Tuning Interfacial Magnetic Ordering via Polarization Control in Ferroelectric SrTiO₃/PbTiO₃ Heterostructure

The electromagnetic properties at the interface of heterostructure are sensitive to the interfacial crystal structure and external field. For example, the two-dimensional magnetic states at the interface of LaAlO₃/SrTiO₃ are discovered and can further be controlled by electric field. Here, we study two types of heterostructures, TiO₂/PbTiO₃ and SrTiO₃/PbTiO₃, using first-principle electronic structure calculations. We find that the ferroelectric polarization discontinuity at the interface leads to partially occupied Ti 3d states and the magnetic moments. The magnitude of the magnetic moments and the ground-state magnetic coupling are sensitive to the polarization intensity of PbTiO₃. As the ferroelectric polarization of PbTiO₃ increases, the two heterostructures show different magnetic ordering that strongly depends on the electron occupation of the Ti t_2g orbitals. For the TiO₂/PbTiO₃ interface, the magnetic moments are mostly contributed by degenerated d _yz/d _xz orbitals of interfacial Ti atoms and the neighboring interfacial Ti atoms form ferromagnetic coupling. For SrTiO₃/PbTiO₃ interface, the interfacial magnetic moments are mainly contributed by occupied d _xy orbital because of the increased polarization intensity, and as the electron occupation increases, there exists a transition of the magnetic coupling between neighboring Ti atoms from ferromagnetism to antiferromagnetism via the superexchange interaction. Our study suggests that manipulating the polarization intensity is one effective way to control interfacial magnetic ordering in the perovskite oxide heterostructures.