Self-assembled FePt nanocrystals with large coercivity: reduction of the fcc-to-L1(0) ordering temperature.
Herein we report the synthesis and properties of Fe(55)Pt(45) nanoparticles, both monodisperse and self-assembled into hexagonal close-packed and cubic arrays of 4.0 +/- 0.2 nm size in an L1(0) structure, obtained by a modified polyol process. The new synthetic route improved the control over the particle composition, thereby reducing the temperature required to convert from face-centered cubic (fcc) to face-centered tetragonal (fct) phase by some 30-50 degrees C without additives. Annealing at 550 degrees C for 30 min converts the self-assembled nanoparticles into ferromagnetic nanocrystals with large coercivity, H(C) = 11.1 kOe. Reducing the fcc-to-fct (L1(0)) ordering temperature avoided particle coalescence and decreased the loss in particle positional order without compromising the magnetic properties, as is generally observed when additives are used.
Varanda
Laudemir Carlos
LC
Laboratory of Magnetic Materials and Colloids, Department of Physical Chemistry, Institute of Chemistry, Universidade Estadual Paulista (UNESP), P.O. Box 355, 14801-970 Araraquara, São Paulo, Brazil.
Jafelicci
Miguel
M