Wide Band Low Noise Love Wave Magnetic Field Sensor System

TLDR

The sensor concept is motivated by magnetic and mechanical simulations. The study presents a magnetic sensor system that uses a new technique to substantially increase magnetoelastic coupling of surface acoustic waves, and investigates additional measures to further enhance sensitivity through simulations. The sensor employs shear horizontal Love waves guided by a fused silica layer with an FeCoSiB magnetostrictive film, operating at ~150 MHz in a delay‑line configuration where magnetic‑field‑induced changes in shear modulus alter wave velocity, producing time‑delay and phase‑shift signals that are experimentally verified with low‑noise readout electronics. The sensor achieves an extremely low magnetic noise level of ~100 pT/√Hz, a 50 kHz bandwidth, and a 120 dB dynamic range, demonstrating outstanding performance.

Abstract

Abstract We present a comprehensive study of a magnetic sensor system that benefits from a new technique to substantially increase the magnetoelastic coupling of surface acoustic waves (SAW). The device uses shear horizontal acoustic surface waves that are guided by a fused silica layer with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these so-called Love waves follows the magnetoelastically-induced changes of the shear modulus according to the magnetic field present. The SAW sensor is operated in a delay line configuration at approximately 150 MHz and translates the magnetic field to a time delay and a related phase shift. The fundamentals of this sensor concept are motivated by magnetic and mechanical simulations. They are experimentally verified using customized low-noise readout electronics. With an extremely low magnetic noise level of ≈100 pT/ $$\sqrt{{\rm{Hz}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mrow> <mml:mi>Hz</mml:mi> </mml:mrow> </mml:msqrt> </mml:math> , a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows outstanding characteristics. A range of additional measures to further increase the sensitivity are investigated with simulations.