RUI: Magnetic Studies of Thin Films of Graphite Encapsulated Nanocrystals

该项目是关于薄膜生长的CoPT、FePT和R2Fe17(R=稀土)纳米晶的磁性测量。这些薄膜被包裹在辉石涂层中，以防止它们被氧化和环境退化。石墨涂层还增加了相邻纳米晶之间的有效距离，导致粒子-粒子交换作用的减弱，这是目前正在开发的高密度磁记录介质薄膜的一个重要问题。CoPT和FePT的有序相表现出高的磁晶各向异性，这导致了对极小的铁磁纳米晶的磁矩的热激活转换产生了很强的能垒。R2Fe17结构中微量碳的存在增加了Fe-Fe交换作用。这导致了铁磁转变温度的提高，从而使这些材料在广泛的温度范围内用作磁体成为可能。这些材料是在西北大学(Vinayak P.Dravid教授和他的研究小组)制造的，而这项研究的目的是在本科生研究机构(圣何塞州立大学)使用磁测量、穆斯堡尔谱和磁力显微镜来表征它们的磁性。%这里提出的活动完全符合NSF-Rui计划加强SJSU研究基础设施的目标。与西北大学在合成和结构领域的互动是拟议研究的另一个特点，使上海州立大学能够研究先进材料。上海州立大学是一所少数民族和女性比例很高的多元化学校，其结果将对磁盘驱动器技术非常有用。*

The project is on the measurement of magnetic properties of nanocrystals of CoPt, FePt, and R2Fe17 (R=Rare earth) grown as films. The films are encapsulated in gaphite coatings to protect them from oxidation and environmental degradation. The graphite coating also increases the effective distance of neighboring nanocrystals, and causes the decrease of the particle-particle exchange interaction, which is an important issue in the ongoing development of films for high-density magnetic recording medium. The ordered phases of CoPt and FePt exhibit high magnetocrystalline anisotropy that results in a strong energy barrier against thermally activated switching of the magnetic moments for extremely small ferromagnetic nanocrystals. The presence of minute amount of carbon in R2Fe17 structure increases Fe-Fe exchange interaction. This causes the increase in the ferromagnetic transition temperature that makes the utilization of these materials as magnets over a wide range of temperature possible. The materials are fabricated at Northwestern University (Professor Vinayak P. Dravid and his research group) while this study is aimed at the characterization of their magnetic properties using magnetometry, Mossbauer spectroscopy and magnetic force microscopy at the undergraduate research institution (San Jose State).%%%The activities proposed here are fully compatible with the goals of NSF-RUI program in enhancing the research infrastructure of SJSU. Interaction with Northwestern University in areas of synthesis and structure is additional feature of the proposed research making the study of advanced materials possible at SJSU. SJSU is a diversified school with high percentage of minorities and women while the results will be very useful to disk drive technology.***