Frustration, strain and phase co-existence in the mixed valent hexagonal iridate Ba$_{3}$NaIr$_{2}$O$_{9}$

TL;DR

This study explores how mixed valence, lattice strain, and structural phase coexistence influence the magnetic properties of the frustrated iridate Ba₃NaIr₂O₉, revealing complex interactions and a cluster glass magnetic ground state.

Contribution

It provides new insights into the interplay between lattice strain, structural phases, and magnetic states in a geometrically frustrated iridate compound.

Findings

Lattice strain and phase coexistence are prominent and unusual in this compound.

Absence of long-range magnetic order at low temperatures.

Evidence of a cluster glass magnetic state from short-range correlations.

Abstract

Using detailed synchrotron diffraction, magnetization, thermodynamic and transport measurements, we investigate the relationship between the mixed valence of Ir, lattice strain and the resultant structural and magnetic ground states in the geometrically frustrated triple perovskite iridate Ba$_{3}$NaIr$_{2}$O$_{9}$. We observe a complex interplay between lattice strain and structural phase co-existence, which is in sharp contrast to what is typically observed in this family of compounds. The low temperature magnetic ground state is characterized by the absence of long range order, and points towards the condensation of a cluster glass state from an extended regime of short range magnetic correlations.