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Title: Micro-raman study of mechanically activated ferroelectrics and advanced magnetic materials
Authors: YU TING
Keywords: Micro-raman scattering; mechanical activation; ferroelectrics; magnetic; phase transition; size effect; spin-phonon coupling
Issue Date: 7-Jun-2004
Citation: YU TING (2004-06-07). Micro-raman study of mechanically activated ferroelectrics and advanced magnetic materials. ScholarBank@NUS Repository.
Abstract: PbTiO3 (PT) powder with nanometer-sized crystallites was formed by one-step mechanical activation (MA) process from the amorphous co-precipitated Pb-Ti-O precursor. The activation energies (Ea) for the formation of PT from the precursor with/without MA process were calculated and the results show that MA can dramatically decrease the Ea. The size effect on the ferroelectric (FE) phase transition in SrBi2Ta2O9 (SBT) nanoparticles synthesized by MA was also studied by in-situ Raman scattering. The critical size, below which ferroelectricity in SBT nanoparticles diminishes, was obtained. This smaller critical size as compared with the other well-known FE materials indicates SBTa??s potential application in nano-sized FE device. In-situ and magnetic micro-Raman scattering were used to investigate the cation migration and magnetic ordering in spinel CoFe2O4 powder as well as spin-phonon coupling in CrO2 powder. The results show that Raman scattering, especially magnetic Raman is a powerful method to probe the magnetism-lattice coupling in many kinds of magnetic materials.
Appears in Collections:Ph.D Theses (Open)

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