Epitaxial Growth of Strain-Induced Ferromagnetic LaCoO3 Thin Films by Simple Sol-Gel Technique
Epitaxial Growth of Strain-Induced Ferromagnetic LaCoO3 Thin Films by Simple Sol-Gel Technique
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通过简单的溶胶-凝胶技术外延生长应变诱导铁磁 LaCoO3 薄膜
DOI：
10.1142/s1793292016500302
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发表时间：
2016-03-01
期刊：
影响因子：
1.2
通讯作者：
Ma, Guohua
中科院分区：
文献类型：
--
作者：
Liu, Haifeng;Guo, Yuqiao;Ma, Guohua
采用简单的溶胶-凝胶法在（001）LaAlO 3（LAO）衬底上生长了LaCoO 3（LCO）外延薄膜。X射线衍射（XRD）和横截面透射电子显微镜（TEM）测量表明，在（001）LAO上成功地生长了具有双轴压应变和CoO 6八面体拉长变形的单相（001）取向LCO外延膜。LCO薄膜与LAO衬底之间的外延关系被证实为（001）（LCO）平行于（001）（LAO）和[100]（LCO）平行于[100]（LAO）。与多晶薄膜相比，在LAO上生长的LCO具有更大的平均Co-O键长和晶胞尺寸。此外，磁性测试表明，LCO外延薄膜在T-C（85 K）附近出现明显的铁磁（FM）转变，这与多晶LCO的基态不同.结合结构分析表明，LCO外延薄膜中应变诱导铁磁性的产生是由于Co-O键长的增加和CoO 6八面体旋转的抑制，通过降低e（g）- t（2g）能隙稳定了Co 3+的高自旋态.
LaCoO3 (LCO) epitaxial films were grown on (001) LaAlO3 (LAO) substrates by the simple sol-gel technique. X-ray diffraction (XRD) and the cross-section transmission electron microscope (TEM) measurements indicate that single-phase (001) oriented LCO epitaxial films with biaxial compressive strain and elongated distortion of CoO6 octahedrons were grown on (001) LAO successfully. The epitaxial relationship between the LCO films and the LAO substrate is confirmed to be (001)(LCO)parallel to(001)(LAO) and [100](LCO)parallel to[100](LAO). It is also found that LCO grown on LAO has a larger mean Co-O bond length and unit-cell size, compared with those of polycrystalline film. In addition, the magnetic characterization shows that LCO epitaxial films exhibits an obvious ferromagnetic (FM) transition at T-C similar to 85 K, which is different from the nonmagnetic ground state of polycrystalline LCO. Combined with the structural analyses, it reveals that the strain-induced ferromagnetism observed in LCO epitaxial films originates from an increase of the mean Co-O bond length and a suppression of the CoO6 octahedral rotations, which can stabilize higher spin state of Co3+ by a decrease of the e(g) - t(2g) gap energy.