Enhancing the orthorhombicity and antiferromagnetic-insulating state in epitaxial La0.67Ca0.33MnO3/NdGaO3(001) films by inserting a SmFeO3 buffer layer
Enhancing the orthorhombicity and antiferromagnetic-insulating state in epitaxial La0.67Ca0.33MnO3/NdGaO3(001) films by inserting a SmFeO3 buffer layer
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通过插入 SmFeO3 缓冲层增强外延 La0.67Ca0.33MnO3/NdGaO3(001) 薄膜的正交性和反铁磁绝缘态
DOI：
10.1063/1.4902951
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发表时间：
2014-11
期刊：
影响因子：
--
通讯作者：
B. W.
中科院分区：
文献类型：
--
作者：
X. L. Tan;G. Y. Gao;P. F. Chen;H. R. Xu;B. W.
通过插入不同厚度（t）的SmFeO 3（SFO）缓冲层，对外延La 0. 67 Ca 0. 33 MnO 3（30 nm）/NdGaO 3（001）[LCMO/NGO（001）]薄膜的结构和磁输运性质进行了调谐.所有的层和NGO衬底具有相同的Pbnm对称性，其中八面体围绕b轴倾斜，但具有不同的正交性（d）。我们发现，随着t的增加，完全应变（≤15 nm）或部分弛豫（30-60 nm）的SFO层可以在上部LCMO膜中产生不同的d。相应地，LCMO中的诱导反铁磁绝缘态（AFI）随着TAFI从t ≤ 15 nm时的约250 K移动到t = 30-60 nm时的约263 K而大大增强。当t ≥ 30 nm时，应变弛豫表现出明显的各向异性，非晶薄膜的晶格常数a与非晶薄膜相同，但SFO和LCMO薄膜的B均增大.这表明八面体耦合穿过界面，使得应变沿着a轴由八面体倾斜调节，而沿着b轴最可能由八面体变形调节。在LCMO层中的AFI状态可以归因于增强的正交性与合作增加的Jahn-Teller样扭曲和MnO 6八面体的倾斜。结果表明，界面八面体耦合在钙钛矿氧化物薄膜的外延生长和功能调谐中起着至关重要的作用。
Structural and magnetotransport properties of epitaxial La0.67Ca0.33MnO3(30 nm)/NdGaO3(001) [LCMO/NGO(001)] films are tuned by inserting an insulating SmFeO3 (SFO) buffer layer at various thicknesses (t). All the layers and the NGO substrates have the same Pbnm symmetry with the octahedra tilting about the b-axis, but different orthorhombicity (d). We found that as t increases, the fully strained (≤15 nm) or partially relaxed (30–60 nm) SFO layers can produce different d in the upper LCMO films. Correspondingly, the induced antiferromagnetic-insulating (AFI) state in LCMO is greatly enhanced with TAFI shifted from ∼250 K for t ≤ 15 nm to ∼263 K for t = 30–60 nm. We also show that the strain relaxation for t ≥ 30 nm is remarkably anisotropic, with a stable lattice constant a as that of the NGO substrates but increasing b of both SFO and LCMO layers. This indicates the octahedral coupling across the interfaces, leaving the strain along the a-axis accommodated by the octahedral tilts, while along the b-axis most probably by the octahedral deformations. The AFI state in the LCMO layer could be ascribed to the enhanced orthorhombicity with cooperatively increased Jahn-Teller-like distortions and tilting of the MnO6 octahedra. The results strongly suggest that the interfacial octahedral coupling plays a crucial role in epitaxial growth and in tuning functionalities of the perovskite oxide films.
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