Influence of the Rare Earth Cation on the Magnetic Properties of Layered 12R-Ba 4 M 4+ Mn 3 O 12 (M = Ce, Pr) Perovskites.

Material design is increasingly used to realize desired functional properties, and the perovskite structure family is one of the richest and most diverse: perovskites are employed in many applications due to their structural flexibility and compositional diversity. Hexagonal, layered perovskite structures with chains of face-sharing transition metal oxide octahedra have attracted great interest as quantum materials due to their magnetic and electronic properties. Ba 4 MMn 3 O 12 , a member of the "12R" class of hexagonal, layered perovskites, contains trimers of face-sharing MnO 6 octahedra that are linked by a corner-sharing, bridging MO 6 octahedron. Here, we investigate cluster magnetism in the Mn 3 O 12 trimers and the role of this bridging octahedron on the magnetic properties of two isostructural 12R materials by systematically changing the M 4+ cation from nonmagnetic Ce 4+ (f 0 ) to magnetic Pr 4+ (f 1 ). We synthesized 12R-Ba 4 MMn 3 O 12 (M= Ce, Pr) with high phase purity and characterized their low-temperature crystal structures and magnetic properties. Using substantially higher purity samples than previously reported, we confirm the frustrated antiferromagnetic ground state of 12R-Ba 4 PrMn 3 O 12 below T N ≈ 7.75 K and explore the cluster magnetism of its Mn 3 O 12 trimers. Despite being atomically isostructural with 12R-Ba 4 CeMn 3 O 12 , the f 1 electron associated with Pr 4+ causes much more complex magnetic properties in 12R-Ba 4 PrMn 3 O 12 . In 12R-Ba 4 PrMn 3 O 12 , we observe a sharp, likely antiferromagnetic transition at T 2 ≈ 12.15 K and an additional transition at T 1 ≈ 200 K, likely in canted antiferromagnetic order. These results suggest that careful variation of composition within the family of hexagonal, layered perovskites can be used to tune material properties using the complex role of the Pr 4+ ion in magnetism.