  The sandwich structure as the core layer of PDMS resonator is proposed for
single-axis magnetic sensor with high sensitivity. The small Young's modulus of
flexible material corresponds to larger variation, resulting in a highly
sensitive magnetic response. The sandwich structure pre-set magnetic field
provides directional sensing feature. The experimental results show that the
redshift sensitivity of 1.08 nm/mT and the blueshift sensitivity of 1.12 nm/mT
in the unshielded environment, which is attributed to slight variation in PDMS
Young's modulus. At 1.4 kHz, a minimum detectable magnetic field of 0.96 nT
Hz-1/2 is realized.
