Structural, optical and magnetic proprieties of a new pyrochlore type structure (Bi1.44□0.24Fe0.32)(Sb1.36Fe0.64)O7 compound derived from the Bi1.56 – x/8Sb1.48-x/8Co0.96-xFexO7 (0 ≤ x ≤ 0.96) solid solution | Synapse