Mesoscale simulations of atomic ordering in nano-layered FePt

The present paper deals with structural transformations in nano-layered FePt considered as a material for ultra-high density magnetic storage media. Within these studies the Mesoscale Monte Carlo model has been constructed in order to investigate kinetics of antiphase interfaces motion. The motion of the interfaces is realized by local FePt domains reorientation due to energy minimalization. The data of energy barriers for all the transformation types were taken from previously performed atomistic simulations. The results show that the thin layer of energetically preferred domains forms at the free surface. The thickness of such a layer is controlled by temperature. The results obtained here present also kinetics of FePt domains growth at free surface. It can be observed that the growth of the domains is driven by the curvature of interfaces related to domains size

Saddle-point energies and Monte Carlo simulation of the long-range order relaxation in CoPt

We present atomic-scale computer simulations in equiatomic L1 0-CoPt where Molecular Dynamics and Monte Carlo techniques have both been applied to study the vacancy-atom exchange and kinetics relaxation. The atomic potential is determined using a Tight-Binding formalism within the Second-Moment Approximation. It is used to evaluate the different saddle-point energies involved in a vacancy-atom exchange between nearest-neighbour sites. The potential and the saddle-point energies have been used to simulate the relaxation of the long-range order in CoPt using a Monte Carlo technique. A vacancy migration energy of 0.73±0.15 eV and an order-disorder transition temperature of 935 K have been found. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005