9704110 Gavrin This vibrating sample magnetometer will be used to perform research on the magnetic properties of metal-rich granular ferromagnetic solids. These are nanocomposite materials in which there exists a continuous meal matrix with inclusions of an immiscible nonmagnetic phase (e.g., Al2 O3). Using the language of percolation theory, they may be described as well above the critical concentration, with a percolating magnetic phase. While recent years have seen an upsurge in granular metals research, metal-rich materials have been largely ignored due to the absence of the giant magnetoresistance effect. Although natural in the course of research, this state of affairs should not persist; metal rich systems offer several promising avenues of research, both in applied and fundamental science. Compared with granular metals below the percolation transition, these materials are both easier to study and more technologically promising. There are two principle reasons for this: There is no difficulty evaluating the effects of a particle size distribution, and The net magnetization is much greater, and Tc may be well above room temperature. This proposal will detail two studies of these materials. The first deals with the fundamental nature of magnetism in disordered systems, while the second addresses a possible application. Respectively the projects are: A study of the magnetic phase transition as the nonmagnetic impurities reduce the magnetic correlation length, and An evaluation of potential magnetic recording characteristics of hard magnetic alloys with nonmagnetic impurities. %%% This vibrating sample magnetometer will be used to perform research on the magnetic properties of metal-rich granular ferromagnetic solids. These are nanocomposite materials in which there exists a continuous meal matrix with inclusions of an immiscible nonmagnetic phase (e.g., Al2 O3). Using the language of percolation theory, they may be described as well above t he critical concentration, with a percolating magnetic phase. While recent years have seen an upsurge in granular metals research, metal-rich materials have been largely ignored due to the absence of the giant magnetoresistance effect. Although natural in the course of research, this state of affairs should not persist; metal rich systems offer several promising avenues of research, both in applied and fundamental science. Compared with granular metals below the percolation transition, these materials are both easier to study and more technologically promising. There are two principle reasons for this: There is no difficulty evaluating the effects of a particle size distribution, and The net magnetization is much greater, and Tc may be well above room temperature. This proposal will detail two studies of these materials. The first deals with the fundamental nature of magnetism in disordered systems, while the second addresses a possible application. Respectively the projects are: A study of the magnetic phase transition as the nonmagnetic impurities reduce the magnetic correlation length, and An evaluation of potential magnetic recording characteristics of hard magnetic alloys with nonmagnetic impurities. ***
