Electrical transport in magnetic sandwich with interface inter-diffusional roughness and/or alloying

摘要

A thin transition sublayer with its own spin-dependent lattice potentials and relaxation times of the conduction electrons is introduced to describe the interface inter-diffusional roughness and/or alloying. Within the real-space Kubo formalism, the contribution of the spin-dependent lattice potentials to the giant magnetoresistance (GMR) effect, the dependence of the GMR effect on the spin asymmetry ratio and the spin-down relaxation time of the transition sublayers, the GMR effect versus the thickness of the ferromagnetic (FM) and nonmagnetic (NM) layers are discussed based on the jellium model with step-like and spin-dependent lattice potentials. The interesting results emerging in our calculations are that (1) the contribution of the spin-dependent lattice potentials to the GMR effect may be positive or negative, it is decided by the thicknesses of the FM and NM layers; (2) the contribution of spin-dependent lattice potentials to the GMR effect is much weaker than that of the spin-dependent relaxation times; (3) the increase or decrease of the GMR effect is not simply decided by the increased or decreased interface disorder but decided by the increased or decreased spin asymmetry ratio of the interface structure, which is caused by the change of the interface disorder; (4) for the case of the spin asymmetry ratio of the transition sublayers smaller than that of the FM layers, there exists a critical thickness d_c for the thickness d_F of the FM layers, when d_F > d_c, the existence of the interface inter-diffusional roughness and/or alloying increases the GMR effect, however, when d_F < d_c, it is on the contrary.