Experimental Evidence of Chiral Ferrimagnetism in Amorphous GdCo Films

Streubel, Robert; Lambert, Charles‐Henri; Kent, Noah; Ercius, Peter; N’Diaye, Alpha T.; Ophus, Colin; Salahuddin, Sayeef; Fischer, Peter

doi:10.1002/adma.201800199

Cited by 49 publications

(35 citation statements)

References 49 publications

(35 reference statements)

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“…3(a) results for the bulk DMI energy density between Dy and Co moments. The remaining question is whether the DMI is inherently present in the whole Dy-Co layer [48] or exists only in the Dy-Co atomic layers next to the interface [19] triggered by the adjacent Ni-Fe layer. Very recently, a bulk DMI in (Gd,Fe),Co amorphous ferrimagnets has been reported, and was attributed to an asymmetric distribution of the elemental content [48].…”

Section: Origin Of the Chiral Domain Wallmentioning

confidence: 99%

Observation of a Chirality-Induced Exchange-Bias Effect

et al. 2019

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Chiral magnetism that manifests in the existence of skyrmions or chiral domain walls offers an alternative way for creating anisotropies in magnetic materials that might have large potential for application in future spintronic devices. Here we show experimental evidence for an alternative type of in-plane exchange-bias effect present at room temperature that is created from a chiral 90 • domain wall at the interface of a ferrimagnetic-ferromagnetic Dy-Co/Ni-Fe bilayer system. The chiral interfacial domain wall forms due to the exchange coupling of Ni-Fe and Dy-Co at the interface and the presence of Dzyaloshinskii-Moriya interaction in the Dy-Co layer. As a consequence of the preferred chirality of the interfacial domain wall, the sign of the exchange-bias effect can be reversed by changing the perpendicular orientation of the Dy-Co magnetization. The chirality-created tunable exchange bias in Dy-Co/Ni-Fe is very robust against high in-plane magnetic fields (μ 0 H ≤ 6 T) and does not show any aging effects. Therefore, it overcomes the limitations of conventional exchange-bias systems.

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Section: Origin Of the Chiral Domain Wallmentioning

confidence: 99%

Observation of a Chirality-Induced Exchange-Bias Effect

et al. 2019

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“…Note that sputtered Co/Pd or Co/Pt thin films are ferromagnetic polycrystalline materials that are known to have large domain wall pinning that limits their application potential for spintronics applications using skyrmions. An alternative, which is from synthesis challenges equivalent, are amorphous ferrimagnetic GdCo films [10,50] that promise large domain wall and skyrmion velocities owing to low spin damping, negligible pinning at grain boundaries and nearly compensated moments. This material may also be a good prototypical system to observe curvature driven chirality selection.…”

Section: Resultsmentioning

confidence: 99%

“…domain wall type, dictates the longitudinal component of the local magnetization, the latter does not directly translate to a longitudinal stray field component. Namely, Bloch walls observed in symmetric Co/Pd multilayers [13] generate a longitudinal magnetization [10], parallel to the z-direction discussed here; Néel walls cause a perpendicular component at the expense of a longitudinal one [10]. Either wall has a normal (radial) approach is a promising way to circumvent such limitations in future studies [23,24].…”

Section: Stray-field Mapping At Steep Surfacesmentioning

confidence: 88%

“…Hence, a profound understanding of underlying mechanisms, and the optimization of device performance demand the visualization of magnetization configuration. Addressing the transformative challenge of imaging the magnetic vector field, numerous techniques have been developed and advanced, including high-resolution Lorentz microscopy [10], vector field electron tomography [11,12], and magnetic x-ray microscopy and tomography [13,14]. In addition to these expensive tools operated at large-scale user facilities, cost-efficient table-top setups have been explored based on magneto-optical Kerr effect magnetometry [15] and, as outlined in this work, multi-frequency magnetic force microscopy.…”

Section: Introductionmentioning

confidence: 99%

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Magnetization reversal and local switching fields of ferromagnetic Co/Pd microtubes with radial magnetization

et al. 2019

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Three-dimensional nanomagnetism is a rapidly growing field of research covering both non-collinear spin textures and curved magnetic geometries including micro-tubular structures. We spatially resolve the fieldinduced magnetization reversal of free-standing ferromagnetic microtubes utilizing multi-frequency magnetic force microscopy (MFM). The microtubes are composed of Co/Pd multilayer films with perpendicular magnetic anisotropy that translates to an anisotropy with radial easy axis upon rolling-up. Simultaneously mapping the topography and the perpendicular magnetostatic force derivative, the relation between surface angle and local magnetization configuration is evaluated for a large number of locations with slopes exceeding 45 degrees. The angle-dependence of the switching field is concurrent with the Kondorsky model, i.e. the rolled-up nanomembrane behaves like a planar magnetic film with perpendicular anisotropy and a pinning dominated magnetization reversal. Additionally, we discuss methodological challenges when detecting magnetostatic force derivatives near steep surfaces.

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“…However, in many systems DWs also have an internal degree of freedom, chirality, that could also be used to encode data. The realization of significant Dzyaloshinskii–Moriya interactions (DMI) in thin magnetic films has made chirality a key topic in contemporary nanomagnetism research . For example, manipulating DMI in thin films with out‐of‐plane magnetization allows DW chirality and structure to be uniquely defined, allowing efficient spin‐torque driven DW transport via the spin Hall effect; although this obviously precludes devices where chirality is used as a data carrier.…”

Section: Introductionmentioning

confidence: 99%

Toward Chirality‐Encoded Domain Wall Logic

Omari

Broomhall

Dawidek

et al. 2019

Adv Funct Materials

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Nonvolatile logic networks based on spintronic and nanomagnetic technologies have the potential to create high‐speed, ultralow power computational architectures. This article explores the feasibility of “chirality‐encoded domain wall logic,” a nanomagnetic logic architecture where data are encoded by the chiral structures of mobile domain walls in networks of ferromagnetic nanowires and processed by the chiral structures' interactions with geometric features of the networks. High‐resolution magnetic imaging is used to test two critical functionalities: the inversion of domain wall chirality at tailored artificial defect sites (logical NOT gates) and the chirality‐selective output of domain walls from 2‐in‐1‐out nanowire junctions (common operation to AND/NAND/OR/NOR gates). The measurements demonstrate both operations can be performed to a good degree of fidelity even in the presence of complex magnetization dynamics that would normally be expected to destroy chirality‐encoded information. Together, these results represent a strong indication of the feasibility of devices where chiral magnetization textures are used to directly carry, rather than merely delineate, data.

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Experimental Evidence of Chiral Ferrimagnetism in Amorphous GdCo Films

Cited by 49 publications

References 49 publications

Observation of a Chirality-Induced Exchange-Bias Effect

Observation of a Chirality-Induced Exchange-Bias Effect

Magnetization reversal and local switching fields of ferromagnetic Co/Pd microtubes with radial magnetization

Toward Chirality‐Encoded Domain Wall Logic

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