Stabilisation of Fe2O3-rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO3 Films.
Stabilisation of Fe2O3-rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO3 Films.
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DOI：
10.1038/srep13066
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发表时间：
2015-08-14
影响因子：
4.6
通讯作者：
Rainforth WM
中科院分区：
文献类型：
--
作者：
Zhang H;Reaney IM;Marincel DM;Trolier-McKinstry S;Ramasse QM;MacLaren I;Findlay SD;Fraleigh RD;Ross IM;Hu S;Ren W;Rainforth WM
研究人员已经证明，BiFeO₃具有铁电滞后现象，但在未经重大结构或成分改性的情况下，无论是块状还是薄膜形式，都没有显示出强烈的铁磁响应。当在基于BiFeO₃的薄膜中观察到剩余磁化时，经常会检测到氧化铁第二相。利用像差校正扫描透射电子显微镜、原子分辨率电子能量损失谱映射以及定量能量色散X射线光谱分析，我们揭示了一种新的富含Fe₂O₃的钙钛矿纳米相的存在，其近似化学式为(Fe₀.₆Bi₀.₂₅Nd₀.₁₅)³⁺Fe³⁺O₃，它形成于通过脉冲激光沉积生长的外延Ti和Nd掺杂的BiFeO₃钙钛矿薄膜内。Nd和Bi离子在A位的掺入以及与基体的共格生长稳定了富含Fe₂O₃的钙钛矿相，初步的密度泛函理论计算表明它应该具有亚铁磁响应。此前已有关于钙钛矿结构Fe₂O₃的报道，但在高压高温制备时从未有确凿的证据。这项工作表明，掺入大的A位离子可能有助于稳定钙钛矿结构的Fe₂O₃。因此，这一发现不仅对薄膜领域，而且对高压研究领域都具有重要意义。
Researchers have demonstrated that BiFeO3 exhibits ferroelectric hysteresis but none have shown a strong ferromagnetic response in either bulk or thin film without significant structural or compositional modification. When remanent magnetisations are observed in BiFeO3 based thin films, iron oxide second phases are often detected. Using aberration-corrected scanning transmission electron microscopy, atomic resolution electron energy loss spectrum-mapping and quantitative energy dispersive X-ray spectroscopy analysis, we reveal the existence of a new Fe2O3-rich perovskite nanophase, with an approximate formula (Fe0.6Bi0.25Nd0.15)3+ Fe3+O3, formed within epitaxial Ti and Nd doped BiFeO3 perovskite films grown by pulsed laser deposition. The incorporation of Nd and Bi ions on the A-site and coherent growth with the matrix stabilise the Fe2O3-rich perovskite phase and preliminary density functional theory calculations suggest that it should have a ferrimagnetic response. Perovskite-structured Fe2O3 has been reported previously but never conclusively proven when fabricated at high-pressure high-temperature. This work suggests the incorporation of large A-site species may help stabilise perovskite-structured Fe2O3. This finding is therefore significant not only to the thin film but also to the high-pressure community.