Trilayer and Superlattice Half Metal Thin Films

学术价值：人们对硅基自旋电子材料，特别是半金属材料，在室温器件中的应用产生了浓厚的兴趣。 在以前的研究中，半金属度已被预测在Mn掺杂的Si薄膜。然而，Mn原子需要占据需要破坏Si-Si键的能量昂贵的取代位点。这种键断裂过程一直是实现这类可以利用成熟Si技术的材料的主要障碍。最近，PI预测半金属度在两个Mn/Si/Mn三层与Mn浓度在0.5单层和占据积极有利的间隙位点，和0.5单层空穴掺杂的间隔层。这些令人兴奋的结果表明，半金属硅基三层膜及其相关的超晶格是触手可及的。本计画结合理论与实验的努力，设计并实现以薄膜形式的硅基半金属三层与超晶格赝自旋阀。寻找理想的半金属三层和超晶格在铁磁或反铁磁相，和修改现有的算法来处理拟议的伪自旋阀的输运性质将提供新的知识，磁性和电子性质的层状结构。Si间隔层中的掺杂将用于增强两个Mn层之间的磁耦合。磁化率的新算法将允许在任何磁性系统中精确确定居里温度。将进行结构，磁性和磁输运测量，以表征制造的结构，并将其性能与理论预测进行比较。硅基材料的使用将使自旋电子器件的技术应用得到迅速发展。理论和实验的协同作用的努力，预计将有利于优化设计和制造这些新颖的devices.Broader影响：拟议的伪自旋阀有望表现出新的和有趣的半金属属性，这是高度相关的新型自旋电子器件的发展，如传感器，开关，磁存储器和逻辑器件。此外，还对以下问题有了新的认识：（1）过渡金属元素的两层间空穴掺杂是如何引起三层结构中Mn层间的半金属性和磁矩耦合的？(ii)独特的新知识，操纵生长参数，以获得样品的硅基三层和超晶格赝自旋阀的预测性能的合成方法。这些进展将大大促进自旋电子器件的未来发展。PI将积极招募代表性不足的少数民族学生与他们一起工作。他们与美国、瑞典、德国、中国、西班牙和土耳其的研究小组合作。研究生将有机会与国内和国际上该领域的领先研究人员进行互动。PI还努力将研究与教育和推广活动相结合，以提高从初中到研究生院学生的学习经验。

Intellectual Merit:There has been intense interest in silicon based spintronic materials, particularly half-metals, for room temperature device applications. In previous studies, half-metallicity has been predicted in thin films of Mn-doped Si. However, the Mn atoms need to occupy the energetically costly substitutional sites that require breaking of Si-Si bonds. This bond breaking process has been the major obstacle for achieving this class of materials that may take advantage of the mature Si technology. Very recently, the PI has predicted half-metallicity in two Mn/Si/Mn trilayers with Mn concentration at 0.5 monolayer and occupying the energetically favorable interstitial sites, and a 0.5 monolayer hole doping in the spacer layer. These exciting results suggest that half metallic Si-based trilayers and their related superlattices are within reach. This project combines theoretical and experimental efforts to design and realize such trilayer and superlattice pseudo-spin valves of silicon-based half-metal in thin film forms. The search for the ideal half-metallic trilayers and superlattices in ferromagnetic or antiferromagnetic phases, and modifications of existing algorithms to treat transport properties for proposed pseudo-spin valves will provide new knowledge concerning magnetism and electronic properties in layered structures. Doping in the Si spacer layer will be used to enhance the magnetic coupling between the two Mn layers. New algorithms of magnetic susceptibility will allow accurate determination of Curie temperature in any magnetic systems. Structural, magnetic, and magneto-transport measurements will be performed in order to characterize the fabricated structures and compare their properties with theoretical predictions. The use of silicon-based materials would enable rapid development of technological applications for spintronic devices. The synergy of the theoretical and experimental efforts is expected to facilitate the optimal design and fabrication of these novel devices.Broader Impacts:The proposed pseudo-spin valves are expected to exhibit new and intriguing half-metallic properties, which are highly relevant for the development of novel spintronic devices, such as sensors, switches, magnetic memory, and logic devices. Furthermore, new understandings will be gained on: (i) how can the hole doping between two layers of transition metal elements cause the half metallicity and couple the magnetic moments between Mn layers in the trilayers and superlattices? (ii) unique new knowledge about manipulating growth parameters to obtain samples of Si-based trilayer and superlattice pseudo-spin valves with predicted properties by the synthesis method. These advancements will significantly facilitate future developments of spintronic devices. The PIs will actively recruit underrepresented minority students to work with them. They have collaborations with research groups in the US, as well as in Sweden, Germany, China, Spain and Turkey. Graduate students will have the opportunity to interact with leading researchers in the field nationally, as well as internationally. The PIs also strive to integrate research with educational and outreach activities to enhance the learning experience of students from junior high school through graduate school.