Electron transport through disordered domain walls: Coherent and incoherent regimes

Abstract

We study electron transport through a domain wall in a ferromagnetic nanowire subject to spindependent scattering. A scattering matrix formalism is developed to address both coherent and incoherent transport properties. The coherent case corresponds to elastic scattering by static defects, which is dominant at low temperatures, while the incoherent case provides a phenomenological description of the inelastic scattering present in real physical systems at room temperature. It is found that disorder scattering increases the amount of spin-mixing of transmitted electrons, reducing the adiabaticity. This leads, in the incoherent case, to a reduction of conductance through the domain wall as compared to a uniformly magnetized region which is similar to the giant magnetoresistance effect. In the coherent case, a reduction of weak localization, together with a suppression of spin-reversing scattering amplitudes, leads to an enhancement of conductance due to the domain wall in the regime of strong disorder. The total effect of a domain wall on the conductance of a nanowire is studied by incorporating the disordered regions on either side of the wall. It is found that spin-dependent scattering in these regions increases the domain wall magnetoconductance as compared to the effect found by considering only the scattering inside the wall. This increase is most dramatic in the narrow wall limit, but remains significant for wide walls.

Magnetoresistance in an amorphous exchange-coupled bilayer

“…In particular, the influence of a magnetic domain wall on disordered system electrical resistance has been studied theoretically. [20][21][22][23] Contrary to what has been observed so far in crystalline magnets, the introduction of a DW in disordered metals is believed to decrease the resistivity due to either electron-electron interference destruction 20 or weak localization suppression. [21][22][23] Exchange-coupled bilayers using rare-earth transitionmetal alloys, such as GdFe/TbFe, 24,25 GdCo/Co, 26 DyFe 2 / YFe 2 , 13,27 or Gd x Co 1−x / Gd y Co 1−y , 28 have been extensively used to study interfacial domain-wall ͑iDW͒ behaviors.…”

High domain wall magneto-resistance in amorphous TbFeCo wires

“…17,18 For theoretical prediction, the introduction of a DW in disordered metals can decrease the resistivity due to either electron-electron interference destruction 21 or weak localization suppression. 6,22 Meanwhile, for disordered materials, impurity scattering inside DW will cause an increase in transmission and reflection with spin-mistracking, or equivalently a reduction in the adiabaticity of spin transport through the wall, 23 which will lead to an enhanced spin-dependent scattering inside the wall based on the model of Levy and Zhang, 5 thus notable resistivity increment can be expected. Different from the work of Hauet et al 8 who extracted a negative contribution from wide interfacial DW in amorphous Gd 40 Fe 60 /Gd 10 Fe 90 bilayer, our experimental result suggests, for amorphous systems possessing narrow DWs, the impurity scattering dominates the MR effects inside DWs leading to positive MR. More than that another important reason for the high DW MR ratio is that the narrow DW is still survived after the special FIB process, which does not bring on anisotropy degradation to sample.…”

Dynamic Magnetic Properties of Ferroic Films, Multilayers, and Patterned Elements

“…Interestingly, this precession involves a change in angular momentum upon traversal of the wall 36–38. Conservation of angular momentum then requires the wall to move.…”