Rhombic skyrmion lattice coupled with orthorhombic structural distortion in EuAl 4

2021

Sci Rep

We theoretically investigate a new stabilization mechanism of a skyrmion crystal (SkX) in centrosymmetric itinerant magnets with magnetic anisotropy. By considering a trigonal crystal system without the horizontal mirror plane, we derive an effective spin model with an anisotropic Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction for a multi-band periodic Anderson model. We find that the anisotropic RKKY interaction gives rise to two distinct SkXs with different skyrmion numbers of one and two depending on a magnetic field. We also clarify that a phase arising from the multiple-Q spin density waves becomes a control parameter for a field-induced topological phase transition between the SkXs. The mechanism will be useful not only for understanding the SkXs, such as that in Gd$$_2$$ 2 PdSi$$_3$$ 3 , but also for exploring further skyrmion-hosting materials in trigonal itinerant magnets.

Section: Introductionmentioning

confidence: 99%

Skyrmion crystals in centrosymmetric itinerant magnets without horizontal mirror plane

Yambe

2021

Sci Rep

“…Another example is a centrosymmetric tetragonal magnet EuAl 4 . In contrast to MnSi and Co 8 Zn 8 Mn 4 , two types of SkXs, which were identified as the S-SkX and a rhombic SkX, have been observed as thermodynamics phases by changing the magnetic field [30][31][32][33]. In this compound, the model calculations have shown that the competition of the interactions in momentum space that arise from the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mediated by itinerant electrons [34][35][36] or frustrated exchange interactions plays an important role [30,32,33].…”

Section: Introductionmentioning

confidence: 99%

“…In contrast to MnSi and Co 8 Zn 8 Mn 4 , two types of SkXs, which were identified as the S-SkX and a rhombic SkX, have been observed as thermodynamics phases by changing the magnetic field [30][31][32][33]. In this compound, the model calculations have shown that the competition of the interactions in momentum space that arise from the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mediated by itinerant electrons [34][35][36] or frustrated exchange interactions plays an important role [30,32,33]. More recently, such structural transition of the equilibrium SkX phases has also been observed in a polar magnet EuNiGe 3 , where the long-range Dzyaloshinskii-Moriya (DM) interaction [37,38], as well as the RKKY interaction, contributes to the emergence of the multiple SkXs [39].…”

Section: Introductionmentioning

confidence: 99%

Uniaxial Distortion Effect on Magnetic Skyrmion Crystals in a Frustrated Triangular-Lattice System

Proceedings of the 29th International Conference on Low Temperature Physics (LT29)

2023

Magnetic skyrmions with topologically nontrivial spin textures form a variety of periodic structures depending on microscopic interactions and lattice symmetry. We theoretically investigate a transformation between triangular and square skyrmion crystals against an external magnetic field in a polar tetragonal magnet. By performing the simulated annealing for a classical spin model, we show that the competition of the Dzyaloshinskii-Moriya interaction at multiple wave vectors is a key ingredient in inducing the structural transition in terms of the skyrmion crystals. The present results indicate the importance of magnetic frustration in momentum space as the origin of exotic topological phase transitions.

“…Meanwhile, it has not been clarified the possibility of the SkXs under the in-plane field on a centrosymmetric square lattice, where the effect of geometrical frustration does not appear. Although the * hayami@phys.sci.hokudai.ac.jp emergence of the SkXs on such a square lattice in the out-of-plane magnetic field has been shown by the theoretical model calculations [31][32][33][34] and experiments in GdRu 2 Si 2 [15,[35][36][37][38][39] and EuAl 4 [40][41][42][43], its stabilization condition under the in-plane magnetic field has been unclear yet.…”

Section: Introductionmentioning

confidence: 99%

Rectangular and square skyrmion crystals on a centrosymmetric square lattice with easy-axis anisotropy

2022

Phys. Rev. B

We investigate the instability toward a skyrmion crystal under an in-plane magnetic field in centrosymmetric tetragonal magnets. By performing the simulated annealing for a spin model on the square lattice, we find that the interplay among the easy-plane two-spin anisotropic interaction, positive biquadratic interaction, and high-harmonic wave-vector interaction plays an important role in stabilizing the skyrmion crystal in the in-plane external magnetic field. The obtained skyrmion crystal consists of a pair of vortex and antivortex with opposite polarization in terms of the out-ofplane spin component. We also show that various multiple-Q states emerge depending on the model parameters. Our results indicate the possibility of topological spin textures in centrosymmetric tetragonal magnets with easy-plane magnetic anisotropy when the ground-state spin configuration at zero field is characterized by a single-Q in-plane cycloidal spiral state.