Novel Ternary AgIICoIIIF5 Fluoride: Synthesis, Structure and Magnetic Characteristics

We present a new compound in the silver cobalt fluoride system, featuring paramagnetic silver (d9) and high-spin cobalt (d6), synthesized by solid state method in an autoclave under F2 overpressure. Based on powder X ray diffraction, we determined that AgIICoIIIF5 crystallizes in a monoclinic system with space group C2/c. The calculated fundamental band gap falls in the visible range of the electromagnetic spectrum, and the compound has the character of charge-transfer insulator. AgCoF5 is a ferrimagnet with one predominant superexchange magnetic interaction constant between mixed spin cations (Ag ... Co) of minus 62 meV (SCAN result). Magnetometric measurements conducted on a powdered sample allowed the identification of a transition at 128 K, which could indicate magnetic ordering.