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

一个美国-新西兰小组对稀土和过渡金属氮化物进行了研究。这项合作由波士顿大学的凯文·史密斯领导的同步加速器光谱学小组和沃尔特·R·里德尔领导的计算理论小组组成。L. Lambrecht和新西兰惠灵顿的维多利亚大学麦克迪尔米德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谱学小组。稀土氮化物形成磁性半导体或半金属材料的密切相关的家庭，表现出有趣的性质，因为强烈相关的4f电子。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），角分辨光电子能谱（ARPES）被用来检查薄膜，后者覆盖有保护层或在光束线原位生长。电子结构的计算使用LSDA+U方法（局部自旋密度近似补充与轨道相关的库仑和交换相互作用），并在全势能线性muffin-tin轨道方法中实现。光谱的理论分析将确定理论发展的需要，超越目前的LSDA+U所体现的平均场近似。计算还通过计算磁交换参数将电子结构与磁性联系起来。作为温度函数的磁化率测量由NZ小组进行。此外，我们还研究了一些过渡金属氮化物材料，这些材料表现出有趣的相关性和d电子的磁效应，这些磁性半导体和半金属材料在自旋电子学技术中有着重要的应用。这项研究为其他半导体（特别是GaN）中稀土和过渡金属的掺杂提供了见解，或者为自旋注入和其他自旋相关电子器件形成具有此类半导体的混合结构。该项目支持几名研究生，他们在跨学科和国际背景下接受培训，包括光谱学和增长问题以及理论和实验之间的合作。这一努力也通过研究人员影响了本科生？参与本科生咨询和教学，并计划将本提案的研究纳入其课程和推广活动。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。

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.