Out-of-plane chiral domain wall spin-structures in ultrathin in-plane magnets

Chen, Gong; Kang, Sung‐Oong; Ophus, Colin; N’Diaye, Alpha T.; Kwon, Hee Young; Qiu, Ryan T; Won, C.; Liu, Kai; Wu, Y. Z.; Schmid, Andreas K.

doi:10.1038/ncomms15302

Cited by 43 publications

(31 citation statements)

References 56 publications

(97 reference statements)

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“…We return to this value when measuring by the in-focus DPC method later in the paper. Direct measurements of Néel domain wall width has been made using SPLEEM, although that was on a single crystal system with thicker Fe/Ni having in-plane magnetisation where the width was reported as 110 nm 20 .…”

Section: Introductionmentioning

confidence: 99%

A transmission electron microscope study of Néel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction

McVitie

Hughes

Fallon

et al. 2018

Sci Rep

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Skyrmions in ultrathin ferromagnetic metal (FM)/heavy metal (HM) multilayer systems produced by conventional sputtering methods have recently generated huge interest due to their applications in the field of spintronics. The sandwich structure with two correctly-chosen heavy metal layers provides an additive interfacial exchange interaction which promotes domain wall or skyrmion spin textures that are Néel in character and with a fixed chirality. Lorentz transmission electron microscopy (TEM) is a high resolution method ideally suited to quantitatively image such chiral magnetic configurations. When allied with physical and chemical TEM analysis of both planar and cross-sectional samples, key length scales such as grain size and the chiral variation of the magnetisation variation have been identified and measured. We present data showing the importance of the grain size (mostly < 10 nm) measured from direct imaging and its potential role in describing observed behaviour of isolated skyrmions (diameter < 100 nm). In the latter the region in which the magnetization rotates is measured to be around 30 nm. Such quantitative information on the multiscale magnetisation variations in the system is key to understanding and exploiting the behaviour of skyrmions for future applications in information storage and logic devices.

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Section: Introductionmentioning

confidence: 99%

A transmission electron microscope study of Néel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction

McVitie

Hughes

Fallon

et al. 2018

Sci Rep

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“…A number of microscopy methods have been used to determine the magnetic texture, domain wall type and to characterise length scales of both domain walls and skyrmions in such multilayer systems. These include magnetic force microscopy (MFM) [20,21] spin polarised scanning tunnelling microscopy (SP-STM) [22], scanning transmission X-ray microscopy (STXM) [10,23], spin polarised low energy electron microscopy (SPLEEM) [24], magnetic transmission soft X-ray microscopy (MTXM) [23] and X-ray photoemission electron microscopy (X-PEEM) [25]. The technique of Lorentz TEM is used in this study and has previously been utilised in a number of investigations into the structure and magnetic behaviour of domain walls and skyrmions in chiral systems [26][27][28].…”

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confidence: 99%

Quantitative imaging of hybrid chiral spin textures in magnetic multilayer systems by Lorentz microscopy

et al. 2019

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Chiral magnetic textures in ultrathin perpendicularly magnetised multilayer film stacks with an interfacial Dzyaloshinskii-Moriya interaction have been the focus of much research recently. The chirality associated with the broken inversion symmetry at the interface between an ultrathin ferromagnetic layer and a heavy metal with large spin-orbit coupling supports homochiral Néel domain walls and hedgehog (Néel) skyrmions. Under spin-orbit torques these Néel type magnetic structures are predicted, and have been measured, to move at high velocities. However recent studies have indicated that some multilayered systems may possess a more complex hybrid domain wall configuration, due to the competition between interfacial DMI and interlayer dipolar fields. These twisted textures are expected to have thickness dependent Néel and Bloch contributions to the domain or skyrmion walls. In this work, we use the methods of Lorentz microscopy to measure quantitatively for the first time experimentally both; i) the contributions of the Néel and Bloch contributions and ii) their spatial spin variation at high resolution. These are compared with modelled and simulated structures which are in excellent agreement with our experimental results. Our quantitative analysis provides powerful direct evidence of the Bloch wall component which exists in these hybrid walls and will be significant when exploiting such phenomena in spintronic applications. DOI: xxxxxxxxxxPACS numbers: 75.50.Ak, 75.60.Jk

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“…Hence, it confirms by a direct measurement and without assumptions, that the DW texture is Néel (CW or CCW) as already known for this multilayer system with additive interfacial DM interaction either indirectly through analysis of the skyrmion size and comparison with micromagnetic simulations [15] or directly through Lorentz transmission electron microscopy [27]. Other methods have already been utilized to access to the texture of the DW or skyrmions such as spin-polarized STM [1,28], scanning nitrogen-vacancies-magnetometry (NV) [29,30] or spinpolarized low-energy electron microscopy (SPLEEM) [31]. On the other hand, DM interaction has also been probed by spin wave spectroscopy techniques such as Brillouin light scattering (BLS) [32] or time-resolved Kerr microscopy [33].…”

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confidence: 99%

Chirality in Magnetic Multilayers Probed by the Symmetry and the Amplitude of Dichroism in X-Ray Resonant Magnetic Scattering

et al. 2018

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Chirality is central to understand many fundamental mechanisms in various domains of physics and chemistry. In condensed matter, a large variety of physical phenomena hinge on the emergence of these complex chiral windings of order parameters, their observation and subsequently their control especially in magnetism and spintransport at the nanoscale. The ability to probe the nature of these chiral magnetic textures has now become a crucial element of modern magnetism and is therefore essential to gain a deeper understanding of these mechanisms. Spin-polarized scanning tunneling microscopy (SP-STM) revealed that magnetic textures with a cycloidal configuration of the magnetization and Néel domain walls are stabilized in ultra-thin magnetic films (one or a few atomic layers) on heavy metal substrates [1] . It was realized that these magnetic textures are stabilized by Dzyaloshinskii-Moriya (DM) interaction [2,3], (∑ 〈 〉• × , with Si and Sj two neighboring spins) which is the anti-symmetric analog of the Heisenberg interaction favoring a curling magnetization textures around the DM vector . The DM interaction requires spin-orbit coupling (SOC) and broken inversion symmetry, found either in specific crystalline structures, such as B20 materials [4], or at film interfaces [5,6].In this letter, we demonstrate that XRMS experiments (Figure 1a) allow us to reveal the actual magnetic textures existing in ultrathin magnetic multilayers with perpendicular anisotropy and large interfacial chiral interaction. Importantly, this determination is straightforward and does not require any assumptions or careful comparison to parameter-dependent micromagnetic simulations. Moreover, the circular dichroism in XMRS enables to identify directly not only the direction but also the sense of the magnetic winding and therefore of the actual sign of DM interaction as we proved by a thorough analysis. This information has a far-reaching impact in particular for spin-orbitronics and spin-orbit torque (SOT) studies. Indeed, SOT is a recent very promising approach to move efficiently domain walls [7] and magnetic skyrmions along magnetic race-tracks and shows therefore a great potential for future spintronic devices. Yet, the detailed texture of the domain walls plays a major role in their motion [8]: the DW high speed is related to its nature (Néel or Bloch) while its direction of motion depends on its chirality [7]. Besides, DM interaction can play an important role for existing technological applications in spintronics already using ultrathin magnetic multilayers with perpendicular magnetic anisotropy such as MRAM or detectors, in which the presence and the impact of non-negligible DM interaction has been largely overlooked (see e.g. [9,10]), emphasizing thus the need to probe its consequences on magnetic textures. XRMS presents several advantages that might soon turn it to a standard way to characterize and quantify the DM interaction. First, XMRS is a non-perturbative technique contrary to the approach based on magnetic domain analysis th...

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Out-of-plane chiral domain wall spin-structures in ultrathin in-plane magnets

Cited by 43 publications

References 56 publications

A transmission electron microscope study of Néel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction

A transmission electron microscope study of Néel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction

Quantitative imaging of hybrid chiral spin textures in magnetic multilayer systems by Lorentz microscopy

Chirality in Magnetic Multilayers Probed by the Symmetry and the Amplitude of Dichroism in X-Ray Resonant Magnetic Scattering

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