Extended elliptic skyrmion gratings in epitaxial MnSi thin films

Wilson, M. N.; Karhu, Eric; Quigley, Andrew; Rößler, U.; Butenko, A. B.; Bogdanov, A. N.; Robertson, M.; Monchesky, T. L.

doi:10.1103/physrevb.86.144420

Cited by 106 publications

(138 citation statements)

References 33 publications

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“…The period of the helix is about 68 nm, similar to the value in bulk λ ≈ 70 nm (18). However, the spatial confinement effect in the lateral direction yields an incomplete helix around the disk edge due to the specific form of the boundary conditions (20,21).…”

Section: Significancesupporting

confidence: 58%

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

113

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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...

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Section: Significancesupporting

confidence: 58%

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

113

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“…The uniaxial magnetic anisotropy enhanced at low temperatures is perhaps the major contribution as theoretically suggested. 18 To highlight the hysteretic formation of the in-plane skyrmion, we map in Fig. 5(b) the ∆ρ PHE, Hys yx defined as difference calculated by subtracting ρ PHE yx with decreasing field from that with increasing field, which removes the M-induced PHE showing a significant contribution above H c between 20-50 K. As described above, the in-plane skyrmion formation largely depends on the magnetic field history; namely, skyrmions tend to coexist with the ferromagnetic (helical) state in the increasing (decreasing) field process.…”

Section: Resultsmentioning

confidence: 99%

Formation of In-plane Skyrmions in Epitaxial MnSi Thin Films as Revealed by Planar Hall Effect

et al. 2015

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We investigate skyrmion formation in both a single crystalline bulk and epitaxial thin films of MnSi by measurements of planar Hall effect. A prominent stepwise field profile of planar Hall effect is observed in the well-established skyrmion phase region in the bulk sample, which is assigned to anisotropic magnetoresistance effect with respect to the magnetic modulation direction. We also detect the characteristic planar Hall anomalies in the thin films under the inplane magnetic field at low temperatures, which indicates the formation of skyrmion strings lying in the film plane. Uniaxial magnetic anisotropy plays an important role in stabilizing the in-plane skyrmions in the MnSi thin film.

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“…In this paper, we focus on MnSi films L D < d < 2L D , where only one row of skrymions are theoretically expected to form in the middle of the film 27 . MnSi films with thicknesses of either d = 25.2 nm or 26.7 nm were grown by molecular beam epitaxy on Si(111) substrates.…”

Section: Methodsmentioning

confidence: 99%

“…The filled (unfilled) circles correspond to peaks in dM/dH measured in decreasing (increasing) magnetic fields for a d = 26.7 nm sample. The blue squares are minima in dM 2 /dH 2 for increasing magnetic fields 27 . The PNR experiments were performed in successively decreasing magnetic fields at the (H, T ) points shown by the yellow stars (this study), and by the yellow triangles (Ref.…”

Section: Introductionmentioning

confidence: 99%

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Neutron study of in-plane skyrmions in MnSi thin films

et al. 2017

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The magnetic structure of the in-plane skyrmions in epitaxial MnSi/Si(111) thin films is probed in three dimensions by the combination of polarized neutron reflectometry (PNR) and small angle neutron scattering (SANS). We demonstrate that skyrmions exist in a region of the phase diagram above at temperature of 10 K. PNR shows the skyrmions are confined to the middle of the film due to the potential well formed by the surface twists. However, SANS shows that there is considerable disorder within the plane indicating that the magnetic structure is a 2D skyrmion glass.

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Extended elliptic skyrmion gratings in epitaxial MnSi thin films

Cited by 106 publications

References 33 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

Formation of In-plane Skyrmions in Epitaxial MnSi Thin Films as Revealed by Planar Hall Effect

Neutron study of in-plane skyrmions in MnSi thin films

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