Surface acoustic wave sensors are well known as robust and reliable sensors for a wide range of applications, one of which is magnetic field sensing. The sensor concept presented is a surface acoustic wave sensor in a shear wave delay line configuration using magnetostrictive layers of FeCoSiB on top of the delay line in different thicknesses. The magnetic field influences the elastic properties of the magnetostrictive material via the ΔE effect, which has an effect on the wave propagation velocity c of the surface acoustic wave. The altered velocity results in a magnetic field dependent relative phase change between a reference signal and the output signal of the delay line. A sensitivity of 25 %c/T is reached leading to a limit of detection of 28 nT/Hz1/2 at 10 Hz and 3.5 nT/Hz1/2 at 100 Hz. Measurements up to 1 MHz are possible. The influences of different piezoelectric substrates and different magnetostrictive materials are discussed. The presented sensor concept is a good solution to measure weak magnetic fields at high bandwidth.
Funding by DARPA (BAA-15-19 MATRIX) and the DFG (SFB 1261) is gratefully acknowledged.