Structural studies with usovites: Ba2CaMIIV2F14 (MII = Mn, Fe), Ba2CaMnFe2F14 and Ba2CaCuM2IIIF14 (MIII = Mn, Fe, Ga)

V. Kaiser (1) , Antoine Le Lirzin (2) , Jacques Darriet (2) , Alain Tressaud (2) , H. Holler (3) , Dietrich Babel (3)

1 Institut für Kristallographie der Technischen Hochschule
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 Philipps Universität Marburg = Philipps University of Marburg

Single crystals of six compounds Ba2CaMIIM2IIIF14 were prepared to refine their usovite type structure (space group C2/c, Z = 4) using X-ray diffractometer data. The cell parameters of the phases studied with MIIM2III= MnV2, FeV2, CuMn2, MnFe2, CuFe2 und CuGa2 are within the range 1374≤a/pm≤1384, 534≤b/pm≤542, 1474≤c/pm≤1510, 91, 3≤ß/°≤93, 2. The atoms Ca and MII are incompletely ordered on the 8- and 6-coordinated positions, 4e and 4b, respectively. In the case of Ba2CaFeV2F14 and Ba2CaCuGa2F14 there is reciprocal substitution (x≈0, 1): (Ca1-xMxII) (4e) and (M1-xIICax) (4b). In the case of the other usovites Ca-enriched phases Ba2Ca(M1-yIICay)M2IIIF14 occured (up to y≈0, 35), exhibiting partial substitution at the octahedral position (4b) only, showing a corresponding increase in MII-F distances. The distortion of [MIIF6] and [MIIIF6] octahedra within the structure is considerably enhanced on replacement by CuII and MnIII. The results of powder magnetic susceptibility measurements of Ba2CaMnV2F14 and Ba2CaFeV2F14 (TN≈7K) are reported.

Mots clés: Structure elucidation; Transition metals; Jahn-Teller distortion; Magnetic properties

Domaines: Matériaux

V. Kaiser, Antoine Le Lirzin, Jacques Darriet, Alain Tressaud, H. Holler, et al.. Structural studies with usovites: Ba2CaMIIV2F14 (MII = Mn, Fe), Ba2CaMnFe2F14 and Ba2CaCuM2IIIF14 (MIII = Mn, Fe, Ga). Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, 2002, 628 (12), pp.2617-2624. ⟨10.1002/1521-3749(200212)628:12<2617::AID-ZAAC2617>3.0.CO;2-4⟩. ⟨hal-00817302⟩