Magnetic skyrmions: from fundamental to applications

Finocchio, G.; Büttner, Felix; Tomasello, Riccardo; Carpentieri, Mario; Kläui, Mathias

doi:10.1088/0022-3727/49/42/423001

Cited by 414 publications

(346 citation statements)

References 139 publications

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“…Magnetic skyrmions were the subject of a recent topical review in this journal [51]. They are chiral objects stabilised by a DMI (see figure 6(b)) [52], and were first discovered in materials where the inversion symmetry of the lattice is broken (e.g.…”

Section: University Of Leedsmentioning

confidence: 99%

“…Whilst a domain wall horizontal racetrack memory has been demonstrated, memories at high density (especially in 3D) are still largely at a conceptual level. There are also several designs for skyrmion based racetrack memories and also for logic devices [51]. One of the more intriguing concepts that has been simulated is to perform logic operations by colliding objects from different homotopy groups [58].…”

Section: University Of Leedsmentioning

confidence: 99%

“…The topology of the physical structure, electronic structure (recognised by the 2016 Nobel Prize in Physics), and (here) spin structure all affect the physical properties of a condensed matter system. Novel topological spin structures present technological opportunities, such as skyrmion racetracks or logic gates [51]. As is often the case, magnetism also provides model systems where phenomena can be studied in depth before being generalised to other systems: for instance skyrmion concepts, having come from high-energy physics, are found in the physics of classical liquids, liquid crystals, Bose-Einstein condensates and quantum Hall magnets.…”

Section: Advances In Science and Technology To Meet Challengesmentioning

confidence: 99%

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The 2017 Magnetism Roadmap

Sander

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Makarov

et al. 2017

J. Phys. D: Appl. Phys.

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Building upon the success and relevance of the 2014 Magnetism Roadmap, this 2017 Magnetism Roadmap edition follows a similar general layout, even if its focus is naturally shifted, and a different group of experts and, thus, viewpoints are being collected and presented. More importantly, key developments have changed the research landscape in very relevant ways, so that a novel view onto some of the most crucial developments is warranted, and thus, this 2017 Magnetism Roadmap article is a timely endeavour. The change in landscape is hereby not exclusively scientific, but also reflects the magnetism related industrial application portfolio. Specifically, Hard Disk Drive technology, which still dominates digital storage and will continue to do so for many years, if not decades, has now limited its footprint in the scientific Topical ReviewOriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. and research community, whereas significantly growing interest in magnetism and magnetic materials in relation to energy applications is noticeable, and other technological fields are emerging as well. Also, more and more work is occurring in which complex topologies of magnetically ordered states are being explored, hereby aiming at a technological utilization of the very theoretical concepts that were recognised by the 2016 Nobel Prize in Physics.Given this somewhat shifted scenario, it seemed appropriate to select topics for this Roadmap article that represent the three core pillars of magnetism, namely magnetic materials, magnetic phenomena and associated characterization techniques, as well as applications of magnetism. While many of the contributions in this Roadmap have clearly overlapping relevance in all three fields, their relative focus is mostly associated to one of the three pillars. In this way, the interconnecting roles of having suitable magnetic materials, understanding (and being able to characterize) the underlying physics of their behaviour and utilizing them for applications and devices is well illustrated, thus giving an accurate snapshot of the world of magnetism in 2017.The article consists of 14 sections, each written by an expert in the field and addressing a specific subject on two pages. Evidently, the depth at which each contribution can describe the subject matter is limited and a full review of their statuses, advances, challenges and perspectives cannot be fully accomplished. Also, magnetism, as a vibrant research field, is too diverse, so that a number of areas will not be adequately represented here, leaving space for further Roadmap editions in the future. However, this 2017 Magnetism Roadmap article can provide a frame that will enable the reader to judge where each subject and magnetism research field stands overall today and which directions it might take in the foreseeable future.The first mater...

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Section: University Of Leedsmentioning

confidence: 99%

Section: University Of Leedsmentioning

confidence: 99%

Section: Advances In Science and Technology To Meet Challengesmentioning

confidence: 99%

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The 2017 Magnetism Roadmap

Sander

Valenzuela

Makarov

et al. 2017

J. Phys. D: Appl. Phys.

326

207

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“…The stability of magnetic skyrmions with respect to thermal fluctuations is a principal issue for their application in devices such as magnetic data storage [2]. Stochastic modeling of skyrmion dynamics to assess stability proves to be a difficult problem due to the large difference in time scales between a typical vibrational period of magnetic moments and the lifetime of a reasonably stable skyrmion.…”

Section: Introductionmentioning

confidence: 99%

Energy surface and lifetime of magnetic skyrmions

Uzdin

Potkina

Lobanov

et al. 2018

Journal of Magnetism and Magnetic Materials

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This is not the published version of the article / Þetta er ekki útgefna útgáfa greinarinnar AbstractThe stability of skyrmions in various environments is estimated by analyzing the multidimensional surface describing the energy of the system as a function of the directions of the magnetic moments in the system. The energy is given by a Heisenberg-like Hamiltonian that includes Dzyaloshinskii-Moriya interaction, anisotropy and external magnetic field. Local minima on this surface correspond to the ferromagnetic and skyrmion states. Minimum energy paths (MEP) between the minima are calculated using the geodesic nudged elastic band method. The maximum energy along an MEP corresponds to a first order saddle point on the energy surface and gives an estimate of the activation energy for the magnetic transition, such as creation and annihilation of a skyrmion. The pre-exponential factor in the Arrhenius law for the rate, the so-called attempt frequency, is estimated within harmonic transition state theory where the eigenvalues of the Hessian at the saddle point and the local minima are used to characterize the shape of the energy surface. For some degrees of freedom, so-called "zero modes", the energy of the system remains invariant. They need to be treated separately and give rise to temperature dependence of the attempt frequency. As an example application of this general theory, the lifetime of a skyrmion in a track of finite width for a PdFe overlayer on a Ir(111) substrate is calculated as a function of track width and external magnetic field. Also, the effect of non-magnetic impurities is studied. Various MEPs for annihilation inside a track, via the boundary of a track and at an impurity are presented. The attempt frequency as well as the activation energy has been calculated for each mechanism to estimate the transition rate as a function of temperature.

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“…Skyrmion lattices [6][7][8][9] constitute the ground state for some systems, while isolated Skyrmions can appear as metastable states of some magnetic nanostructures [10]. Isolated Skyrmions have been recently considered [11][12][13][14] as the building blocks for ultradense magnetic storage devices [15].Skyrmions carry a topological charge Q = ±1 defined as [16]:where A is the area of the system and m the unit magnetization vector. Since transitions that change Q are forbidden [16] in a continuum description of m, such structures are topologically protected.…”

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confidence: 99%

Multiscale simulations of topological transformations in magnetic-skyrmion spin structures

Lucia¹,

Litzius²,

Krüger³

et al. 2017

Phys. Rev. B

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Magnetic Skyrmions belong to the most interesting spin structures for the development of future information technology as they have been predicted to be topologically protected. To quantify their stability, we use an innovative multiscale approach to simulating spin dynamics based on the Landau-Lifshitz-Gilbert equation. The multiscale approach overcomes the micromagnetic limitations that have hindered realistic studies using conventional techniques. We first demonstrate how the stability of a Skyrmion is influenced by the refinement of the computational mesh and reveal that conventionally employed traditional micromagnetic simulations are inadequate for this task. Furthermore, we determine the stability quantitatively using our multiscale approach. As a key operation for devices, the process of annihilating a Skyrmion by exciting it with a spin polarized current pulse is analyzed, showing that Skyrmions can be reliably deleted by designing the pulse shape.Magnetic Skyrmions [1] are topological spin structures that arise in the spin pattern of ferromagnetic systems with broken inversion symmetry, such as chiral crystals [2,3] or thin magnetic films with different top and bottom interfaces [4,5]. Skyrmion lattices [6][7][8][9] constitute the ground state for some systems, while isolated Skyrmions can appear as metastable states of some magnetic nanostructures [10]. Isolated Skyrmions have been recently considered [11][12][13][14] as the building blocks for ultradense magnetic storage devices [15].Skyrmions carry a topological charge Q = ±1 defined as [16]:where A is the area of the system and m the unit magnetization vector. Since transitions that change Q are forbidden [16] in a continuum description of m, such structures are topologically protected. Nevertheless, in a real system composed of discrete magnetic moments localized on the atomic lattice sites, no strict topological protection exists [17]. Thus it is necessary to overcome a finite energy barrier to induce transformations that change Q, such as the annihilation of a Bloch line (BL) [16,[18][19][20][21][22][23][24]. The stability against external fields is indeed a key feature of Skyrmions, making them a good candidate as information carriers in next generation storage devices [25][26][27]. The fundamental prerequisites for applications are ascertaining the stability of Skyrmions, as well as reliably annihilating them. However, the computational treatment of processes involving annihilating Skyrmions is very delicate. In analytical micromagnetic theory, singularities in the exchange field tend to arise during topological transformations, making numerical simulations very susceptible to the mesh being used [28] and therefore often inaccurate. The necessity for a computational model, capable of performing quantitatively accurate simulations is therefore obvious and a key step. While more accurate atomistic simulations would overcome this problem, the computational power required to run such simulations for a sample of realistic experimental size makes th...

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Magnetic skyrmions: from fundamental to applications

Cited by 414 publications

References 139 publications

The 2017 Magnetism Roadmap

The 2017 Magnetism Roadmap

Energy surface and lifetime of magnetic skyrmions

Multiscale simulations of topological transformations in magnetic-skyrmion spin structures

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