COLL 282 |
| Xiangcheng Sun1, Zhiyong Jia2, David E. NIkles1, and J. W. Harrell3. (1) Center for Materials for Information Technology, The University of Alabama, Box 870209, Tuscaloosa, AL 35487, (2) MINT center, The University of Alabama, P.O. Box 870209, Tuscaloosa, AL 35487, (3) Department of Physics and Center for Materials for Information Technology, The University of Alabama, Box 870209, Tuscaloosa, AL 35487-0209 |
| Magnetic CoPt particles, average particle size of 8nm, were synthesized by superhydride reduction of CoCl2 (anhydrous) and Pt(acac)2 at high temperature in the presence of oleic acid and oleyl amine. The initial molar ratio of the Co and Pt was retained in the CoPt nanoparticles, allowing the particle composition to be tuned. The particles could be dispersed in hydrocarbon solvents, and self-assembled into particles arrays films that could be prepared in a manner similar to that widely reported for FePt nanoparticles. As prepared the particles showed disordered face-centered cubic (fcc) lattice and were superparamagnetic. Upon heat treatment at temperatures above 600oC, the particles transformed to the L10 phase, as indicated by the appearance of the superlattice peaks in the x-ray diffraction. The coercivity of the annealed magnetic particles arrays increased with increasing heat treatment temperatures and times. The temperature dependence of the coercivity was measured from 10 K to 300 K and analyzed using a Sharrock type formula. After annealing at 650oC, the anisotropy of the nanoparticles was K≈1.7 x 107 erg/cc and the room temperature thermal stability factor was KV/kBT=163, which corresponds to a magnetic switching diameter of 9.4 nm. |
|
Nanoscience and Nanotechnology
6:00 PM-8:00 PM, Monday, March 29, 2004 Disneyland -- North Exhibit Hall, Poster
Division of Colloid and Surface Chemistry |