23Na NMR Study of Spin-Peierls Transition in NaV 2O 5

Ohama, Tetsuo; Isobe, Masahiko; Yaśuoka, Hiroshi; Ueda, Yutaka

doi:10.1143/jpsj.66.545

Cited by 57 publications

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“…We deduced the following EFG parameters vZZ-bb = -641 kHz (-678 kHz), = +522 kHz (+581 kHz), v,,,_QO = +118 kHz (+99 kHz) and 77 = 0.630 (0.711) for T = 290 K (T = 50 K, respectively) (Fig. 3) in agreement with earlier powder data obtained at T = 50 K[20]. The room temperature MHS tensor is given by Khh, = -49 ppm, K,, = -34 ppm and K., = 15 ppm.…”

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confidence: 89%

23Na nuclear magnetic resonance investigation of the lattice distortion in α-NaxV2O5

et al. 2000

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The full temperature dependence of the electric field gradient tensor at the Na sites has been determined by nuclear magnetic resonance (NMR) in the temperature range 8-330 K in aNa,.V205 (x = 0.996). Above the spin-Peierls transition (T, = 34.7 K), only a single Na site is observed in agreement with the Pmmn space group proposed to describe this compound as the first example of a 1/4-filled ladder system. Below T,, eight distinct quadrupolar 23 Na sites are observed according to the distortion wave vector k c = ( 1/2, 1/2, 1/4) previously reported. In addition, the opening of a spin gap is evidenced by a rapid drop of the magnetic hyperfine shift 23 K at T.. The results are discussed in the context of a charge-order-driven spin-Peierls transition. I IntroductionAmong the growing family of interesting low-dimensional magnetic systems the vanadium oxide bronzes have attracted considerable interest in recent years. Various ground states of quantum magnetism can be experimentally realized such as an S = 1/2 Heisenberg antiferromagnetic (HAF) chain for y-LiV 2 O5, S = 1/2 HAF dimers for CsV2O5, an S = 1/2 HAF spin-ladder for CaV2O5 , an S = 1/2 HAF frustated spin-ladder for MgV 2 O5 and a possible two-dimensional (2 -D) spin liquid state for CaV,O 9 [1]. A magneto-elastic transition at TT 34 K has been reported for another compound of this family, a-NaV 2 O5, by Isobe et al. [2] which showed typical signatures of a spin-Peierls (SP) transition, resulting as purely due to quantum effects [3]. a-NaV 2 O5 was thus conjectured to represent the second inorganic spin-Peierls compound after CuGeO 3 discovered in 1993 [4,5]. An early room-temperature crystal structure determination of this compound in the space group (SG) P2,mn [6] revealed V double chains to run along [010] but required two different vanadium sites in the unit cell being occupied either by magnetic V 4 + ions with a 3d' configuration or spinless V 5 + ions. The proposed discrimination of two different vanadium sites in the unit cell leads to

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23Na nuclear magnetic resonance investigation of the lattice distortion in α-NaxV2O5

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“…Above 34 K the temperature dependency of the magnetic susceptibility is indeed consistent with that of a S 1=2 antiferromagnetic (AF) Heisenberg chain [2,3]. The rapid decrease of the susceptibility below 34 K [2], a lattice distortion [4], and the spin gap behavior [4] were then assigned to a spin-Peierls transition, where dimerization of the V 4 ions occurs. However, further XRD [5,6] and nuclear magnetic resonance (NMR) [7] experiments have shown that at high temperature (HT) all V ions are equivalent, and the model proposed in Ref.…”

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Theoretical Characterization of the Ground and Optically Excited States ofα′−NaV2O5
Hozoi
¹
,
Vries
²
,
Oosten
³

et al. 2002
Phys. Rev. Lett.
28
1
29
0
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Theoretical characterization of the ground and optically excited states of alpha Hozoi, L.; de Vries, Alexander; van Oosten, A.B.; Broer, Ria; Cabrero, J.; de Graaf, Cornelis Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. The character of the ground and optically excited states was investigated by quantum chemical calculations. We propose a rung ground state with V 3d 1 xy -O 2p 1 y -V 3d 1 xy character, instead of the conventional picture of one unpaired electron shared by 2 V ions. The unpaired electron on O is low-spin coupled to the V d electrons and spin density is predicted to be localized on vanadium. The absorption peak at 0.9 eV is assigned to a state with similar orbital occupations but a different spin coupling scheme, resulting in spin density localized on the bridging oxygen.

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“…Moreover, the observation of atomic displacements with the modulation wave vector q ͑ 1 2 , 1 2 , 1 4 ͒ by x-ray and spin gap formation at the ͑1, 1 2 , 0͒ by neutron scattering strongly suggested the SP state below T C [3]. NMR [4] and Raman scattering [5] experiments also supported this transition.…”

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X-Ray Anomalous Scattering Study of a Charge-Ordered State inNaV2O5

et al. 2000

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Charge ordering of V4+ and V5+ in NaV2O5 has been studied by an x-ray diffraction technique using anomalous scattering near a vanadium K-absorption edge to critically enhance a contrast between the two ions. A dramatic energy dependence of the superlattice intensities is observed below T(C) = 35 K. The charge ordering pattern is the fully charged zigzag-type ladder with the unit cell 2ax2bx4c, but not the chain-type originally proposed for the spin-Peierls state. Charge disproportionation suggested in our model as the average valence V(4.5+/-delta(c)/2) is observed below T(C), showing continuous variation of delta(c) as a function of temperature.

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²³Na NMR Study of Spin-Peierls Transition in NaV₂O₅

Cited by 57 publications

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23Na nuclear magnetic resonance investigation of the lattice distortion in α-NaxV2O5

23Na nuclear magnetic resonance investigation of the lattice distortion in α-NaxV2O5

Theoretical Characterization of the Ground and Optically Excited States ofα′−NaV2O5
Hozoi
¹
,
Vries
²
,
Oosten
³

et al. 2002
Phys. Rev. Lett.
28
1
29
0
View full text Add to dashboard Cite

X-Ray Anomalous Scattering Study of a Charge-Ordered State inNaV2O5

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23Na NMR Study of Spin-Peierls Transition in NaV 2O 5

Cited by 57 publications

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23Na nuclear magnetic resonance investigation of the lattice distortion in α-NaxV2O5

23Na nuclear magnetic resonance investigation of the lattice distortion in α-NaxV2O5

Theoretical Characterization of the Ground and Optically Excited States ofα′−NaV2O5Hozoi1, Vries2, Oosten3 et al. 2002Phys. Rev. Lett.281290View full textAdd to dashboardCite

X-Ray Anomalous Scattering Study of a Charge-Ordered State inNaV2O5

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²³Na NMR Study of Spin-Peierls Transition in NaV₂O₅

Theoretical Characterization of the Ground and Optically Excited States ofα′−NaV2O5
Hozoi
¹
,
Vries
²
,
Oosten
³

et al. 2002
Phys. Rev. Lett.
28
1
29
0
View full text Add to dashboard Cite