Magnetoresistance through a single nickel atom

The magnetoresistance (MR) of a nickel atomic contact has been measured using the break junction technique. When the contact is only between two atoms, the change of resistance with applied field reaches 40%. It is composed of a continuous bell-shaped curve on which discrete jumps are superimposed. The MR changes sign when the applied field is rotated, which we explain by a spin-orbit coupling change of orbital overlap between the Ni atoms forming the junction. Reproducible jumps in the MR curve are attributed to a field induced change of spin configuration within the few atoms composing the contact.