Investigating the Effects of Charge Carrier Modulation in the Development of Ferromagnetic Order in Semiconducting Oxides

****非技术摘要****磁性是人类已知的最古老的现象之一，但也是最难理解的现象之一。磁性材料，通常由金属离子如镍或钴制成，已经被发现和使用了几个世纪。该项目将进行一系列实验，以测试磁性是否会在没有任何成分本身具有磁性的材料中产生。这一目标将通过引入原子尺度的点缺陷来修饰氧基半导体，特别是在氧原子的有序网络中制造空穴。这些缺陷有望导致这些氧化物半导体电导率的增加，从而引发铁磁性的发展。成像和分析技术的结合，移动电子之间的相互作用，电门控和光激发，将用于阐明磁性如何在这些半导体系统中发展。该奖项将大大促进对介于金属和绝缘体之间的材料中铁磁性如何发展的基本理解，并为制造新型磁存储器和逻辑器件的材料提供重要见解，这些材料可用于高级计算。参与该项目的学生将接受先进的分析技术培训，适用于半导体/纳米技术行业以及学术界的职业生涯。****技术摘要****该项目将进行一系列实验，以测试一些已经提出的在半导体过渡金属氧化物中发展室温铁磁性的机制，使介于局部磁矩磁性和流动磁性之间的材料的性质合理化。这些性质包括局域矩、移动电荷载流子和点缺陷（特别是氧空位）之间的相互作用。这将通过将缺氧氧化物半导体中电导率的增加与铁磁性的发展联系起来来实现。利用成像和分析技术的独特组合，有望阐明载流子浓度的变化（包括非磁性离子和点缺陷）、电门控和光激发如何影响这些磁性，以及过渡金属的局部力矩如何与氧空位相互作用以诱导铁磁性。该奖项将通过以可控的方式探测绝缘体和导体之间系统的磁性，大大推进对铁磁性的基本理解。参与该项目的两名博士生和多名本科生将接受先进的分析技术培训，适用于半导体/纳米技术行业以及学术界。

****NON-TECHNICAL ABSTRACT****Magnetism is one of the oldest phenomena known to men, yet one of the most difficult to understand. Magnetic materials, typically made from metallic ions such as nickel or cobalt, have been known and used for centuries. This project will pursue a series of experiments to test whether magnetism can arise in materials where none of the constituents are magnetic by themselves. This goal will be pursued by modifying oxygen-based semiconductors through the introduction of atomic scale point defects, specifically making holes in the ordered network of oxygen atoms. These defects are expected to lead to an increase in the electrical conductivity of these oxide semiconductors, which can trigger the development of ferromagnetism. A combination of imaging and analytical techniques, the interplay among mobile electrons, electrical gating, and optical excitations, will be used to elucidate how magnetism develops in these semiconducting systems. This award will substantially advance the fundamental understanding of how ferromagnetism develops in materials that are intermediate between metals and insulators as well as provide important insight into materials for making new magnetic memory and logic devices, which could be used for advanced computing. The students participating in this project will be trained in advanced analytical techniques applicable to careers in the semiconductor/nanotechnology industries, as well as in academia. ****TECHNICAL ABSTRACT****This project will pursue a series of experiments to test a number of mechanisms that have been proposed for the development of room temperature ferromagnetism in semiconducting transition metal oxides, rationalizing the properties of materials intermediate between local moment magnetism and itinerant magnetism. These properties include the interplay between localized moments, mobile charge carriers, and point defects, specifically oxygen vacancies. This will be accomplished by correlating the emergence of an increased electrical conductivity in oxygen deficient oxide semiconductors with the development of ferromagnetism. Using a unique combination of imaging and analytical techniques it is expected to be possible to elucidate how the shift in carrier concentration with the inclusion of non-magnetic ions and point defects, electrical gating, and optical excitations affects these magnetic properties and how local moments from transition metals interact with the oxygen vacancy to induce ferromagnetism. This award will substantially advance the fundamental understanding of ferromagnetism by probing in a controlled manner the magnetism in systems intermediate between insulators and conductors. The two Ph.D. students and multiple undergraduates participating in this project will be trained in advanced analytical techniques applicable to careers in the semiconductor/nanotechnology industries, as well as in academia.