Fan Shiyu, Das Hena, Rébola Alejandro, Smith Kevin A, Mundy Julia, Brooks Charles, Holtz Megan E, Muller David A, Fennie Craig J, Ramesh Ramamoorthy, Schlom Darrell G, McGill Stephen, Musfeldt Janice L
Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA.
School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA.
Nat Commun. 2020 Nov 4;11(1):5582. doi: 10.1038/s41467-020-19285-9.
Interface materials offer a means to achieve electrical control of ferrimagnetism at room temperature as was recently demonstrated in (LuFeO)/(LuFeO) superlattices. A challenge to understanding the inner workings of these complex magnetoelectric multiferroics is the multitude of distinct Fe centres and their associated environments. This is because macroscopic techniques characterize average responses rather than the role of individual iron centres. Here, we combine optical absorption, magnetic circular dichroism and first-principles calculations to uncover the origin of high-temperature magnetism in these superlattices and the charge-ordering pattern in the m = 3 member. In a significant conceptual advance, interface spectra establish how Lu-layer distortion selectively enhances the Fe → Fe charge-transfer contribution in the spin-up channel, strengthens the exchange interactions and increases the Curie temperature. Comparison of predicted and measured spectra also identifies a non-polar charge ordering arrangement in the LuFeO layer. This site-specific spectroscopic approach opens the door to understanding engineered materials with multiple metal centres and strong entanglement.
界面材料提供了一种在室温下实现铁磁电控制的方法，最近在（LuFeO）/（LuFeO）超晶格中得到了证明。理解这些复杂的磁电多铁性材料内部工作原理的一个挑战是众多不同的铁中心及其相关环境。这是因为宏观技术表征的是平均响应，而不是单个铁中心的作用。在这里，我们结合光吸收、磁圆二色性和第一性原理计算，以揭示这些超晶格中高温磁性的起源以及m = 3成员中的电荷有序模式。在一个重大的概念进展中，界面光谱确定了Lu层畸变如何选择性地增强自旋向上通道中Fe→Fe电荷转移贡献，加强交换相互作用并提高居里温度。预测光谱与测量光谱的比较还确定了LuFeO层中的一种非极性电荷有序排列。这种位点特异性光谱方法为理解具有多个金属中心和强纠缠的工程材料打开了大门。
