Acquisition of a Vibrating Sample Magnetometer for the Characterization of Nanocomposite Magnetic Materials

该振动样品磁强计将用于富金属粒状铁磁固体的磁性研究。这些是纳米复合材料，其中存在一个含有不混溶的非磁性相（例如al2o3）的连续粉状基体。使用渗透理论的语言，它们可以被描述为高于临界浓度，具有渗透磁相。近年来，颗粒金属的研究兴起，但由于缺乏巨磁阻效应，富金属材料在很大程度上被忽视了。虽然在研究过程中很自然，但这种状况不应该持续下去；富金属系统在应用科学和基础科学方面都提供了一些有前途的研究途径。与渗透过渡下的颗粒金属相比，这些材料更容易研究，技术上也更有前景。这主要有两个原因：评估粒度分布的影响没有困难，净磁化强度要大得多，Tc可能远高于室温。本提案将详细介绍对这些材料的两项研究。第一个研究的是无序系统中磁性的基本性质，而第二个研究的是一个可能的应用。项目分别为：研究非磁性杂质减少磁相关长度时的磁相变；评价含非磁性杂质的硬磁合金的潜在磁记录特性。该振动样品磁强计将用于富金属粒状铁磁固体的磁性研究。这些是纳米复合材料，其中存在一个含有不混溶的非磁性相（例如al2o3）的连续粉状基体。使用渗透理论的语言，它们可以被描述为高于临界浓度，具有渗透磁相。近年来，颗粒金属的研究兴起，但由于缺乏巨磁阻效应，富金属材料在很大程度上被忽视了。虽然在研究过程中很自然，但这种状况不应该持续下去；富金属系统在应用科学和基础科学方面都提供了一些有前途的研究途径。与渗透过渡下的颗粒金属相比，这些材料更容易研究，技术上也更有前景。这主要有两个原因：评估粒度分布的影响没有困难，净磁化强度要大得多，Tc可能远高于室温。本提案将详细介绍对这些材料的两项研究。第一个研究的是无序系统中磁性的基本性质，而第二个研究的是一个可能的应用。项目分别为：研究非磁性杂质减少磁相关长度时的磁相变；评价含非磁性杂质的硬磁合金的潜在磁记录特性。＊＊＊

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. ***