Transport properties of Co-Ni superlattices

MARIANA WEISSMANN; ANA MARÍA LLOIS

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 1996 vol. 54 p. 15335 - 15340

1098-0121

We calculate the ballistic conductance G and the diffusive conductivity s for Co-Ni superlattices grown in the ~111! direction, with the intention of investigating the effect of the superlattice band structure on the electric transport properties. The calculation is carried out as a function of the number of atomic layers of each material, in the framework of the semiclassical approximation ~Boltzmann?s equation! and assuming that each spin component contributes independently. A Hubbard tight-binding Hamiltonian, solved in the unrestrictedHartree-Fock approximation and parametrized to fit bulk equilibrium values, is used to obtain the band structure min each case. We find that the presence of interfaces reduces the in plane and, more strongly, the perpendicular to the plane electric conduction, even when impurity scattering is disregarded. The results for G and s show qualitative differences and thus, in the interpretation of the experiments, it is important to ascertain the precise nature of the transport regime. We do not find the oscillatory behavior of the conductivity as a function of the number of layers, found in recently reported experimental results. This certainly is not amatter of accuracy of the calculations and therefore rules out the hypothesis that the oscillatory behavior is due to simple band structure effects.