Resonant magnetoelectric response of cantilevers with magnetostrictive and piezoelectric layers on opposite sides of the substrate

Abstract

A theory is derived for the bending-mode magnetoelectric coefficients at resonance for magnetostrictive and piezoelectric layers on opposite sides of a substrate. Results are given for the transverse ME coefficient in the Metglas-Si-AlN system with magnetic field excitation parallel and electric polarization perpendicular to the cantilever. The center-substrate layer sequence is found to produce about 50 % enhancement of the magnetoelectric effect compared to magnetoelectric bilayers on one side of a substrate. Up to about 10 % additional enhancement of the ME effect is predicted if the magnetostrictive and piezoelectric layers are separated from the substrate by spacer layers with lower Youngs modulus. Lowest order bending mode resonance frequencies are given

Resonant magnetoelectric response of composite cantilevers: Theory of short vs. open circuit operation and layer sequence effects

“…Recently near bulk piezoelectric properties were achieved for 10nm AlN. 42 The open circuit results 36,37 and corresponding neutral plane behavior are briefly reiterated here. Minima regions producing primary and secondary maxima of the ME response are observed only in the layer sequences with functional materials at the central layer.…”

“…Low frequencies required for biomagnetic applications in medical diagnostic and imaging techniques (Magnetoencephalography, Magnetocardiography) have focused research on cantilever sensors using the resonance enhanced bending-mode magnetoelectric effect. [9][10][11]21,23 In recent papers [36][37][38] we investigated the static and resonant bending mode magnetoelectric effect in multilayer cantilevers of arbitrary layer number and different sequences on a substrate identifying optimized device geometries in a large multidimensional parameter space.…”

Effect of excitation mode on the magnetic field detection limit of magnetoelectric composite cantilevers

“…for free-free modes. Equations (15) and (16) are derived from the results for dQ dH using Eqs. (6) and (8) and additional calculation of dH dz at the cantilever tip x = a for the bound-free and free-free mode cases.…”

“…The derivation of Eqs. (15) and (16) as well as Eqs. (6)-(9) is based on the ME cantilever amplitudes of the resonant ME response , with ρp, ρm, and ρs being the layer specific densities (Table IV).…”

“…[9][10][11][12][13] The results have encouraged investigations to enable the detection of weak low frequency biomagnetic fields with room temperature sensors. 14 This has involved research to increase the effect size of the ME response, e.g., materials, effects of device geometry and operation modes, [15][16][17][18] resonance-enhancement and loss mechanisms, 13 and investigation of noise effects and their behavior including the Johnson-Nyquist noise [19][20][21][22][23] from dielectric losses in piezoelectric materials 24 in ME cantilevers and electronics, noise in magnetostrictive (MS) materials, and thermal vibration noise. 23,[25][26][27][28] Different operation modes investigated for low frequency biomagnetic field sensing 14 include (1) direct detection, where magnetic fields oscillating at the cantilever resonance directly excite magnetostrictivepiezoelectric strain coupling and resonance-enhanced signals; (2) modulation techniques, [29][30][31] where signal fields are detected as sidebands to a carrier as a result of frequency mixing in non-linear functional materials; and (3) the ΔE effect, 32,33 where the field dependence of the elastic modulus in magnetostrictive materials is used.…”