Influence of the shape on exchange bias in core/shell nanoparticles

Abstract

Abstract We evaluate the influence of the shape on hysteretic properties in ferromagnetic/antiferromagnetic core/shell nanoparticles using Monte Carlo simulations. Exchange bias and coercive fields were estimated in nanoparticles with shapes ranging from octahedra to spheres to cubes. The net magnetic moment in the shell interface, produced by uncompensated spins responsible for the appearance of exchange bias, was found to vary significantly with the nanoparticle shape. Strong and intermediate exchange bias fields were found in octahedral and spherical nanoparticles, respectively, while a nearly zero exchange bias field was found in cubical nanoparticles. In general, decreasing exchange bias and increasing coercive fields were observed as the nanoparticle shape varied from nanoparticles with many to few uncompensated spins in the shell interface. A faster increase (decrease) of the exchange bias field (coercive field) as function of the magnitude of the interfacial exchange interaction was observed in nanoparticles with higher uncompensated interfaces. Furthermore, a predominance of shape effects over size effects on the hysteretic behavior of the nanoparticles was observed in the results.