Direct synthesis and easy axis alignment of L 1 0 - Fe Pt nanoparticles

• Published in: Journal of applied physics 2005-05, Vol.97 (10), p.10J318-10J318-3
• Main Authors: Kang, Shishou, Jia, Zhiyong, Shi, Shifan, Nikles, David E., Harrell, J. W.
• Format: Article
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1855203

Partially ordered Fe 53 Pt 47 nanoparticles with size around 8 nm were prepared by the simultaneous decomposition of iron pentacarbonyl and platinum acetylacetonate. The high boiling point chemical, hexadecylamine, was used as a solvent, and 1-adamantanecarboxylic acid was used as a stabilizer. The reflux temperature of the solution could exceed 360 ° C , where disordered FePt particles could be partially transformed into the ordered L 1 0 phase. A nonmagnetic mechanical stirrer was used in order to avoid agglomeration of the fct-FePt particles during synthesis. The particles were dispersed in toluene and films of the particles were cast onto silicon wafers from the solution. X-ray diffraction patterns of as-made samples showed weak superlattice peaks, indicating partial chemical ordering of the Fe 53 Pt 47 particles. The room-temperature hysteresis loop of the as-made sample reveals a small coercivity ( ∼ 600 Oe ) because of thermal fluctuations; however, the loop is wide open and hard to saturate. The remanence coercivity from the dcd curve is about 2.5 kOe , which is four times larger than the hysteresis coercivity. The large remanent to hysteresis coercivity ratio and the shapes of the hysteresis loop and dcd curve suggest a broad distribution of anisotropies in the partially ordered particles. By coating the ordered nanoparticles with a polymer binder, the easy axis of the particles could be aligned under an external field.