Enhanced magnetism and persistent insulating state in Mn doped Sr₂IrO₄

The influences of Mn substitution at the Ir site of Sr₂IrO₄are investigated via a comprehensive study of the variation of structural parameters, the transport and magnetic properties of the Sr₂Ir_1-MnO₄samples. The incorporation of Mn leads to an increase of the in-plane Ir-O-Ir bond angle, while it is not sufficient to drive the Mott-insulating state to a metallic state. Interestingly, we find a coexistence of Ir⁴⁺-O^2--Ir⁴⁺super-exchange interaction and Mn³⁺-O^2--Mn⁴⁺double exchange interaction inx⩾ 0.06 samples. The Mn³⁺-O^2--Mn⁴⁺ferromagnetic domains are isolated by the Ir⁴⁺-O^2--Ir⁴⁺antiferromagnetic areas, leading to a severely localized electronic and magnetic states. The electron hopping between the localized states dominates the conductivity of the Sr₂Ir_1-MnO₄samples.