The goals of this CAREER proposal are 1) to fabricate cluster-assembled magnetic materials using a novel evaporation-condensation-compaction deposition technique; 2) to correlate magnetic and magnetotransport properties to sample structure to understand the role of disorder in magnetism; and 3) to investigate the potential for applications ranging from permanent magnets to sensors. A gas-entrained evaporation-condensation technique is used to form clusters with diameters from 5 - 50 nm. The clusters are compacted under high pressure to form a nano-grained bulk material. Extensive structural characterization is performed, including x-ray diffraction, electron microscopy, neutron scattering and EXAFS. The resulting nanostructures have two components: crystalline grains, and the atoms between the grains, which are collectively called the interphase. The interphase is a large fraction of the sample when the grain size is small - up to 50% for 5-nm grains - and can be a significant factor in determining overall sample magnetic properties. A range of static and dynamic magnetic and magnetotransport measurements will determine the intrinsic properties of the grains and the interphase, and how the two components interact. Ordering on multiple length scales is investigated using scaling to elucidate the similarities and differences between these systems and other random magnetic systems such as spin glasses, random anisotropy magnets and amorphous ferromagnets. The two-part education plan addresses some of the factors that cause students to choose not to pursue science as a profession. Two one-credit courses will be developed to prepare students for undergraduate research and develop the skills necessary to communicate with scientists and non-scientists. The second part of the education project involves the UNL Society of Physics Students in outreach to a low-income elementary school in Lincoln. %%% This project addresses several fundamental issues in cluster-assembled magnetic nanostructures: 1) fabrication of these magnetic materials using an evaporation-condensation-compaction technique; 2) correlation of their magnetic and magnetotransport properties to sample structure to explain the role of disorder in magnetism; and 3) investigation of their potential applications ranging from permanent magnets to magnetic sensors. A novel deposition technique is used to form clusters with diameters from 5 - 50 nm. The clusters are compacted under high pressure to form a nano-grained bulk material. Using clusters as "building blocks" offers great versatility in tailoring magnetic nanostructures to have specific characteristics. A unique feature of these materials is that samples with very small grains display magnetic properties impossible to achieve with traditional bulk materials. This project will determine the mechanisms responsible for these extraordinary properties. The two-part education plan addresses some of the factors that cause students to choose not to pursue science as a profession. Two one-credit courses will be developed to prepare students for undergraduate research and develop the skills necessary to communicate with scientists and non-scientists. The second part of the education project involves the UNL Society of Physics Students in outreach to a low-income elementary school in Lincoln. ***
