The experiments described in this thesis relate to the recently emerging and rapidly growing field of spin electronics or spintronics. This area of study allies electronics and magnetism. It uses the spin of the electron to obtain new proporties or functions. These developments concern a new type of non-volatile memories. In contrast, conventional electronics is based on the use of an electric field to act on the charge of electrons. The electronic spin gives rise to the magnetism of solids, but also provides a means to influence the electrons by a magnetic field. Thus, in ferromagnetic (FM) materials, the motion of an electron depends on its spin orientation with respect to local magnetization. This gives rise to interesting new effects to the field of spintronics.

Spintronic effects occur on a length scale in which spin is conserved, called the spin diffusion length, which is of the order of a few nanometers. Another milestone in the spintronic was the observation of the tunnel magnetoresistance effect in magnetic tunnel junctions which have a thin layer of an insulating material sandwich between two FM materials. The dielectric reliability of the insulating layer is a major reliability concern in spintronic devices. Currently, the understanding of materials, physics, and reliability at the ano, or atomic, level is vital to the proper design and manufacturing of these devices.