Transport Studies of Novel Electronic and Magnetic Materials

w：\awards\awards96\*.doc 9801738 Zettl 本实验研究项目的重点是新型钙钛矿锰氧化物磁电阻（CMR）材料的电子输运性质。重点是通过输运和磁性测量研究其电子、热和磁性。大部分的研究将集中在使用高的压力，CMR效应是特别敏感的。 将采用聚四氟乙烯密封和金刚石砧座。 同位素 替代品还将 被 独立进行，并与压力研究一起进行。 这项研究的目的是澄清基本的相互作用，如极化子的形成和动力学，负责不寻常的 输运和磁输运行为 这些在科学上很有趣而且可能非常有用的材料。 使用相同实验方法的其他感兴趣的材料是钙钛矿超晶格和富勒烯聚合物。后一个系统显示出类似于CMR系统中所见的压力诱导绝缘体-金属转变，尽管潜在的物理学预计是不同的。这项研究计划是跨学科的性质，涉及 几 研究生，谁接受良好的培训，在工业，政府实验室或学术界的职业生涯做准备。 本实验基础研究项目主要研究一类氧化物材料的电阻对磁场的高灵敏度。这种效应被称为“巨磁阻”（CMR），在科学上是有趣的，在改进技术方面可能具有重要意义。 在这种情况下，材料的电阻通过施加的磁场而改变，并且在这些材料中通常非常小的这种效应是有用的。 磁阻传感器的一个优点是它比许多传统的磁拾取装置中的线圈更容易小型化、更简单、更便宜。 磁传感器在计算机硬盘驱动器、磁带记录器和其他电子应用中是众所周知的，但 实际上广泛应用于更简单的应用，如转速传感器（转速计）和许多其他应用。这项实验工作的重点是锰氧化物钙钛矿类CMR材料，并试图澄清效果的物理基础。 实验 关注电子、热 和 磁性能 研究 通过 运输工具 和 磁性测量 大部分的研究将集中在使用高的压力，CMR效应是特别敏感的。将采用聚四氟乙烯密封和金刚石砧座。 同位素取代也将独立进行， 结合压力研究。 其他材料 使用相同的实验方法感兴趣的是钙钛矿超晶格和富勒烯聚合物。后一个系统显示出类似于CMR系统中所见的压力诱导绝缘体-金属转变，尽管潜在的物理学预计是不同的。该研究计划是跨学科的，涉及几名研究生，他们接受了良好的培训，为工业，政府实验室或学术界的职业生涯做准备。 ***

w:\awards\awards96\*.doc 9801738 Zettl This experimental research project focuses on the electronic transport properties of novel collossal magnetoresistance (CMR) manganite perovskite materials. Emphasis is on the electronic, thermal and magnetic properties studied by means of transport annd magnetic measurements. Much of the study will focus on the use of high pressures to which the CMR effect is particularly sensitive. Both teflon-seal and diamond anvil cells will be employed. Isotopic substitution will also be performed, independently and in conjunction with the pressure studies. The aim of the research is to clarify the fundamental interactions, such as polaron formation and dynamics, responsible for the unusual transport and magnetotransport behaviors of these scientifically intriguing and potentially very useful materials. Other materials of interest using the same experimental methods are perovskite superlattices and fullerene polymers. The latter system displays a pressure-induced insulator-metal transition similar to that seen in CMR systems, although the underlying physics is expected to be different. This research program is interdisciplinary in nature and involves several graduate students, who receive excellent training in preparation for careers in industry, government laboratories or academia. %%% This experimental basic research project focuses on the high sensitivity of the electrical resistance of a class of oxide materials to a magnetic field. This effect, which has become known as "colossal magnetoresistance" (CMR) is scientifically interesting and potentially of importance in improved technology. In this situation, the electrical resistance of the material is changed by an applied magnetic field, and such effects, which are usually very small, in these materials are usefully large. An attra ction of a magnetoresistive sensor is that it is more easlily minaturized, simpler, and cheaper to produce, than, say, the coil of wire in many traditional magnetic pickup devices. Magnetic sensors are well known in computer hard drives, magnetic tape recorders and other electronic applications, but are actually widespread in simpler applications like rotation speed sensors (tachometers) and many others. This experimental work focuses on CMR materials in the manganite perovskite class, and seeks to clarify the physical basis for the effect. The experiments concern the electronic, thermal and magnetic properties studied by means of transport and magnetic measurements. Much of the study will focus on the use of high pressures to which the CMR effect is particularly sensitive. Both teflon-seal and diamond anvil cells will be employed. Isotopic substitution will also be performed, independently and in conjunction with the pressure studies. Other materials of interest using the same experimental methods are perovskite superlattices and fullerene polymers. The latter system displays a pressure-induced insulator-metal transition similar to that seen in CMR systems, although the underlying physics is expected to be different. This research program is interdisciplinary in nature and involves several graduate students, who receive excellent training in preparation for careers in industry, government laboratories or academia. ***