Diplomarbeit
Theorie des Transports durch magnetische Nanokontakte
Ab initio calculations of the electronic structure and transport properties of magnetic nanocontacts consisting of cobalt (Co) and nickel (Ni) are presented.
The electronic structure of the nanocontacts was calculated self-consistently in the framework of the density functional theory by using the Korringa-Kohn-Rostoker multiple scattering Greens function method. The transport properties in the linear response regime were described by means of the Landauer approach in the formulation of Baranger and Stone.
At first conductance values of linear Co wires bridging two semi-infinite Co electrodes (leads) were calculated with respect to the number of atoms in the chain and the relative magnetization orientation of the electrodes. The ballistic magnetoresistance ratio (BMR) defined as the conductance change caused by the magnetization reorientation was also investigated. The obtained conductance values and the BMR are in agreement with experimental results.
In the second part different geometries of Ni nanocontacts were studied. Strain and compression along the wire axis of a monatomic contact were investigated and it was found that those effects have minor influence. By the consideration of small clusters with four atoms instead of the monatomic wire the strong impact of a symmetry breaking on the conductance values has been demonstrated. A good agreement between the obtained conductance values and the experimental results was observed.