Relationship between A-site Cation and Magnetic Structure in 3d-5d-4f Double Perovskite Iridates Ln2NiIrO6 (Ln=La, Pr, Nd)

TL;DR

This study explores how different A-site cations influence the magnetic structures and properties of Ln2NiIrO6 double perovskites, revealing diverse magnetic orders and the role of spin-orbit coupling through experimental and computational methods.

Contribution

It provides a comprehensive analysis of magnetic interactions in Ln2NiIrO6 compounds, highlighting the impact of A-site cations on magnetic structure and elucidating the electronic states via DFT and RIXS.

Findings

La2NiIrO6 is antiferromagnetic.

Nd2NiIrO6 exhibits long-range antiferromagnetism with Nd ordering.

Pr2NiIrO6 has a non-collinear ferrimagnetic Ni/Ir sublattice and a ferromagnetic Pr lattice.

Abstract

We report a comprehensive investigation of Ln2NiIrO6 (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/Ir state that is driven to long range antiferromagnetism upon the onset of Nd ordering in Nd2NiIrO6, and a non-collinear ferrimagnetic Ni/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. 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 t2g manifold of octahedral Ir4+ into a Jeff = 1/2 and Jeff = 3/2 state for all members of the series considered.