Transport properties in nano-scaled ferromagnetic tunnel junctions within a two-band tight-binding model

Abstract

A two-band tight-binding Hubbard model Hamiltonian, in which a planar-pinning field was included, was employed to study the transport properties in nano-scaled ferromagnetic tunnel junctions. Within the self-consistent Hartree–Fock (SCHF) approximation to the model Hamiltonian, the temperature-dependent and bias-dependent conductivity and magnetoresistance in the junctions were calculated. The calculated conductivity increases with temperature due to thermal excitation and electron–phonon scattering, while the calculated tunnelling magnetoresistance (TMR) decreases with temperature due to the imbalance of electron–phonon scattering between spin-up state and spin-down state when the magnetic moments of the electrodes are aligned parallel to each other. The conductivity and magnetoresistance nonlinearly depend on bias voltage. The decrease of TMR and increase of conductivity with bias voltage originate from the leaned potential barrier at low bias voltage, and from the electric polarization in insulator layer at high bias voltage.