From ballistic to non-ballistic magnetoresistance in nanocontacts: theory and experiments

This paper reports on a large set of experiments using different materials and samples to explore the ballistic and non-ballistic magnetoresistence in magnetic nanocontacts. Ballistic contacts are obtained with 3-d magnetic c rystalline metals and non-ballistic by using permalloy, amorphous metal, ce ramic perovskites and Heusler alloys that have large resistivity values. Tt is shown that while the ballistic nanocontacts can present 200% magnetores istance. the non-ballistic exhibit a non-noticeable value(< 2%) at room tem perature. Two criteria are given according to theory and in good agreement with experiments to obtain large magnetoresistance values. (C) 2001 Elsevie r Science B.V. All rights reserved.