Local magnetoresistance of nanoconstrictions

In this paper, we investigate the local magnetoresistance of nanoconstrictions fabricated on thin magnetic films by e-beam lithography. The magnetoresistance is measured using electrostatic force microscopy (EFM) with tens of nanometer spatial resolution. We found a large positive MR within hundreds of nanometers around the constriction, if we go away from the constriction about 2 μm, a negative MR appears on both sides of the constriction. Therefore, by ordinary MR measurements through electric pads separated several or tens of micrometers it is almost impossible to detect the MR of a constriction because the addition of these two kinds of MR cancelled the contribution from the constriction.