Imaging stripe phases in Mn- and Ti-doped bilayer calcium ruthenates*

As a prototypical transition-metal oxide compound, the bilayer calcium ruthenate Ca₃Ru₂O₇ exhibits exotic electronic phases under various temperatures and magnetic fields. Upon doping with a small concentration of 3d metals on the Ru sites, the quasi-two-dimensional metallic state of Ca₃Ru₂O₇ could transition into a Mott insulating state with a G-type antiferromagnetic order. Using microwave impedance microscopy, we report the nanoscale imaging of metal-insulator phase transition in Mn- and Ti-doped Ca₃Ru₂O₇. For the Ti-doped single crystal, a new stripe phase different from the two terminal phases emerges within a narrow window across the transition [1]. Interestingly, while stripe-like metallic features are present in the Mn-doped sample, their orientation, evolution across the phase transition, and electronic properties are distinct from the Ti-counterparts. Our work highlights the doping effect in complex oxides that critically impacts phase transitions in the parent compound.