Exchange bias effect in polycrystalline SR2IrO4

Abstract

We report the presence of an exchange bias effect in a layered iridate compound, Sr2IrO4, in polycrystalline form. The Rietveld refinement of the x-ray diffraction pattern shows that Sr2IrO4 crystallizes in a tetragonal structure (I41acd). The temperature dependence of zero-field cooled (ZFC) and field cooled (FC) magnetization measurements show a magnetic ordering temperature of ~240 K, which is considered as its canted antiferromagnetic ordering temperature. An irreversibility between ZFC and FC curves is observed at Tirr, which decreases with an increasing field (H). The Tirr vs. H2/3 plot follows the Almeida-Thouless (AT) line. The presence of an AT line and a significant amount of coercivity (~0.3 T) at 5 K hint a cluster-glass like behaviour in Sr2IrO4 polycrystals. A negative exchange bias effect has been observed at 5 K with an exchange bias field of 0.018 T, which is attributed to an interfacial exchange interaction between a canted antiferromagnetic phase and a probable cluster-glass phase. This is the first report on the observation of an exchange bias effect in Sr2IrO4. Further studies are underway for a detailed understanding.