Synthesis and Characterization of the Solid Solution Na\(_{2}\)Sn\(_{1-x}\)Ir\(_{x}\)O\(_{3}\)

Abstract

Motivated by the search for tin-based compounds with novel physical properties, a revised monoclinic unit cell for the compound Na\(_{2}\)Sn\(_{1-x}\)Ir\(_{x}\)O\(_{3}\) is presented here. Though previously reported with space group #166, R \(\bar{3}\)m, a Rietveld refinement of neutron diffraction data supports a crystal structure of lower symmetry with space group #15, C2/c. By replacing some or all of the tin with iridium, the synthesis of the previously unreported solid solution Na\(_{2}\)Sn\(_{1-x}\)Ir\(_{x}\)O\(_{3}\) has been optimized experimentally. As a function of increasing iridium concentration, the lattice parameters contract accordingly. This shift in the lattice parameters generally follows the linear trend predicted by Vegard’s law, though the contraction along the a-axis reaches a minimum at an iridium concentration of ~80%. Measurements of the solid solution’s magnetic susceptibility versus temperature decrease with higher iridium concentration as antiferromagnetic coupling replaces the paramagnetic behavior observed at lower concentrations. A critical concentration of iridium x ≈ 0.92 produces an antiferromagnetic ordering transition at 15.75 K. A second, previously unreported magnetic transition at ~4.5 K is also observed, which corresponds to complex, long-range ordering. Given the intricacies of this system’s structural and magnetic properties, further research on this system is warranted.