Charge transitions in perovskite oxides containing unusually high-valent Fe

Perovskite materials containing unusually high valent Fe cations are prone to undergoing charge transitions in order to relieve their inherent electronic instability. The charge transitions are often accompanied by significant changes to the structural transport, and magnetic properties. The distribution of charge in disproportionated and transferred perovskites is susceptible to small structural and electronic differences, leading to complex structural and magnetic behaviour. Here, we review the structural and magnetic behaviour of perovskites containing unusually high-valent Fe cations.