Structural phase transition and ferromagnetism in monodisperse 3 nm FePt particles

Authors

Chuan-bing Rong, University of Texas at Arlington
Narayan Poudyal, University of Texas at Arlington
Girija S. Chaubey, University of Texas at Arlington
Vikas Nandwana, University of Texas at Arlington
Ralph Skomski, University of Nebraska-LincolnFollow
Y. Q. Wu, Iowa State University
Matthew J. Kramer, Iowa State UniversityFollow
J. Ping Liu, University of Texas at ArlingtonFollow

Date of this Version

8-30-2007

Comments

Published by Am Inst of Physics. J. Appl. Phys. 102, 043913 2007. Copyright 2007. Permission to use. http://www.aip.org/.

Abstract

FePt nanoparticles with a size of 3 nm and thermally stable room-temperature ferromagnetism are investigated. The monodisperse nanoparticles were prepared by chemical synthesis and a salt-matrix annealing technique. Structural and magnetic characterizations confirmed the phase transition from the disordered face-centered cubic structure to the L1₀ structure with the chemical ordering parameter of 0.62±0.05. Analysis in blocking temperature and fitting of temperature dependence of switching field reveals that the transformed 3 nm nanoparticles have a magnetic anisotropy constant of (2.8±0.2) x 10⁶ J/m³, smaller than those for the bigger particles and the fully ordered L1₀ bulk phase.