Magnetic clusters and ferromagnetic spin glass in the novel hexagonal perovskite 12R-Ba4SbMn3O12

A 12-layer hexagonal perovskite Ba4SbMn3O12 (space group: R (3) over barm; a = 5.72733(3) angstrom, and c = 28.1770(3)angstrom) 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 MnO6 octahedra per formula unit. Ba4SbMn3O12 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 Mn3+ at the M1 site, leading to dynamic ferromagnetic clusters below T-D = similar to 70 K and ferromagnetic spin freezing transition at T-g = similar to 11.5 K. The stability of Mn-3 magnetic clusters in the 12R polytypes is related to the intracluster Mn-Mn distance.