Redetermination of the crystal structure of sodium vanadate, α'-NaV2O5

Schnering, H. G. von; Grin, Yu.; Kaupp, Martin; Somer, M.; Kremer, Reinhard K.; Jepsen, O.; Chatterji, Tapan; Weiden, M.

doi:10.1524/ncrs.1998.213.14.260

Cited by 38 publications

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“…The opening of a gap in the magnetic excitation spectrum below T c leads to a vanishing of a low-frequency continuum and to the appropriate transformation of the line shapes. Subsequent structure redetermination for the HT phase of α ′ -NaV 2 O 5 [2][3][4][5] does not, however, allow to ascribe E a polarized spectral continuum to a pure twospinon absorption. Symmetry considerations show that for both HT-and LT-structure of α ′ -NaV 2 O 5 the two-spinon (two-magnon) absorption is allowed only in E c polarization [33,34].…”

Section: Resultsmentioning

confidence: 98%

Lattice vibrations ofα′−NaV2O5
Popova
¹
,
Sushkov
²
,
Климин
³

et al. 2002
Phys. Rev. B
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We report high resolution polarized infrared studies of the quarter-filled spin ladder compound α ′ -NaV2O5 as a function of temperature (5 K≤ T ≤ 300 K). Numerous new modes were detected below the temperature Tc = 34 K of the phase transition into a charge ordered nonmagnetic state accompanied by a lattice dimerization. We analyse the Brillouin zone (BZ) folding due to lattice dimerization at Tc and show that some peculiarities of the low-temperature vibrational spectrum come from quadruplets folded from the BZ point ( ). We discuss an earlier interpretation of the 70, 107, and 133 cm −1 modes as magnetic bound states and propose the alternative interpretation as folded phonon modes strongly interacting with charge and spin excitations.

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Section: Resultsmentioning

confidence: 98%

Lattice vibrations ofα′−NaV2O5
Popova
¹
,
Sushkov
²
,
Климин
³

et al. 2002
Phys. Rev. B
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“…These are closely related to the crystal structure and the site symmetry. The roomtemperature structure of α ′ -NaV 2 O 5 belongs to space group P mmn, [2][3][4] in which structure Na ions occupy a unique atomic position of site symmetry mm2 . The principal axes of the electrical field gradient and NMR shift tensors are identical to the crystallographic axes accordingly.…”

Section: +mentioning

confidence: 99%

Zigzag Charge Ordering in α^′-NaV₂O₅

et al. 2000

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23 Na NMR spectrum measurements in α ′ -NaV2O5 with a single-crystalline sample are reported. In the charge-ordered phase, the number of inequivalent Na sites observed is more than that expected from the low-temperature structures of space group Fmm2 reported so far. This disagreement indicates that the real structure including both atomic displacement and charge disproportionation is of lower symmetry. It is suggested that zigzag ordering is the most probable. The temperature variation of the NMR spectra near the transition temperature is incompatible with that of second-order transitions. It is thus concluded that the charge ordering transition is first-order.KEYWORDS: α ′ -NaV 2 O 5 , NMR, charge ordering, crystal structure, spin-ladder, trellis latticeSince the phase transition into a spin-gapped phase in α ′ -NaV 2 O 5 was reported, 1) a lot of experimental efforts have been devoted to understand the nature of this transition. Although it was initially identified as a spin-Peierls transition, a recent room-temperature structural study 2) questioned this interpretation: it concluded that all V ions are in a uniform oxidation state of V 4.5+and form a quarter-filled trellis lattice composed of twoleg ladders. After that, 51 V NMR measurements 5) revealed charge ordering of V 4+ and V 5+ states below the transition temperature T C ∼ 34 K. Subsequent theoretical studies showed that long-range Coulomb interaction can induce charge ordering in a quarter-filled trellis lattice. 6-9) These studies suggest zigzag or linear chain ordering depending on the strength of the longrange Coulomb interactions. The proposed mechanism of charge ordering is similar to that for charge density wave in quarter-filled systems of low-dimensional organic compounds, 10) suggesting some common physics to α ′ -NaV 2 O 5 and these systems. Soon after the finding of the transition, an x-ray diffraction measurement revealed superlattice formation of 2a × 2b × 4c in the charge-ordered phase, 11) but the detailed low-temperature structure has been unknown yet. Recently, two x-ray diffraction studies of the lowtemperature structure were reported. These indicate almost the same structure of space group Fmm2 , but their assignments of V electronic states are different. One suggests a structure consists of half-filled (V 4+ ) and empty (V 5+ ) ladders. 12) This charge distribution disagrees with a recent x-ray anomalous scattering measurement, which indicates charge modulation along b axis.13) The other suggests a structure including three different electronic state of V 4+ , V 5+ and V 4.5+ . 14) This structure is incom- * E-mail: ohama@physics.s.chiba-u.ac.jp patible with the 51 V NMR measurement, 5) which clearly shows that all the V sites split into two groups of V 4+and V 5+ states and that no V sites remains to be V 4.5+ . Thus, the low-temperature structure and the charge ordering pattern are still under discussion.In this letter, we report 23 Na NMR spectrum measurements with a single-crystalline sample. The obtained NMR spectra in the c...

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“…Parameters a and b, are similar in both compounds [6,22]. The c axis of LiV 2 O 5 is approximately twice as large, since the LiV 2 O 5 unit cell comprises four formula units (two in NaV 2 O 5 ).…”

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confidence: 90%

“…Up to now, accumulated experimental data [4,[6][7][8][9] suggested that NaV 2 O 5 exhibits the CO phase transition at T=34 K into a gapped spin-liquid ground state. The arguments are mostly based on the insensitivity of the phase-transition effects associated with magnetic fields.…”

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confidence: 99%

“…At room temperatures the α ′ −NaV 2 O 5 and γ−LiV 2 O 5 have orthorhombic unit cells [6,22] (described with space groups P mmn, and P nma, respectively), and crystal structures consisting of layers of VO 5 square pyramids which are mutually connected via common edges and corners making the characteristic V "zigzag" chains along the b axis. Parameters a and b, are similar in both compounds [6,22].…”

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confidence: 99%

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Charge ordering and optical transitions ofLiV2O5and
Konstantinović
¹
,
Dong
²
,
Ziaei
³

et al. 2001
Phys. Rev. B
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We present measurements of the polarized optical spectra of NaV 2 O 5 and LiV 2 O 5 . In an energy range from 0.5 to 5.5 eV, we observe similar peaks in the E a spectra of NaV 2 O 5 and LiV 2 O 5 , which suggests similar electronic structures along the a axis in both materials. On the other hand, we find an almost complete suppression of the peaks in σ b of LiV 2 O 5 around 1 and 5 eV. We attribute this suppression to the charge localization effect originating from the existence of a double-chain charge-ordering pattern in LiV 2 O 5 . : 78.40.-q, 71.35.-y, 75.50.-y In the past several years, quantum phenomena resulting from the low dimensionality of effective electron interactions in solids have been investigated with increasing intensity from both experimental and theoretical points of view. The increase in interest was partially motivated by the discovery of inorganic materials which exhibit quantum effects, such as the PACS, and by a common belief that these studies would give us a better understanding of electron correlations in general.The vanadate family of AV 2 O 5 oxides have demonstrated a variety of the low-dimensional phenomena which originate from their peculiar crystal structures [3]. These oxides are quasi two-dimensional (2D) materials with layers formed by V O 5 square pyramids. The A atoms are situated between layers as intercalants, but in fact they determine the valence state of vanadium atoms (acting as charge reservoirs). If the A atoms belong to the first column in the periodic table, such as A = Li, Na, each valence electron is shared between two vanadium atoms. As a result the V ions are in a mixed valence-state with an average valence of +4.5. The common consequence of mixed valence in these structures is the appearance of a quasi-1D magnetic interaction, since chains carrying the spin (made of V 4+ , S=1/2) are separated from each other by nonmagnetic chains (V 5+ ). In both LiV 2 O 5 and NaV 2 O 5 the 1D character of the magnetic ordering was confirmed [4,5]. In addition, there is a possibility of the existence of strong valence fluctuations, and eventually charge ordering (CO) effects.

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Redetermination of the crystal structure of sodium vanadate, α'-NaV2O5

Cited by 38 publications

References 0 publications

Lattice vibrations ofα′−NaV2O5
Popova
¹
,
Sushkov
²
,
Климин
³

et al. 2002
Phys. Rev. B
21
5
12
0
View full text Add to dashboard Cite

Lattice vibrations ofα′−NaV2O5
Popova
¹
,
Sushkov
²
,
Климин
³

et al. 2002
Phys. Rev. B
21
5
12
0
View full text Add to dashboard Cite

Zigzag Charge Ordering in α^′-NaV₂O₅

Charge ordering and optical transitions ofLiV2O5and
Konstantinović
¹
,
Dong
²
,
Ziaei
³

et al. 2001
Phys. Rev. B
12
1
13
0
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Redetermination of the crystal structure of sodium vanadate, α'-NaV2O5

Cited by 38 publications

References 0 publications

Lattice vibrations ofα′−NaV2O5Popova1, Sushkov2, Климин3 et al. 2002Phys. Rev. B215120View full textAdd to dashboardCite

Lattice vibrations ofα′−NaV2O5Popova1, Sushkov2, Климин3 et al. 2002Phys. Rev. B215120View full textAdd to dashboardCite

Zigzag Charge Ordering in α′-NaV 2O 5

Charge ordering and optical transitions ofLiV2O5andKonstantinović1, Dong2, Ziaei3 et al. 2001Phys. Rev. B121130View full textAdd to dashboardCite

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Lattice vibrations ofα′−NaV2O5
Popova
¹
,
Sushkov
²
,
Климин
³

et al. 2002
Phys. Rev. B
21
5
12
0
View full text Add to dashboard Cite

Lattice vibrations ofα′−NaV2O5
Popova
¹
,
Sushkov
²
,
Климин
³

et al. 2002
Phys. Rev. B
21
5
12
0
View full text Add to dashboard Cite

Zigzag Charge Ordering in α^′-NaV₂O₅

Charge ordering and optical transitions ofLiV2O5and
Konstantinović
¹
,
Dong
²
,
Ziaei
³

et al. 2001
Phys. Rev. B
12
1
13
0
View full text Add to dashboard Cite