Berlin 2018 – scientific programme

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MA: Fachverband Magnetismus

MA 21: Poster I

MA 21.79: Poster

Tuesday, March 13, 2018, 09:30–13:00, Poster A

Downscaling of planar Hall effect sensors for optical transparency and small volumes — •Luca Marnitz, Karsten Rott, Karl-Josef Dietz, Dario Anselmetti, and Günter Reiss — Bielefeld University

Magnetic field sensors based on the Planar Hall Effect (PHE) have been used to sense the stray field of magnetic nanoparticles induced by the self-field of the sensor current. Prior reports either use the shape anisotropy of the sensor to induce effective single domain behaviour [1] or use exchange-biased ferromagnets for example in a PHE Bridge (PHEB) layout [2].
However, these sensors either have a large surface area of up to several mm² [1], which is problematic for small sample volumes and/or are optically non-transparent due to their relatively large thickness.
In this work we prepared µ m-sized optically transparent PHE-sensors for magnetic nanoparticle detection and simultaneous optical observation in an optical microscope.
Both the effects of downscaling the area and the thickness of the active sensors are analyzed regarding their feasibility for detecting the particle-surface distance in an optical microscope equipped with a magnetic tweezer. This technique could allow the use of smaller particles and tailored particle shapes to analyze the stretching and twisting of biomolecules.
Mor et al., JAP 111, 07E519 (2012)
Henriksen et al., JAP 119, 093910 (2016)