Search for magnetoresistance in excess of 1000% in Ni point contacts: Density functional calculations

Electronic transport in nickel magnetic point contacts is investigated with a combination of density functional theory and the nonequilibrium Green's function method in the linear response limit. 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 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 1000% cannot have solely electronic origin.