A novel phosphate with Co II square planar coordination, BaCo 0.5 Fe(PO 4 ) 2 : structural and magnetic features.

A novel phosphate containing barium, cobalt, and iron was synthesized in single-crystal and polycrystalline forms. Single crystal-based X-ray measurements revealed that it crystallizes in the monoclinic system with the P 2 1 / c space group. The structure is made up of linkages between FeO 6 octahedra, CoO 4 square planar units, CoO 5 square pyramidal units, and PO 4 tetrahedra through edges and/or vertices. The interconnection of these polyhedra leads to a three-dimensional framework with tunnels along the a -axis where the Ba 2+ cations are located. The polycrystalline form was prepared via the sol-gel method and its XRD pattern was refined by the Le Bail method. Morphological and elemental mapping analyses of this phosphate were performed by scanning electron microscopy. In addition, infrared and Raman spectroscopy provided more insights into chemical bonding. The magnetic behavior was antiferromagnetic below T N ∼ 20 K. Optical measurements revealed a direct bandgap with an energy E g of 2.83 eV.