What is the Physical Explanation for the Very Large Ballistic Magnetoresitance Observed in Electrodeposited Nanocontacts?

TL;DR

This paper investigates the unusually large ballistic magnetoresistance in electrodeposited Ni-Ni nanocontacts, proposing a new explanation involving a thin dead magnetic layer that enhances electron spin polarization.

Contribution

It introduces a novel explanation for large magnetoresistance in nanocontacts, emphasizing the role of a thin dead magnetic layer formed during electrodeposition.

Findings

Large magnetoresistance values up to 3000% observed.

Proposed dead magnetic layer preserves spin and enhances polarization.

Scattering and quantized effects do not account for the observed values.

Abstract

Recent experiments in approximately 10nm size electrodeposited Ni-Ni nanocontacts have shown ballistic magnetoresitance values of 700% stable during a week (Garcia et al Appl. Phys. Lett. 79, 4550(2001) and very recently up to 3000% (Chopra and Hua, Phys. Rev. B 66,020403-1 (2002)). These values can provide very interesting magnetoelectronic devices integrated in the terabyte/square inch. Scattering in thin domain wall of the Ni-Ni nanocontacts, or quantized effects phenomena do not explain these values. An explanation is presented that requires the existence of a very thin, less than 1nm, dead magnetic layer grown during the electrodeposition process that is transparent to the electrons and has two roles: one, is to conserve spin in the electron conduction and the other, is to change and increase the polarization at Fermi level in the Ni.