Unique Electronic States of Eu-based Compounds

Ōnuki, Yoshichika; Hedo, Masato; Honda, Fuminori

doi:10.7566/jpsj.89.102001

Cited by 49 publications

(22 citation statements)

References 103 publications

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“…The candidate materials are Y 3 Co 8 Sn 4 hosting the 3Q vortex crystal 92 , EuPtSi [93][94][95][96][97] and Gd 3 Ru 4 Al 12 [98][99][100] hosting the 3Q SkX, and MnSi 1−x Ge x 69,101-105 and SrFeO 3 106-109 hosting the 3Q and 4Q hedgehog crystals. Furthermore, our finding will provide a clue to understand complex charge and magnetic orderings recently found in materials, such as GdSb x Te 2−x−δ 110 and EuAl 4 [111][112][113] . Thus, the present results stimulate a further study of exotic spin-charge entanglement in itinerant magnets.…”

Section: Discussionmentioning

confidence: 73%

Charge density waves in multiple-$Q$ spin states

Hayami,

Motome

2021

Preprint

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Coupling between spin and charge degrees of freedom in electrons is a source of various electronic and magnetic properties of solids. We theoretically study charge density waves induced by the spin-charge coupling in the presence of magnetic orderings in itinerant magnets. By performing a perturbative calculation in the weakcoupling limit of the Kondo lattice model, we derive a useful formula for the relationship between charge and spin density waves, which can be applied to any magnetic orderings, including noncollinear and noncoplanar ones composed of multiple spin density waves called multiple-Q magnetic orderings. We demonstrate the predictive power for single-Q and double-Q states including skyrmion and meron-antimeron crystals on a square lattice, in comparison with the numerical calculations. Moreover, we show that the charge density waves contain richer information than the spin density waves, and are indeed useful in distinguishing the spin textures with similar spin structure factors. We discuss the relation to bond modulation in terms of the kinetic bond energy and the vector spin chirality. We also perform numerical calculations beyond the perturbative regime and find that the charge density waves can be enhanced when the electron filling is commensurate. Furthermore, we investigate the effect of the spin-orbit coupling, which can lead to additional charge density waves owing to effective anisotropic magnetic interactions in momentum space. Our result will provide a way to identify complex magnetic orderings and their origins from the charge modulations.

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Section: Discussionmentioning

confidence: 73%

Charge density waves in multiple-$Q$ spin states

Hayami,

Motome

2021

Preprint

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“…Recently, a symmetry-protected non-trivial topology of the electronic band structure was proposed for BaAl 4 (Wang et al, 2021). In case of magnetic EuAl 4 , a chiral spin structure, like skyrmions reported in some divalent Eu compounds such as EuPtSi (Kaneko et al, 2019;Ōnuki et al, 2020), was proposed on the basis of the observation of the topological Hall resistivity and muon-spin rotation and relaxation (µSR) studies (Shang et al, 2021;Zhu et al, 2022). If such a nontrivial texture would be confirmed, EuAl 4 would represent a rare case of a compound where one could observe the coexistence of exotic magnetic order and a CDW.…”

Section: Introductionmentioning

confidence: 99%

“…1. It belongs to a large family of isostructural compounds, including magnetic EuGa 4 , fully ordered EuAl 2 Ga 2 and IUCr macros version 2.1.15: 2021/03/05 non-magnetic SrAl 4 and BaAl 4 (Nakamura et al, 2016;Stavinoha et al, 2018;Ōnuki et al, 2020). Recently, a symmetry-protected non-trivial topology of the electronic band structure was proposed for BaAl 4 (Wang et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Orthorhombic charge density wave on the tetragonal lattice of EuAl4

Ramakrishnan,

Kotla,

Rekis

et al. 2022

Preprint

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PREPRINT: IUCrJ A Journal of the International Union of Crystallography EuAl 4 possesses the BaAl 4 crystal structure type with tetragonal symmetry I4/mmm. It undergoes a charge-density-wave (CDW) transition at T CDW = 145 K and it features four consecutive antiferromagnetic phase transitions below 16 K. Here, we use single-crystal x-ray diffraction to determine incommensurately modulated crystal structure of EuAl 4 in its CDW state. The CDW is shown to be incommensurate with modulation wave vector q = (0, 0, 0.1781(3)) at 70 K. The symmetry of the incommensurately modulated crystal structure is orthorhombic with superspace group F mmm(00σ)s00, where F mmm is a subgroup of I4/mmm of index 2. Both the lattice and the atomic coordinates of the basic structure remain tetragonal. Symmetry breaking is entirely due to the modulation wave, where atoms Eu and Al1 have displacements exclusively along a, while the fourfold rotation would require equal displacement amplitudes along a and b. The calculated band structure of the basic structure and interatomic distances in the modulated crystal structure both indicate the aluminum atoms as location of the CDW. The temperature dependence of the specific heat reveals an anomaly at T CDW = 145 K of a magnitude similar to canonical CDW systems. The present discovery of orthorhombic symmetry for the CDW state of EuAl 4 leads to the suggestion of monoclinic instead of orthorhombic symmetry for the third AFM state.

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“…Although more realistic model parameters based on the density-functional theory calculation might be desired for a further comparison, the effective spin model will be a good starting model to capture SkX physics in EuPtSi. Moreover, as the effective model is universal in RKKY-driven itinerant magnets, the present results will be a useful reference to understand complex magnetic phases in other f -electron compounds, where the recent experiments imply the SkXs, such as EuPtGe 55) and EuAl 4 . 55,56)…”

mentioning

confidence: 72%

Field-Direction Sensitive Skyrmion Crystals in Cubic Chiral Systems: Implication to $4f$-Electron Compound EuPtSi

Hayami,

Yambe

2021

Preprint

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We theoretically study the stability of magnetic skyrmion crystals (SkXs) in chiral cubic antiferromagnets with the EuPtSi hosting unconventional nanometric SkXs in mind. By performing numerical simulations for a minimal effective spin model with the long-range Dzyaloshinskii-Moriya interaction and the multiple-spin interaction arising from itinerant nature of electrons, we clarify two key ingredients for the emergence of the SkXs in EuPtSi: One is the lowsymmetric ordering vectors that lead to the field-direction sensitive SkXs in an external magnetic field, while the other is the synergy between spin-charge and spin-orbit couplings in itinerant magnets that results in the nanometric SkXs. The present study will not only provide the microscopic mechanism of the SkXs in EuPtSi but also guide for a search of further materials hosting short-period SkXs.

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Unique Electronic States of Eu-based Compounds

Cited by 49 publications

References 103 publications

Charge density waves in multiple-$Q$ spin states

Charge density waves in multiple-$Q$ spin states

Orthorhombic charge density wave on the tetragonal lattice of EuAl4

Field-Direction Sensitive Skyrmion Crystals in Cubic Chiral Systems: Implication to $4f$-Electron Compound EuPtSi

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