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: R 3̄ m ; 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.