Redetermination of Co4Nb2O9 by single-crystal X-ray methods

Castellanos, A R María; Bernès, Syl­vain; Vega-González, Marina

doi:10.1107/s1600536806012141

Cited by 16 publications

(19 citation statements)

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“…Along the crystallographic c axis, the structure of Fe 4 Ta 2 O 9 can be visualized to be made up of two distinct layers. The first layer (A) comprises of hexagonal rings of edge sharing Fe1O 6 octahedra, with the adjacent layer (B) being made up of alternating edge sharing Fe2O 6 and TaO 6 octahedra, as is schematically shown in Fig.1(b) [20]. The structural details as obtained from the Rietveld refinement of room temperature diffraction data are summarized in TableI.…”

Section: Resultsmentioning

confidence: 99%

Coupled magnetic and ferroelectric states in the distorted honeycomb system Fe4Ta2O9

et al. 2018

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We report on the magnetic, thermodynamic, dielectric, and pyroelectric measurements on the hitherto unreported Fe4Ta2O9. This system is seen to exhibit a series of magnetic transitions, many of which are coupled to the emergence of ferroelectric order, making Fe4Ta2O9 the only genuine multiferroic in its material class. We suggest that the observed properties arise as a consequence of an effective reduction in the dimensionality of the magnetic lattice, with the magnetically active Fe 2+ ions preferentially occupying a quasi 2D buckled honeycomb structure. The low temperature H-T phase diagram of Fe4Ta2O9 reveals a rich variety of coupled magnetic and ferroelectric phases, in similarity with that observed in the distorted Kagome systems.

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Section: Resultsmentioning

confidence: 99%

Coupled magnetic and ferroelectric states in the distorted honeycomb system Fe4Ta2O9

et al. 2018

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“…In our theoretical calculations we used the experimental structure parameters, measured around the room temperature: T = 297 K for Co 4 Nb 2 O 9 and T = 298 K for Co 4 Ta 2 O 9 . 15,16 These parameters do not take into account some possible change of the crystal structure, which may occur below T N . Indeed, since the magnetic alignment in the hexagonal plane lowers the original P 3c1 symmetry, it is reasonable to expect also some changes in the crystal structure, which adjust to the change of the magnetic structure.…”

Section: Discussionmentioning

confidence: 99%

Experimental and first-principles studies of magnetism and magnetoelectric effect in Co4Nb2O9 and Co4Ta2O9

Solovyev,

Kolodiazhnyi

2016

Preprint

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We report results of joint experimental and theoretical studies on magnetoelectric (ME) compounds Co 4 Nb 2 O 9 and Co 4 Ta 2 O 9 . On the experimental side, we present results of the magnetization and dielectric permittivity measurements in the magnetic field. On the theoretical side, we construct the low-energy Hubbard-type model for the magnetically active Co3d bands in the Wannier basis, using the input of first-principles electronic structure calculations, solve this model in the mean-field Hartree-Fock approximation, and evaluate the electric polarization in terms of the Berry phase theory. Both experimental and theoretical results suggest that Co 4 Ta 2 O 9 is magnetically softer than Co 4 Nb 2 O 9 . Therefore, it is reasonable to expect that the antiferromagnetic structure of Co 4 Ta 2 O 9 can be easier deformed by the external magnetic field, yielding larger polarization. This trend is indeed reproduced by our theoretical calculations, but does not seem to be consistent with the experimental behavior of the polarization and dielectric permittivity. Thus, we suggest that there should be a hidden mechanism controlling the ME coupling in these compounds, probably related to the magnetic striction or a spontaneous change of the magnetic structure, which breaks the inversion symmetry. Furthermore, we argue that unlike in other ME systems (e.g. Cr 2 O 3 ), in Co 4 Nb 2 O 9 and Co 4 Ta 2 O 9 there are two crystallographic sublattices, which contribute to the ME effect. These contributions are found to be of the opposite sign and tend to compensate each other. The latter mechanism can be also used to control and reverse the electric polarization in these compounds.

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“…1. 1,10,31 Co 2+ ions form a honeycomb lattice structure along the ab-plane through O 2− ions. The space group is P 3c1 and the local symmetry at the Co site is represented by the C 3 point group with no inversion symmetry at the Co site.…”

Section: Spin-dependent Electric Dipolementioning

confidence: 99%

“…The space group is P 3c1 and the local symmetry at the Co site is represented by the C 3 point group with no inversion symmetry at the Co site. 1,10,31 Non-equivalent Co sites are denoted by Co(1) and Co(2). In the trigonal P 3c1 space group, there are inversion centers and twofold axes in a unit cell.…”

Section: Spin-dependent Electric Dipolementioning

confidence: 99%

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Symmetry Analysis of Magnetoelectric Effects in Honeycomb Antiferromagnet Co₄Nb₂O₉

Matsumoto

Koga

2019

J. Phys. Soc. Jpn.

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Magnetoelectric effects in honeycomb antiferromagnet Co4Nb2O9 are investigated on the basis of symmetry analyses of Co 2+ ions in trigonal P3c1 space group. For each Co 2+ ion, the possible spin dependence is classified by C3 point-group symmetry. This accounts for the observed main effect that an electric polarization rotates in the opposite direction at the twice speed relative to the rotation of the external magnetic field applied in the ab-plane. Inversion centers and twofold axes in the unit cell restrict the active spin-dependence of the electric polarization, which well explains the observed experimental results. Expected optical properties of quadrupolar excitation and various types of dichroism are also discussed. arXiv:1908.03004v1 [cond-mat.str-el]

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Redetermination of Co₄Nb₂O₉ by single-crystal X-ray methods

Abstract: Key indicatorsSingle-crystal X-ray study T = 297 K Mean (Co-O) = 0.004 Å R factor = 0.031 wR factor = 0.079 Data-to-parameter ratio = 13.1 For details of how these key indicators were automatically derived from the article, see

Cited by 16 publications

References 4 publications

Coupled magnetic and ferroelectric states in the distorted honeycomb system Fe4Ta2O9

Coupled magnetic and ferroelectric states in the distorted honeycomb system Fe4Ta2O9

Experimental and first-principles studies of magnetism and magnetoelectric effect in Co4Nb2O9 and Co4Ta2O9

Symmetry Analysis of Magnetoelectric Effects in Honeycomb Antiferromagnet Co₄Nb₂O₉

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Redetermination of Co4Nb2O9 by single-crystal X-ray methods

Abstract: Key indicatorsSingle-crystal X-ray study T = 297 K Mean (Co-O) = 0.004 Å R factor = 0.031 wR factor = 0.079 Data-to-parameter ratio = 13.1 For details of how these key indicators were automatically derived from the article, see

Cited by 16 publications

References 4 publications

Coupled magnetic and ferroelectric states in the distorted honeycomb system Fe4Ta2O9

Coupled magnetic and ferroelectric states in the distorted honeycomb system Fe4Ta2O9

Experimental and first-principles studies of magnetism and magnetoelectric effect in Co4Nb2O9 and Co4Ta2O9

Symmetry Analysis of Magnetoelectric Effects in Honeycomb Antiferromagnet Co4Nb2O9

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Redetermination of Co₄Nb₂O₉ by single-crystal X-ray methods

Symmetry Analysis of Magnetoelectric Effects in Honeycomb Antiferromagnet Co₄Nb₂O₉