Single crystal growth of iridates without platinum impurities

 Iridates have attracted much interest in the last decade for their novel magnetism emerging in the limit of strong spin-orbit coupling and possible unconventional superconductivity. A standard for growing single crystalline iridate has been the flux method using a platinum crucible. In this talk, we show that this widely used method compromises the sample quality by inclusion of platinum impurities. We find that single crystals of Sr₂IrO₄ grown in iridium crucibles show remarkable differences in characterizations using Raman spectroscopy, resonant inelastic X-ray scattering, and resistivity measurements. In particular, our Raman spectra are free of previously unidentified A_1g peaks of sizable magnitudes, which point to their defect origin creating in-gap states. This interpretation is supported by the much larger activation energy extracted from our resistivity data. While the platinum inclusion went unnoticed in the stoichiometric insulating phase for a long time, its effects can be much more detrimental to transport properties of doping-induced metallic states. Therefore, our result suggests using growth methods that avoid platinum impurities for exploration of possible superconducting phases in iridates.