ABSTRACT
100This chapter is dedicated to the study of ballistic transport in magnetic nanostructures. Ballistic means that the charges carrying the electrical current go through the sample without experiencing scattering. This condition requires that sample dimensions are smaller than the carriers mean free path. This concept is therefore in immediate contrast with the diffusive transport model, extensively used to explain giant magnetoresistance (GMR) properties. The spin dependent resistivities of the ferromagnetic layers and the interfaces largely determine the GMR properties; however, for a diminishing sample size this is not solely the case. An example of transport occurring essentially without scattering is the tunnel regime, where the conduction of the system is ensured by evanescent waves through a dielectric barrier. The related tunnel magnetoresistance (TMR) is described in detail in Chapters 11–13, Volume 1, but let us recall that it relies on spin-dependent density of states in the ferromagnetic layers (more precisely at the interface), as well as the transmission properties of the barrier.
