Hefei National Laboratory for Physical Sciences at Microscale , University of Science and Technology of China , Hefei 230026 , China.
Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory and Hefei Science Center , Chinese Academy of Sciences , Hefei 230031 , China.
ACS Appl Mater Interfaces. 2019 Mar 13;11(10):10399-10408. doi: 10.1021/acsami.8b22055. Epub 2019 Feb 28.
Interfacial charge transfer and structural proximity effects are the two essential routes to trigger and tune numerous functionalities of perovskite oxide heterostructures. However, the cooperation and competition of these two interfacial effects in one epitaxial system have not been fully understood. Herein, we fabricate a series of LaCaMnO/CaRuO superlattices and introduce various chemical doping in the nonmagnetic CaRuO interlayers. We found that Ti, Sr, and La doping in the CaRuO layer can effectively tune the interfacial charge transfer and octahedral rotation, thus modulating the ferromagnetism of the superlattices. Specifically, the B-site Ti doping depletes the Ru 4d band and suppresses the interfacial charge transfer, leading to a decay of ferromagnetic Curie temperature ( T). In contrast, the A-site Sr doping maintains a sizable charge transfer and meanwhile suppresses the octahedral rotation, which facilitates ferromagnetism and significantly enhances the T up to 291 K. The La doping turns out to localize the itinerant electrons in the CaRuO layer, which suppresses both the interfacial charge transfer and ferromagnetism. The observed intriguing interfacial engineering of magnetism would pave a new way to understand the collective effects of interfacial charge transfer and structural proximity on the physical properties of oxide heterostructures.
界面电荷转移和结构近邻效应是触发和调节钙钛矿氧化物异质结构多种功能的两个重要途径。然而，这两种界面效应在一个外延系统中的协同和竞争尚未得到充分理解。在此，我们制备了一系列 LaCaMnO/CaRuO 超晶格，并在非磁性 CaRuO 层间引入了各种化学掺杂。我们发现，CaRuO 层中的 Ti、Sr 和 La 掺杂可以有效调节界面电荷转移和八面体旋转，从而调节超晶格的铁磁性。具体来说，B 位 Ti 掺杂耗尽 Ru 4d 带并抑制界面电荷转移，导致铁磁共振居里温度（ T）衰减。相比之下，A 位 Sr 掺杂保持了相当大的电荷转移，同时抑制了八面体旋转，这有利于铁磁性并显著提高 T 至 291 K。La 掺杂使 CaRuO 层中的巡游电子局域化，这抑制了界面电荷转移和铁磁性。观察到的有趣的界面工程磁性将为理解氧化物异质结构中界面电荷转移和结构近邻对物理性质的集体效应开辟新途径。
