Materials World Network on Rare-Earth and Transition-Metal Nitride Spectroscopic Studies

稀土和过渡金属氮化物光谱研究材料世界网络

• 批准号: 0710485
• 负责人: Walter Lambrecht
• 金额: $ 52.7万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-15 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0710485&HistoricalAwards=false
• 关键词: Materials; World; Network; Rare; Earth

An investigation on rare-earth and transition metal nitrides is carried out by a US-New Zealand team. The collaboration consists of a synchrotron spectroscopy group led by Kevin Smith at Boston University and a computational theory group led by Walter R. L. Lambrecht at Case Western Reserve University, with a thin film growth and optical spectroscopies group led by Joe Trodahl and Ben Ruck at the MacDiarmid Institute for Advanced Materials and Nanotechnology at Victoria University in Wellington, New Zealand. The rare-earth nitrides form a closely related family of magnetic semi-conducting or semimetallic materials, exhibiting interesting properties because of the strongly correlated 4f electrons. An array of different spectroscopic techniques, including X-ray emission (XES) and absorption (XAS) spectroscopy, Resonant Inelastic X-ray scattering (RIXS), and Angular Resolved Photoemission Spectroscopy (ARPES) are used to examine films, the latter capped with protective layers or grown in-situ at the beamline. Calculations are carried out of the electronic structure using the LSDA+U approach (Local spin-density approximation complemented with orbital dependent Coulomb and exchange interactions) and implemented in the full-potential linear muffin-tin orbital method. Theoretical analysis of the spectra will identify the need for theoretical developments beyond the mean-field approximation embodied by current LSDA+U. The calculations also tie the electronic structure to magnetic properties by calculation of the magnetic exchange parameters. Magnetic susceptibility measurements as function of temperature are carried out by the NZ group. Selected transition-metal nitrides, which exhibit interesting correlation and magnetic effects arising from the d-electrons are also investigated.Besides their fundamental interest, the magnetic semiconductor and semi-metallic materials may find applications in spintronic technology. This research provides insights into the doping of rare-earth and transition metals in other semiconductors, in particular GaN, or the formation of hybrid structures with such semiconductors for spin-injection and other spin-dependent electronics. The project supports several graduate students, who receive training in an interdisciplinary and international context, including collaborations between spectroscopy and growth issues and theory and experiment. The effort also impacts undergraduate students through the researchers? involvement with undergraduate advising and teaching and their plans to incorporate the research of this proposal in their courses and outreach activities. The international collaboration is anticipated to foster new collaborative research projects. This award is co-funded by the Office of International Science and Engineering.

美国和新西兰的一个研究小组对稀土和过渡金属氮化物进行了研究。此次合作包括由波士顿大学Kevin Smith领导的同步加速器光谱学小组和凯斯西储大学Walter R. L. Lambrecht领导的计算理论小组，以及由新西兰惠灵顿维多利亚大学MacDiarmid先进材料和纳米技术研究所的Joe Trodahl和Ben Ruck领导的薄膜生长和光学光谱学小组。稀土氮化物形成了一个密切相关的磁性半导体或半金属材料家族，由于强相关的4f电子而表现出有趣的性质。使用一系列不同的光谱技术，包括x射线发射（XES）和吸收（XAS）光谱，共振非弹性x射线散射（RIXS）和角分辨光电发射光谱（ARPES）来检查薄膜，后者覆盖有保护层或在光束线上原位生长。利用LSDA+U方法（局域自旋密度近似加上轨道依赖的库仑和交换相互作用）对电子结构进行了计算，并用全势线性松饼锡轨道方法实现了计算。光谱的理论分析将确定需要在目前的LSDA+U所体现的平均场近似之外进行理论发展。计算还通过计算磁交换参数将电子结构与磁性联系起来。磁化率随温度变化的测量由NZ组进行。我们还研究了一些过渡金属氮化物，它们表现出有趣的相关性和由d电子引起的磁效应。磁性半导体和半金属材料在自旋电子技术中也有应用。这项研究为稀土和过渡金属在其他半导体中的掺杂提供了见解，特别是氮化镓，或者与这些半导体形成混合结构，用于自旋注入和其他自旋依赖的电子器件。该项目支持几名研究生，他们接受跨学科和国际背景下的培训，包括光谱学和生长问题以及理论和实验之间的合作。这项工作还通过研究人员影响了本科生。参与本科生的指导和教学，并计划将本提案的研究纳入他们的课程和外展活动。预计国际合作将促进新的合作研究项目。该奖项由国际科学与工程办公室共同资助。