Synthesis, Structure and Properties of Magnetic Nanocrystalsand Nanocrystalline Arrays

9803700麦克亨利，这项研究通过合成和表征磁性纳米晶体的独特性质来探索。它延续了先前关于改变合金化学、纳米晶体形态和界面结构以影响磁性纳米晶和纳米晶阵列中的磁各向异性的研究工作。纳米晶和纳米晶阵列中的磁各向异性取决于磁晶各向异性、形状各向异性、界面各向异性和/或由磁弹性耦合提供的各向异性。这些问题在(1)碳包覆纳米颗粒；(2)碳化物纳米棒填充的碳纳米管；以及(3)具有铁磁性或亚铁磁性物种的介孔硅酸盐中渗透、周期性排列的孔中得到解决。等离子体合成产生的纳米颗粒通常是球形的，并且不会因为形状各向异性而受益，因为它是磁化强度热激活转换的障碍。这项研究详细考察了形状各向异性在新型纳米颗粒和纳米颗粒阵列中的影响，在这些纳米颗粒和纳米颗粒阵列中，磁性颗粒的大长宽比可以被用来利用形状各向异性。通过比较具有碳涂层和氧化物涂层的纳米颗粒的磁性，解决了界面各向异性的问题。这项研究旨在了解纳米颗粒中的磁反转机制，以确定各种磁性应用的基本限制。纳米团簇表现出与块状晶体固体不同的性质。纳米晶形式的例子包括巴克球和巴克管，碳包覆纳米粒子和纳米棒，以及其他自组装结构。了解这些材料的性质有助于开发具有大量应用的新型材料。***

9803700 McHenry This research explores through synthesis and characterization the unique properties of magnetic nanocrystals. It continues a previous effort on varying alloy chemistry, nanocrystal morphology, and interfacial structure to influence the magnetic anisotropy in magnetic nanocrystals and nanocrystalline arrays. Magnetic anisotropy in nanocrystals and nanocrystalline arrays depends on magnetic crystalline anisotropy, shape anisotropy, interfacial anisotropy, and/or the anisotropy provided by magnetoelastic coupling. These issues are addressed in (1) C-coated nanoparticles; (2) filled C- nanotubes with carbide nanorods; and (3) infiltrated, periodically arranged pores in mesoporous silicates with ferromagnetic or ferrimagnetic species. Nanoparticles produced by plasma synthesis are usually spherical and do not benefit from shape anisotropy as a barrier to the thermally activated switching of the magnetization. The research examines the effects of shape anisotropy in detail in novel nanoparticles and nanoparticle arrays in which large aspect ratios in the magnetic particles can be used to exploit shape anisotropy. Issues of interfacial anisotropy are addressed by comparing the magnetic properties of nanoparticles having carbon and oxide coatings. %%% This research is aimed at understanding the magnetic reversal mechanisms in nanoparticles in order to determine fundamental limitations for a variety of magnetic applications. Nanosized clusters have demonstrated properties that differ from those of bulk crystalline solids. Examples of nanocrystalline forms include Buckyballs and Buckytubes, C-coated nanoparticles and nanorods, and other self-assembled structures. Understanding properties of these materials enables the development of novel materials with a host of applications. ***