Theoretical study of the magnetic moments and anisotropy energy of CoRh nanoparticles

The role of size, structure and chemical order on the magnetic moments and magnetic anisotropy energy (MAE) of CoRh nanoparticles are studied in the framework of a self-consistent real-space tight-binding method. Our results show that a Rh core in a geometry having a large surface/volume ratio and with Co–Rh mixing at the interface is the most likely chemical arrangement. A local analysis reveals that the orbital and spin moments at the Co–Rh interface are largely responsible for the increase of the magnetic moments and magnetic anisotropy. Moreover, the local moments induced at the Rh atoms, which amount to about 20% of the moment per Co atom [ μ Rh = (0.2–0.3) μ B ] and the orbital moments of Co atoms play a crucial role on the interpretation of experiment. The results are discussed in the context of the interplay between chemical order and magnetic properties.