Crystal Structures and Magnetic Properties of MV3O7 (M = Cd, Ca, Sr) with Square Pyramidal V(IV)

doi:10.1006/jssc.1993.1086

Journal of Solid State Chemistry

Volume 103, Issue 1, March 1993, Pages 139-151

https://doi.org/10.1006/jssc.1993.1086 Get rights and content

Abstract

Crystal structures of CdV₃O₇ and SrV₃O₇ are refined using X-ray powder diffraction data for CdV₃O₇ and a combination of neutron and X-ray powder data for SrV₃O₇. The pseudo two-dimensional feature and possible chain formation of the crystal structures are described. Magnetic properties are examined in the temperature range from 5 to 300 K and magnetic susceptibility data of these insulating antiferromagnets are analyzed according to a linear chain (1-D) Heisenberg model.

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In this paper, Eu³⁺-doped calcium vanadium oxides (Ca₂V₂O₇: Eu³⁺) have been successfully synthesized using hydrothermal method through altering the hydrothermal temperature, reaction time and surfactant. The microstructure and morphology information of the phosphors were investigated via the technique of X-ray powder diffraction (XRD) and scanning electronic microscopy, which shows that the phosphors wear anorthic phase and the products present various regular morphologies under the different reaction condition such as bulk, nano-rod, flake and so on. Moreover, the morphologies of the products have been controlled by altering reaction temperature. Besides the surfactant was also included to control the morphologies of the products and the phosphors present different morphologies. All the phosphors exhibit the characteristic fluorescence of Eu³⁺ ion. The electric dipole transition ⁵D₀ → ⁷F₂ of Eu³⁺ is dominant indicating that the sites of Eu³⁺ ions in Ca₂V₂O₇ have no inversion center. Furthermore, we found that the reaction time and the morphologies have great influence on optical properties.
Spin exchange interactions and magnetic structures of extended magnetic solids with localized spins: Theoretical descriptions on formal, quantitative and qualitative levels
2003, Journal of Solid State Chemistry
Citation Excerpt :
In such spin dimers, the two magnetic orbitals ψ interact to form bonding and antibonding levels (ψ+ and ψ−, respectively), and these levels are each singly occupied (Fig. 56b). There is only one unpaired spin per formula unit in α′-NaV2O5, and all vanadium atoms are equivalent [154,160]. Therefore, in the spin dimers representing two adjacent vanadium atoms of α′-NaV2O5, namely, (V2O9)9− (Fig. 55a and b) and (V2O8)7− (Fig. 55c), the ψ+ level is singly occupied and the ψ− level is empty so that one of these spin dimers should act as a spin monomer.
Low-energy excitation energies of a magnetic solid with localized spins are probed by magnetic susceptibility, neutron scattering and Raman scattering measurements, and are analyzed using a spin Hamiltonian with a set of spin exchange parameters. The nature and values of the spin exchange parameters deduced from this analysis depend on what spin exchange paths one includes in the spin Hamiltonian. In this article, we review how spin exchange interactions of magnetic solids with localized spins are described on formal, quantitative and qualitative theoretical levels, investigate antisymmetric and anisotropic interactions for general spin dimers, and discuss the spin exchange interactions and magnetic structures of various extended magnetic solids on the basis of spin dimer analysis. Strongly interacting spin exchange paths of a magnetic solid are determined by the overlap between its magnetic orbitals, so that the strongly interacting spin unit of a magnetic solid does not necessarily have the same geometrical feature as does the arrangement of its magnetic ions or spin-carrying molecules. Therefore, in interpreting results of magnetic susceptibility, inelastic neutron scattering or Raman scattering measurements, it is essential to employ a set of spin exchange parameters chosen on the basis of proper electronic structure considerations. Spin dimer analyses based on extended Hückel tight binding calculations provide a reliable and expedient means to study the relative strengths of superexchange and super-superexchange spin exchange interactions.
Crystallization of quasi-two-dimensional vanadates in the CaO-V<inf>2</inf>O<inf>3</inf>-VO<inf>2</inf>-V<inf>2</inf>O<inf>5</inf> system
2002, Journal of Crystal Growth
Investigations of the CaO–V₂O₃–VO₂–V₂O₅ system under various oxygen pressure and with addition of sodium in starting mixture are described. A diagram of CaV₄O₉ and CaV₃O₇ stability and the reaction CaV₃O₇₊VO₂⇔CaV₄O₉ have been studied depending on temperature and oxygen partial pressure. As a result, single-phase CaV₄O₉ and CaV₃O₇ ceramics were prepared, and plate-like single crystals of CaV₄O₉ were grown. Magnetic susceptibility data confirmed the existence of a disordered spin liquid state with spin gap Δ=100±15 K in CaV₄O₉ and of an antiferromagnetic order below T_N=22 K in CaV₃O₇.
Analysis of nearest-neighbor spin exchange interactions by molecular orbital calculations: Anisotropic spin exchange interactions in MV<inf>3</inf>O<inf>7</inf> (M = Cd, Ca, Sr) and α′-NaV<inf>2</inf>O<inf>5</inf>
2000, Solid State Communications
Spin-dimer analysis was carried out for the room temperature structures of MV₃O₇ (M=Cd, Ca, Sr) and the 15 K structure of α′-NaV₂O₅ reported by Lüdecke et al. to examine the relative magnitudes of the nearest-neighbor spin exchange interactions between their unpaired spins. Our analysis explains why the magnetic susceptibility of the stripe spin structure of MV₃O₇ (M=Cd, Ca, Sr) exhibits a one-dimensional spin-1/2 Heisenberg chain-like behavior. Our study indicates that the 15 K crystal structure of α′-NaV₂O₅ is likely to have a spin gap and exhibit spin frustration. The predicted spin frustration is not consistent with the singlet ground state expected for a spin-Peierls system.
Synthesis and crystal structure of SrV<inf>4</inf>O<inf>9</inf> in a metastable state
2000, Journal of Solid State Chemistry
In the SrO–VO₂ phase diagram there exists no SrV₄O₉ phase corresponding to the CaV₄O₉ phase in the CaO–VO₂ diagram and synthesis of SrV₄O₉ has not been reported so far. We are successful in hydrothermal synthesis of the synthesis of SrV₄O₉: hydrothermal treatment of SrCl₂–NaVO₃–(CH₃)₄NCl solutions above 300°C yielded light-green plate crystals identified as SrV₄O₉. Single-crystal X-ray diffractometry confirmed the CaV₄O₉-type structure consisting of V₄O₉ layers and interstitial Sr atoms: P4/n, a=8.379(2) Å, c=5.259(3) Å, and Z=2. The refinements based on 826 reflections with I>3σ(I) converged to R=0.039 and R_w=0.048. Temperature variation of magnetic susceptibility exhibits a low-dimensional feature of a broad maximum around 100 K, just like that of CaV₄O₉. Single crystals of CaV₄O₉ were similarly grown in the hydrothermal CaCl₂–NaVO₃–(CH₃)₄NCl system at 280°C and its single-crystal X-ray study was also made to compare with those of SrV₄O₉.
Magnetic neutron scattering study of SrV<inf>3</inf>O<inf>7</inf>
1999, Journal of Physics and Chemistry of Solids
Neutron powder diffraction experiments were performed for SrV₃O₇, which is characterized by the 1/4 depleted V⁴⁺(S=1/2) square lattice model. An antiferromagnetic three-dimensional (3D) long-range order was observed below T_N=34.3 K. The ‘Stripe Order’ spin structure, which is not expected from a classical Heisenberg model, is realized. This spin structure is the same as found in CaV₃O₇, but the spin direction here is parallel to the a(stacking)-axis, instead of the c-axis for CaV₃O₇.

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Regular ArticleCrystal Structures and Magnetic Properties of MV3O7 (M = Cd, Ca, Sr) with Square Pyramidal V(IV)

Abstract

Regular Article
Crystal Structures and Magnetic Properties of MV₃O₇ (M = Cd, Ca, Sr) with Square Pyramidal V(IV)