Anisotropy magnetoresistance of quantum ballistic nickel nanocontacts

Magnetoresistance properties of Ni nanocontacts in the ballistic quantum regime are investigated in situ for several orientations between applied magnetic field and current direction. The symmetry properties of the magnetoresistance curves are similar to anisotropy magnetoresistance effects, even if the shape of the contact is modified. A change of conductance under magnetic field has a magnitude between 0.2e2/h and e2/h, varying little with the absolute conductance values ranging between e2/h and 100e2/h. We discuss possible mechanical artifacts to our magnetoresistance curves, showing that the shear of the substrate might contribute to conductance changes. However, replacing the metal used as substrate does not modify our observations.