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Nowadays, giant magnetoresistance (GMR) – based products are commercially available and research moves into diverse areas, e.g. combining standard GMR with magnetostriction. Following this development in the present paper the pseudo spin-valve (SV) structures are studied with the aim to apply them as strain sensors. Co and Fe-Co based SV structures with Cu and Au spacers were e-beam evaporated onto Si wafers at RT in UHV (10-7 Pa). Magnetostriction in Co layers is well understood, being – 6 x 10-5 for pure element, whereas in alloys it is mostly positive. Ten types of SV structures were studied applying different thickness and various adhesion and top layers. The thickness of layers was obtained from the simulation of X-ray reflectivity spectra using CuKα radiation. The GMR ratio of structures was between 3.3 and 5.6 %. The effect of strain upon samples was studied in bending configuration. Force was exerted by the weight of the loading block. The bowing depth was 40 μm/50 g, increasing linearly with the mass. The applied stress in structures was tensile or compressive. The results contain the relative GMR vs. magnetic field H at different strains, coercivity field Hc and field in the point of inflection of GMR characteristics Hip vs. strain. The different dependences of Hc and Hip vs. strain were found. E.g. for sample with Co(5)/Au(2.2)/Co(2) core structure (numbers denote thickness in nm) both quantities increase with increasing compressive stress, whereas for sample with Co(0.5)/Cu(3)/Co(5) core structure they increase with tensile stress. This difference could be explained by the presence of Fe underlayer in the second SV. In fact, because 0.5 nm thick Co is discontinuous, we have SV with bottom FeCo film, showing positive magnetostriction. The relative change of GMR ratio vs. loading in the strain interval ± 280x10-6 is 1-2 % near to the point of inflection of GMR vs. H curve for our samples, which means that the structures can be used and also further developed (as discussed in the paper) for the sensitive sensors of mechanical quantities. |