Sol–Gel Synthesis and Micro-Raman Characterization of ε-Fe2O3 Micro- and Nanoparticles,Chemistry of Materials

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Sol–Gel Synthesis and Micro-Raman Characterization of ε-Fe2O3 Micro- and Nanoparticles
Chemistry of Materials ( IF 7.2 ) Pub Date : 2016-01-14 00:00:00 , DOI: 10.1021/acs.chemmater.5b03566
J. López-Sánchez _{1,

2} , A. Serrano _{1,

3} , A. Del Campo ₃ , M. Abuín _{1,

4} , O. Rodríguez de la Fuente _{1,

2} , N. Carmona _{1,

2}

Affiliation

In this work, we present a sol–gel synthesis of ε-Fe₂O₃ nano and microparticles stabilized in silica thin films. Thanks to the relatively high size of the synthesized particles, we have been able to discriminate the Raman signal of the ε- and α-Fe₂O₃ phases, thus presenting the first Confocal Raman Microscopy study of isolated ε-Fe₂O₃ particles. The vibrational modes of each phase are identified at room temperature. The phase transition from ε- to α-Fe₂O₃ and the morphological modifications are analyzed as a function of the in situ output laser power. A complete study of the Raman spectra for ε-Fe₂O₃ particles has been performed for a wide range of temperatures (80–570 K). The phonon frequencies and line widths show a behavior in which the contributions from lattice thermal expansion and anharmonic interactions have to be considered. We have also identified a two-magnon mode in the ε-Fe₂O₃ phase. Its intensity increases close to the Néel transition (T_N) and persists well above it. This observation could be one of the few experimental examples of a paramagnon, i.e., a magnetic excitation in a paramagnetic state.

中文翻译：

溶胶-凝胶合成和的显微拉曼表征ε -铁₂ ö ₃微米和纳米粒子

在这项工作中，我们提出ε-Fe的溶胶-凝胶合成₂ ö ₃纳米和在二氧化硅薄膜稳定化的微粒。由于合成的颗粒的相对高的尺寸，我们已经能够以辨别ε-和的拉曼信号的α-Fe _2个ö ₃相，由此呈现分离的第一共焦拉曼显微镜研究ε -铁₂ ö _3个颗粒。在室温下识别每个相的振动模式。从ε-相转变到的α-Fe ₂ ö ₃和形态的修改进行了分析作为原位输出的激光功率的函数。拉曼光谱的为ε-Fe系完整的研究₂ ö在很宽的温度范围（80–570 K）中执行了_3个粒子。声子频率和线宽显示了一种行为，其中必须考虑晶格热膨胀和非谐相互作用的影响。我们还确定在ε -铁的两磁振子模式₂ ö ₃相。它的强度在接近Néel转变（T _N）时增加，并在其上方持续存在。该观察结果可能是顺磁性的少数实验例子之一，即顺磁性状态下的磁激发。

更新日期：2016-01-14

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