Search for Displacive-type Multiferroics with a Huge Magnetoelectric Coupling

Abstract (abbreviated by J. Hlinka, full version enclosed):

Until only recently, it was proven challenging to achieve the displacive ferroelectric distortion in the d³ manganites because the [Mn⁴⁺-O] bonds have not been put under sufficient tension. By advancing elaborate synthesis processes, which are necessary to avoid the more stable hexagonal polymorphs, we were recently able to extended the substitution limit of the large size Ba ion in bulk Sr_1-xBa_xMnO₃ samples to x = 0.45 with two-step “in situ” synthesis in a thermogravimetric furnace in flowing H₂/Ar gas followed by oxygen anneal. The achieved perovskite ceramics exhibit ferroelectricity (T_F > 300 K) and G-type antiferromagnetism (T_N ~ 200 K) originating exclusively from the Mn cations.