Decoupling of the Antiferromagnetic and Insulating States in Tb doped Sr2 IrO4

We report results of a comprehensive study of single-crystal Sr₂Ir_1-xTb_xO₄ (0 <=x <=0.03). This study found that mere 3% (x =0.03) tetravalent Tb4⁺ substituting for Ir4⁺ (rather than Sr2⁺) completely suppresses the long-range collinear AFM transition but retains the insulating state. Tb doping effectively changes the relative strength of the SOI and the tetragonal CEF and enhances the Hund's rule coupling that competes with the SOI, and destabilizes the AFM state. We observe unconventional correlation between the AFM and insulating states in which the magnetic transition plays no critical role in the formation of the charge gap in the iridate.

This work was supported by NSF through Grant DMR-1265162.