Building New Spintronic Materials with Layered Chalcogenides

材料研究部凝聚态物理项目的这一奖项支持田纳西大学诺克斯维尔分校的一个项目，该项目专注于自旋电子学新材料的设计、发现和表征。自旋电子学是一种利用电子的电荷和自旋(电子的磁矩)来创造新的节能设备功能的领域。自旋电子学是一个快速发展的领域，预计将通过开发一类被称为硫族化合物的材料的性质来进一步改变它。原子薄层的硫化物是真正的半导体，可以催生下一代高性能的电子设备，如场效应管和光电晶体管。自旋电子学与二维硫化物半导体的融合有望带来纳米电子学的革命性进展。由于合成和晶体生长是接触到本科生的极好工具，该研究计划旨在积极吸引本科生并激发他们对科学的兴趣。除了学生的实践经验，还有一门将在本科生高级阶段教授的名为“纳米磁学和自旋电子学”的新课程。此外，该计划还支持P.I.S的推广活动，允许为中学生开发基于超导和磁学的新演示。技术摘要该项目的目标是基于层状硫化物的显著电和磁性质设计、发现和表征新的自旋电子材料。该项目的重点是两类自旋电子材料。其中一类涉及在层状金属螺旋磁体中形成手性孤子晶格(CSL)。CSL是由铁磁区隔开的孤子(磁区壁边界)的晶格。CSL的周期性可以用适度的外加磁场来调节，这种效应被预测为导致独特的自旋电子功能，如自旋电流感应、孤子输运和电流驱动的集体输运。第二类材料包括化学计量比的高迁移率的准2D磁性半导体。这些材料是磁性有序的，可能用于单层器件，可能用作自旋注入器、传感器或换能器。该项目的目标之一是阐明CSL材料和准2D磁性半导体的设计原则。使用助熔剂和蒸汽传输技术生长目标材料的单晶。用SQUID磁测量和电输运表征了材料的各向异性性质。用小角中子衍射法表征了CSL材料的螺旋有序性，并探索了它们对磁场的响应。利用半导体二维铁磁体制备了单层场效应器件，并对其电学性能进行了表征。由于合成和晶体生长是接触到本科生的极好工具，该研究计划旨在积极吸引本科生并激发他们对科学的兴趣。除了学生的实践经验，还有一门将在本科生高级阶段教授的名为“纳米磁学和自旋电子学”的新课程。此外，该项目还支持P.I.S的外联活动，允许为中学生开发基于超导和磁学的新演示。

NON-TECHNICAL ABSTRACTThis award from the Condensed Matter Physics Program of the Division of Materials Research supports the University of Tennessee at Knoxville with a project focused on the design, discovery, and characterization of new materials for spintronics. Spintronics is the field that makes use of the electric charge and the spin (magnetic moment of the electron)of the electron to create new energy efficient device functionalities. Spintronics is a fast-developing field and it is expected to be further transformed by exploiting the properties of a class of material known as chalcogenides. Atomically thin layers of chalcogenides are true semiconductors and can lead to next generation of high performance electronic devices such as field-effect and photo- transistors. The fusion of spintronics with two dimensional chalcogenide semiconductors is expected to lead to revolutionary advances in nanoelectronics. As synthesis and crystal growth are excellent tools to reach undergraduate students, the research program is designed to actively involve undergraduates and kindle their interest in science. The hands-on experience of the students is complemented by a new course entitled "Nanomagnetism and Spintronics" to be taught at the advanced undergraduate level. In addition, the program supports the P.I.'s outreach activities, allowing the development of new demonstrations for middle school students based on superconductivity and magnetism.TECHNICAL ABSTRACTThe objective of this project is to design, discover, and characterize new spintronic materials based on the remarkable electronic and magnetic properties of layered chalcogenides. The project is focused on two classes of spintronic materials. One class involves the formation of a chiral soliton lattice (CSL) in layered, metallic helical magnets. The CSL is a lattice of solitons (domain wall boundaries) separated by ferromagnetic regions. The CSL periodicity is tunable using modest applied fields and this effect is predicted to lead to unique spintronic functionalities, such as spin current induction, soliton transport, and current-driven collective transport. The second class of materials involves stoichiometric quasi-2D magnetic semiconductors with high mobility. These materials order magnetically and potentially can be used in single-layer devices that may be useful as spin injectors, sensors, or transducers. One of the goals of this project is to elucidate design principles for CSL materials and quasi-2D magnetic semiconductors. Single crystals of targeted materials are grown using both flux and vapor transport techniques. The anisotropic properties of the materials are characterized using SQUID magnetometry and electrical transport. Small angle neutron diffraction is performed to characterize the helical order of the CSL materials and probe their response to magnetic fields. Single-layer field-effect devices made from semiconducting 2D ferromagnets are fabricated and their electrical properties characterized. As synthesis and crystal growth are excellent tools to reach undergraduate students, the research program is designed to actively involve undergraduates and kindle their interest in science. The hands-on experience of the students is complemented by a new course entitled "Nanomagnetism and Spintronics" to be taught at the advanced undergraduate level. In addition, the program supports the P.I.'s outreach activities, allowing the development of new demonstrations for middle school students based on superconductivity and magnetism.