We consider coherent electronic transport between two ferromagnetic electrodes separated either by a metallic nanoparticle or by a conducting molecule. Correlations between electrons with opposite spins lead to the Kondo resonance, which manifests a formation of the singlet state. Although tunnelling rates for electrons with opposite spin orientations are different the conductance reaches the unitary limit in the Kondo regime. We predict a negative magnetoresistance effect, which can be observed for asymmetric magnetic junctions.

Using nonequilibrium Green functions and several complementary many-body approximations we calculate shot noise and spin dependent conductance in carbon nanotube semiconducting quantum dot in spin-orbital Kondo regime. We point out on the possibility of reaching giant values of tunnel magnetoresistance in this range and discuss a prospect of its gate control. We also analyze the influence of symmetry breaking perturbations on the shot noise with special emphasis on spin dependent effects. The gate and bias dependencies of noise Fano factors influenced by magnetic field, polarization of electrodes and spin-flip processes are presented.

Based on ab-initio calculations we discuss Kondo effect due to Co adatom on graphene zigzag nanoribbon. Co atom located at hollow site behaves as spin S = 1/2 impurity with d xz and d yz orbitals contributing to magnetic moment. Dynamical correlations are analyzed with the use of complementary approximations: mean field slave boson approach, noncrossing approximation and equation of motion method. The impact of interplay between spin and orbital degrees of freedom together with the effect of peculiarities of electronic and magnetic structure of nanoribbon on many-body resonances is examined. PACS numbers: 73.22.Pr, 73.23.-b, 75.20.Hr, 85.75.-d arXiv:1307.5872v1 [cond-mat.mes-hall]