Slater Insulator in Iridate Perovskites with Strong Spin-Orbit Coupling

TL;DR

This study demonstrates that substituting Sn for Ir in SrIrO3 induces a second-order metal-insulator transition with antiferromagnetic order, highlighting a Slater-type insulator driven by electron correlations and spin-orbit coupling effects.

Contribution

It reveals how Sn substitution in SrIrO3 induces a Slater insulator phase with antiferromagnetic order, expanding understanding of metal-insulator transitions in spin-orbit coupled systems.

Findings

Sn substitution causes a second-order metal-insulator transition.

Antiferromagnetic order develops below TN > 225 K.

Structural changes reduce SOC, leading to electron gap opening.

Abstract

The perovskite SrIrO3 is an exotic narrow-band metal owing to a confluence of the strengths of the spin-orbit coupling (SOC) and the electron-electron correlations. It has been proposed that topological and magnetic insulating phases can be achieved by tuning the SOC, Hubbard interactions, and/or lattice symmetry. Here, we report that the substitution of nonmagnetic, isovalent Sn4+ for Ir4+ in the SrIr1-xSnxO3 perovskites synthesized under high pressure leads to a metal-insulator transition to an antiferromagnetic (AF) phase at TN > 225 K. The continuous change of the cell volume as detected by x-ray diffraction and the lamda-shape transition of the specific heat on cooling through TN demonstrate that the metal-insulator transition is of second-order. Neutron powder diffraction results indicate that the Sn substitution enlarges an octahedral-site distortion that reduces the SOC relative to the spin-spin exchange interaction and results in the type-G AF spin ordering below TN. Measurement of high-temperature magnetic susceptibility shows the evolution of magnetic coupling in the paramagnetic phase typical of weak itinerant-electron magnetism in the Sn-substituted samples. A reduced structural symmetry in the magnetically ordered phase leads to an electron gap opening at the Brillouin zone boundary below TN in the same way as proposed by Slater.