Magnetic properties of two copper II fluorides : Ba2Cu2AlF11 and Ba5Sc2CuF18

Abstract The magnetic properties of two copper II fluorides: Ba 2 Cu 2 AlF 11 and Ba 5 Sc 2 CuF 18 are characterized using the data recorded on a magneto-susceptometer. Ba 2 Cu 2 AlF 11 is trigonal, space group P 3 2 ; its crystal structure was previously solved on a single crystal. The copper–fluorine octahedra connected alternately by one edge and one vertex, form infinite twisted chains parallel to the c -axis. These chains are three-dimensionally linked by aluminum–fluorine octahedra. The magnetic behavior of Ba 2 Cu 2 AlF 11 is characteristic of alternate antiferromagnetic chains. Ba 5 Sc 2 CuF 18 is tetragonal and isostructural with Ba 5 Cr III 2 Cr II F 18 . Its structure can be described as constituted by a diamagnetic subnetwork [Sc 2 F 12 ] of isolated [ScF 6 ] octahedra forming two kinds of channels in which are inserted, in the first one, isolated [Cu 2 F 10 ] dimers and, in the second one, chains of vertex sharing [FBa 4 ] tetrahedra. The magnetic behavior of this fluoride is characteristic of independent ferromagnetic dimers [Cu 2 F 10 ].