Bubble and skyrmion crystals in frustrated magnets with easy-axis anisotropy

Hayami, Satoru; Lin, Shi-Zeng; Batista, Cristian D.

doi:10.1103/physrevb.93.184413

Cited by 189 publications

(196 citation statements)

References 37 publications

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“…In addition, several frustrated magnets such as the triangular antiferromagnets are predicted to host the skyrmion lattice phase . Instead of the DM interaction, the competition between the nearest‐neighbor (NN) and next‐nearest‐neighbor (NNN) interactions is essential for stabilizing the skyrmions . Moreover, the first observation of skyrmionic magnetic bubbles formed at room temperature has been reported experimentally in the frustrated kagome Fe 3 Sn 2 magnet, well confirming the earlier predictions.…”

supporting

confidence: 77%

Skyrmion Crystals in Frustrated Shastry–Sutherland Magnets

Huang

et al. 2019

Physica Rapid Research Ltrs

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The phase diagrams of the frustrated classical spin model with the Dzyaloshinskii–Moriya (DM) interaction on the Shastry–Sutherland lattice are studied by means of Monte Carlo simulations. For ferromagnetic next‐nearest‐neighboring (J2) interactions, the introduced exchange frustration enhances the effect of the DM interaction, which enlarges the magnetic field‐range with the skyrmion lattice phase and increases the skyrmion density. For antiferromagnetic J2 interactions, the so‐called 2q phase (two‐sublattice skyrmion crystal) and the spin‐flop phase are observed, and their stabilizations are closely dependent on the DM interaction and J2 interaction, respectively. The simulated results are qualitatively explained from the energy competitions among these couplings, which provide an important guidance for finding skyrmion crystals in frustrated magnets.

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supporting

confidence: 77%

Skyrmion Crystals in Frustrated Shastry–Sutherland Magnets

Huang

et al. 2019

Physica Rapid Research Ltrs

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“…This is in contrast to the presence of the six peaks in the chirality structure factor in the Skyrmion crystal phase, e.g., found in Ref. [17]. Following Ref.…”

Section: Triangular Latticementioning

confidence: 70%

Effective bilinear-biquadratic model for noncoplanar ordering in itinerant magnets

2017

Self Cite

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Noncollinear and noncoplanar magnetic textures including Skyrmions and vortices act as emergent electromagnetic fields and give rise to novel electronic and transport properties. We here report a unified understanding of noncoplanar magnetic orderings emergent from the spin-charge coupling in itinerant magnets. The mechanism has its roots in effective multiple spin interactions beyond the conventional Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism, which are ubiquitously generated in itinerant electron systems with local magnetic moments. By carefully examining the higher-order perturbations in terms of the spin-charge coupling, we construct a minimal effective spin model composed of the bilinear and biquadratic interactions with particular wave numbers dictated by the Fermi surface. Taking two-dimensional systems as examples, we find that our effective model captures the underlying physics of the instability toward noncoplanar multiple-Q states discovered recently: a single-Q helical state expected from the RKKY theory is replaced by a double-Q vortex crystal with chirality density waves even for an infinitely small spin-charge coupling on generic lattices [R. Ozawa et al., J. Phys. Soc. Jpn. 85, 103703 (2016)], and a triple-Q Skyrmion crystal with a high topological number of two appears while increasing the spin-charge coupling on a triangular lattice [R. Ozawa, S. Hayami, and Y. Motome, Phys. Rev. Lett. 118, 147205 (2017)]. We find that by introducing an external magnetic field, our effective model exhibits a plethora of multiple-Q states. Our effective model will serve as a guide for exploring further exotic magnetic orderings in itinerant magnets, not only in two dimensions but also in three dimensions.

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“…Our results also apply to double exchange systems with orbital degeneracy [30], since the non-Bravais honeycomb, kagome and pyrocholore lattices can be considered as block lattices with several electron orbitals per block. The instability of the FM state can lead to more complex non-collinear and non-coplanar magnetic orders: an applied magnetic field, magnetic anisotropies and thermal fluctuations can stabilize multiply periodic states, such as the skyrmion crystal [31][32][33], which may explain the complexity of the phase diagram of the itinerant cubic magnet, SrFeO 3 [34]. In this section we derive Eq.(4).…”

Section: Instablity Of the Fm Statementioning

confidence: 99%

Incommensurate Spiral Order from Double-Exchange Interactions

Azhar

Mostovoy

2017

Phys. Rev. Lett.

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The double exchange model describing interactions of itinerant electrons with localized spins is usually used to explain ferromagnetism in metals. We show that for a variety of crystal lattices of different dimensionalities and for a wide range of model parameters the ferromagnetic state is unstable against a non-collinear spiral magnetic order. We revisit the phase diagram of the double exchange model on a triangular lattice and show in a large part of the diagram the incommensurate spiral state has a lower energy than the previously discussed commensurate states. These results indicate that double exchange systems are inherently frustrated and can host unconventional spin orders. Introduction: Non-collinear spin orders are inextricably related to inversion symmetry breaking in crystals and give rise to unconventional physical phenomena, such as magnetically-induced ferroelectricity and electric excitation of magnons in spiral magnets [1,2]. Non-coplanar spin structures of skyrmions induce effective electromagnetic fields resulting in topological electron and magnon Hall effects [3]. Skyrmion dynamics induced by applied electric currents can be used in high-density magnetic memory devices [4]. Non-collinear magnetic orders are, however, relatively rare and it is of great interest to find new materials showing such states.There are several well-understood microscopic mechanisms for non-collinear spin ordering. One of them is the relativistic Dzyaloshinskii-Moriya interaction which stabilizes spiral and skyrmion crystal states in chiral magnets [5,6]. Non-collinear magnetism in Mott insulators is often a result of competing ferromagnetic (FM) and antiferromagnetic (AFM) Heisenberg interactions between spins, while in magnets with both itinerant and localized electrons it can originate from the RKKY interaction [7][8][9] closely related to Fermi surface instability.Here we focus on the double exchange (DE), which was originally invoked to explain ferromagnetism in doped manganites [10,11]. The DE model, also known as the ferromagnetic Kondo lattice model, describes a lattice of classical spins interacting with the conduction electrons through the Hund's rule coupling which aligns the spins of the conduction and localized electrons occupying the same lattice site. If the spins on neighboring sites are not parallel, the effective electron hopping amplitude decreases, which increases kinetic energy of the conduction electrons. In this way conduction electrons provide an effective FM interaction between the lattice spins.This argument, however, cannot hold for all values of the model parameters, which is clear already from the fact that in the limit of small Hund's rule coupling constant, J, the model yields the RKKY interactions that can be FM or AFM, depending on the distance between

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Bubble and skyrmion crystals in frustrated magnets with easy-axis anisotropy

Cited by 189 publications

References 37 publications

Skyrmion Crystals in Frustrated Shastry–Sutherland Magnets

Skyrmion Crystals in Frustrated Shastry–Sutherland Magnets

Effective bilinear-biquadratic model for noncoplanar ordering in itinerant magnets

Incommensurate Spiral Order from Double-Exchange Interactions

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