Direct observation of ferroelectricity in Ca${}_3$Mn${}_2$O${}_7$ and its prominent light absorption

Meifeng Liu, Yang Zhang, Ling-Fang Lin +10

Layered perovskites $A_3{M}_2$O${}_7$ are known to exhibit the so-called hybrid improper ferroelectricity. Despite experimentally confirmed cases (e.g. nonmagnetic $M$=Ti and Sn), the…