Realization of large-volume crystals of Sr₂IrO₄ grown via high-pressure laser floating zone

The study of 5d transition metal oxides provides a rich bed for exploring the interplay of spin-orbit coupling with electron-electron interactions. Of these, the spin-orbit-coupled Mott insulator Sr₂IrO₄ has received particular attention, particularly for its similarity to La₂CuO₄, a parent material to high-T_c superconductivity upon doping. For studies utilizing weakly interacting probes such as neutron scattering, obtaining large-volume, high-quality crystals is of the utmost importance. Historically, studies on bulk crystals of Sr₂IrO₄ have been limited by the small (<5 mm²), plate-like crystals resulting from conventional flux growth techniques. The state-of-the-art growth method for large crystals of transition metal oxides is the floating zone growth technique, though iridates have historically suffered from extreme material losses and decomposition due to the volatility of IrO₂ upon melting. Here we present an advancement in iridate synthesis using a custom high-pressure laser-based floating zone furnace to realize the first floating zone samples of high-quality Sr₂IrO₄ grown from a self-flux under a high pressure 80:20 Ar:O₂ gas mixture. We report characterization of the microstructure, magnetic, and electronic properties and compare these to flux-grown crystals.