Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 29: Magnetic Measuring Methods / Sensors / Actuators

MA 29.4: Vortrag

Donnerstag, 29. März 2007, 16:00–16:15, H5

Noise in anisotropic magnetoresistive sensor elements — •Thomas Heuer, Jörg Wolff, Haibin Gao, and Uwe Hartmann — Fachrichtung Experimentalpysik, Universität des Saarlandes, Postfach 151150, 66041 Saarbrücken

The field resolution of magnetometers based on anisotropic magnetoresistive (AMR) sensors is mainly limited by noise. Besides environmental factors, the main source of noise is the sensor element itself. Thus, knowledge of the mechanisms producing noise and the factors influencing it is essential.

The detector noise has been found to be strongly influenced by the peak magnitude of periodic magnetic field pulses perpendicular to the sensor's sensing direction ("flipping"). Other factors, as temperature and pulse width, also affect the sensor noise, albeit to a much lower degree. It is well established that domain wall-related processes, e.g. Barkhausen noise, are the primary source of noise in magnetoresistive sensors. Thus removing the domain walls by applying field pulses strong enough to fully saturate the sensor will result in a significant noise reduction.

Sensors of same type but from different batches have been found to exhibit considerable differences in their characteristics, with sensor noise varying by several orders of magnitude for identical conditions. It is believed that variations of the magnetic and electric properties of the magnetoresistive films play a key role. Thus detector noise is being examined with respect to its dependence on pulse parameters and sensor temperature in order to deduce differences in material properties.