CRYSTAL STRUCTURE OF  -Cu2V2O7 AND ITS COMPARISON TO BLOSSITE ( -Cu2V2O7) AND ZIESITE ( -Cu2V2O7)

Abstract

Single crystals of ␥-Cu 2 V 2 O 7 were obtained by the method of chemical transport reactions. The crystal structure [triclinic, P1, a 5.0873(10), b 5.8233(11), c 9.4020(18) Å, ␣ 99.780(3), ␤ 97.253(3), ␥ 97.202(3)°, V 269.20(9) Å 3 , Z = 2] has been solved by direct methods and refined to R 1 = 0.021 (wR 2 = 0.049) using 949 unique observed reflections with |F o | ≥ 4 F . The atomic arrangement contains two symmetrically independent Cu 2+ cations. The Cu(1) site is coordinated by six O atoms to form a distorted Cu(1)O 6 octahedron, whereas the Cu (2) site is coordinated by five O atoms arranged at the vertices of an elongate Cu(2)O 5 square pyramid. Two symmetrically independent V 5+ cations are tetrahedrally coordinated by four O atoms each. The O(5) atom bridges the V(1)O 4 and V(2)O 4 tetrahedra. The Cu(1)O 6 octahedra and Cu(2)O 5 square pyramids form two types of chains running parallel to the a axis. The chains are linked by V 2 O 7 groups into a complex heteropolyhedral framework. The structure of ␥-Cu 2 V 2 O 7 is closely related to the structures of ␣-Cu 2 V 2 O 7 (blossite) and ␤-Cu 2 V 2 O 7 (ziesite). The three structures are based upon chains of edge-sharing Cu 2+ polyhedra linked by V 2 O 7 groups. Similarity of the structure of ␥-Cu 2 V 2 O 7 to the structures of blossite and ziesite indicates possible formation of this phase under natural conditions, such as those that occur in "dry" high-temperature fumaroles of the Izalco (El Salvador) and Tolbachik (Kamchatka, Russia) volcanoes. The structure of ␥-Cu 2 V 2 O 7 can also be considered as a triclinically distorted derivative of the ␤-A 2 P 2 O 7 structure-type.

Magnetoelastic coupling and ferromagnetic-type in-gap spin excitations in multiferroic α-Cu2V2O7

“…The recent discovery of giant ferroelectric polarization and large magnetoelectric coupling in the magnetically ordered phase of α-Cu 2 V 2 O 7 somehow reaffirms this general concept as the system may be described by spin-1/2 zig-zag chains with strong interchain coupling [5,6]. While the chains consist of edge-sharing distorted CuO 5 -polyhedra, the non-centrosymmetric orthorhombic Fdd2 structure of the α-phase permits stronger interchain interaction than the other polymorphs of Cu 2 V 2 O 7 [7][8][9]. Magnetism in α-Cu 2 V 2 O 7 is rather three-dimensional as inelastic neutron studies suggest dominant interchain exchange interaction J 3 between third-nearest-neighbours, in addition to the nearest-and next-nearest neighbour interactions J 1 and J 2 [10].…”

Magnetic structure and Dzyaloshinskii-Moriya interaction in theS=12helical-honeycomb antiferromagnetα−Cu2V2Gitgeatpong1, Zhao2, Avdeev3 et al. 2015Phys. Rev. B483210View full textAdd to dashboardCite

“…[14][15][16] The α-phase of Cu 2 V 2 O 7 crystallizes in the orthorhombic system of space group Fdd2 with a = 20.645(2)Å, b = 8.383(7)Å, and c = 6.442(1)Å. 17,18 Structurally, Cu 2+ ions that are surrounded by five oxygen ions appear to form a chain of edge sharing CuO 5 polyhedra while the nonmagnetic V 5+ ions, each of which is surrounded by four oxygen ions to form V 2 O 7 double corner-sharing tetrahedra, are intercalated between the chains as shown in Fig.…”

Electronic structure and magnetic properties of monoclinicβ-Cu2V2O7: AGGAYashima1, Suzuki2 2009Phys. Rev. B321260View full textAdd to dashboardCite

“…16,18,19 Other forms of ␥-Cu 2 V 2 O 7 and ␤Ј-Cu 2 V 2 O 7 were reported recently. [20][21][22] A number of researchers have investigated the electrical, magnetic, and thermoelectric properties of ␤-͑Cu, Zn͒ 2 V 2 O 7 . 6,[8][9][10][11] The ͑Cu, Zn͒ 2 V 2 O 7 solid solutions have large negative values of Seebeck coefficient.…”