Direct observation of transverse and vortex metastable magnetic domains in cylindrical nanowires

Bran, Cristina; Fernández-Roldán, José Ángel; Palmero, Ester M.; Berganza, Eider; Guzman, J.; Real, R. P. del; Asenjo, A.; Rodríguez, A. Fraile; Foerster, Michael; Aballe, Lucía; Chubykalo‐Fesenko, O.; Vázquez, M.

doi:10.1103/physrevb.96.125415

Cited by 34 publications

(52 citation statements)

References 28 publications

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“…The magnetic curling state has been reported by Ruiz-Gómez et al 32 and is described by a magnetization at the core of the NW pointing in the direction of the nanowire axis, surrounded by a helical magnetic configuration. As previously stated, we observe a change in measured induction between regions C1 and C4 ( Figure 1e) that could arise from a difference in size of the core of such a vortex state as discussed by Bran et al and Ivanov et al 31,33 or from a change in rotation angle of the curling with respect to the nanowire axis. The distribution of the magnetic shift and deeper analysis suggest that it is the curling state that occur in our system, where the highest phase shift value in region C4 comes from a smaller curling angle, i.e.…”

Section: Resultssupporting

confidence: 82%

Exotic Transverse-Vortex Magnetic Configurations in CoNi Nanowires

et al. 2019

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The magnetic configurations of cylindrical Co-rich CoNi nanowires have been quantitatively analyzed at the nanoscale by electron holography and correlated to local structural and chemical properties.The nanowires display grains of both face-centered cubic (fcc) and hexagonal close packed (hcp) crystal structures, with grain boundaries parallel to the nanowire axis direction. Electron holography evidences the existence of a complex exotic magnetic configuration characterized by two distinctly different types of magnetic configurations within a single nanowire: an array of periodical vortices separating small transverse domains in hcp rich regions with perpendicular easy axis orientation, and a mostly axial configuration parallel to the nanowire axis in regions with fcc grains. These vastly different domains are found to be caused by local variations in the chemical composition modifying the crystalline orientation and/or structure, which give rise to change in magnetic anisotropies. Micromagnetic simulations, including the structural properties that have been experimentally determined, allows for a deeper understanding of the complex magnetic states observed by electron holography.KEYWORDS magnetic configuration, magnetic nanowire, electron holography, vortex state, micromagnetic simulation, nanocylinder.One-dimensional magnetic nanostructures have for the past two decades been of increased interest for the development of future spintronic devices 1-4 motivated by concepts like Magnetic Race Track Memory 5 and the wish to manipulate magnetic domain walls (DW). Cylindrical nanowires (NWs) are particularly interesting candidates to reach this goal, much due to the fast DW motion induced by an external magnetic field or electric current, where theoretical studies have anticipated the absence of a Walker breakdown. 6,7 In addition, curvature effects have recently been proved to induce effects related to topology, chirality, and symmetry, 8 and unidirectional reversal process has been reported by engineering the geometry in multi-segmented nanowires. 9 However, to further technical developments in spintronics and a better control of DW motion, a thorough understanding of the fine structures of DWs in magnetic NWs, in which shape and crystal structure are contributing factors to the minimization of the system's magnetic energy, 10-13 is required.The magnetic configurations in various Co-based cylindrical nanowires have previously been studied in several publications, [13][14][15][16] which have revealed a strong influence of the NW's structural properties, 17 and thus a dependence of their fabrication process. 10,18,19 For instance, it has been shown that monocrystalline hcp phase can be obtained in pure Co NWs with the c-axis engineered with nearly perpendicular orientation to the NW axis. 10,20 The corresponding uniaxial magnetocrystalline anisotropy is then strong enough to challenge the large shape anisotropy of NWs. 10,21,22 In CoNi-alloy NWs, the amount of Ni content can modify the crystallographic phase: while C...

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Section: Resultssupporting

confidence: 82%

Exotic Transverse-Vortex Magnetic Configurations in CoNi Nanowires

et al. 2019

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“…This way of partly closing the flux often competes with the existence of global curling states (also called vortex states), in which magnetization curls around the wire axis. These have been reported for, e.g., CoNi alloys (Bran et al 2017a; Fig. 13a), single-crystalline hcp Co , Ivanov et al 2013b, Chen et al 2016, single-crystal CVD Ni wire (Kan et al 2018b).…”

Section: Anisotropic Magnetic Materialssupporting

confidence: 67%

“…These feature alternating hard and soft magnetic segments such as Co/Ni (Fig. 6c), or the combination of magnetic/nonmagnetic sections such as Co/Au for magnetic nano-oscillators (Bran et al 2017a). The method of choice for the fabrication of multisegmented structures is electroplating in nanoporous membranes.…”

Section: Segmented Structuresmentioning

confidence: 99%

Magnetic Nanowires and Nanotubes

Staňo

Fruchart

2018

Handbook of Magnetic Materials

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We propose a review of the current knowledge about the synthesis, magnetic properties and applications of magnetic cylindrical nanowires and nanotubes. By nano we consider diameters reasonably smaller than a micrometer. At this scale, comparable to micromagnetic and transport length scales, novel properties appear. At the same time, this makes the underlying physics easier to understand due to the limiter number of degrees of freedom involved. The three-dimensional nature and the curvature of these objects contribute also to their specific properties, compared to patterns flat elements. While the topic of nanowires and later nanotubes started now decades ago, it is nevertheless flourishing, thanks to the progress of synthesis, theory and characterization tools. These give access to ever more complex and thus functional structures, and also shifting the focus from material-type measurements of large assemblies, to single-object investigations. We first provide an overview of common fabrication methods yielding nanowires, nanotubes and structures engineered in geometry (change in diameter, shape) or material (segments, core-shell structures), shape or core-shell. We then review their magnetic properties: global measurements, magnetization states and switching, single domain wall statics and dynamics, and spin waves. For each aspect, both theory and experiments are surveyed. We also mention standard characterization techniques useful for these. We finally mention emerging applications of magnetic nanowires and nanotubes, along with the foreseen perspectives in the topic.

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“…Nevertheless, it is important to remark that this approximation is valid for thin NWs, where axial configuration of magnetization is expected. For thicker wires, different configuration of magnetic domains, with orthoradial components, would appear, introducing new contributions of the total anisotropy energy …”

mentioning

confidence: 99%

Tailoring Magnetic Anisotropy at Will in 3D Interconnected Nanowire Networks

Ruiz‐Clavijo

Ruiz-Gómez

Caballero-Calero

et al. 2019

Physica Rapid Research Ltrs

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The control of magnetic anisotropy has been the driving force for the development of magnetic applications in a wide range of technological fields from sensing to spintronics. In recent years, the possibility of tailoring the magnetic properties goes together with a need for new 3D materials to expand the applications to a new generation of devices. Herein, the possibility of designing the magnetic anisotropy of 3D magnetic nanowire networks is shown just by modifying the geometry of the structure or by composition. It is also shown that this is possible when the magnetic properties of the structure are governed by magnetostatic anisotropy. The present approach can guide systematic tuning of the magnetic easy axis and coercivity in the desired direction at the nanoscale. Importantly, this can be achieved on virtually any magnetic material, alloy, or multilayers that can be prepared inside porous alumina. These results are promising for engineering novel magnetic devices that exploit tailored magnetic anisotropy using metamaterials concept.

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Direct observation of transverse and vortex metastable magnetic domains in cylindrical nanowires

Cited by 34 publications

References 28 publications

Exotic Transverse-Vortex Magnetic Configurations in CoNi Nanowires

Exotic Transverse-Vortex Magnetic Configurations in CoNi Nanowires

Magnetic Nanowires and Nanotubes

Tailoring Magnetic Anisotropy at Will in 3D Interconnected Nanowire Networks

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