Ballistic magnetoresistance of electrodeposited nanocontacts in thin film and micrometer wire gaps

Abstract

In this paper, we review the recent advances and progress in ballistic magnetoresistance (BMR) in magnetic nanocontacts electrodeposited in thin films and micrometer gaps. We report the influence of magnetostriction in the measurements under different configurations and substrates, as well as the contribution of the magnetic material forming the contacts. To avoid the magnetostriction effect, we have fabricated magnetic nanocontacts in Cu wires and Cu films. Similar BMR results can be observed in these systems. Our results showthat the BMR effect should depend on the microproperties of the nanocontacts and should not be related with the macroproperties of the electrodes. The magnetostriction results, measured by an atomic force microscopy system with a built-in electromagnet, clearly show that there is no direct relationship between the displacement (caused by the magnetostriction effect) and the value of BMR. In fact, we present large magnetoresistance values for permalloy, coinciding with displacements in the latter’s structure less than 1 nm, which is the smallest clearly observable shift allowed by our atomic force microscope. Repetitions of hundreds of RðHÞ curves are presented for different materials with different coercive fields. The interpretation of the results is based on the formation of an interfacial transparent layer (non-stoichiometric oxide, sulfur, etc.) at the nanocontact where the theory can explain large magnetoresistance values.