Magnetic field sensing with magnetostrictive materials using a tunneling tip detector

This paper is a feasibility study for the design and construction of a magnetic field sensor using a tunneling tip as the detection system. In this experiment, a scanning tunneling microscope is used to measure dimensional changes of a short, thin amorphous FeBSi magnetostrictive ribbon exposed to d.c. and a.c. magnetic fields. A response of the system to a.c. magnetic fields was observed down to 0.020 G at a frequency of 1 Hz. The calculated sensitivity of the system can be near 10⁻⁶ G if the vibrational stability of the device can be improved and if the demagnetizing field associated with short ribbons can be reduced. A mode of sensor operation involving the modulation of the tip-to-specimen separation is reported. Methods to improve the stability of the device are also discussed.