RESUMO
Magnetic properties of ferromagnetic nanostructures were studied by atomistic simulations following Monte Carlo and Landau-Lifshitz-Gilbert approaches. First, we investigated the influence of particle size and shape on the temperature dependence of magnetization for single cobalt and gadolinium nanoparticles and also in bi-magnetic Co@Gd core-shell nanoparticles with different sizes. The Landau-Lifshitz-Gilbert approach was subsequently applied for inspecting the magnetic hysteresis behavior of 2 and 4 nm Co@Gd core-shell nanoparticles with negative, positive, and zero values of interfacial magnetic exchange. We were able to demonstrate the influence of finite-size effect on the dependence of the Curie temperature of Co and Gd nanoparticles. In the Co@Gd core-shell framework, it was possible to handle the critical temperature of the hybrid system by adjusting the Co core size. In addition, we found an improvement in the coercive field values for a negative interfacial exchange energy and for a different core size, suggesting an exchange spring behavior, while positive and zero values of interfacial exchange constant showed no strong influence on the hysteresis behavior.
RESUMO
Structural, mechanical, elastic, and dielectric properties of the AMgF3 (A = K, Rb, and Cs) compounds were investigated using classical atomistic simulation. A new set of interatomic potentials was developed for these compounds. Lattice parameters and interatomic distances have shown to accurately reproduce all structures, with very close agreement to the experimental data. In all cases, the relative error is below 0.5%. Effect of hydrostatic pressure in the structural, mechanical, elastic, and dielectric properties of these materials were studied from 0 up to 50 GPa. Compounds behavior and stability under pressure were analyzed. KMgF3 and RbMgF3 changed from brittle to ductile at approximately 2 GPa. These calculations play an important role in understanding the properties of the AMgF3 (A = K, Rb, and Cs) compounds under pressure, and open up a new opportunity to study defects in this class of materials. © 2019 Wiley Periodicals, Inc.