Magnetic clusters and ferromagnetic spin glass in the novel hexagonal perovskite 12R-Ba(4)SbMn(3)O(12)

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.