Transport In Magnetic Multilayers Research Articles

Effects of domains on magnetoresistance (abstract)

Our present understanding of the giant magnetoresistance observed in magnetic multilayered structures is based on the premise that the layers are either monodomains or that the sizes of the domains are much larger than all other length scales (mean free path, spin-diffusion length, and layer thickness) relevant to the magnetoresistance. We extend our theory of magnetoresistance to include multilayers with small in-plane domains where there is the possibility that their size may be limited by columnar growth. We study magnetoresistance in the presence of in-plane domains both for the current parallel and perpendicular to the plane of layers. The domain boundaries introduce additional scattering and the direction of the internal current will be different from that of the driven current. In the presence of spin-dependent scattering, a transverse spin current develops so that the current in each of the spin channels is ‘‘mixed’’ even without spin-flip processes. Analytical expressions will be given for limiting cases where the mean free path is either much larger or much smaller than the layer thickness and the domain size. We find that the domain size is a relevant length scale and contributes to the spin diffusion length λsdl in the equations that govern the spin diffusion attendant to charge transport in magnetic multilayers. If one does not know the domain structure, nor the amount of spin-flip scattering, both mechanisms are equally plausible for producing spin diffusion which suppresses the magnetoresistance for the current perpendicular to the plane of the layers.

Interfacial scattering and interface resistance for penpendicular transport in magnetic multilayers

The spin-dependent interface resistance due to specular electron reflections from potential steps and to diffuse scattering by the defects of the interfaces is calculated within the Landauer approach. The appropriate transmission matrix is calculated in the approximation in which the vertex corrections are included. Numerical data show that both potential steps and defects should contribute to the interface resistance.

Scattering theory of perpendicular transport in metallic multilayers (invited)

Electronic transport in metallic multilayers is discussed in the language of the Landauer–Büttiker scattering formalism. The semiclassical conductance through a disordered interface can be unambiguously separated into specular and diffuse scattering contributions. Analytical results are derived for the perpendicular conductance of multiple disordered interfaces. Predictions for the transport properties of interfaces with dilute but strongly scattering defects should be accessible to verification by experiments. First results of first-principles calculations of ballistic transport in magnetic multilayers are presented.

Transport in magnetic multilayers from the quantum Boltzmann equation.

Transport in magnetic multilayers from the quantum Boltzmann equation.

Classical theory of perpendicular giant magnetoresistance in magnetic multilayers

We treat the problem of perpendicular transport in magnetic multilayers by starting from the Boltzmann equation formalism. Our model reduces to the macroscopic model first introduced by Johnson and Silsbee when the spin diffusion length is much longer than the mean free path. However, by taking into account the interplay between successive interfaces, we obtain different results from those of Johnson. Furthermore, we find simple expressions of the magnetoresistance that can be used to separate the volume and interface contributions to the spin dependent scattering.

Influence of Superlattice Potentials on Transport in magnetic multilayers

ABSTRACTWe discuss the effect of the superlattice potential on the magnetotransport properties of magnetic multilayers for current parallel and perpendicular to the plane of the layers. While quantum well states affect the Magnetotransport, they are not the primary origin of the giant Magnetoresistance observed in these materials for currents in the plane of the layers. In general, it is necessary to include both spin-dependent scattering and the effects of superlattice potentials in order to explain the magnetoresistance of multilayered structures.