Formation and strain distribution of Ni/NiO core/shell magnetic nanoparticles fabricated by pulsed laser deposition

Nucleation and growth lead to substantial strain in nanoparticles embedded in a host matrix.The distribution of strain field plays an important role in the physical properties of nanoparticles.Magnetic Ni/NiO core/shell nanoparticles embedded in the amorphous Al2O3 matrix were fabricated by pulsed laser deposition.The results from a high-resolution transmission electron microscope also revealed that the core/shell nanoparticles consist of a single crystal Ni core with a faced-centered cubic structure(Space Group FM-3M) and polycrystalline NiO shell with a trigonal/rhombohedral structure(Space Group R-3mH).The growth strain of Ni/NiO core/shell nanoparticles embedded in the Al2O3 matrix was investigated.Finite element calculations clearly indicate that the NiO shell incurs large compressive strain.The compressive strain existing at the NiO shell area ena-bles the shell material at the interface to adapt to the lattice parameters of Ni core.This process results in a relatively good crystallinity near the interface,which may be associated with the higher exchange coupling between the ferromagnetic Ni core and antiferromagnetic NiO shell.