Crystal structure and physical properties of the Sr-vacant spin-orbit-coupling induced Mott insulator Sr2−xIrO4

• According to the Raman analysis results, the modes of apical oxygen showing up in the frequency range of 500–800 cm−1 move towards the lower frequency obviously, which indicates the increasing of the apical Ir–O2 bond length. This is in good agreement with Rietveld analysis of the XRD data.
• It can be seen from the temperature-dependent resistance that all the samples display a semiconducting feature in the wide temperature range in accordance with the 3D-VRH behavior.
• The temperature-dependent magnetization reveals the magnetic anomalies around both 40 K and 180 K. Meanwhile, the curves exhibit antiferromagnetic properties under ZFC and FC conditions.

A series of polycrystalline samples of Sr2−xIrO4 (0≤x≤0.3) have been synthesized by a solid-state reaction method. The crystal structure of this doped system can be explained on the basis of the extended nature of 5d electrons and strontium vacancies in Sr2−xIrO4. The analysis of the temperature-dependent resistance of these samples reveals the semiconducting feature, in which the three-dimensional variable range hopping (3D-VRH) behavior is observed at temperatures lower than 120 K, the Arrhenius type in intermediate temperatures from 140 K to 200 K, and the two-dimensional (2D) weak-localization at high temperatures from 220 K to 300 K. Correspondingly, temperature-dependent magnetic properties in the range of x≤0.30 can be described by the antiferromagnetically ordered spin system.