Surface and interface effects in magnetic core–shell nanoparticles

Using computational modeling, we describe and explain the effects resulting from surfaces and interfaces in core–shell nanoparticles. We outline the basis of the atomistic spin model, which is used to simulate the equilibrium and dynamic magnetic properties of magnetic nanoparticles. The physical origin of magnetic surface anisotropy is described, along with its effect on the magnetic spin configuration and energy landscape. Importantly, it is shown that a cubic anisotropic surface can be induced, which leads to a complex energy landscape with a non-trivial size dependence. Additional microstructural effects in realistic nanoparticle microstructures are investigated, and fundamental magnetic properties can be significantly altered as a result. Finally, an important effect known as exchange bias is also described. Exchange bias causes an enhancement of the thermal stability of magnetic nanoparticles, but due to its atomic origin, it also leads to complicated physical behavior.