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CoFeBSi and FeCo magnetostrictive micro-and nano-dot arrays are fabricated on Si/sub 3/N/sub 4/ membranes with different diameters (50 to 300 /spl mu/m) by combining MEMS fabrication processes and thin film technology. Compressive or tensile mechanical strain is introduced in order to observe the inverse magnetostriction effect or the Villary effect. Magnetic force microscopy and MOKE measurements are employed in order to investigate the strain induced switching properties and resolve the domain structure of the amorphous micro- and nano-dot arrays. The local strain distribution of the various membrane structures is obtained by finite-element method. The results of the simulations are then compared to the experimental results.

This study investigates magnetic layer structures suitable for devices measuring mechanical responses such as stress, strain and pressure. The sensors are based either on giant magnetoresistiance (GMR) structures or on magnetic tunneling junctions (MTJ's) both intentionally prepared with highly magnetostrictive free layer materials. Results for magnetostrictive Fe 50 Co 50 materials or amorphous Co- or Fe-based alloys serving as sensing (or free) layers are discussed in view of possible applications. In general, gauge factors in the range of 300-600 have been obtained for strain sensors based on MTJ's, whereas gauge factors of 2-4 are typical for metal based thin film, and 40-180 for piezoresistive strain gauges.

Magnetic tunneling junctions (MTJs) incorporating magnetostrictive free layer materials are developed and characterized for the application as highly sensitive strain sensors. Gauge factors of the order of 400–600 have already been demonstrated compared to typical values of 2–4 for metal film based strain sensors. Here, different magnetostrictive materials such as amorphous FeCoSiB alloy and polycrystalline Ni films have been investigated in order to characterize and optimize the MTJ based sensor properties.