Exchange bias effect in polycrystalline SR₂IrO₄

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 T_irr, which decreases with an increasing field (H). The T_irr vs. H^2/3 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