Exchange coupling between ferromagnetic and antiferromagnetic layers via Ru and application for a linear magnetic field sensor

Abstract

Exchange coupling is observed in a trilayer structure of ferromagnet-Ru-antiferromagnet and the coupling strength is found to be a function of the thickness of the Ru spacer layer. This is the first observation for such a trilayer structure and may help to shed light on the illusive mechanism of exchange coupling in these systems. This unique coupling is used to bias the sense layer in a magnetic tunnel junction structure so that the magnetization orientations of the sense layer and the pinned layer can be independently controlled. Sensor devices are fabricated with a bipolar output, a medium sensitivity, and a wide field range. The results show that this biasing scheme is well suited for magnetic tunnel junctions used in magnetic field sensors.