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Monolithic integration of focused 2D GMR spin valve magnetic field sensor for high-sensitivity (compass) applications

: Ueberschär, O.; Almeida, M.J.; Matthes, P.; Müller, M.; Ecke, R.; Exner, H.; Schulz, S.E.


Drouhin, H.-J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Spintronics VIII : 9 - 13 August 2015, San Diego, California, United States
Bellingham, WA: SPIE, 2015 (SPIE Proceedings 9551)
ISBN: 978-1-62841-717-3
Paper 955129
Spintronics Symposium <2015, San Diego/Calif.>
Conference "Optics and Photonics" <2015, San Diego/Calif.>
Fraunhofer ENAS ()

We have designed and fabricated 2D GMR spin valve sensors on the basis of IrMn/CoFe/Cu/CoFe/NiFe nanolayers in monolithic integration for high sensitivity applications. For a maximum signal-to-noise ratio, we realize a focused double full bridge layout featuring an antiparallel exchange bias pinning for neighbouring meanders and an orthogonal pinning for different bridges. This precise alignment is achieved with microscopic precision by laser heating and subsequent in-field cooling. Striving for maximum signal sensitivity and minimum hysteresis, we study in detail the impact of single meander geometry on the total magnetic structure and electronic transport properties. The investigated geometrical parameters include stripe width, stripe length, cross bar material and total meander length. In addition, the influence of the relative alignment between reference magnetization (pinned layer) and shape anisotropy (free layer) is studied. The experimentally obtained data are moreover compared to the predictions of tailored micromagnetic simulations. Using a set of optimum parameters, we demonstrate that our sensor may readily be employed to measure small magnetic fields, such as the ambient (geomagnetic) field, in terms of a 2D vector with high spatial (~200 μm) and temporal (~1 ms) resolution.