JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, vol.351, pp.47-51, 2014 (SCI-Expanded)
Magnetic properties of spherical, cubic, star and rod shaped FePt nanostructures have been investigated. Field dependence of magnetization measurements showed that approach to saturation magnetization behavior of the samples is shape dependent. When compared to spherical nanoparticles, eightfold magnetic field has to be applied to saturate nanorods. The effective magnetic anisotropies were determined by using temperature dependence of magnetization experiments and Stoner-Wohlfarth theory. The key result of the work is that engineering on the shape of the nanostructures leads to significant increase of their effective magnetic anisotropy. Cubic nanoparticles were found to have the lowest and nanorods the highest effective magnetic anisotropy constant of 1.3 x 10(5) Jm(-3) and 2.7 x 10(5) Jm(-3), respectively. The physical origin of this difference was ascribed to the high shape anisotropy of the rod shaped nanostructures combined with the low magnetocrysralline anisotropy of fcc FePt. By evaluating rod-shaped nanocrystals as prolate spheroids, their shape anisotropy was calculated as 1.0 x 10(5) Jm(-3), which is in very good agreement with the experimental result. (C) 2013 Elsevier B.V. All rights reserved.