Composition tuning of Mg/Ir ratio and crystallization of a spinel-related structure in Mg-Ir-O films by pulsed-laser deposition

•Control of composition in films is a crucial issue in pulsed-laser deposition.•Mg/Ir ratio in Mg-Ir-O films was regulated in 0.2 ≤ Mg/Ir ≤ 2.•Mg/Ir ratio in films increased with increasing temperature and fluence, decreasing O2 pressure.•A new Mg-Ir-O phase was crystalized in Mg-rich films.•The discovered phase was characterized as disordered inverse spinel Mg2IrO4. Pulsed-laser deposition is one of widely used methods to fabricate complex oxide thin films. In pulsed-laser deposition processes, composition of films is regulated by balance of supply and re-evaporation via various conditions such as laser pulses for target ablation, composition of target, substrate temperature, and oxidizing atmosphere. In this study, we report an experimental scheme to tune Mg/Ir composition ratio in Mg-Ir-O films fabricated by pulsed-laser deposition. In contrast to usual situations of oxide films, it was difficult to attain the composition of Mg/Ir ∼ 1 in the Mg-Ir-O films by ablating a target of Mg/Ir ∼ 1. By examining three targets with different Mg/Ir ratios, various laser fluences, substrate temperature, and oxygen partial pressure, a wide range of Mg/Ir composition ratio was regulated in the Mg-Ir-O thin films. We discovered a spinel-related crystalline phase in the Mg-Ir-O films controlled in Mg-rich compositions.