在鈦酸鉛及氧化鐵鈷的多重鐵性系統中研究受應力影響之介面聲子與鐵磁特性

Abstract

在此篇論文中，我們藉由顯微拉曼光譜研究在以鈦酸鉛為基質而含有三種不同幾何結構的氧化鐵鈷之多重複合鐵性材料中之介面聲子及鐵磁特性與應力的相關性。多重複合鐵性材料在介面上的聲子能量和鐵磁特性跟應力的關係不只源自於氧化鐵鈷跟鈦酸鉛基底的晶格大小差異，也跟他們在介面上的化學鍵結強度相關。其中，以disk-3型態的多重複合鐵性材料，即為自組裝的盤狀氧化鐵鈷鑲嵌於鈦酸鉛基質中，顯現出在鐵磁相與鐵電相間有最強的彈性交互作用力。相較於氧化鐵鈷與鈦酸鉛的層狀結構(2-2)或氧化鐵鈷粒子懸浮於鈦酸鉛中的結構(0-3)而言，disk-3的氧化鐵鈷在磁滯曲線上有較低且較不對稱的矯頑場及難以被飽和的磁化量，這些皆與鈦酸鉛在拉曼光譜中的A1(2TO)和A1(3TO)模態有較多的紅位移相吻合。

We report on the relationship between local behavior of interfacial phonon and ferromagnetic properties in three multiferroics consisting of different geometric shapes of ferromagnetic CoFe2O4 (CFO) embedded in ferroelectrics PbTiO3 (PTO) studied by micro-Raman spectroscopy. The energy of interfacial phonon and ferromagnetic properties depend on stress due to not only the lattice misfit but also the degree of chemical bonding at the interface between CoFe2O4 and PbTiO3 matrix. In one dimension (1D) embedded in 3D or disk-3 type structure, the self-assembled CFO disks embedded in a PTO matrix, illustrates strong elastic interactions between the two phases. The larger nonsymmetrical coercivity Hc and the absence of saturation magnetization Ms of CFO matche with the more Raman shift of A1(2TO) and A1(3TO) modes of PTO found in the disk-3 type than the other types of CFO and PTO multilayered structure and the CFO particles embedded in PTO matrix.