Annealing assisted substrate coherency and high-temperature antiferromagnetic insulating transition in epitaxial La 0.67 Ca 0.33 MnO 3 /NdGaO 3 (001) films
Annealing assisted substrate coherency and high-temperature antiferromagnetic insulating transition in epitaxial La 0.67 Ca 0.33 MnO 3 /NdGaO 3 (001) films
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DOI：
10.1063/1.4804541
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发表时间：
2013-05
期刊：
影响因子：
1.6
通讯作者：
Lingfei Wang;X. Tan;Pingfan Chen;B. Zhi;Binbin Chen;Z. Huang;Guan-Yin GAO;Wenxuan Wu
中科院分区：
文献类型：
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作者：
Lingfei Wang;X. Tan;Pingfan Chen;B. Zhi;Binbin Chen;Z. Huang;Guan-Yin GAO;Wenxuan Wu
块体La0.67Ca0.33MnO3 （LCMO）和NdGaO3 （NGO）具有相同的Pbnm对称性，但具有不同的正交晶格畸变，在NGO（001）衬底上生长的LCMO外延膜呈现各向异性应变状态。在氧气氛中进行非原位退火后，薄膜在铁磁-金属基态中掺杂最佳，然而，它们在250 K附近表现出明显的反铁磁-绝缘（AFI）转变，导致在以下温度下具有可调相不稳定性的相分离状态。为了解释这种剧烈的应变效应，在不同的退火参数下对不同厚度的薄膜进行了非原位退火。我们证明了非原位退火可以惊人地提高外延质量，使薄膜具有真正的衬底相干性和AFI基态。薄膜形貌与电子相演化之间的密切联系表明，非原位退火可以辅助应变介导的八面体变形和旋转，并且在控制氧化物异质结构的性能方面发挥关键作用。
Bulk La0.67Ca0.33MnO3 (LCMO) and NdGaO3 (NGO) have the same Pbnm symmetry but different orthorhombic lattice distortions, yielding an anisotropic strain state in the LCMO epitaxial film grown on the NGO(001) substrate. The films are optimally doped in a ferromagnetic-metal ground state, after being ex-situ annealed in oxygen atmosphere, however, they show strikingly an antiferromagnetic-insulating (AFI) transition near 250 K, leading to a phase separation state with tunable phase instability at the temperatures below. To explain this drastic strain effect, the films with various thicknesses were ex-situ annealed under various annealing parameters. We demonstrate that the ex-situ annealing can surprisingly improve the epitaxial quality, resulting in the films with true substrate coherency and the AFI ground state. And the close linkage between the film morphology and electronic phase evolution implies that the strain-mediated octahedral deformation and rotation could be assisted by ex-situ annealing, and moreover, play a key role in controlling the properties of oxide heterostructures.