Inducing ferromagnetism by structural engineering in a strongly spin-orbit coupled oxide

TL;DR

This study demonstrates that structural engineering in SrIrO3 thin films can induce ferromagnetism by enhancing the density of states at the Fermi level, opening new avenues for spin-orbitronic device applications.

Contribution

It reveals a method to induce ferromagnetism in 5d oxides through substrate-induced structural modifications, specifically zigzag stacking along the [111] direction.

Findings

Ferromagnetism observed in SrIrO3 thin films on SrTiO3 (111).

Anomalous Hall effect and hysteresis indicate magnetic ordering.

Structural engineering stabilizes ferromagnetism via enhanced density of states.

Abstract

Magnetic materials with strong spin-orbit coupling (SOC) are essential for the advancement of spin-orbitronic devices, as they enable efficient spin-charge conversion, complex magnetic structures, spin-valley physics, topological phases and other exotic phenomena. 5d transition-metal oxides such as SrIrO3 feature large SOC, but usually show paramagnetic behavior due to broad bands and a low density of states at the Fermi level, accompanied by a relatively low Coulomb repulsion. Here, we unveil ferromagnetism in 5d SrIrO3 thin films grown on SrTiO3 (111). Through substrate-induced structural engineering, a zigzag stacking of three-unit-cell thick layers along the [111] direction is achieved, stabilizing a ferromagnetic state at the interfaces. Magnetotransport measurements reveal an anomalous Hall effect below ~30 K and hysteresis in the Hall conductivity below 7 K, indicating ferromagnetic ordering. X-ray magnetic circular dichroism further supports these results. Theoretical analysis suggests that the structural engineering of the IrO6 octahedral network enhances the density of states at the Fermi level and thus stabilizes Stoner ferromagnetism. This work highlights the potential of structurally engineered 5d oxides for spin-orbitronic devices, where efficient control of SOC-induced magnetic phases by electric currents can lead to lower energy consumption and improved performance in next-generation device technologies.