|Schematic of an magnetoelectric cantilever sensorthe magnified region represents the layer stacking of piezolectric (AlN), and the self biased magnetostrictive stack (Ta, Cu, MnIr, FeCoSiB). The arrow represents the bias field orientation.|
For his work about magnetoelectric sensors in medical engineering Dr. Enno Lage, post doc at Kiel University, received an award for young researchers from the German Society for Materials Science (DGM, Deutsche Gesellschaft für Materialkunde). The prize was awarded at the annual conference of the DGM in Darmstadt on September 26th 2016. It honors outstanding achievements of young researchers in material science.
During his PhD, Enno Lage conducted his research on highly sensitive magnetoelectric sensors within the collaborative research center “Magnetoelectric Composites” at the Faculty of Engineering.
Those sensors show their highest sensitivity in presence of well-defined magnetic bias fields. For vector sensors and in densely arranged sensor-arrays each component needs an individually oriented bias field. Thus, the sources of bias fields, either generated with electromagnetic coils or with permanent magnets, are detrimental in terms of miniaturization.
In order to overcome these limitations, the researchers utilized the exchange bias effect which is well established in magneto-resistive sensing. The challenge in their approach was the precise adjustment of the bias field. The orientation of the internal bias field is crucial for the sensitivity. If one would simply substitute the external bias field by an internal field with same orientation and strength, the sensors would show a vanishingly small response and hence an alternative orientation had to be considered. Additionally, if the field is too large the sensitivity decreases, if it is too small the sensor behaves partially unbiased.
The followed approach led to the successful realization of self-biased magnetoelectric sensors and was suitable to combine sensor elements for vector sensing.
Lage, E., Kirchhof, C., Hrkac, V., Kienle, L., Jahns, R., Knöchel, R., Quandt, E. and Meyners, D., 2012. Exchange biasing of magnetoelectric composites. Nature materials, 11(6), pp.523-529.
Lage, E., Woltering, F., Quandt, E. and Meyners, D., 2013. Exchange biased magnetoelectric composites for vector field magnetometers. Journal of Applied Physics, 113(17), p.17C725.
Lage, E., Urs, N.O., Röbisch, V., Teliban, I., Knöchel, R., Meyners, D., McCord, J. and Quandt, E., 2014. Magnetic domain control and voltage response of exchange biased magnetoelectric composites. Applied Physics Letters, 104(13), p.132405.