Applications of Neutron Scattering Techniques to the Investigation of Prototypical Magnetic Systems

本项目将探索利用极化和非极化中子散射技术进行研究的三个一般途径。第一个涉及氧化物超导体中与铜和稀土矩相关的磁有序和自旋波动。第二部分涉及这些系统的超导方面，包括对这些“磁性超导体”材料中涡旋状态性质的研究，以及通过极化中子反射计测定超导体中的磁穿透深度。第三个项目涉及各向同性铁磁体的自旋动力学。极化束技术将用于分离材料的纵向和横向自旋动力学，例如因瓦尔合金，其中直接用中子观察到的磁激发谱与磁化的温度依赖性之间存在实质性差异。研究居里温度以下的纵向和横向波动谱，以及它们随外加场的变化规律。本项目将探索利用中子散射技术进行材料研究的三种一般途径。第一个涉及铜超导体的基本结构和磁性，努力建立这些新系统中超导状态的起源。第二个方面涉及材料特性的确定和理解，这些特性控制着对商业应用至关重要的超导参数，例如用于生产高临界电流材料的涡流钉钉。最后一个领域涉及软磁材料的基本和实用特性，软磁材料在变压器铁芯、磁屏蔽等方面具有商业应用。我们将特别强调因瓦尔类软磁体，因为它们在技术上很重要，因为它们的密度不随温度变化，而大多数金属在受热时会膨胀。

This project will explore three general avenuew of research using both polarized and unpolarized neutron scattering techniques. The first involves the magnetic ordering and spin fluctuations associated with copper and rare earth moments in the oxide superconductors. the second concerns the superconducting aspects of these systems, including the investigation of the nature of the vortex state in these 'magnetic-superconductor' materials, as well as the determination of the magnetic penetration depth in superconductors via polarized neutron reflectometry. The third project deals with the spin dynamics of isotropic ferromagnets. Polarized beam techniques will be used to separate the longitudinal and transverse spin dynamics of materials, such as Invar alloys where substantial discrepencies have been found between the magnetic excitation spectrum observed directly with neutrons and the temperature dependence of the magnetization. Investigation of the longitudinal and transverse fluctuation spectra just below the Curie temperature, and their behavior as a function of applied field will be undertaken. %%% This project will explore three general avenues of materials research using neutron scattering techniques. The first involves the fundamental structural and magnetic properties of the cuprate superconductors, in an effort to establish the origins of the superconducting state in these novel systems. The second aspect concerns the determination and understanding of the materials properties which control the superconducting parameters of central importance to commercial applications, such as vortex pinning to produce high critical current materials. The final area deals with the fundamental and practical properties of soft magnetic materials, which have commercial applications as transformer cores, magnetic shielding, etc. Particular emphasis will be placed on the Invar class of soft magnets, as these are of technical importance because their density does not change with temperature, in contrast to most metals which expand upon heating.