4.21 Inßuence of the MgO barrier thickness on the lifetime characteristics of magnetic tunneling junctions for sensors

Magnetic tunneling junctions (MTJs) are commonly used in hard disc read heads. As magnetic Þeld sensors they are entering the Þeld of industrial applications in the automotive branch, in robotics and in machine automation in general. Due to the higher tunneling magnetoresistance values in comparison with AMR and GMR technologies (anisotropic and giant magnetoresistance, respectively), MTJs can provide higher sensitivity in sensors. This eliminates the need of a signal preampliÞer with the subsequent simpliÞcation of the chip design. Additionally, their typically larger resistance values make them promising candidates for green energy applications with lowconsumption requirements, due to the reduction of the current needed to obtain a voltage signal. For these reasons, it is no wonder that the main sensors producers are developing new prototypes and products based on MTJs [1–3].