Is magnetoresistance in excess of 1,000 % possible in Ni point contacts?

Electronic transport in nickel magnetic point contacts is investigated with a combination of density functional theory and the non-equilibrium Green functions method. In particular we address the possibility of huge ballistic magnetoresistance in impurity-free point contacts and the effects of oxygen impurities. On-site corrections over the local spin density approximation (LSDA) for the exchange and correlation potential, namely the LDA+U method, are applied in order to account for low-coordination and strong correlations. We show that impurity-free point contacts present magnetoresistance never in excess of 50%. This value can raise up to about 450 % in the case of oxygen contamination. These results suggest that magnetoresistance in excess of 1,000 % can not have solely electronic origin.