Electronic and magnetic properties of transition metal ferrites and superlattices studied by X-ray absorption spectroscopy

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Title:	Electronic and magnetic properties of transition metal ferrites and superlattices studied by X-ray absorption spectroscopy
Other Titles:	X-光吸收光譜對過渡金屬陶鐵磁體薄膜和超晶格的電子結構與磁性之研究
Authors:	陳啟亮;Chen, Chi-liang
Contributors:	淡江大學物理學系博士班張經霖;Chang, Ching-lin
Date:	2005
Issue Date:	2010-01-11 02:23:55 (UTC+8)
Abstract:	過渡金屬陶鐵磁體的電子結構與磁性的特性，在過去的數十年間，無論在工業以及學術研究上，都受到相當廣泛的應用與重視。過渡金屬氧化物中，由於它們具有較強的電子電荷與自旋間的交互作用，以及晶格結構上的轉變，產生了許多豐富的物理特性。而這些特性的產生可以藉由控制不同的樣品製備以及量測的條件，諸如溫度、參雜濃度、磁場大小、或者是其他物理上的變因等，來獲得。使用分子束磊晶(MBE)長晶技術，以氧化鎂MgO為基底，可以製作出一系列高品質的過渡金屬氧化物薄膜以及超晶格樣品。本篇論文將著重在這些新穎材料與塊材之間有所不同的物理特性之分析，主要是以它們結構中的陽離子分配、電子結構、晶格結構上的轉變以及磁性的變化..等，一系列的陳述。論文中主要分為兩個部份：第一個部份是以研究過渡金屬氧化物陶鐵磁體 Fe-M-O (M 表示不同的過渡金屬元素，如: Mn、Co、Ni) 的電子結構、陽離子分配、晶格結構上的改變..等。第二部份描述了超晶格樣品Mn3O4/Fe3O4和Fe3O4/MgO 的電子結構與磁性的特性。研究中，運用了台灣新竹國家同步輻射研究中心(NSRRC)的高強度且連續可調的第三代同步幅射光源，配合著X光吸收光譜(XAS)的分析技術，其中包含了X光吸收光譜鄰近邊緣結構(XANES)和X光磁圓偏振二向性(XMCD)，來探討這些樣品的物理性質。 The electronic and magnetic structures of transition metal ferrites have been of interest for more than a decade. The rich of physical properties are attributed to the strong correlations between charge and spin of the electrons and the wealth of lattice structures in transition metal oxides. These properties can be tuned by controlling the composition, temperature or other physical variables such as magnetic field. The epitaxial growth of ferrites on single crystal MgO substrate allows the preparation of high quality thin films and superlattices. We have investigated the cation distributions, electronic and magnetic variations, and structural changes on these novel materials. Significant differences from their bulk forms are found and the grounds of these variations are discussed. This thesis comprises of two parts. First part describes study of the electronic strucure, cation distribution and structural change of transition metal oxide ferrites Fe-M-O (M is transition metal Mn, Co, Ni) thin films. Second part illustrates the electronic and magnetic properties of superlattices of Fe3O4/MgO and Mn3O4/Fe3O4. In these studies, principally x-ray absorption spectroscopy (XAS) including the X-ray Absorption Near Edge Structure (XANES) and the X-ray magnetic circular dichroism (XMCD) techniques, the intense and continuously tunable x-rays produced at third generation synchrotron facilities (National Synchrotron Radiation Research Centre, Taiwan) were employed.
Appears in Collections:	[Graduate Institute & Department of Physics] Thesis

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