Magnetoelectric (ME) cantilever-type thin film composites consisting of a piezoelectric (PE) and a magnetostrictive (MS) layer are usually employed for detection of magnetic fields directly, i.e. an AC magnetic field generates a ME voltage by coupling a MS deformation to the PE phase. In order to achieve high sensitivities, mechanical resonances are exploited along with a magnetic bias field, necessary to operate at the maximum piezomagnetic coefficient of the MS phase. Despite being able to detect very small field amplitudes within biomagnetic requirements, one is limited to narrowband, rather high frequency magnetic signals coinciding to mechanical resonances.
In the presented work the PE phase of the sensor composite is piezoelectrically excited. In this case we are exploiting a high mode mechanical resonance, which leads to voltage induction in a surrounding pickup coil. This induced voltage amplitude, caused by magnetoelastic mixing within the MS phase, proves to be sensitive to even small DC and AC magnetic fields, exceeding a sensitivity of 28 kV/T. This passive, converse ME readout makes ME composites suitable for DC sensing  (1.2nT@200mHz) as well as achieving less than 100 pT/sqrt(Hz) at 5 Hz magnetic field without the need of an external magnetic AC or DC bias field, enabling integration into sensor arrays. We demonstrate the sensing performance of electrically modulated ME composites and give insight into magnetoelastic detail revealed by time-resolved magneto-optical Kerr microscopy .
Funding via DFG, SFB1261 is gratefully acknowledged.
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