Magnetic Flux Concentration Effects in Cantilever Magnetoelectric Sensors

This paper investigates the resonant bending-mode response of cantilever magnetoelectric (ME) sensors, with focus on the magnetic behavior in an external applied magnetic field, in a theoretical study. A system of coupled linear elastostatic/elastodynamic and electrostatic/magnetostatic equations is solved using 2-D and 3-D finite-element method simulations. The magnetic field is applied at the boundaries of an air-filled volume, surrounding the whole ME sensor, to consider the geometry-dependent deformation of the magnetic field in the presence of materials with high permeability. The deformation of the magnetostrictive (MS) material is calculated and generates an electric potential across a piezoelectric (PE) layer. Structuring the conductive MS layer is necessary to define a pickup region, if the MS layer is produced on top of the PE layer, to enhance the sensor output. For efficient excitation of the resonant bending mode, the tip of the cantilever also needs to be covered with an MS material. Thus, an air gap is necessary to electrically insulate both MS regions and has to be as small as possible to not decrease the magnetic field penetrating into the MS layer. The induced electric potential across the pickup region is optimized for a Metglas-AlN-Si thin-film ME sensor with an length:width:height ratio of 100:20:3. 2-D simulations are performed showing reasonable agreement in induced voltage with approximately 20% deviation compared with 3-D simulations, but with much lower computation times.