Itinerant to localized electronic behavior in phase segregated ruthenates

• Simultaneous doping of Ba and Zr in SrRuO3 leads to phase separation of ruthenates.
• Substitution of Ru by non-magnetic Zr localizes electron and induces M–I transition.
• Competition between lattice disorder and spin order leads to double M–I transition.
• Critical behavior study supports 3D Heisenberg-type ferromagnet.
• Dilution of ferromagnetic phase along with separate chemical phase produces Griffiths phase.

Simultaneous doping of Ba and Zr for Sr and Ru in SrRuO3 leads to phase separation of orthorhombic SrRuO3 (SRO) and nine layer rhombohedral BaRuO3 (9R-BRO). Differences in ionic radius and electronegativity between the cations are responsible for the chemical phase separation with increase of doping concentration. Random substitution of Ru by Zr localizes electron and induces Metal-Insulator (M−I) transition for lower doping concentration (5% and 10%). Electron–electron interaction dominates electrical conduction process due to cationic disorder in SRO lattice. Dilution of ferromagnetic interaction due to non-magnetic element Zr decreases both Curie temperature and Curie-Wiess constant and produces Griffiths phase just above the Curie temperature. At higher doping concentration (40%), solid solution of ruthenates reveals magnetism purely related to 9R-BRO phase.

Random substitution of Sr and Ru by Ba and Zr respectively localizes electron and induces Metal-Insulator (M−I) transition for lower doping concentration. Insulating state at low temperature originates from Weak localization (WL) and electron–electron interaction (EEI) due to diffusive motion of electrons in the presence of disorder, introduced by random substitution.Figure optionsDownload as PowerPoint slide