Large-Pore Mesoporous Ho3Fe5O12 Thin Films with a Strong Room-Temperature Perpendicular Magnetic Anisotropy by Sol鈥揋el Processing

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• 作者：Christian Suchomski ; Christian Reitz ; Damir Pajic ; Zvonko Jaglicic ; Igor Djerdj ; Torsten Brezesinski
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：April 8, 2014
• 年：2014
• 卷：26
• 期：7
• 页码：2337-2343
• 全文大小：401K
• 年卷期：v.26,no.7(April 8, 2014)
• ISSN：1520-5002

文摘

We report the evaporation-induced self-assembly synthesis of large-pore mesoporous thin films of ferrimagnetic holmium iron garnet (Ho₃Fe₅O₁₂) from nitrate salt precursors and a polyisobutylene-block-poly(ethylene oxide) polymer structure-directing agent. The phase composition, atomic bonding configuration, and pore structure of the top surface and the interior of the films were investigated by microscopy, scattering, and spectroscopy techniques, including synchrotron-based grazing incidence small-angle X-ray scattering, X-ray photoelectron spectroscopy, X-ray diffraction (including Rietveld refinement), and others. The data provide evidence that the sol鈥揼el-derived material is single-phase garnet with 27 nm diameter crystallites and few defects after being heated to 850 掳C in air, and the continuous network of pores averaging 23 nm in diameter is preserved to a large extent, despite a solid鈥搒olid conversion from metastable h-HoFeO₃ to Ho₃Fe₅O₁₂ during the crystallization process. Furthermore, dc magnetometry measurements show the thin films are magnetically stable with a room-temperature coercivity of 170 Oe and exhibit an out-of-plane easy axis with a significant perpendicular magnetic anisotropy. A strong preference for out-of-plane magnetic alignment in solution-processed mesostructured films is unique, making them attractive for application in spintronics and nanomagnetics.