Rare Earth Chalcogenides: Structural, Magnetic, and Electrical Properties at Ambient and High Pressures

稀土硫属化物：常压和高压下的结构、磁性和电学性质

• 批准号: 1004459
• 负责人: Thomas Albrecht-Schoenzart
• 金额: $ 33万
• 依托单位: University of Notre Dame
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1004459&HistoricalAwards=false
• 关键词: Rare; Earth; Chalcogenides; Structural; Magnetic

TECHNICAL SUMMARYThe aim of this research program, which is supported by the National Science Foundation, Solid State and Materials Chemistry Program, is to use flux techniques to synthesize lanthanide chalcogenides with both the known Th3P4 structure and the novel M2YbCuQ5 (M = La, Ce, Pr, Nd, Sm; Q = S, Se) structure. Magnetic and transport properties of a unique rare earth chalcogenide compound system, Ln3-xVACxQ4, employing several low temperature, high magnetic field, and high-pressure experiments will be investigated. In Ln3-xVACxQ4, Ln represents a trivalent rare earth, VAC represents a cation vacancy with a concentration range from x=0 to x=1/3, and Q represents a divalent chalcogenide anion, normally S or Se. For x=1/3 there is one vacancy per nine Ln atoms. All Ln3-xVACxQ4 compositions in this study have the generic cubic Th3P4 structure. By merely varying the vacancy concentration and/or the rare earth species in Ln3-xVACxQ4, it is thus possible to obtain a remarkably broad array of magnetic and electrical properties: from semiconducting to superconducting and from diamagnetic to ferromagnetic. In the pseudobinary continuum of compositional space between these extremes lie dilute magnetic semiconductors, magnetically doped superconductors, metallic spin glasses, possible quantum critical points, and very likely some highly correlated electron systems. Ln2YbCuQ5 was recently discovered, and in addition to adopting a novel structure type, these compounds display magnetic properties that range from simple Curie-Weiss paramagnetism to short-range antiferromagnetic coupling to long-range ordering in Sm2YbCuS5. In this latter phase negative susceptibility and substantial diamagnetism is observed in low-temperature magnetism experiments, perhaps indicating the presence of a superconducting component. Large single crystals are needed for a variety of studies to better understand the magnetic behavior of this unusual compound that will include neutron scattering/diffraction experiments, magnetic anisotropy, and resistivity measurements.NON-TECHNICAL SUMMARYThe preparation and characterization of new magnetic materials that utilize the abundant and readily available lanthanide elements is important in the development of novel technologies. This research program is aimed at training the next generation of materials scientists and solid state chemists to deeply probe materials synthesis and characterization, and to discover how novel properties can be used to solve technological problems. Specific classes continue to be developed to provide a fundamental education in this area of research, as well as to determine how best to capitalize on the knowledge of the unusual behavior of lanthanide elements. There is a strong focus in this program on training underrepresented groups, particularly African-Americans, and a strong track-record in recruiting and retaining these individuals has been established and will be significantly enhanced by the support from the National Science Foundation, Solid State and Materials Chemistry Program.

本研究计划由美国国家科学基金会固态与材料化学计划资助，其目的是使用助熔剂技术合成具有已知Th 3 P4结构和新型M2 YbCuQ 5（M = La，Ce，Pr，Nd，Sm; Q = S，Se）结构的镧系硫属元素。 本论文将研究一种独特的稀土硫属化合物系统Ln 3-xVAC xQ 4的磁性和输运性质，采用几种低温、高磁场和高压实验。 在Ln 3-xVAC xQ 4中，Ln表示三价稀土，VAC表示浓度范围为x=0至x=1/3的阳离子空位，Q表示二价硫属阴离子，通常为S或Se。 当x=1/3时，每9个Ln原子有一个空位。 本研究中的所有Ln 3-xVAC xQ 4组合物都具有一般的立方Th 3 P4结构。 通过仅仅改变Ln 3-xVAC xQ 4中的空位浓度和/或稀土物质，就可以获得非常广泛的磁和电特性：从半导体到超导，从抗磁性到铁磁性。 在这两个极端之间的组成空间的伪二元连续体中，存在着稀磁半导体、磁掺杂超导体、金属自旋玻璃、可能的量子临界点，并且很可能存在着一些高度关联的电子系统。 Ln 2 YbCuQ 5是最近发现的，除了采用一种新的结构类型，这些化合物显示出从简单的居里-外斯顺磁性到短程反铁磁耦合到Sm 2 YbCuS 5中的长程有序的磁性。 在后一阶段，在低温磁性实验中观察到负磁化率和大量的抗磁性，这可能表明超导成分的存在。 大单晶需要各种各样的研究，以更好地了解这种不寻常的化合物，将包括中子散射/衍射实验，磁各向异性和电阻率measurement.Non-Technical总结的磁性材料，利用丰富的和容易获得的镧系元素的制备和表征是很重要的新技术的发展。 该研究计划旨在培养下一代材料科学家和固态化学家，以深入探索材料合成和表征，并发现如何利用新特性来解决技术问题。 具体的课程将继续开发，以提供这一研究领域的基础教育，以及确定如何最好地利用镧系元素的不寻常行为的知识。 有一个强烈的重点是在这个程序上培训代表性不足的群体，特别是非洲裔美国人，并在招聘和留住这些人已经建立了良好的跟踪记录，并将显着提高从国家科学基金会，固态和材料化学计划的支持。