  In this communication we apply the Landauer method and transfer matrix
formalism to the calculation of spin current in magnetic multilayered
structures within a ballistic quantum-mechanical regime. The method provides an
elegant and intuitive formalism with which to study spin current properties and
within which closed-form expressions with a transparent physical interpretation
can be obtained. We apply the method to illuminate origin and the symmetry
properties of the various spin current components within the parabolic band
approximation. We also apply the stationary phase approximation to develop
asymptotic approximations to the total spin current within this formalism, and
show that these give excellent agreement with full numerical calculations for
both barrier and well systems.
