technologies. This study provides fresh insight into the possibilities of skyrmionic devices in future spintronic applications.

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Direct Imaging of Chiral Domain Walls and Néel‐Type Skyrmionium in Ferrimagnetic Alloys

Cited by 23 publications

References 52 publications

Seeding and Emergence of Composite Skyrmions in a van der Waals Magnet

Seeding and Emergence of Composite Skyrmions in a van der Waals Magnet

Controlling interface anisotropy in CoFeB/MgO/HfO2 using dusting layers and magneto-ionic gating

Voltage-Controlled Skyrmionic Interconnect with Multiple Magnetic Information Carriers

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