Influence of interface structure of Co/Cu (100) superlattices on electronic structure and giant magnetoresistance

Electronic structures and magnetoresistance (MR) of Co₃Cu ₅ and Co₃Cu₇ models as well as their interface atom exchange models Co₂CuCoCu₄ and Co ₂CuCoCu₆ are investigated by the first-principles pseudopotential plane-wave method based on density functional theory. Charge transfer, magnetic moment, density of states, spin asymmetry factor, and MR ratio are discussed. The results show that the values of charge transfer and spin asymmetry factor at the Fermi level of Co layers are closely related to the neighbouring background of the Co layer. The Co layer with two sides adjacent to the Cu layer would transfer more charge to the Cu layer than other neighbouring background and have the largest spin asymmetry factor at the Fermi level. The Co layer with two neighbouring Co layers (interior Co) would gain a little charge and have the smallest spin asymmetry factor at the Fermi level. Two-current model is used to evaluate the MR ratio of Co₂CuCoCu ₄ (Co₂CuCoCu₆) to be larger than that of Co₃Cu₅ (Co₃Cu₇), which can be explained by the charge transfer and spin asymmetry factor.