Analytical result of the effect of spin scattering and impurity-assistance on magnetoresistance in doped magnetic tunneling junctions

Abstract

An extended tunneling Hamiltonian method is proposed to study the temperature-dependent tunneling magnetoresistance (TMR) in doped magnetic tunnel junctions. It is found that for nonmagnetic dopants (Si), impurity-assisted tunneling is mainly elastic, giving rise to a weak spin polarization, thereby reduces the overall TMR, while for magnetic ions (Ni), the collective excitation of local spins in δ-doped magnetic layer contributes to the severe drop of TMR and the behavior of the variation of TMR with temperature different from that for Si-doping. The theoretical results can reproduce the main characteristic features of experiments.