Demagnetizing Field Effect on the Detection Range of a Galfenol-Based Magnetic Field Sensor

This paper investigates the new developments of a class of magnetic field sensors based on the integration of Iron-Gallium magnetostrictive alloys (Galfenol) and fiber Bragg gratings used to detect the magneto-induced mechanical strain. This kind of sensor has the advantage of being able to work also in harsh environments, but on the other hand cannot detect fields beyond 10 kA/m, because of the magnetic softness of the active material. A simple solution consists in the exploitation of the demagnetizing field experienced by the ferromagnetic alloy by effect of its magnetization, generated by the application of the external magnetic field. Since the demagnetizing field effect depends only on geometrical parameters, the use of samples with different aspect ratios allows us to check how the shape of the active material can be used as a control parameter of the sensor detection range.