Fano Mechanism of the Giant Magnetoresistance Formation in a Spin Nanostructure

It is shown that, upon the electron quantum transport via the nanostructure containing a spin dimer, the spin-flip processes caused by the s-f exchange interaction between electron and dimer spins lead to the Fano resonance effects. An applied magnetic field eliminates degeneracy of the upper triplet states of the dimer, changes the conditions for implementation of the Fano resonances and antiresonances, and induces the new Fano resonance and antiresonance. It results in the occurrence of a sharp peak and dip in the energy dependence of transmittance. These effects strongly modify the current--voltage characteristic of the spin-dimer structure in a magnetic field and form giant magnetoresistance.