Micron size GMR magnetic sensor with needle structure

The work presents inimitable shaped needle type probe with spin valve giant magnetoresistance (SV-GMR) elements. Sensitive elements with 75 μm width are connected in the Wheatstone bridge structure. The length of the needle is 20-30 mm and its cross section is square. The magnetic sensor probe has the advantage of micron order spatial resolution. The needle type probe works as a gradient meter which concurrently suppresses the influence of externally applied field and detects magnetic fields emanating from nano or micro order size sources. Sensing elements present high sensitivity 260 μV/μT and are capable of detecting the magnetic fields in order of few nT. SV-GMR elements present flat amplitude and phase characteristics in wide frequency range. The novel characteristicsof the probe allow it to be utilized in detection of the in-phase and out of phase signal components. An additional merit of this design is extremely small liftoff height between sensing element and the source of magnetic field. The SV-GMR elements are isolated only by very thin protection layer (a few μm), that gives opportunity to apply the probe in biological (in vivo) experiments, and in non destructive evaluation of current detection. The needle shape allows the sensing element toapproach the examined materials in a distance of few ten μm. © 2012 American Institute of Physics