Negative and Positive Magnetoresistance Manipulation in an Electrodeposited Nanometer Ni Contact

We show that, in a nanometric size stable electrodeposited Ni contact, it is possible to modify the magnetoresistance by applying current pulses and external magnetic fields whereby the same current path is used for detection and modification. We can pass from positive to negative magnetoresistance with values as large as $25\%$ at room temperature, all in the same contact. We propose that the effect may be due to switching and moving domain walls in the contact region under the combination of current effects and external fields.