Third type of domain wall in soft magnetic nanostrips

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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“…Other examples include magnetization processes inside domain walls [30,31] and dimensional cross-over from vortices to domain walls [32,33].…”

Section: Arxiv:150602866v2 [Cond-matmtrl-sci] 23 Sep 2015mentioning

confidence: 99%

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

et al. 2015

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“…The structure of domain walls (DWs) in these magnets is extremely diverse and exhibits a complex behavior in dc and ac magnetic fields. Depending on the geometry of stripes (the ratio between their linear sizes) and their magnetic characteristics, DWs of different types are implemented, including conventional Néel (transverse) walls (TWs), vortex walls (VWs), and their complex combinations . Different types of DWs have been intensively theoretically (see, for example, ref.…”

Section: Introductionmentioning

confidence: 99%

On the Effect of Magnetostatic Interaction on the Collective Motion of Vortex Domain Walls in a Pair of Nanostripes

Орлов

Иванов

Orlova

2019

Physica Status Solidi (b)

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The periodic motion of interacting vortex domain walls in a pair of nanostripes has been analytically and numerically investigated. A model consisting of two parallel nanostripes with the domain magnetization structure has been proposed, where domains are separated by vortex walls. The magnetic subsystems of the stripes magnetostatically interact, which causes the existence of normal magnetic vortex motion modes in the latter. Frequencies of the collective magnetization modes have been calculated using empirical expressions for the magnetic energy of interaction between vortex walls. It is shown that not any combinations of the polarity and chirality lead to the resonance magnetization behavior in ac fields.

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“…For the imaging of the domain wall spin configurations in rings of other materials, previous work has employed electron holography [21] or Lorentz microscopy, which require that the samples are fabricated on delicate membranes for the transmission measurements [10], photo-emission electron microscopy [17,18,31], which is mainly available at large-scale facilities and can be limited in its resolution, or magnetic force microscopy (MFM) [9,[32][33][34], which can modify the spin configuration of the sample and is however sensitive only to the stray magnetic field from a sample and therefore harder to relate directly to the spin structures obtained from simulations. Therefore, in this paper we chose the imaging technique SEMPA [26], which is a powerful lab-based method with an excellent spatial resolution of less than 20 nm and which can provide quantitative direct information concerning the spin configurations [35].…”

Section: Experimental and Numericsmentioning

confidence: 99%

Domain wall spin structures in mesoscopic Fe rings probed by high resolution SEMPA

Krautscheid¹,

Reeve²,

Lauf³

et al. 2016

J. Phys. D: Appl. Phys.

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We present a combined theoretical and experimental study of the energetic stability and accessibility of different domain wall spin configurations in mesoscopic magnetic iron rings. The evolution is investigated as a function of the width and thickness in a regime of relevance to devices, while Fe is chosen as a material due to its simple growth in combination with attractive magnetic properties including high saturation magnetization and low intrinsic anisotropy. Micromagnetic simulations are performed to predict the lowest energy states of the domain walls, which can be either the transverse or vortex wall spin structure, in good agreement with analytical models, with further simulations revealing the expected low temperature configurations observable on relaxation of the magnetic structure from saturation in an external field. In the latter case, following the domain wall nucleation process, transverse domain walls are found at larger widths and thicknesses than would be expected by just comparing the competing energy terms demonstrating the importance of metastability of the states. The simulations are compared to high spatial resolution experimental images of the magnetization using scanning electron microscopy with polarization analysis to provide a phase diagram of the various spin configurations. In addition to the vortex and simple symmetric transverse domain wall, a significant range of geometries are found to exhibit highly asymmetric transverse domain walls with properties distinct from the symmetric transverse wall.Simulations of the asymmetric walls reveal an evolution of the domain wall tilting angle with ring thickness which can be understood from the thickness dependencies of the contributing energy terms. Analysis of all the data reveals that in addition to the geometry, the influence of materials properties, defects and thermal activation all need to be taken into account in order to understand and reliably control the experimentally accessible states, as needed for devices.2

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Third type of domain wall in soft magnetic nanostrips

Cited by 29 publications

References 34 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

On the Effect of Magnetostatic Interaction on the Collective Motion of Vortex Domain Walls in a Pair of Nanostripes

Domain wall spin structures in mesoscopic Fe rings probed by high resolution SEMPA

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