School of Materials Science and Engineering , Zhejiang University , Hangzhou 310027 , China.
Department of Physics , China Jiliang University , Hangzhou 310018 , China.
ACS Appl Mater Interfaces. 2018 Mar 28;10(12):10536-10542. doi: 10.1021/acsami.7b19112. Epub 2018 Mar 19.
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 LaAlO/SrTiO are discovered and can further be controlled by electric field. Here, we study two types of heterostructures, TiO/PbTiO and SrTiO/PbTiO, 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 PbTiO. As the ferroelectric polarization of PbTiO increases, the two heterostructures show different magnetic ordering that strongly depends on the electron occupation of the Ti t orbitals. For the TiO/PbTiO interface, the magnetic moments are mostly contributed by degenerated d /d orbitals of interfacial Ti atoms and the neighboring interfacial Ti atoms form ferromagnetic coupling. For SrTiO/PbTiO interface, the interfacial magnetic moments are mainly contributed by occupied d 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.
异质结构界面的电磁性质对界面晶体结构和外场敏感。例如，在 LaAlO/SrTiO 界面发现了二维磁态，并可以通过电场进一步控制。在这里，我们使用第一性原理电子结构计算研究了两种异质结构，TiO/PbTiO 和 SrTiO/PbTiO。我们发现界面处的铁电极化不连续性导致部分占据的 Ti 3d 态和磁矩。磁矩的大小和基态磁耦合对 PbTiO 的极化强度敏感。随着 PbTiO 的铁电极化增加，两种异质结构表现出不同的磁序，这强烈依赖于 Ti t 轨道的电子占据。对于 TiO/PbTiO 界面，磁矩主要由界面 Ti 原子的简并 d/d 轨道贡献，并且相邻的界面 Ti 原子形成铁磁耦合。对于 SrTiO/PbTiO 界面，由于极化强度增加，占据的 d 轨道主要贡献界面磁矩，并且随着电子占据的增加，通过超交换相互作用，相邻 Ti 原子之间的磁耦合从铁磁转变为反铁磁。我们的研究表明，控制极化强度是控制钙钛矿氧化物异质结构中界面磁序的一种有效方法。
