Beijing National Laboratory for Condensed Matter and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, People's Republic of China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
Nat Commun. 2018 May 15;9(1):1923. doi: 10.1038/s41467-018-04304-7.
Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite LaSrMnO and brownmillerite LaCoO causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO octahedra and CoO tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.
通过界面工程将不同的过渡金属氧化物组合在一起是实现新现象的重要途径。虽然之前的大多数工作都集中在钙钛矿/钙钛矿异质结构中的界面效应，但在这里，我们报告了在钙钛矿/褐锰矿异质结构中，由于对称性不连续性引起的沿垂直方向的磁各向异性的自旋重取向，这在拉伸钙钛矿/钙钛矿异质结构中很少见。我们表明，通过交替堆叠钙钛矿 LaSrMnO 和褐锰矿 LaCoO，由于界面处的对称性不连续，会导致强烈的界面重构：钙钛矿/褐锰矿界面处的相邻 MnO 八面体和 CoO 四面体以钙钛矿/钙钛矿界面上无法实现的方式协同弛豫，导致明显的轨道重构，从而产生垂直磁各向异性。此外，垂直磁各向异性非常稳定，各向异性常数比钙钛矿/钙钛矿界面的平面各向异性大两个数量级。本工作展示了在按需设计人工材料方面，对称性工程的巨大潜力。
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