Quantum transport in oxidized Ni nanocontacts under mechanical strain

We report density functional theory based simulations of the final stages in the formation process of oxidized Ni nanocontacts along with their measurable conductance under mechanical strain. Not surprisingly, the presence of O atoms drastically changes the overall conductance as well as its spin polarization character. We have considered up to two O atoms in our simulations and found that their placement near the atomic constriction largely determines the conductance values. An overall picture emerges where the stability of the nanocontact improves with respect to that of pure Ni ones, supporting longer elongations as seen in the experiments. Also a remarkable effect takes place: the emergence of half metallicity (a fully spin polarized current), which seems to be a robust effect, but not necessarily translated into a very large magnetoresistance.