Abstract
We have synthesized and studied an iridate, Ba13Ir6O30, with unusual Ir oxidation states: 2/3 Ir6+(5d3) ions and 1/3 Ir5+(5d4) ions. Its crystal structure features dimers of face-sharing IrO6 octahedra, and IrO6 monomers that are linked via long, zigzag Ir-O-Ba-O-Ir pathways. Nevertheless, Ba13Ir6O30 exhibits two transitions at TN1=4.7K and TN2=1.6K. This magnetic order is accompanied by a huge Sommerfeld coefficient 200 mJ/mole K2 below TN2, signaling a coexisting frustrated/disordered state persisting down to at least 0.05 K. This iridate hosts unusually large Jeff=3/2 degrees of freedom, which is enabled by strong spin-orbit interactions (SOI) in the monomers with Ir6+ ions and a joint effect of molecular orbitals and SOI in the dimers occupied by Ir5+ and Ir6+ ions. Features displayed by the magnetization and heat capacity suggest that the combination of covalency, SOI, and large effective spins leads to highly frustrated ferrimagnetic ordering, an interesting feature of this high-spin iridate.
| Original language | English |
|---|---|
| Article number | 064418 |
| Journal | Physical Review B |
| Volume | 100 |
| Issue number | 6 |
| DOIs | |
| State | Published - Aug 23 2019 |
Funding
This work was supported by the National Science Foundation via Grants No. DMR-1712101 and No. DMR 1903888. I.K. was supported by a National Research Council Fellowship through the National Institute of Standards and Technology. We thank Professor Arun Paramekanti for a discussion of his work on skyrmion crystals. This work was supported by the National Science Foundation via Grants No. DMR-1712101 and No. DMR 1903888. I.K. was supported by a National Research Council Fellowship through the National Institute of Standards and Technology. We thank Professor Arun Paramekanti for a discussion of his work on skyrmion crystals