Structural, Optical, and Magnetic Properties of Highly Ordered Mesoporous MCr2O4 and MCr2鈥?i>xFexO4 (M = Co, Zn) Spinel Thin Films wit

详细信息    查看全文

• 作者：Christian Suchomski ; Christian Reitz ; Kirstin Brezesinski ; C茅lia Tavares de Sousa ; Marcus Rohnke ; Ken-ichi Iimura ; Joao Pedro Esteves de Araujo ; Torsten Brezesinski
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：January 10, 2012
• 年：2012
• 卷：24
• 期：1
• 页码：155-165
• 全文大小：741K
• 年卷期：v.24,no.1(January 10, 2012)
• ISSN：1520-5002

文摘

Herein is reported the synthesis and characterization of nanocrystalline cobalt chromite (CoCr₂O₄) and zinc chromite (ZnCr₂O₄) thin films with highly ordered cubic networks of open pores averaging 15 nm in diameter. We also show that the synthesis method employed in this work is readily extendable to solid solutions of the type MCr_2鈥?i>xFe_xO₄ (M = Co, Zn), which could pave the way for innovative device design. All of these materials can be prepared by facile coassembly of hydrated nitrate salts with an amphiphilic diblock copolymer, referred to as KLE. The as-made materials are amorphous thin films with face-centered-cubic close-packed pore structures. Electron microscopy, X-ray diffraction, grazing incidence small-angle X-ray scattering, krypton physisorption, UV鈥搗is spectroscopy, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and Raman spectroscopy studies collectively verify that both the transition metal chromites and the solid solutions are well-defined at the nanoscale and the microscale. In addition, the data show that the different thin film materials are nanocrystalline after annealing in air at 600 掳C, adopt the spinel structure in phase-pure form, and that the conversion of the initially amorphous frameworks comes at little cost to the ordering of the cubic pore-solid architectures. Magnetization studies as a function of temperature and field further reveal the high quality of the KLE-templated CoCr₂O₄ thin films with both long-range ferrimagnetic order and spiral magnetic order at low temperatures, in agreement with previous findings.

Keywords:

chromite; ferrite; spinel; thin film; self-assembly; mesoporous; magnetic; multiferroic