Resonant Magnetoelectric Effect at Low Frequencies in Layered Polymeric Cantilevers Containing a Magnetoactive Elastomer

Abstract

In this work, the resonance enhancement of magnetoelectric (ME) coupling at the two lowest bending resonance frequencies was investigated in layered cantilever structures comprising a magnetoactive elastomer (MAE) slab and a commercially available piezoelectric polymer multilayer. A cantilever was fixed at one end in the horizontal plane and the magnetic field was applied horizontally. Five composite structures, each containing an MAE layer of different thicknesses from 0.85 to 4 mm, were fabricated. The fundamental bending resonance frequency in the absence of a magnetic field varied between roughly 23 and 55 Hz. It decreased with the increasing thickness of the MAE layer, which was explained by a simple theory. The largest ME voltage coefficient of about 7.85 V/A was measured in a sample where the thickness of the MAE layer was ≈2 mm. A significant increase in the bending resonance frequencies in the applied DC magnetic field of 240 kA/m up to 200% was observed. The results were compared with alternative designs for layered multiferroic structures. Directions for future research were also discussed.

Multiferroic Cantilevers Containing a Magnetoactive Elastomer: Magnetoelectric Response to Low-Frequency Magnetic Fields of Triangular and Sinusoidal Waveform

“…The output signal (generated voltage or charge) and the applied magnetic field strength were recorded. Since MAEs exhibit hysteretic behavior of measured quantities with respect to the applied magnetic field [ 24 , 25 , 34 , 35 ], the response to each period of an applied magnetic field is somewhat different. A hysteresis in MAEs is commonly attributed to the magnetic-field-induced restructuring of filler particles, which is also the origin of magnetic hysteresis in such a material.…”

“…The corresponding resonance frequency in the absence of a magnetic field was low ( Hz). The first results [ 16 , 24 , 25 ], obtained on multiferroic layered structures containing an MAE layer and a PE polymer, confirmed that these heterostructures are promising for the development of magnetic field sensors and energy harvesting devices. It seems that contrary to the conventional paradigm, the T-T configuration leads to a higher ME voltage coefficient than the L-T configuration.…”

“…A giant extensional strain up to ≈20% was recently observed in soft MAE cylinders [ 23 ], which makes the MAEs promising candidates for ME composites. MAEs can be combined with PE polymers in layered composite materials, where a significant direct ME effect is observable [ 24 , 25 ]. If a magnetic field is applied perpendicularly to the plane of the layered cantilever, the cantilever is bent due to the torque acting on the MAE layer [ 26 , 27 ], and the resulting deformation of the PE layer leads to the generation of an electric voltage.…”

“…Such an arrangement is commonly designated as the T-T (transverse magnetic field and transverse electric field) configuration [ 1 ]. Very recently, a conventional L-T (longitudional magnetic field and transverse electric field) configuration was also investigated, where a superposition of constant and small alternating magnetic fields (standard method of sinusoidal field excitation [ 28 ]) was applied in the plane of the composite heterostructure [ 25 ]. The highest ME voltage coefficient of about 7.85 V/A was measured in a sample where the thickness of the MAE layer was ≈2 mm.…”

“…It seems that contrary to the conventional paradigm, the T-T configuration leads to a higher ME voltage coefficient than the L-T configuration. Mechanically soft, multiferroic cantilevers, such as those presented in this paper, can easily morph (bend to a great extent) towards the direction of an applied magnetic field so that their demagnetizing factor drastically decreases and the ME coupling becomes highly efficient [ 25 ]. Hitherto, multiferroic layered composites containing an MAE layer are not well investigated and not all the specific features of ME coupling in them are well understood, for example, the unexceptionally large increase in the resonance frequency in magnetic fields [ 25 ] or the retarded deflection and voltage response with respect to the magnetic field [ 24 ].…”