Exotic chemical arrangements and magnetic moment evolution of Ni x Pt 1 - x ( 0 ≤ x ≤ 1 ) nanoparticles

Highlights: • A deep understanding on the magnetic nanoalloys is crucial for designing functional nanoparticles. • Chemical ordering pattern and the magnetic properties of NiPt nanoparticles investigated using theoretical means. • A sharp phase transition from non-magnetic to ferromagnetic behavior found for an intermediate composition. We present a systematic study on the chemical ordering pattern and the magnetic properties of ${\text{Ni}}_x{\text{Pt}}_{1-x}$ ($0⩽x\le 1$) nanoparticles having a size of 1.5 nm by means of an approach which combines basin hopping structure sampling technique and spin-polarized density functional theory. We found exotic chemical ordering patterns for different Ni/Pt ratios. In addition, we observed a sharp phase transition from non-magnetic to ferromagnetic behaviour around x = 67%. We show that this is a direct consequence of a unique atomic arrangement on the surface in which Ni atoms club together causing the strong Ni-Ni magnetic interaction. The observed magnetic properties are correlated to the electronic density of states.