Novel magnetism of Ir5+ ions in the double perovskite Sr2YIrO6

TL;DR

This study reports the discovery of unexpected magnetism in Sr2YIrO6, a double perovskite with Ir5+ ions, driven by complex crystal field effects and intermediate spin-orbit coupling, defying typical expectations for such compounds.

Contribution

It reveals a novel magnetic transition in Sr2YIrO6 caused by interplay between crystal fields and spin-orbit coupling, challenging the assumption of non-magnetic Ir5+ in similar structures.

Findings

Magnetic transition observed below 1.3 K.

Magnetism arises from interplay between crystal fields and SOC.

Ir2YIrO6 exhibits unconventional magnetic behavior.

Abstract

We synthesize and study single crystals of a new double-perovskite Sr2YIrO6. Despite two strongly unfavorable conditions for magnetic order, namely, pentavalent Ir5+(5d4) ions which are anticipated to have Jeff=0 singlet ground states in the strong spin-orbit coupling (SOC) limit, and geometric frustration in a face centered cubic structure formed by the Ir5+ ions, we observe this iridate to undergo a novel magnetic transition at temperatures below 1.3 K. We provide compelling experimental and theoretical evidence that the origin of magnetism is in an unusual interplay between strong non-cubic crystal fields and intermediate-strength SOC. Sr2YIrO6 provides a rare example of the failed dominance of SOC in the iridates.