Noise measurements on NiFe/Ag multilayered structures

Noise in NiFe/Ag giant magnetoresistive (GMR) multilayers and in magnetic field sensors based on this material has been studied in order to evaluate the potential of such material and such sensors for low field applications. GMR stripes were used to study the material intrinsic noise for varying DC sense current density, applied field and device dimensions. Noise measurements were then carried out on a magnetic field sensor for which thermal and magnetic characteristics have also been studied. The noise in NiFe/Ag multilayers is dominated by a 1/f noise at low frequencies and shows a flat spectrum at higher frequencies due to Johnson noise. The 1/f noise increases with the current density and is field and device-dimensions dependent. Magnetic field sensors based on NiFe/Ag are good candidates for the realization of low field micromagnetometers because they have suitable characteristics and relatively low noise