Conductance of Ni Nanocontacts

 

K. Solanki, R. F. Sabiryanov ¹, E. Y. Tsymbal, and S. S. Jaswal

¹ Department of Physics, University of Nebraska, Omaha, Nebraska

 

The influence of the atomic and magnetic structure on spin-dependent conductance and magnetoresistance of  magnetic ballistic point contacts is studied within first-principles electronic band structure methods. Funded by ONR, NSF, and NRI.

High values of magnetoresistance (MR) observed in mechanically-formed and electrodeposited ferromagnetic nanoconstrictions at room temperature have aroused considerable interest. In order to understand the underlying physical mechanisms which are responsible for the MR in these systems, we have performed first-principles calculations of the electronic and transport properties of atomic-size Ni contacts.

We model a Ni contact by two fcc slabs connected through a narrow constriction as shown in the figure below. The calculations are performed for two geometries: the ideal, unrelaxed fcc structure and the relaxed structure. Structural relaxation is performed using Vienna Ab-Initio Simulation Package (VASP). The spin-polarized electronic structure is calculated self-consistently using a tight-binding linear muffin-tin orbital method (TB-LMTO) within the real-space recursion technique. The conductance is obtained using Landauer-Büttiker approach. 

We find that the structural relaxation produces a 30% contraction of the interlayer spacing in the nanoconstriction region, resulting in significant changes of the electronic and magnetic structure. This leads to a considerable reduction of the overall conductance through the nanocontact. The total conductance at the Fermi energy is higher by a factor of 5 for the unrelaxed structure than for the relaxed structure. Thus, variation of the interatomic distance at the nanocontact (for example due to magnetostriction) can have strong effects on the conductance.

Spin-resolved conductance as a function of energy for relaxed and unrelaxed atomicstructure of the Ni nanocontact.

 

Paper:

A. K. Solanki, R. F. Sabiryanov, E. Y. Tsymbal and S. S. Jaswal, "Conductance of Ni Nanocontacts within First-Principle Approach" , J. Magn. Magn. Mater. 272–276, 1730–1731 (2004).

 

 

 

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