Trilayer and Superlattice Half Metal Thin Films

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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.