外延锰/钌氧化物异质结构是少数具有独特界面效应的外延体系之一。在前期项目中，我们依此制备出全氧化物人工反铁磁体，首次观测到随外磁场清晰的具有层分辨的分步磁化翻转模式，发表于Science上。近期工作显示：1、当La2/3Ca1/3MnO3层厚为2uc时，LCMO/SrRuO3超晶格的TC仍可达290K；2、前文中，反铁磁层间交换耦合（AF-IEC）归咎为自旋极化隧穿机制，但当选择不同掺杂钌氧化物间隔层时，观测到AF-IEC随某些间隔层厚度的变化有振荡行为的迹象，表明在同一体系中或可实现从自旋极化隧穿到RKKY-型层间耦合机制的度越。显然，1、锰氧化物磁性“死层”的厚度有否极限？是否存在类-2D的铁磁薄层？这些超薄层间是否仍存在AF-IEC且可调？2、这类外延体系的磁性既然受控于电荷属性，是否有电场效应？本项目力图阐释这些新奇现象和基本问题，以期为氧化物自旋电子学器件的发展提供参考。

The heterostructuring of manganites and ruthenates can lead to one of the few all-oxide heterostructures exhibiting remarkable interfacial phenomena. In the last NSFC project, we have succeeded in fabricating the all-oxide synthetic antiferromagnets based on this system, and observed for the first time the layer-resolved magnetization reversal [Chen et al., Science 357, 191 (2017)]. Recently, we get some more interesting observations. First, for the La2/3Ca1/3MnO3/SrRuO3 superlattices (SLs) with the LCMO layer fixed at even 2 unit-cell thick, the Curie temperatures TC can be as high as 290 K, and more strikingly, they are found to depend on both the repeat number of the SLs and the SrRuO3 spacer thicknesses. This implies that the high-TC is not driven by the atomic layer intermixing, but the interlayer exchange coupling (IEC) may play a role. Second, when we dope the ruthenates at different electrical conductivity, some SLs show a sign of the oscillating antiferromagnetic (AF) IEC with the spacer thicknesses. This is different from the one observed for the previous system, where the CaRu1/2Ti1/2O3 spacer is doped as an insulator. That means it is possible for us to get a crossover from the spin-polarized tunneling to the RKKY-type AF-IEC for the same epitaxial system, which has never been demonstrated. It is clear that the following questions concerning more fundamental issues may arise, e.g., can the limit of the manganite dead layer be put to just one unit cell thick? does the 2D-like magnetism exist? can the AF-IEC still be realized and modulated for those ultrathin SLs? Further, since the high-TC is controlled by the interfacial charge transfer and the carrier-determined IEC as well, can the magnetism in the SLs, such as the ferromagnetic on-and-off states, be manipulated by electric field? In this project, we will try to make clear all these issues, so as to facilitate the development of all-oxide spintronic devices.