Relationship between A-site cation and magnetic structure in 3d-5d-4f double perovskite iridates Ln2NiIrO6 (Ln = La, Pr, Nd)

We report a comprehensive investigation of Ln(2)NiIrO(6) (Ln = La, Pr, Nd) using thermodynamic and transport properties, neutron powder diffraction, resonant inelastic x-ray scattering, and density-functional theory (DFT) calculations to investigate the role of A-site cations on the magnetic interactions in this family of hybrid 3d-5d-4f compositions. Magnetic structure determination using neutron diffraction reveals antiferromagnetism for La2NiIrO6, a collinear ferrimagnetic Ni and Jr state that is driven to long-range antiferromagnetism upon the onset of Nd ordering in Nd2NiIrO6, and a noncollinear ferrimagnetic Ni and Ir sublattice interpenetrated by a ferromagnetic Pr lattice for Pr2NiIrO6. For Pr2NiIrO6, heat-capacity results reveal the presence of two independent magnetic sublattices, and transport resistivity indicates insulating behavior and a conduction pathway that is thermally mediated. A first principles DFT calculation elucidates the existence of the two independent magnetic sublattices within Pr2NiIrO6 and offers insight into the behavior in La2NiIrO6 and Nd2NiIrO6. Resonant inelastic x-ray scattering is consistent with spin-orbit coupling splitting the t(2g) manifold of octahedral Ir4+ into a J(eff) = and J(eff) = 3/2 state for all members of the series considered.

Automated summary

The study provides a comprehensive investigation into the role of A-site cations on magnetic interactions in Ln(2)NiIrO(6) compounds, revealing different magnetic structures and transport properties in La2NiIrO6, Nd2NiIrO6, and Pr2NiIrO6. The presence of two independent magnetic sublattices is observed in each compound, showing unique magnetic behaviors. Theoretical calculations using density-functional theory shed light on the behavior of these compounds and the influence of A-site cations.