Three-Dimensional Observation of Magnetic Vortex Cores in Stacked Ferromagnetic Discs

Tanigaki, Toshiaki; Takahashi, Yoshio; Shimakura, Tomokazu; Akashi, Takumi; Tsuneta, Ruriko; Sugawara, Akira; Shindo, Daisuke

doi:10.1021/nl504473a

Cited by 92 publications

(71 citation statements)

References 31 publications

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“…Stacking several disks provides additional degrees of freedom to control the precessional modes or the spectrum purity, for instance allowing to consider vortices with cores aligned parallel or antiparallel [13]. While coupled nanocubes had been imaged by electron holography in the case of parallel cores [14], stacked disks could be imaged recently with magnetic tomography holography, revealing fine details in the case of (repulsive) antiparallel cores [15]. The topological identity of such structures with so-called merons has been highlighted [16].…”

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confidence: 99%

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

et al. 2015

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Shadow X-ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy (XMCD-PEEM) is a recent technique, in which the photon intensity in the shadow of an object lying on a surface, may be used to gather information about the three-dimensional magnetization texture inside the object. Our purpose here is to lay the basis of a quantitative analysis of this technique. We first discuss the principle and implementation of a method to simulate the contrast expected from an arbitrary micromagnetic state. Text book examples and successful comparison with experiments are then given. Instrumental settings are finally discussed, having an impact on the contrast and spatial resolution : photon energy, microscope extraction voltage and plane of focus, microscope background level, electric-field related distortion of three-dimensional objects, Fresnel diffraction or photon scattering.Progress is continuous in the decreasing size and increasing complexity of nanosized magnetic systems being designed for either fundamental science or devices. Magnetic microscopies are crucial tools to monitor and understand the properties of such systems. Various types of information are desirable to gather, leading to multiple criteria to classify microscopies: spatial and time resolution, compatibility with environmental parameters such as variable temperature and applied magnetic field, requirements on the sample preparation and compatibility for ex-situ processing such as lithography, correlation with structural information, elemental sensitivity, quantity measured (magnetization, induction, stray field etc.), sensitivity. The most common magnetic microscopies offering spatial resolution below 50 nm and direct sensitivity to magnetization are X-ray Magnetic Circular Dichroism PhotoEmission Electron Microscopy (XMCD-PEEM) [ [7][8][9].Yet another criterion is the volume of the sample probed. This criterium is gaining in importance in the context of the emergence of three-dimensional (3D) magnetic objects and textures. The distribution of magnetization may be truly 3D if along the three directions in space the size of a system lies above magnetic characteristic length scales, such as the dipolar exchange length ∆ d for soft magnetic materials, or the anisotropy exchange length ∆ u for a hard magnetic material [10]. While this is obviously fulfilled in macroscopic materials, the complexity of magnetic textures is such that it cannot be measured in detail, and besides it cannot be controlled to achieve specific functions. The progress in nanofabrication techniques now allows to design suitable systems, both with top-down and bottom-up approaches. Let us give some examples. Flat magnetic elements are basic building blocks in spintronics, being patterned with great 2D versatility with thin film and lithography technologies. Large lateral dimensions may give rise to 2D magnetic textures, such as the so-called vortex state in disks [11]. Such textures are being investigated to design RF oscillator components, relying on the gyrotropic motion ...

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confidence: 99%

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

et al. 2015

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“…We introduce an additional dimension to the collective gyrations of vortices known from spin-torque oscillators [22]. Stacking the vortices allows for a strongly increased packing density and has thus stimulated recent studies [23][24][25][26][27][28][29][30]. While for two-dimensional arrangements the minimization of the stray fields at the side surfaces creates the vortices and mediates their interaction, we observe a second coupling mechanism for three-dimensional stacks that has been investigated theoretically [26,31,32].…”

Section: Introductionmentioning

confidence: 85%

Two-body problem of core-region coupled magnetic vortex stacks

et al. 2016

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The dynamics of all four combinations of possible polarity and circularity states in a stack of two vortices is investigated by time-resolved scanning transmission x-ray microscopy. The vortex stacks are excited by unidirectional magnetic fields leading to a collective oscillation. Four different modes are observed that depend on the relative polarizations and circularities of the stacks. They are excited to a driven oscillation. We observe a repulsive and attractive interaction of the vortex cores depending on their relative polarizations. The nonlinearity of this core interaction results in different trajectories that describe a two-body problem.

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“…1,2 Because both circularity and polarity can be specified by two independent values, that is, c = ± 1 and p = ± 1, four distinct spin states can exist in a single magnetic element with the combination of circularity and polarity. Magnetic vortices have been intensively studied due to their compelling physical behavior [3][4][5][6][7] and their potential in a wide range of applications such as data storage, 8,9 signal transfer, [10][11][12] logic devices, 13 transistors 14 and artificial skyrmion crystals. [15][16][17][18] With respect to practical application of magnetic vortices in advanced nanotechnologies, one of the critical factors is the effective reconfigurability of two topologies, c and p, particularly within large and densely packed arrays of magnetic elements.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous control of magnetic topologies for reconfigurable vortex arrays

Fischer

Han

et al. 2017

NPG Asia Mater

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The topological spin textures in magnetic vortices in confined magnetic elements offer a platform for understanding the fundamental physics of nanoscale spin behavior and the potential of harnessing their unique spin structures for advanced magnetic technologies. For magnetic vortices to be practical, an effective reconfigurability of the two topologies of magnetic vortices, that is, the circularity and the polarity, is an essential prerequisite. The reconfiguration issue is highly relevant to the question of whether both circularity and polarity are reliably and efficiently controllable. In this work, we report the first direct observation of simultaneous control of both circularity and polarity by the sole application of an in-plane magnetic field to arrays of asymmetrically shaped permalloy disks. Our investigation demonstrates that a high degree of reliability for control of both topologies can be achieved by tailoring the geometry of the disk arrays. We also propose a new approach to control the vortex structures by manipulating the effect of the stray field on the dynamics of vortex creation. The current study is expected to facilitate complete and effective reconfiguration of magnetic vortex structures, thereby enhancing the prospects for technological applications of magnetic vortices.

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Three-Dimensional Observation of Magnetic Vortex Cores in Stacked Ferromagnetic Discs

Cited by 92 publications

References 31 publications

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

Two-body problem of core-region coupled magnetic vortex stacks

Simultaneous control of magnetic topologies for reconfigurable vortex arrays

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