Importance of oxygen content in La doped Sr₂IrO_4-δ

We perform a systematical investigation on the influence of oxygen content in Sr_2-xLa_xIrO_4-δcompounds by comparing the physical properties of the as-prepared Sr_2-xLa_xIrO_4-δsamples, the Sr_2-xLa_xIrO_4-δsamples after annealing under high oxygen pressure and the samples synthesized directly under high oxygen pressure. It is found that there are a lot of oxygen vacancies in the as-prepared Sr_2-xLa_xIrO_4-δsamples, which is rarely reported before. The annealing treatment to the Sr_2-xLa_xIrO_4-δsamples and the synthesis of Sr_2-xLa_xIrO_4-δsamples under oxygen pressure could substantially increase the oxygen content of the samples. The charge carrier densities are much higher in the Sr_2-xLa_xIrO_4-δsamples after annealing treatment and in the samples synthesized under oxygen pressure comparing to those in the as-prepared samples. With the increase of oxygen content, the electrical conductivity of the Sr_2-xLa_xIrO_4-δsamples is substantially enhanced. The present work suggests that the annealing treatment and the synthesis of doped Sr₂IrO_4-δsamples under high oxygen pressure could be meaningful approaches in further exploration of new physical phenomena and possible superconductivity in doped Sr₂IrO_4-δcompounds.