Eur. Phys. J. B 60, 187-192 (2007)
https://doi.org/10.1140/epjb/e2007-00335-8

Mean-free path effects in magnetoresistance of ferromagnetic nanocontacts

¹ Kazan State University, Kremlevskaya str. 18, Kazan, 420008, Russian Federation
² CRIST, University of Plymouth, Plymouth, Devon, PL4 8AA, UK

Corresponding author: ^a Raphael.Deminov@ksu.ru

Received: 11 May 2007
Revised: 3 October 2007
Published online: 8 December 2007

Abstract

We investigated the mean-free path effects on the magnetoresistance of ferromagnetic nanocontacts. For most combinations of parameters the magnetoresistance monotonously decreases with increasing the contact cross-section. However, for a certain choice of parameters the calculations show non-monotonous behavior of the magnetoresistance in the region in which the diameter of the contact becomes comparable with the mean-free path of electrons. We attribute this effect to different conduction regimes in the vicinity of the nanocontact: ballistic for electrons of one spin projection, and simultaneously diffusive for the other. Furthermore, at certain combinations of spin asymmetries of the bulk mean-free paths in a heterocontact, the magnetoresistance can be almost constant, or may even grow as the contact diameter increases. Thus, our calculations suggest a way to search for combinations of material parameters, for which high magnetoresistances can be achieved not only at the nanometric size of the contact, but also at much larger cross-sections of nanocontacts which can be easier for fabriaction with current technologies. The trial calculations of the magnetoresistance with material parameters close to those for the Mumetal-Ni heterocontacts agree satisfactorily with the available experimental data.