Selective synthesis and crystal chemistry of candidate rare earth Kitaev materials: honeycomb and hyperhoneycomb Na$_2$PrO$_3$

TL;DR

This study reports the successful synthesis and structural characterization of honeycomb and hyperhoneycomb Na$_2$PrO$_3$ polymorphs, which are promising candidates for realizing Kitaev-type magnetic interactions in rare earth materials.

Contribution

The paper presents new synthetic methods and refined crystal structures for Na$_2$PrO$_3$ polymorphs, enabling further exploration of their magnetic properties.

Findings

Successful growth of powder and single crystals of both polymorphs.

Refined crystal structures from single-crystal X-ray diffraction.

Potential for realizing antiferromagnetic Kitaev interactions.

Abstract

Rare earth oxides have attracted interest as a platform for studying frustrated magnetism arising from bond dependent anisotropic interactions. Ordered rock salt compounds Na$_2$PrO$_3$ crystallize in two polymorphs ($\alpha$ and $\beta$) comprising honeycomb and hyperhoneycomb lattices of octahedrally coordinated Pr$^{4+}$ (4$f^1$). Although possible realization of antiferromagnetic Kitaev interactions is anticipated for these phases on the basis of ab initio models, the air-sensitivity of the two polymorphs has hampered reliable crystal growth and physical property measurements. Here, we have succeeded in preparing powder and single crystals of both $\alpha$- and $\beta$-Na$_2$PrO$_3$ using modified synthetic procedures. Revised crystal structures for both polymorphs are obtained from refinement of untwinned single-crystal X-ray diffraction data.