Abstract
A 12-layer hexagonal perovskite Ba(4)SbMn(3)O(12) (space group: R3̄m; a = 5.72733(3) Å, and c = 28.1770(3) Å) has been synthesized by high-temperature solid-state reactions and studied using powder X-ray and neutron diffraction and magnetization measurements. This 12R polytype structure contains one corner-sharing (Sb, Mn)O(6) octahedron and a trimer of face-sharing MnO(6) octahedra per formula unit. Ba(4)SbMn(3)O(12) displays a paramagnetic state of the Mn(3) magnetic cluster at 100-200 K, which partially disassociates into individual Mn ions at 250-300 K. The ferromagnetic interaction between these Mn(3) clusters is mainly mediated by Mn(3+) at the M1 site, leading to dynamic ferromagnetic clusters below T (D) = ∼70 K and ferromagnetic spin freezing transition at T (g) = ∼11.5 K. The stability of Mn(3) magnetic clusters in the 12R polytypes is related to the intracluster Mn-Mn distance.