Phase modulated magnetoelectric delta-E effect sensor for sub-nano tesla magnetic fields

We present a resonant micromechanical magnetic field sensor, which utilizes the magnetically induced change in elastic modulus, i.e, the delta-E effect. The sensor is based on magnetoelectric thin film composites, resulting in high sensitivity at room temperature and at low frequencies. The cantilever is electrically excited and read out by a 2 pm AIN piezoelectric layer. Depending on its magnetization, the 2 pm thin film of amorphous (Fe90Co10)(78)Si12B10 changes its elasticity, which results in a shift of the cantilever's resonance frequency. The sensor is operated in the first or second transversal bending mode at 7.6 kHz or 47.4 kHz. With a limit of detection of 140 pTHz(-0.5) at 20 Hz under a magnetic bias field and 1 nTHz(-0.5) without external bias field, this sensor exceeds all comparable designs by one order of magnitude. (C) 2015 AIP Publishing LLC.