Balistic magnetoresistance in nanocontacts electrochemically grown between macro- and microscopic ferromagnetic electrodes

Abstract

Our results prove the local origin of magnetoresistance in electrochemically deposited Ni nanocontacts. Experiments have been done using a complex setup for both in situ growth and ballistic magnetoresistance (BMR) measurements. Nanocontacts have been grown between two macroscopic Ni wires. In situ experiments with variation of the nanocontact diameter from 3 to 20 nm have been done using the same pair of wires. BMR values from 0.5% to 100% have been observed but no correlation of BMR value with the sample resistance, i.e., with the nanocontact cross section, has been found. These results show that the BMR in the nanometric size contact is determined by local geometrical and magnetic structures near the nanocontact rather than by the contact cross section itself. The hypothesis of existence of the intrinsic nonmagnetic dead layer in the ferromagnetic nanocontact is proposed to account for the BMR properties of the nanometric size contacts. Additionally, we report a BMR value of 200% in a Ni nanocontact (5 nm diameter) electrochemically grown between two nonmagnetic macroscopic gold wires. An external magnetic field has been used during the electrochemical deposition to fix the easy magnetic axis of the deposited Ni layer.