Search for point-contact giant magnetoresistance in Co/Cu multilayers

We report the first measurements of the point-contact magnetoresistance (MR) of magnetic multilayers. These measurements were intended to see if the additional local resistance associated with a small contact area between a sharpened tip and a magnetic multilayer shows a giant magnetoresistance (GMR) such as that seen in bulk multilayers. Point-contact measurements on two independent multilayers of Co/Cu revealed MRs dominated simply by that of the square resistance of the multilayer, with little or no contribution from the contact area itself. Further studies are still needed to determine if this result means that a small contact has little or no local GMR, or if the needle point-contact technique used destroyed the multilayer around the contact, thereby suppressing the GMR.