Since the turn of the millennium, multi-phase magnetoelectric (ME) composites have been subject to attention and development, and giant ME effects have been found in laminate composites of piezoelectric and magnetostrictive layers. From an application perspective, the practical usefulness of a magnetic sensor is determined not only by the output signal of the sensor in response to an incident magnetic field, but also by the equivalent magnetic noise generated in the absence of such an incident field. Here, a short review of developments in equivalent magnetic noise reduction for ME sensors is presented. This review focuses on internal noise, the analysis of the noise contributions and a summary of noise reduction strategies. Furthermore, external vibration noise is also discussed. The review concludes with an outlook on future possibilities and scientific challenges in the field of ME magnetic sensors.

Articles you may be interested inThe effects of interface misfit strain and surface tension on magnetoelectric effects in layered magnetostrictivepiezoelectric composites J. Appl. Phys. 114, 044109 (2013) In this paper, we discuss a theoretical model with experimental verification for the resonance enhancement of magnetoelectric (ME) interactions at frequencies corresponding to bending-tension oscillations. A dynamic theory of arbitrary laminated magneto-elasto-electric bars was constructed. The model included bending and longitudinal vibration effects for predicting ME coefficients in laminate bar composite structures consisting of magnetostrictive, piezoelectric, and pure elastic layers. The thickness dependence of stress, strain, and magnetic and electric fields within a sample are taken into account, as such the bending deformations should be considered in an applied magnetic or electric field. The frequency dependence of the ME voltage coefficients has obtained by solving electrostatic, magnetostatic, and elastodynamic equations. We consider boundary conditions corresponding to free vibrations at both ends. As a demonstration, our theory for multilayer ME composites was then applied to ferromagnetic-ferroelectric bilayers, specifically Metglas-PZT ones. A theoretical model is presented for static (low-frequency) ME effects in such bilayers. We also performed experiments for these Metglas-PZT bilayers and analyzed the influence of Metglas geometry (length and thickness) and Metglas/PZT volume fraction on the ME coefficient. The frequency dependence of the ME coefficient is also presented for different geometries (length, thickness) of Metglas. The theory shows good agreement with experimental data, even near the resonance frequency. V C 2012 American Institute of Physics.[http://dx

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We study pull-in instabilities in a functionally graded microelectromechanical system (MEMS) due to the heat produced by the electric current. Material properties of two-phase MEMS are assumed to vary continuously in the thickness direction. It is shown that the pull-in voltage strongly depends upon the variation through the thickness of the volume fractions of the two constituents. It is probably the first work to consider Joule's heating, dependence of the electric conductivity upon the temperature, and the gradation of material properties in studying the pull-in instability in micro-thermoelectro-mechanical plates.

A theoretical model is presented for magnetoelectric (ME) effects in multi-push–pull mode magnetostrictive/piezo-fibre laminate composites. Analytical solutions for the ME coefficient (α ME) were derived. The effects of thickness ratio of the magnetostrictive phase, Kapton and multiple layers of epoxy on the value of α ME were discussed. Experimental results agreed well with the theoretical analysis. When the thickness ratio of the magnetostrictive phase was v = 0.63, α ME was found to have a maximum value of 25.6 V cm−1 Oe−1. For thinner Kapton and epoxy layers, the values of α ME became higher. This model presents theoretical guidelines by which one can achieve higher values of α ME.

An ultralow equivalent magnetic noise of 6.2 pT/√Hz at 1 Hz was obtained in a bimorph heterostructure sensor unit consisting of longitudinal-magnetized Metglas layers and a transverse-poled 1 mol. % Mn-doped Pb(Mg1/3Nb2/3)O3-29PbTiO3 (PMN-PT) single crystal. Furthermore, the equivalent magnetic noise was ≤1 pT/√Hz at 10 Hz. Compared with previously reported multi-push-pull configuration Metglas/PMN-PT sensor units, the current heterostructure exhibits a higher magnetoelectric coefficient of 61.5 V/(cm × Oe), a similar equivalent magnetic noise at 1 Hz and a lower noise floor at several hertz range. The ultralow equivalent magnetic noise in this sensor unit is due to the low tangent loss and ultrahigh piezoelectric properties of Mn-doped PMN-PT single crystals.

The equations of magnetoelasticity of magnetoelastic plates remain three dimensional even after adopting the Kirchhoff hypothesis. In the present work, two-dimensional equations of magnetoelasticity are obtained for a magnetoelastic ferromagnetic plate of finite size. In the general case the components of the induced magnetic field inside and outside the plate and the amplitudes of lateral vibrations are connected through both the equations of motion and the boundary conditions. This connection essentially complicates the problem of lateral vibrations of magnetoelastic plates of finite size. Assuming that the magnetic susceptibility is very large compared with unity, the solution of the magnetostatics problem in the interior and exterior domains is constructed through asymptotic series with respect to the reciprocal of the magnetic susceptibility. As a result, a system of separated problems with corresponding boundary conditions is obtained, connected by recurrent relations. This allows us to obtain an analytical representation for the components of the excited magnetic field in the case of a very thin plate. The problem of determining the lateral vibrations of magnetosoft ferromagnetic plates of finite size in a magnetic field reduces to a twodimensional singular integrodifferential equation. Using the Galerkin method, the determination of the frequencies reduces to an infinite system of algebraic equations with a normal-type determinant.

Articles you may be interested inMagnetoelectric coupling in sol-gel synthesized dilute magnetostrictive-piezoelectric composite thin films J. Appl. Phys. 110, 036101 (2011) A quasistatic theoretical model including geometry effect is presented for predicting the magnetoelectric (ME) coefficients in a ME multilayer composite consisting of magnetostrictive and piezoelectric layers. The model is developed based on average-field method considering the geometry effect. The model characterizes the ME coefficient in terms of not only the parameters of two composite components and the thickness fraction but also the length and width fractions for the piezoelectric or magnetostrictive components. Analytical predictions indicate that the width and length fractions strongly influence the maximum ME coefficient and the corresponding thickness fraction also. Clearly, geometry effects cannot be ignored in predicting ME coefficient. Theoretical ME coefficients are also compared to experimental test data, demonstrating excellent agreement. V C 2012 American Institute of Physics.[http://dx