Exploring Resonance Effects on Ferromagnetic Microwire Solenoid Sensitivity for Motion Tracking Applications*

The high frequency GMI effect is a sensitive phenomenon found in amorphous, soft ferromagnetic materials. The GMI effect has potential to introduce a new class of long range, contact-free small field magnetic sensing[1]. GMI sensors allow for low-cost, robust systems capable of a wide range of motion tracking applications. A challenge these sensors present to applications comes from the quick decay of magnetic field lines, restricting their sensing distance. In an attempt to achieve better sensitivity and longer ranges, Cobalt-based microwires have been wound into solenoids around Plexiglas molds with various lengths of wire. Further, the number of turns used, affects the magnitude and frequency of transmission line resonance. GMI responses were measured around resonance to determine the optimal operating frequency for each sensor and to observe the relation to the circuit’s current nodes. Of the solenoids constructed, the 12 turn, 203 mm solenoid had the highest sensitivity. The optimal operating frequency was 32.4 MHz, which allowed for a range of 250 mm. For comparison, GMR sensors have a detection range of 190 mm[2].

[1] Thiabgoh O., Eggers T., Phan M., Sens. Actuators A 265, 120 (2017)
[2] Ribeiro M., Ortner M., Seger M., Bali 28-30, 97 (2014)