GMR films with crossed anisotropies for perpendicular field measurements

As 3-dimensional field sensors require one part being susceptible to perpendicular fields, thin film GMR stacks with a linear and reversible response to such fields are of interest for the development of monolithic sensor devices. Stacks with such a behavior can be achieved by combining a pinning layer with perpendicular easy axis and a free layer with perpendicular hard axis. Furthermore, the stray field of the pinning layer can be minimized and its coercivity enhanced if a ferrimagnet (or antiferromagnet) is used. For the present study, TbxCo100−x alloys have been chosen as the pinning layer material and Ni81Fe19 for the free layer. The single layers have been characterized by SQUID-VSM measurements, the complete layer stack by magneto-resistance measurements. Initial films confirm the expected behavior and exhibit a change in resistivity of 5% in a field range of 10 kOe. Further films will be optimized regarding their magnetic and electric properties. They shall be micro-structured then and equipped with bottom contacts through the substrate.