1. 在Fe3O4(001)/MgO外延薄膜中直接观测到自旋极化现象
南京大学 徐永兵 陆显扬
Appl. Phys. Lett. 120, 182403 (2022) doi.org/10.1063/5.0091241
用XMCD方法研究了不同厚度的单晶Fe3O4(001)/MgO(001)薄膜，发现在厚20nm的Fe3O4薄膜中发现了接近理论值的自旋极化值，而在在膜厚40nm时自旋极化最大。一系列结果表明，不是晶格失配，而是反相畴界降低了自旋极化。
Fig.1 (a) Fe L2,3-edge XAS and XMCD spectra of 20 nm Fe (0 sccm O2), 5 nm Fe3O4 (1.5 sccm O2), and 20 nm γ-Fe2O3 (2 sccm O2). (b) VSM magnetization curves of Fe3O4 films with different thicknesses. (c) MS and moment of Fe3O4 films with different thicknesses. The dashed lines are guidelines for the eye.
2. Engineered Kondo screening and nonzero Berry phase in SrTiO3/LaTiO3/SrTiO3 heterostructures.
中科院物理所 刘笑然
Phys. Rev. B. 106 165421 (2022) DOI: 10.1103/PhysRevB.106.165421
控制氧化物界面上的局部自旋和流动电子之间的相互作用可以导致奇异的磁性状态。设计了SrTiO3/LaTiO3/SrTiO3异质结构，在不同厚度的LaTiO3层（n个单层）来研究二维电子气体系统中的磁相互作用。当LaTiO3层相当薄时（n=2,10），异质结构表现出显著的Kondo效应，体现了流动电子与界面上的局部磁矩之间的强烈相互作用，而当LaTiO3层厚度为n=20时，Kondo效应被大大抑制。该现象一致被解释为由于界面拉什巴自旋轨道耦合和异质结构中的磁性有序性之间的相互作用而导致的子带分裂和对称性破坏。本次研究的发现为探索和操纵复杂的氧化物界面的非三态电子带结构提供了一条途径。
Fig.1 X-ray absorption spectra (XAS) and X-ray linear dichroism (XLD) spectra of n = 20 sample. The photon energy was tuned to the Ti L2,3 absorption edges, and out-of-plane (E//c) and in-plane (E//ab) linearly polarized x-rays were applied to measure the absorption spectra using the total electron yield (TEY) detection mode at 80 K. The XLD spectra is defined as Ic Iab. Since the probing depth of TEY is only about 1-2 nm from surface into the sample, the observed results reflect mainly the topmost interface between SrTiO3 and LaTiO3 layers. The observed XLD signal in our sample indicate a splitting of the dxy and dxz/yz orbitals at the interface with energy Edxy < Edxz/yz. Such a splitting configuration is consistent with published data in LaTiO3/SrTiO3 and LaAlO3/SrTiO3 systems [2, 3]. Nevertheless, considering the fact that the observed XLD signal is rather small (less than 5%), the splitting does not render a complete orbital polarization. As a result, although the carriers would have a tendency to occupy the dxy orbital, both the dxy and dxz/yz bands are located at the Fermi level occupied by carriers, and contribute to the electrical transport. References [1] A. Ohtomo, D. A. Muller, J. L. Grazul, and H. Y. Hwang, Nature 419, 378 (2002). [2] Y. Cao, X. Liu, P. Shafer, S. Middey, D. Meyers, M. Kareev, Z. Zhong, J.-W. Kim, P. J. Ryan, E. Arenholz, and J. Chakhalian, npj Quant. Mater. 1, 16009 (2016)
3. Intrinsically elastic polymer ferroelectric by slight crosslinking
通过轻交联实现本征弹性聚合物的铁电性
中国科学院宁波材料所 胡本林教授
Science (2023) DOI: 10.1126/science.adh25
铁电体在电气、电子和生物医学方面具有很大的吸引力。然而由于其典型的非弹性变形，使得在可穿戴电子产品中的应用受到限制。研究中，试图通过塑料铁电聚合物的轻微交联，将铁电响应和弹性回弹结合到同种材料中，开发出本征弹性铁电。这种轻微的交联可以实现结晶性和高弹性之间的复杂平衡。因此，获得了一种新型材料，即在机械变形下具有铁电响应，应变度高达70%。这种新型的弹性铁电材料在与可穿戴电子设备相关的应用中发挥了很好的潜力，如弹性铁电传感器、信息存储和能量传导。
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