Non-equilibrium Green's function approach to the quasiparticle transport and magnetoresistance in hybrid magnetic tunnel junctions

作者：Jaya S Mathi^*; Valsakumar M C

来源：Journal of Magnetism and Magnetic Materials, 2011, 323(21): 2554-2563.

DOI：10.1016/j.jmmm.2011.05.031

• Magnetoresistance
• Magnetic tunnel junction
• Nonequilibrium Green's function

A generalized approach to study quasiparticle transport across hybrid magnetic tunnel junctions (Mills) is formulated using the non-equilibrium Green's function technique. This formalism allows for arbitrary thicknesses of the electrodes and the central scattering region comprising of materials with multiple electronic bands, and incorporates the many body interactions present in the electrode regions. While the method can be used to study the transport characteristics of various types of MTJs, we have used it to study the tunneling characteristics and magnetoresistance (MR) of MTJs in which s-f interaction is present at the electrode layers. It is also used to study the transport characteristics of MTJs with hybrid electrodes and double barrier. The magnetic correlation present in the electrodes is found to strongly influence the TMR. Eventhough the magnetic correlation in general suppress the TMR, the TMR is found to be enhanced strongly for certain band occupations of the electrodes. We observe a fall of TMR with increase in the number of layers in the insulating region. Band occupation of the metallic layer present at the middle of the insulating layers in the double barrier MTJ is found to be important in deciding its tunnel characteristics. Origin of the different types of behavior of TMR is analyzed in terms of the spin-dependent tunnel currents.

• 出版日期2011-11