Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
Adv Mater. 2017 Aug;29(32). doi: 10.1002/adma.201700790. Epub 2017 Jun 19.
Here, a quantitative magnetic depth profile across the planar interfaces in BiFeO /La Sr MnO (BFO/LSMO) superlattices using polarized neutron reflectometry is obtained. An enhanced magnetization of 1.83 ± 0.16 μ /Fe in BFO layers is observed when they are interleaved between two manganite layers. The enhanced magnetic order in BFO persists up to 200 K. The depth dependence of magnetic moments in BFO/LSMO superlattices as a function of the BFO layer thickness is also explored. The results show the enhanced net magnetic moment in BFO from the LSMO/BFO interface extends 3-4 unit cells into BFO. The interior part of a thicker BFO layer has a much smaller magnetization, suggesting it still keeps the small canted AFM state. The results exclude charge transfer, intermixing, epitaxial strain, and octahedral rotations/tilts as dominating mechanisms for the large net magnetization in BFO. An explanation-one suggested by others previously and consistent with the observations-attributes the temperature dependence of the net magnetization of BFO to strong orbital hybridization between Fe and Mn across the interfaces. Such orbital reconstruction would establish an upper temperature limit for magnetic ordering of BFO.
在这里，我们使用极化中子反射技术获得了 BiFeO/La Sr MnO（BFO/LSMO）超晶格中平面界面的定量磁性深度分布。当 BFO 层夹在两个锰氧化物层之间时，观察到 BFO 层中增强的磁化强度为 1.83±0.16μ/Fe。在 200 K 时，BFO 中的增强磁有序仍然存在。我们还研究了 BFO/LSMO 超晶格中磁矩随 BFO 层厚度的深度依赖性。结果表明，从 LSMO/BFO 界面到 BFO 的增强净磁矩延伸了 3-4 个单元。较厚 BFO 层的内部部分具有小得多的磁化强度，这表明它仍然保持着小倾斜 AFM 状态。结果排除了电荷转移、混合、外延应变和八面体旋转/倾斜作为 BFO 中强净磁化的主要机制。一个先前被其他人提出并与观察结果一致的解释是，BFO 的净磁化强度的温度依赖性归因于界面处 Fe 和 Mn 之间的强轨道杂化。这种轨道重构将为 BFO 的磁有序建立一个上限温度。
