Ballistic transport and tunnelling magnetoresistance in tunnel junctions

In this paper we report the results of a theoretical study of the ballistic tunnelling of electrons in magnetic tunnel junctions. We show how first-principles band-structure calculations and published magnetization data can be used as inputs to the model, which is then used to predict the magnetoresistance of a tunnel junction. This approach provides a convenient way to examine effects not readily treated by purely first-principles calculations such as finite bias and finite temperature as well as providing a way to treat the amorphous nature of most tunnelling barriers. Ultimately, the model is used to show how the tunnelling magnetoresistance depends on extrinsic factors such as applied bias, and temperature, as well as on the intrinsic properties of the junction such as the barrier height and thickness. The model generates the asymmetry in the magnetoresistance often seen for forward and reverse bias in asymmetric junctions.