LaMn₃Ni₂Mn₂O₁₂: An A- and B-Site Ordered Quadruple Perovskite with A-Site Tuning Orthogonal Spin Ordering

A new oxide, LaMn₃Ni₂Mn₂O₁₂, was prepared by high-pressure and high-temperature synthesis methods. The compound crystallizes in an AA'₃B₂B'₂O₁₂-type A-site and B-site ordered quadruple perovskite structure. The charge combination is confirmed to be LaMn³⁺₃Ni²⁺₂Mn⁴⁺₂O₁₂, where La and Mn³⁺ are 1:3 ordered at the A and A' sites and the Ni²⁺ and Mn⁴⁺ are also distributed at the B and B' sites in an orderly fashion in a rocksalt-type manner, respectively. A G-type antiferromagnetic ordering originating from the A'-site Mn³⁺ sublattice is found to occur at T_N ≈ 46 K. Subsequently, the spin coupling between the B-site Ni²⁺ and B'-site Mn⁴⁺ sublattices leads to an orthogonally ordered spin alignment with a net ferromagnetic component near T_C ≈ 34 K. First-principles calculations demonstrate that the A'-site Mn³⁺ spins play a crucial role in determining the spin structure of the B and B' sites. This LaMn₃Ni₂Mn₂O₁₂ provides a rare example that shows orthogonal spin ordering in the B and B' sites assisted by ordered A-site magnetic ions in perovskite systems.