Symmetry-Mismatch-Induced Ferromagnetism in the Interfacial Layers of CaRuO3/SrTiO3 Superlattices

By modifying the entangled multi-degrees of freedom of transition-metal oxides, interlayer coupling usually produces interfacial phases with unusual functionalities. Herein, a symmetry-mismatch-driven interfacial phase transition from paramagnetic to ferromagnetic state is reported. By constructing superlattices using CaRuO3 and SrTiO3, two oxides with different oxygen octahedron networks, the tilting/rotation of oxygen octahedra near interface is tuned dramatically, causing an angle increase from approximate to 150 degrees to approximate to 165 degrees for the Ru-O-Ru bond. This in turn drives the interfacial layer of CaRuO3, approximate to 3 unit cells in thickness, from paramagnetic into ferromagnetic state. The ferromagnetic order is robust, showing the highest Curie temperature of approximate to 120 K and the largest saturation magnetization of approximate to 0.7 mu(B) per formula unit. Density functional theory calculations show that the reduced tilting/rotation of RuO6 octahedra favors an itinerant ferromagnetic ground state. This work demonstrates an effective phase tuning by coupled octahedral rotations, offering a new approach to explore emergent materials with desired functionalities.

Automated summary

By modifying the entangled multi-degrees of freedom of transition-metal oxides, the symmetry-mismatch-driven interfacial phase transition from paramagnetic to ferromagnetic state is achieved in this work. The interfacial layer of CaRuO3, with approximately 3 unit cells in thickness, shows robust ferromagnetic order with a high Curie temperature of approximately 120 K and a large saturation magnetization of approximately 0.7 mu(B) per formula unit. Density functional theory calculations reveal that the reduced tilting/rotation of RuO6 octahedra favors an itinerant ferromagnetic ground state. This study demonstrates an effective approach to tune phases by coupled octahedral rotations and offers new opportunities for the exploration of emergent materials with desired functionalities.