Magnetization reversal process in FePt L10 nanoparticles

We have studied the magnetization reversals of FePt L10 particles. Lithographically fabricated single FePt particles and well isolated epitaxial FePt L10 nanoparticles have been investigated for a wide range of particle diameters D. Careful analyses of the experiments have revealed that for particles larger than 20 nm the magnetization reversal behaviors are governed by either nucleation or expansion of a reversed domain depending on the temperature, and the coherent rotation mode becomes dominant for D < 20 nm.