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

9704110 Gavrin这款振动样品磁强计将用于研究富金属颗粒状铁磁固体的磁性。这些是纳米复合材料，其中存在一个连续的颗粒基质，其中含有不相容的非磁性相(例如，Al_2O_3)的夹杂物。使用渗流理论的语言，它们可以描述为远远高于临界浓度，具有渗流磁相。近年来，颗粒金属的研究掀起了热潮，但由于没有巨磁电阻效应，富金属材料在很大程度上被忽视了。尽管在研究过程中很自然，但这种情况不应该持续下去；富含金属的系统提供了几个有希望的研究途径，无论是在应用科学还是基础科学方面。与渗流转变以下的颗粒金属相比，这些材料更容易研究，在技术上也更有前途。这主要有两个原因：评估颗粒大小分布的影响并不困难，净磁化强度要大得多，T_c可能远高于室温。这项提案将详细说明对这些材料的两项研究。第一个研究无序系统中磁性的基本性质，而第二个研究一个可能的应用。这两个项目分别是：研究非磁性杂质减小磁关联长度时的磁性相变，以及评价含有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研究富金属颗粒状铁磁固体的磁性。这些是纳米复合材料，其中存在一个连续的颗粒基质，其中含有不相容的非磁性相(例如，Al_2O_3)的夹杂物。用渗流理论的语言，它们可以被描述为远远高于临界浓度，具有渗流磁相。近年来，颗粒金属的研究掀起了热潮，但由于没有巨磁电阻效应，富金属材料在很大程度上被忽视了。尽管在研究过程中很自然，但这种情况不应该持续下去；富含金属的系统提供了几个有希望的研究途径，无论是在应用科学还是基础科学方面。与渗流转变以下的颗粒金属相比，这些材料更容易研究，在技术上也更有前途。这主要有两个原因：评估颗粒大小分布的影响并不困难，净磁化强度要大得多，T_c可能远高于室温。这项提案将详细说明对这些材料的两项研究。第一个研究无序系统中磁性的基本性质，而第二个研究一个可能的应用。这两个项目分别是：研究非磁性杂质减小磁关联长度时的磁性相变，以及评价含有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. ***