****NON-TECHNICAL ABSTRACT**** Nanoscale disorder is a common thread in very different classes of technologically important materials such as those used for permanent magnets and information storage. This collaborative project uses model rare-earth-alloy systems to understand the dependence of magnetic properties on nanometer-scale structural and chemical disorder. The model systems will be prepared by different fabrication methods and structurally characterized using x-ray diffraction, electron microscopy and synchrotron techniques. Atomic-level and macroscopic magnetic measurements will be correlated to specific types of disorder. These results will improve our understanding of the relationship between nanoscale disorder and magnetic properties in more complex materials, thus allowing us to develop improved materials for existing and future applications. This collaborative project involves researchers from the University of Nebraska at Lincoln and the University of Northern Iowa, the Advanced Photon Source at Argonne National Laboratory, and Los Alamos National Laboratory. The project provides postdoctoral fellows, graduate students and undergraduate students with interdisciplinary training (including the use of facilities at national laboratories) in an area of critical national need. Workshops and summer activities with Upward Bound math & science students, middle and high school teachers, and high-school students will help educate the future workforce about the importance of nanoscale materials.
Nanoscale inhomogeneity underlies many of the fundamental properties of systems such as colossal magnetoresistance (CMR) materials and high-Tc superconductors. This collaborative project uses nanostructured rare-earth (RE) systems to investigate the relationship between magnetic properties and atomic-level disorder. In particular, disordered RE Laves-phase materials will be prepared by mechanical milling, inert-gas condensation, and melt spinning. RE Laves-phase materials have magnetic characteristics similar to CMR and high-Tc materials, but are structurally simpler. Disorder (coordination number, mean interatomic distances, and variations in the interatomic distances), will be determined by x-ray diffraction and X-Ray Absorption Fine-Structure Spectroscopy (XAFS). Atomic-level and macroscopic magnetic measurements, including magnetic XAFS, XMCD, and ac and dc magnetization, will be correlated to specific types of disorder. Understanding how extrinsic properties such as coercivity depend on disorder will improve materials such as those used for permanent magnets and information storage. Sample fabrication, DC magnetic measurements, and structural characterization will be done at the University of Nebraska-Lincoln, while the University of Northern Iowa will be responsible for ac susceptibility measurements and analysis. The broader impacts of this award include interdisciplinary research training for postdocs, graduate students and undergraduates. Middle and high school teachers and high-school students will be impacted through workshops and summer programs that illustrate the role materials play in society.
