钛基自旋-派尔斯晶体的制备及其掺杂晶体磁序的研究

项目名称： 钛基自旋-派尔斯晶体的制备及其掺杂晶体磁序的研究

项目编号： No.51502157

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 一般工业技术

项目作者： 张健

作者单位： 山东大学

项目金额： 21万元

中文摘要： 低维量子磁性材料的制备与物性研究成为当前材料科学与凝聚态物理交叉领域的前沿课题之一。自旋-派尔斯化合物是此种材料的一类，电荷、自旋、轨道以及晶格自由度之间复杂的相互作用使其成为目前研究晶体自旋磁矩耦合以及高温超导机理的一个热点。本课题采用化学气相传输法制备碱金属Na、K掺杂的自旋-派尔斯晶体TiOCl和TiOBr，通过优化反应条件获得高质量的晶体。采用同步辐射X射线衍射技术观察由于晶体内部强烈的磁耦合而产生的结构形变并得到其调制结构，进而研究晶体在低温下的磁相变。研究碱金属的的引入对低温下自旋磁矩的二聚化的影响以及对自旋-派尔斯相变的抑制。观察掺杂晶体低温下的绝缘体-金属相变并采用从头算的方法计算掺杂晶体的电子能带结构，建立碱金属掺杂TiOCl以及TiOBr的理论模型并进行讨论。本课题对理解掺杂引起的含钛自旋-派尔斯晶体的绝缘体-金属相变以至超导相变有着重要的科学意义。

中文关键词： 低维晶体材料；晶体生长；掺杂；强关联系统；磁序

英文摘要： The preparation and physics properties of low dimensional quantum materials have been a subject of the crossing field of materials science and condensed matter physics. One of such family of quantum magnets are spin-Peierls compounds, the complex interplay between charge, spin, orbital, and lattice degrees of freedom has made spin-Peierls compounds prime candidates for studying unusual magnetic ground states. The project will focus on the improvement of the crystal quality of TiOCl and TiOBr, which are grown by chemical vapor transport method firstly. The distortion of crystal structure in intercalated TiOCl and TiOBr, which is the result of strong magnetoelastic coupling, will be studied by temperature-dependent x-ray diffraction (XRD) experiments. The magnetic phase transition will also be studied by magnetic susceptibility, heat capacity, and dielectric measurements. The dimerization of spin magnetic moment is suppressed due to the introduction of alkalis. A further study is calculations of the band structures of intercalated TiOCl and TiOBr, which are based on the XRD data, by the ab initio quantum mechanical software package CASTEP. The discussion between theoretical and experimental results will be performed to uncover the roles of dopant. This project will improve the understanding of insulator-metal transitions and the superconductivity in doped spin-Peierls crystals, which were caused by the introduction of dopant.

英文关键词： Low dimensional materials;crystal growth;doped system;strong correlation system;magnetic order