Graphene sensor has negligible planar Hall effect

June 11, 2020 //By Julien Happich
Hall effect sensors
Cambridge-based startup Paragraf has embarked on a working partnership with the Magnetic Measurement section at CERN, the European Organization for Nuclear Research, to demonstrate the benefits of its graphene sensor, particularly its negligible planar Hall effect.

CERN operates the largest particle accelerators in the world, for example its 27-km long, Large Hadron Collider (LHC) which straddles the border between Switzerland and France near Geneva. Physicists look at how our world is built at the fundamental level by colliding sub-atomic particles in particle accelerators that rely on large numbers of normal and superconducting magnets to steer and focus the particle beam to their collision points.
The Magnetic Measurements section at CERN is in charge of testing magnets for these accelerators using the latest-available techniques and instruments. High precision and reliable measurements are performed for many of CERN's ongoing projects, and therefore the team is always on the lookout for new sensors and transducers for improving their measurement methods and accuracy.

“This collaboration with CERN demonstrates the potential of graphene-based Hall effect sensors to improve accuracy in magnetic measurement applications. Our Hall effect sensors address key challenges CERN is facing in mapping magnetic fields, namely: highly accurate measurements of local field distributions in accelerator magnets, while eliminating artefacts and reducing uncertainties stemming from the sensors”, explains Simon Thomas, CEO at Paragraf.

Existing Hall effect sensors all exhibit planar Hall effects where field components which are not perpendicular to the sensing plane produce false signals. This is because the sensing layer is effectively three-dimensional, with some amount of depth. These false signals, together with the non-linear response to the field strength, increase the measurement uncertainty and thus limit the application of Hall sensors. Separating the true signals from the systematic errors is a complex and time-consuming process.
The Hall effect sensor from Paragraf solves these problems because the active sensing component is made of atomically thin graphene, which is therefore two-dimensional, and hence truly only senses magnetic fields along one direction; giving a negligible planar Hall effect. This enables the true perpendicular magnetic field value to be obtained, allowing for higher precision mapping of the local magnetic field.


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