新型磁性氧化物单晶薄膜制备及多自由度耦合机理研究

发布时间：2018-03-31 14:59

  本文选题：钙钛矿　切入点：层状钙钛矿　出处：《中国科学技术大学》2017年博士论文

【摘要】：钙钛矿氧化物的研究一直是材料科学和凝聚态物理研究的前沿领域之一。上世纪中叶,钛酸铅、钛酸钡等材料以其优越的压电、铁电性质以及实用性受到了科研工作者的关注。八十年代铜氧化合物高温超导体,提升了人们对这类材料研究的热情。自旋电子学器件及信息存储等领域的高速发展,激发了人们对磁性氧化物进一步的兴趣,尤其是在钙钛矿或层状钙钛矿结构氧化物中。同时,钙钛矿及层状钙钛矿氧化物中的复杂相互作用使其不仅具有丰富的物理性质,还表现出良好的应用前景。探索高质量单晶薄膜的制备,是研究内在物理机制及宏观表现的基础,也是原型器件制备乃至下一步工业化应用的前提。而更好的理解材料中晶格、电荷、自旋与轨道等多种自由度之间的相互作用是探索磁性氧化物内在机理的基本途径,更是将磁性氧化物推向应用的不可或缺的一部分。本文涉及的研究内容,按照研究材料的结构类型可以分为两部分,即简单钙钛矿磁性氧化物和复杂层状钙钛矿磁性氧化物。第一部分研究是基于简单钙钛矿结构的新型磁性氧化物研究,侧重于高质量可控制备薄膜中多自由度耦合机理的研究,并尝试进行调控;第二部分是在第一部分基础上,针对更加复杂的大周期层状钙钛矿结构氧化物的磁性及多铁性研究,在制备单晶外延薄膜的基础上,从周期数目和掺杂两种角度出发,研究薄膜磁性及多铁性表现并探讨其深层物理机制。本论文第一章是文献综述,主要介绍钙钛矿结构的基本特点和磁性相互作用的类型,初步介绍了文献中已有磁性氧化物和多铁磁电耦合材料的基本情况,分别回顾总结了简单钙钛矿结构的LaCo03应力薄膜及复杂层状钙钛矿结构的Aurivilliu相多铁磁电材料的研究进展,确定了本论文的研究方向。第二章是论文研究过程中使用的试验技术总结介绍,其中包括薄膜制备,形貌结构、宏观物性、电子结构等表征分析,与微纳器件的加工制造等。第三章是基于简单钙钛矿结构新型磁性氧化物LaCo03薄膜的研究,重点在于关注多自由度耦合机制的表现和调控。基于良好原子台阶的单一截止面衬底及原位反射式高能电子衍射监控手段,制备了大量不同类型的对比样品,系统研究应力与缺陷共同作用于薄膜铁磁性的机制,发现了一种高温高对称材料体系中的本征铁磁绝缘体,对于自旋电子学器件的发展具有重大意义。同时,详细地探索了薄膜的晶体结构、表面形貌、磁畴图案、磁性(动力学)、导电性、光学等随厚度的变化规律,以及通过厚度控制实现结构畴对薄膜磁畴及磁各向异性的调控。最后在LaCo03/LaA103//SrTi03双层薄膜样品中,依据宏观磁性的调控结果,借助同步辐射半指数峰衍射、扫描透射电子显微学以及软X射线吸收谱学等分析手段,更加深刻地理解了应力、电荷以及氧八面体旋转等多种自由度在界面处的耦合作用。第四章是关于层状复杂钙钛矿结构材料外延薄膜的制备与表征研究。内容主要分成两个部分:其一,基于结构周期物性调制思路,通过制备文献尚未报道的具有超大周期结构的Bi11(Fe5CoTi3)10/9O33薄膜,探索超大周期结构的薄膜制备及其磁电性能,研究发现薄膜内部存在一种自调制的结构形式,同时在室温同样具有铁电铁磁性;其二,基于元素掺杂调控思路,研究精准掺杂条件下Aurivillius多铁薄膜结构和物性的系统变化。发现掺杂浓度存在临界数值大小,且对薄膜晶体结构、电子结构的影响很大,低掺杂的薄膜多铁性有一定的增强,掺杂对物性的调控作用比较明显。最后,第五章是对全文内容的总结,创新点提炼以及对未来工作的展望。
[Abstract]:Study on perovskite oxide is one of the materials science and research frontier in condensed matter physics. The middle of the last century, lead titanate, barium titanate and other materials with excellent piezoelectric, ferroelectric properties and practicability by scientific researchers. In 80s the cuprate superconductors, enhance the enthusiasm for this kind of material study on the rapid development of spintronic devices and information storage and other fields, it inspires people to further magnetic oxides, especially in perovskite or layered perovskite oxides. At the same time, the complex interaction of calcium titanium ore and layered perovskite oxides in which not only has rich physical properties, but also show the application prospect good. To explore the high quality single crystal films, is based on the intrinsic physical mechanism and macro performance, is prepared and a prototype device The premise of step industrial application. And the lattice, a better understanding of the material in charge, spin and orbital interactions between the various degrees of freedom is a basic way to explore the internal mechanism of magnetic oxide, is an integral part of the magnetic oxide to the application. The research content of this paper and the related research materials, according to the type of structure can be is divided into two parts, namely simple perovskite oxides and complex magnetic layered perovskite magnetic oxides. The first part is a study of novel magnetic oxide simple perovskite structure based on the research focus on the high quality control of multi degree of freedom coupling mechanism of preparation of films, and try to control; the second part is on the basis of the first part, according to the study magnetic cycle more complex layered perovskite oxides and multiferroic, based on epitaxial thin film preparation, from the number of cycles And doped with two kinds of point of view, research and multiferroic thin film magnetic performance and explore the underlying physical mechanism. The first chapter is the literature review, the basic characteristics and types of magnetic perovskite structure mainly introduces the interaction, initially introduced the basic situation of coupled magnetic oxide materials of the existing literature and magnetoelectric. Were reviewed and summarized the simple perovskite structure LaCo03 progress in research on stress film and complex layered perovskite Aurivilliu phase multiferroic magnetoelectric materials, determine the research direction of this thesis. The second chapter is the study of test process using summaries, including film preparation, morphology and macroscopic properties. Analysis of the electronic structure, and micro nano device manufacturing. The third chapter is the research on new magnetic oxide LaCo03 films simple perovskite structure based on the focus is off Performance and mechanism of coupling injection of multiple degrees of freedom. A single atomic step of substrate surface as well and in situ reflection high energy electron diffraction monitoring method based on a large number of different types of sample preparation system of the common action of stress and defects in ferromagnetic thin film system, found the intrinsic ferromagnetic insulator high temperature high symmetry material system, is of great significance to the development of spintronics devices. At the same time, explored the film crystal structure, surface morphology, magnetic domain pattern (kinetics), conductivity, optical variations with the thickness, and thickness of the control regulation of the thin film magnetic domain structure domain and the magnetic anisotropy. Finally LaCo03/LaA103//SrTi03 bilayer thin film samples, based on the result of regulation on magnetic properties, using synchrotron radiation diffraction peak half index, scanning transmission electron microscopy to And the soft X ray absorption spectroscopy and other analytical methods, a more profound understanding of the stress, charge and oxygen in eight face rotation and other degrees of freedom at the interface coupling. The fourth chapter is the research on the synthesis and characterization of layered complex perovskite epitaxial films. The main content is divided into two parts: a structure of ideas based on the modulation cycle, making literature had not been reported with a large periodic structure by Bi11 (Fe5CoTi3) 10/9O33 films, explore the superperiod structure preparation and magnetoelectric properties of thin films, the study found that the presence of a self modulated structure within the thin films, but also is the ferroelectric ferromagnetic at room temperature; second based on the ideas of doping, regulation, system changes Aurivillius multiferroic thin film structure and properties of precise doping conditions. It is found that the doping concentration is the critical numerical value, and the crystal structure of the films, The influence of electronic structure is very large. The ferromagnetic properties of low doped films are enhanced. The regulation effect of dopants on physical properties is obvious. The fifth chapter is the summary of the full text, the innovation and the prospect for future work.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ133.3;TB383.2
，

本文编号：1691234