RUI: Magnetic Studies of Thin Films of Graphite Encapsulated Nanocrystals

San Jose State University Foundation, San Jose CA

Investigators

Abstract

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. ***