Ground state search, hysteretic behaviour and reversal mechanism of skyrmionic textures in confined helimagnetic nanostructures

Beg, Marijan; Carey, R.; Wang, Weiwei; Cortés‐Ortuño, David; Vousden, Mark; Bisotti, Marc-Antonio; Albert, Maximilian; Chernyshenko, Dmitri; Hovorka, Ondřej; Stamps, R. L.; Fangohr, Hans

doi:10.1038/srep17137

Cited by 191 publications

(204 citation statements)

References 57 publications

(101 reference statements)

Supporting

Mentioning

199

Contrasting

Order By: Relevance

“…Similar to the giant vortex, a new topological state, named target skyrmion, characterized by a skyrmionic core with a series of circular spin stripes, has been suggested in nanodisks or nanowires under certain conditions (8,30). Especially, the target skyrmion may be the spontaneous ground state, as the disk size is close to the featured helical period (31). Similar target domain structure has been observed in Ni and FePt nanodots (32,33).…”

Section: Discussionmentioning

confidence: 66%

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Zhao

Jin

Wang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

138

114

View full text Add to dashboard Cite

Magnetic skyrmion is a nanosized magnetic whirl with nontrivial topology, which is highly relevant for applications on future memory devices. To enable the applications, theoretical efforts have been made to understand the dynamics of individual skyrmions in magnetic nanostructures. However, directly imaging the evolution of highly geometrically confined individual skyrmions is challenging. Here, we report the magnetic field-driven dynamics of individual skyrmions in FeGe nanodisks with diameters on the order of several skyrmion sizes by using Lorentz transmission electron microscopy. In contrast to the conventional skyrmion lattice in bulk, a series of skyrmion cluster states with different geometrical configurations and the fielddriven cascading phase transitions are identified at temperatures far below the magnetic transition temperature. Furthermore, a dynamics, namely the intermittent jumps between the neighboring skyrmion cluster states, is found at elevated temperatures, at which the thermal energy competes with the energy barrier between the skyrmion cluster states.T he complex spin configurations in helimagnets have attracted considerable attention recently, with the topologically stable particle-like spin texture with a size down to the nanoscale, namely magnetic skyrmion, as the focus of interest (1). Magnetic skyrmion is characterized as a nanoscale topological particle producing unconventional spin electronic phenomena (2, 3) that holds great promise for future spintronic devices, including racetrack memory (4), magnetic random access memory, and magnetic sensors (1). Essentially, such schemes rely on the controllable formation and manipulation of individual skyrmions at nanostructured elements with various shapes such as disks, stripes, or wires (5-7). Investigation of skyrmions in confined geometries has therefore become one of the major topics in the field of skyrmion physics (5-10).Unlike ordinary magnetic vortices in microsized soft magnetic disks due to the minimization of the dipolar energy (11), the key ingredient of stabilizing skyrmions in helimagnets is the antisymmetry Dzyaloshinskii−Moriya (DM) interactions originating from the broken inversion symmetry (12). The competition of the DM coupling with ferromagnetic exchange interaction results in periodic helical ground state in helimagnets. Under the action of a magnetic field and temperature, these magnetic helices transfer into skyrmion crystal with triangular lattice configuration, and finally to the field-polarized ferromagnetic state. Notably, both ferromagnetic and DM couplings occur among the neighboring spins and belong to short-range interaction. Thus, it was demonstrated theoretically that skyrmions cluster states, characterized by certain arrangements of limited skyrmions, still persist even in submicrometer objects (8, 13). There, the longrange lattice form of skyrmions in 2D or bulk helimagnets is broken, but a short-ranged ordering with specific geometrical symmetries still remains, and the number of skyrmions in the cluster...

show abstract

Section: Discussionmentioning

confidence: 66%

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Zhao

Jin

Wang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

138

114

View full text Add to dashboard Cite

show abstract

“…[36] without taking into account anisotropy and that the effects of thermal fluctuations and confining geometry on single-skyrmion dynamics were considered in Refs. [27,37,38].…”

Section: Fig 1 (Color Online)mentioning

confidence: 99%

Degeneracies and fluctuations of Néel skyrmions in confined geometries

et al. 2015

View full text Add to dashboard Cite

The recent discovery of tunable Dzyaloshinskii-Moriya interactions in layered magnetic materials with perpendicular magnetic anisotropy makes them promising candidates for stabilization and manipulation of skyrmions at elevated temperatures. In this article, we use Monte Carlo simulations to investigate the robustness of skyrmions in these materials against thermal fluctuations and finite-size effects. We find that in confined geometries and at finite temperatures skyrmions are present in a large part of the phase diagram. Moreover, we find that the confined geometry favors the skyrmion over the spiral phase when compared to infinitely large systems. Upon tuning the magnetic field through the skyrmion phase, the system undergoes a cascade of transitions in the magnetic structure through states of different number of skyrmions, elongated and half-skyrmions, and spiral states. We consider how quantum and thermal fluctuations lift the degeneracies that occur at these transitions, and find that states with more skyrmions are typically favored by fluctuations over states with less skyrmions. Finally, we comment on electrical detection of the various phases through the topological and anomalous Hall effects.

show abstract

“…Additional reason for that are perspective applications of the RT isolated skyrmions in nanoscale devices 33 . Isolated skyrmions, conditions required for their existence in patterned films [11][12][13][14]23,34,35 , and the dynamics of isolated skyrmions in magnetic films and nanodots have been simulated 29,33,36,37 and experimentally explored 38 . Lin et al 29 simulated dynamics of isolated skyrmion in an infinite film and found one gyrotropic mode, several breathing and non-symmetric skyrmion shape modes in the area of the skyrmion stability.…”

Section: Introductionmentioning

confidence: 99%

Gyrotropic Skyrmion Modes in Ultrathin Magnetic Circular Dots

Guslienko

Gareeva

2017

IEEE Magn. Lett.

View full text Add to dashboard Cite

We calculate low-frequency gyrotropic spin excitation modes of the skyrmion ground state ultrathin cylindrical magnetic dots. The skyrmion is assumed to be stabilized at room temperature and zero external magnetic field due to an interplay of the isotropic and Dzyaloshinskii-Moriya exchange interactions, perpendicular magnetic anisotropy and magnetostatic interaction. We consider Bloch-and Neel-type magnetic skyrmions and assume that the dot magnetization does not depend on the thickness coordinate. The skyrmion gyrotropic frequencies are calculated in GHz range as a function of the skyrmion equilibrium radius, dot radius and the dot magnetic parameters. Recent experiments on magnetic skyrmion gyrotropic dynamics in nanodots are discussed.

show abstract

Ground state search, hysteretic behaviour and reversal mechanism of skyrmionic textures in confined helimagnetic nanostructures

Cited by 191 publications

References 57 publications

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Degeneracies and fluctuations of Néel skyrmions in confined geometries

Gyrotropic Skyrmion Modes in Ultrathin Magnetic Circular Dots

Contact Info

Product

Resources

About