Synthesis and Crystal Growth of Dilute Magnetic Semiconductors and Frustrated Magnets

“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。新材料的合成和晶体生长将集中在稀磁半导体和受抑磁体上，并将这些材料制备为粉末，单晶和薄膜。 该粉末将产生的固溶体形成的程度上的信息;扩散或离子注入到单晶基板的过渡金属将允许组成映射的铁磁性;单晶的通量生长将提供一个途径来合成材料的表征中子散射;和薄膜沉积在低温下将允许研究的组合物，通常表现出相分离。 选择稀磁半导体和受抑磁体这两类材料是因为它们分别对自旋电子学应用和多铁性行为有着浓厚的兴趣。 半导体晶格将被包括钒、铬、锰、铁、钴和镍的各种第一行过渡金属磁性离子取代。 过渡金属替代物将具有约5原子%的浓度，使得磁性离子之间的直接相互作用可忽略不计（稀释）。 这些稀磁半导体材料由于与半导体中的电子载流子的相互作用而表现出长程磁耦合（铁磁性）。 基于载流子诱导铁磁性理论，研究了带隙能量、载流子密度和交换耦合强度对铁磁居里温度的影响。因此，三元磷化物、砷化物、硒化物和碲化物材料被预测为载流子介导铁磁性的强候选主体晶格。 对于受抑磁性材料，将针对以下化合物探索从高温通量生长单晶：ACr 2S 4，其中A= Zn、Cd或Hg，为了研究磁性（以及CdCr 2S 4的可能结构特性）这取决于最近和次最近邻Cr相互作用与Cs2 Cu 3 ZrF 12之间的相互作用，以研究强几何阻挫这导致了不寻常的磁现象。非技术总结：稀磁半导体和受抑磁体的发现和理解可以推进微电子和光子学工业，可能导致基于自旋电子学的新设备。 此外，研究小组的成员，其中包括高中生，本科生和研究生，以及博士后助理将接受科学，技术，工程和数学（STEM）学科的研究培训。 由于纽约市立大学（CUNY）纽约市立学院（CCNY）的人口统计，许多女学生和来自代表性不足的族裔群体的学生将接受研究培训。 CCNY的化学和物理系参加的多组会议将促进内部合作;纽约市地区的固态化学专题讨论会将开始交流和传播结果;磁性材料将与美国和世界各地的其他实验室分享，以寻求对磁相互作用的理解。 为了进一步补充科学和教育方面，当地公众将介绍晶体化学开放日，科学博览会和校园参观当地高中团体。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."TECHNICAL SUMMARY:The synthesis and crystal growth of novel materials will focus on dilute magnetic semiconductors and frustrated magnets with the preparation of these materials as powders, single crystals, and thin films. The powders will yield information on the extent of solid solution formation; diffusion or ion implantation of transition metals into single crystal substrates will allow for compositional mapping of ferromagnetism; flux growth of single crystals will provide a route to synthesize materials for characterization by neutron scattering; and thin film deposition at low temperatures will permit the study of compositions which typically demonstrate phase separation. The two classes of materials to be investigated, dilute magnetic semiconductors and frustrated magnets, are chosen due to the intense interest in spintronic applications and multiferroic behavior, respectively. Semiconductor crystal lattices will be substituted with various first row transition metal magnetic ions including vanadium, chromium, manganese, iron, cobalt and nickel. The transition metal substitution will have concentrations around five atomic percent such that there is negligible direct interaction between magnetic ions (dilute). These dilute magnetic semiconductor materials demonstrate long range magnetic coupling (ferromagnetism) due to interaction with electronic carriers in the semiconductor. Based on theories of carrier-induced ferromagnetism, several variables, including the bandgap energy, carrier density and exchange coupling strength, affect the ferromagnetic Curie temperature. Therefore, ternary phosphide, arsenide, selenide and telluride materials are predicted to be strong candidate host lattices for carrier-mediated ferromagnetism. For the frustrated magnetic materials, the growth of single crystals from high temperature fluxes will be explored for the following compounds: ACr2S4, where A= Zn, Cd or Hg, in order to study the magnetic properties (and possible structural properties in the case of CdCr2S4) which depend on the interplay between the nearest and next nearest neighbor Cr interactions and Cs2Cu3ZrF12 to investigate strong geometrical frustration which leads to unusual magnetic phenomena.NON-TECHNICAL SUMMARY:The discovery and understanding of dilute magnetic semiconductors and frustrated magnets can advance the microelectronics and photonics industries, possibly leading to new devices based on spintronics. In addition, the members of the research group, which consists of high school students, undergraduate and graduate students, and postdoctoral associates will receive research training in the Science, Technology, Engineering and Mathematics (STEM) disciplines. Due to the demographics at The City College of New York (CCNY) of the City University of New York (CUNY), many female students and students from underrepresented ethnic groups will be trained in research. Multi-group meetings involving the chemistry and physics departments at CCNY will promote internal collaboration; a symposium for solid state chemistry in the New York City area will initiate communication and dissemination of results; and magnetic materials will be shared with other laboratories within the United States and around the world to pursue the understanding of the magnetic interactions. To further supplement the science and educational aspects, the local public will be introduced to crystal chemistry on open house days, science fairs and campus visitations by local high school groups.