Bubble domains in magnetostatically coupled garnet films

Lin, Yu-Kun; Grundy, P.J.; Giess, E. A.

doi:10.1063/1.1654968

Cited by 94 publications

(60 citation statements)

References 2 publications

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“…Indeed, realization of magnetic skyrmions was recently discovered in polar magnet GaV 4 S 8 with rhombohedral C 3v symmetry [116]. In addition to these non-centrosymmetric ferromagnets, observations of skyrmions have been reported even for centrosymmetric ferromagnetic insulators with uniaxial anisotropy such as Y 3 Fe 5 O 12 [137,136] [140]. Crystal structures of these materials have spatial inversion symmetry, and thus the Dzyaloshinskii-Moriya interaction is not active.…”

Section: Summary and Perspectivesmentioning

confidence: 99%

Dynamical magnetoelectric phenomena of multiferroic skyrmions

Mochizuki¹,

Seki²

2015

J. Phys.: Condens. Matter

101

112

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Abstract. Magnetic skyrmions, vortex-like swirling spin textures characterized by a quantized topological invariant, realized in chiral-lattice magnets are currently attracting intense research interest. In particular, their dynamics under external fields is an issue of vital importance both for fundamental science and for technical application. Whereas observations of magnetic skyrmions had been limited to metallic magnets so far, their realization was discovered also in a chiral-lattice insulating magnet Cu 2 OSeO 3 in 2012. Skyrmions in the insulator turned out to exhibit multiferroic nature with spin-induced ferroelectricity. Strong magnetoelectric coupling between noncollinear skyrmion spins and electric polarizations mediated by relativistic spin-orbit interaction enables us to drive motion and oscillation of magnetic skyrmions by application of electric fields instead of injection of electric currents. Insulating materials also provide an environment suitable for detection of pure spin dynamics through spectroscopic measurements owing to absence of appreciable charge excitations. In this article, we review recent theoretical and experimental studies on multiferroic properties and dynamical magnetoelectric phenomena of magnetic skyrmions in insulators. We argue that multiferroic skyrmions show unique coupled oscillation modes of magnetizations and polarizations, so-called electromagnon excitations, which are both magnetically and electrically active, and interference between the electric and magnetic activation processes leads to peculiar magnetoelectric effects in a microwave frequency regime. Its magnetizations point in all directions wrapping a sphere. (b) Schematic of the vortextype skyrmion discovered in chiral-lattice ferromagnets, which corresponds to a projection of the hedgehog-type skyrmion onto a two-dimensional plane. Its magnetizations also point everywhere wrapping a sphere. (c) Schematic of a skyrmion crystal realized in chiral-lattice ferromagnets under an external magnetic field, in which skyrmions are hexagonally packed to form a triangular lattice. (d) Helical spin structure (or proper screw spin structure) with magnetizations rotating within a plane normal to propagation vector q.

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Section: Summary and Perspectivesmentioning

confidence: 99%

Dynamical magnetoelectric phenomena of multiferroic skyrmions

Mochizuki¹,

Seki²

2015

J. Phys.: Condens. Matter

101

112

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“…1 However, due to the manifold of interaction mechanisms between spins, the generation of skyrmions is not a trivial matter. [2][3][4][5][6][7][8][9][10][11][12] Spin spirals are also chiral spin textures, and are topologically similar to skyrmions. The close association between these spiral and skyrmion phases necessitates a careful and systematic study of the competing interaction mechanisms, especially the symmetric and antisymmetric exchange in the context of chiral states, and the rationale for their proclivity towards either spin texture in different material systems.…”

Section: Introductionmentioning

confidence: 99%

Exchange and Dzyaloshinskii-Moriya interactions in bulk FeGe: Effects of atomic vacancies

Loh

Gan

2017

AIP Advances

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We examine the effects of atomic vacancies on the (1) spin interaction, and (2) electronic character in the cubic B20 chiral magnet FeGe. For the former, Heisenberg exchange and Dzyaloshinskii-Moriya (DM) interactions are studied. The latter is done via a particular Wannier flavor of the Hamiltonian in the form of maximally-localized Wannier functions (MLWFs). Using first-principles calculations based on full-potential linearized augmented plane-wave (FLAPW)-based density functional theory (DFT), the spin order of bulk FeGe, in its pristine form, and with a Fe (Fe75%Ge100%) or Ge vacancy (Fe100%Ge75%) is investigated. Despite the presence of vacancies, the ground state of FeGe remains helimagnetic, i.e. spin spirals in FeGe are fairly robust. The energetic stability of FeGe increases in the presence of the vacancies. The spiral size is increased by approximately 40%, suggesting that vacancies can be introduced to manipulate the chiral order. The vacancies lift the band degeneracy in the valence manifold of the Wannier-interpolated band structures. Only the spin-down Fermi surfaces are substantially different between the pristine and defective FeGe; it is electron-like in the pristine case, but largely hole-like in the defective ones. The Ge vacancy splits the Fermi surface more than the Fe vacancy. The Heisenberg exchange between nearest Fe pairs is ferromagnetic in pristine FeGe. This Fe-Fe interaction remains ferromagnetic, albeit a slight decrease in strength, in the presence of a Fe vacancy. In contrast, a Ge vacancy in FeGe induces anti-ferromagnetism between nearest Fe pairs. By including spin-orbit coupling effects, we find that the DM interaction of defective FeGe is reversed in sign, and it is more uniform in strength along the three highly symmetric directions, relative to that in pristine FeGe. All in all, the versatility of FeGe makes it an excellent functional material, especially in data storage and spintronics applications.

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“…So far, they have been observed in materials with perpendicular magnetic anisotropy in connection with one of the following stabilization mechanisms: (i) four-spin exchange, leading to the formation of a Skyrmion lattice with each Skyrmion extending over a few lattice sites [2]; (ii) the Dzyaloshinskii-Moriya interaction [3,4], which is active in noncentrosymmetric helimagnets, where Skyrmions have typical dimensions of few tens of nanometers [5][6][7][8]; (iii) the long-range dipoledipole interaction (DDI) [9] stabilizing Skyrmions with a typical lateral size of the order of 1 m [10][11][12]. It has been recently found that the DDI can induce a larger and more complex variety of magnetic textures with respect to the ones that are observed in association with four-spin exchange and the Dzyaloshinskii-Moriya interaction [9].…”

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confidence: 99%

Laser-Induced Magnetic Nanostructures with Tunable Topological Properties

et al. 2013

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We report the creation and real-space observation of magnetic structures with well-defined topological properties and a lateral size as low as about 150 nm. They are generated in a thin ferrimagnetic film by ultrashort single optical laser pulses. Thanks to their topological properties, such structures can be classified as Skyrmions of a particular type that does not require an externally applied magnetic field for stabilization. Besides Skyrmions, we are able to generate magnetic features with topological characteristics that can be tuned by changing the laser fluence. The stability of such features is accounted for by an analytical model based on the interplay between the exchange and the magnetic dipole-dipole interactions.

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Bubble domains in magnetostatically coupled garnet films

Cited by 94 publications

References 2 publications

Dynamical magnetoelectric phenomena of multiferroic skyrmions

Dynamical magnetoelectric phenomena of multiferroic skyrmions

Exchange and Dzyaloshinskii-Moriya interactions in bulk FeGe: Effects of atomic vacancies

Laser-Induced Magnetic Nanostructures with Tunable Topological Properties

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