Browsing by Author "Li, Menghui"

Now showing 1 - 14 of 14
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    Dependence of magnetic field sensitivity of a magnetoelectric laminate sensor pair on separation distance: Effect of mutual inductance
    Li, Menghui; Wang, Yaojin; Gao, Junqi; Gray, David; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2012-02-01)
    The effect of mutual inductance on the performance of a pair of Metglas/Pb(Zr,Ti)O-3 laminate magnetoelectric (ME) sensors has been studied. The effective value of the ME coefficient (alpha(ME)) for the laminates was reduced when the distance between was < 40 mm. Separating the two laminates by distances of > 40 mm, the effect of mutual inductance was small. The laminates exhibited the maximum values of alpha(ME). The ME sensor unit with two laminates connected in parallel had higher magnetic field sensitivities. 2012 American Institute of Physics. [doi:10.1063/1.3684986]
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    Enhanced magnetoelectric effect in self-stressed multi-push-pull mode Metglas/Pb(Zr,Ti)O-3/Metglas laminates
    Li, Menghui; Wang, Yaojin; Gao, Junqi; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2012-07-01)
    Two methods to effectively induce self-stress on Metglas/Pb(Zr,Ti)O-3/Metglas laminate are presented: (i) applying a dc magnetic field to the Metglas layers or (ii) applying a dc electric field to the core piezoelectric composites. An optimum self-stress enhances the magnetoelectric (ME) effect in the laminates. With a 20 Oe dc magnetic bias, the value of alpha(ME) for the self-stressed laminate was enhanced to 31.4 V/cm center dot Oe, which was by a factor of 1.24x compared to the laminate without self-stress. Furthermore, the equivalent magnetic noise floor was reduced by the self-stress at low frequencies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737179]
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    Enhancement in magnetic field sensitivity and reduction in equivalent magnetic noise by magnetoelectric laminate stacks
    Li, Menghui; Gao, Junqi; Wang, Yaojin; Gray, David; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2012-05-15)
    We have investigated the equivalent magnetic noise and magnetic field sensitivity for a magnetoelectric (ME) sensor unit of N numbers of ME laminates stacked together. Our results show with increasing N that the modeled and measured equivalent magnetic noises decreased by a factor of root N and that the magnetic field sensitivities increased by root N. For Metglas/Pb(Mg-1/3,Nb-2/3) O-3-PbTiO3 laminates, the equivalent magnetic noise decreased and the magnetic field sensitivity increased by a factors of 2.1 and 2.3, respectively, for N = 4 relative to that for N = 1. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4718441]
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    Fabrication of reliable, self-biased and nonlinear magnetoelectric composites and their applications
    Li, Menghui (Virginia Tech, 2014-10-31)
    The magnetoelectric (ME) effect, i.e., the induction of magnetization by an applied electric field (E) or a polarization by an applied magnetic field (H), is of great interest to researchers due to its potential applications in magnetic sensors. Moreover, the ME effect in laminate composites is known to be much higher than in single phase and particulate composites due to combination of the magnetostrictive and piezoelectric effects in the individual layers. Given that the highest ME coefficient have been found in Metglas/piezo-fiber laminate composites, this study was designed to investigate and enhance the magnetoelectric (ME) effect in Metglas/piezo-fiber laminate composites, as well as develop their potential for magnetic sensor applications. To initiate this investigation, a theoretical model was derived to analyze the thickness effect of the magnetostrictive, piezoelectric, epoxy and Kapton layers on the ME coefficient. As a result, the importance of the coupling effect by epoxy layers was revealed. I used spin-coating, vacuum bagging, hot pressing, and screen printing techniques to decrease the thickness of the epoxy layer in order to maintain homogeneity, and to obtain good repeatability of the 16 ME laminates fabricated at one time. This protocol resulted in a more efficient way to induce self-stress to Metglas/PZT laminates, which is essential for increasing the ME coefficient. With an enhanced ME effect in the Metglas/piezo-fiber laminates, magnetic field sensitivity could then be increased. An ME sensor unit, which consisted of a Metglas/PMN-PT laminate and a low noise charge amplifier, had a magnetic field sensitivity of 10 pT/Hz0.5 in a well-shielded environment. Stacking four of these ME laminates could further increase the signal-to-noise (SNR) ratio. I studied the optimized distance between a pair of Metglas/PZT ME laminates. A stack of up to four ME sensors was constructed to decrease the equivalent magnetic noise. The magnetic field sensitivity was effectively enhanced compared to a single laminate. Finally, a number of four Metglas/PZT sensor units array was constructed to further increase the sensitivity. ME laminate composites operated in passive mode have typically required an external magnetic bias field in order to maximize the value of the piezomagnetic coefficient, which has many drawbacks. I studied the ME effect in an Ni/Metglas/PZT laminate at zero bias field by utilizing the remnant magnetization between the Ni and Metglas layers. To further enhance this effect, annealed Metglas was bonded on the Metglas/PZT laminate since it is known that hard-soft ferromagnetic bilayers generate built-in magnetic field in these Metglas layers. As a result, giant αME values could be achieved at a zero bias field at low frequency range or at electromechanical resonance (EMR). The sensor unit consisting of self-biased ME laminate arrays is considerably smaller compared to a unit that uses magnet-biased ME laminates. Introducing the converse ME effect and nonlinear ME effect in Metglas/piezo-fiber laminates affords a variety of potential applications. Therefore, I theoretically and experimentally studied converse ME effects in laminates with longitudinally magnetized and longitudinally poled, or (L-L) mode. The optimum structure for producing the maximum effect was obtained for Metglas/PZT laminates. Additionally, the optimum structure and materials for enhancing the nonlinear ME effect in Metglas/PZT laminates are reviewed herein. In particular, this study revealed that modulating the EMR in laminates with high-Q piezo-fibers could enhance the SNR. The stress effect on nonlinear ME effect is also discussed—namely that magnetic field sensitivities can be enhanced by this modulation-demodulation technique.
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    Geometry-induced magnetoelectric effect enhancement and noise floor reduction in Metglas/piezofiber sensors
    Wang, Yaojin; Li, Menghui; Hasanyan, Davresh J.; Gao, Junqi; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2012-08-01)
    The geometry-dependent magnetoelectric (ME) effect was theoretically and experimentally investigated for multi-push-pull mode Metglas/Pb(Zr,Ti)O-3 sandwich-like laminates. Such structures hold promise for passive sensor applications. A geometry-induced significant enhancement in the ME coefficient and an effective reduction in the equivalent magnetic noise was observed due to an increase in the Metglas width fraction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737906]
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    Giant converse magnetoelectric effect in multi-push-pull mode Metglas/Pb(Zr,Ti)O-3/Metglas laminates
    Li, Menghui; Wang, Yaojin; Hasanyan, Davresh J.; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2012-03-01)
    The converse magnetoelectric (CME) effect was investigated theoretically and experimentally for multi-push-pull mode Metglas/Pb(Zr,Ti)O-3/Metglas laminates. The experimental and theoretical values of the CME coefficient (alpha(B)) exhibited similar trends. A large alpha(B) = 6.94 G/V was observed at 1 kHz under a dc magnetic bias of 11 Oe. At an electromechanical resonance frequency of 29.6 kHz, the laminate exhibited a giant value of alpha(B) = 79.5 G/V. These results show significantly enhanced CME effects in multi-push-pull mode laminates, compared to previously reported ones with different structures and materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698114]
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    Giant magnetoelectric effect in self-biased laminates under zero magnetic field
    Li, Menghui; Wang, Zhiguang; Wang, Yaojin; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2013-02-01)
    A giant magnetoelectric (ME) effect in self-biased annealed Metglas/Pb(Zr,Ti)O-3/Metglas laminates under zero magnetic bias is reported. The remanent magnetization was increased by annealing Metglas, which generated an internal bias field. This shifted the M-H hysteresis loops, yielding large values for the ME voltage coefficient of alpha(ME) = 12 V/cm.Oe and 380 V/cm.Oe at 1 kHz and electromechanical resonance under zero magnetic bias, respectively. This self-biased laminate is shown to have a high sensitivity to ac magnetic fields. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794056]
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    Magnetoelectric nonlinearity in magnetoelectric laminate sensors
    Shen, Liangguo; Li, Menghui; Gao, Junqi; Shen, Ying; Li, Jiefang; Viehland, Dwight D.; Zhuang, Xin; Sing, M. Lam Chok; Cordier, Christophe; Saez, Sebastien; Dolabdjian, Christophe (American Institute of Physics, 2011-12-01)
    A nonlinearity in the magnetoelectric coefficient, alpha(Nonlin)(ME), of Metglas/Pb(Zr,Ti)O(3) (PZT) and Metglas/Pb(Mg(1/3),Nb(2/3))O(3)-PbTiO(3) (PMN-PT) laminate sensors has been observed. This nonlinearity was found to be dependent on the dc magnetic bias (H(dc)) and frequency of the ac drive field (H(ac)). The maximum value of alpha(Nonlin)(ME) for both types of composites was found near the electromechanical resonance. For Metglas/PZT laminates, the maximum occurred under a finite bias of H(dc) approximate to 5 Oe; whereas, for Metglas/PMN-PT, the maximum was found near zero dc bias. One application for alpha(Nonlin)(ME) is a cross-modulation scheme that can shift low frequency signals to higher frequency to achieve lower noise floor. For Metglas/PMN-PT, alpha(Nonlin)(ME) has another application: removal of the necessity of a dc bias, which helps to design high-sensitivity sensor arrays and gradiometers. (C) 2011 American Institute of Physics. [doi:10.1063/1.3665130]
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    Modeling of resonant magneto-electric effect in a magnetostrictive and piezoelectric laminate composite structure coupled by a bonding material
    Hasanyan, Davresh J.; Wang, Yaojin; Gao, Junqi; Li, Menghui; Shen, Ying; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2012-09-15)
    The harmonic magneto-electro-elastic vibration of a thin laminated composite was considered. A theoretical model, including shear lag and vibration effects was developed for predicting the magneto-electric (ME) effect in a laminate composite consisting of magnetostrictive and piezoelectric layers. To avoid bending, we assumed that the composite was geometrically symmetric. For finite length symmetrically fabricated laminates, we derived the dynamic strain-stress field and ME coefficients, including shear lag and vibration effects for several boundary conditions. Parametric studies are presented to evaluate the influences of material properties and geometries on the strain distribution and the ME coefficient. Analytical expressions indicate that the shear lag and the vibration frequency strongly influence the strain distribution in the laminates and these effects strongly influence the ME coefficients. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752271]
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    Nonlinear magnetoelectric response of a Metglas/piezofiber laminate to a high-frequency bipolar AC magnetic field
    Wang, Yaojin; Shen, Ying; Gao, Junqi; Li, Menghui; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2013-03-01)
    A nonlinear magnetoelectric (ME) response has been investigated in a Metglas/piezofiber laminate by applying a bipolar AC magnetic field (H-ac) without a DC magnetic bias. The ME voltage (V-ME) was measured for various amplitudes of H-ac of up to 9 Oe over the frequency (f) range 0.1
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    Structural dependence of nonlinear magnetoelectric effect for magnetic field detection by frequency modulation
    Li, Menghui; Wang, Yaojin; Shen, Ying; Gao, Junqi; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2013-10-14)
    The structure differences of magnetoelectric (ME) laminates for passive and active mode sensors are discussed. The Fourier coefficient A(1) calculated from the data of alpha(ME)-H-dc indicates that N = 1 (where N is the number of Metglas layers) should be the optimum structure for the active mode. Experimental investigations of the magnetic field sensitivity agree well with this conjecture. For N = 1, the magnetic field sensitivity was 0.66 nT/Hz(0.5), which was 3.1 times larger than for N = 5. (C) 2013 AIP Publishing LLC.
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    Theoretical and experimental investigation of magnetoelectric effect for bending-tension coupled modes in magnetostrictive-piezoelectric layered composites
    Hasanyan, Davresh J.; Gao, Junqi; Wang, Yaojin; Viswan, Ravindranath; Li, Menghui; Shen, Ying; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2012-07-01)
    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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4732130]
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    Theoretical model for geometry-dependent magnetoelectric effect in magnetostrictive/piezoelectric composites
    Wang, Yaojin; Hasanyan, Davresh J.; Li, Menghui; Gao, Junqi; Li, Jiefang; Viehland, Dwight D.; Luo, Haosu (American Institute of Physics, 2012-06-15)
    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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729832]
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    Ultralow equivalent magnetic noise in a magnetoelectric Metglas/Mn-doped Pb(Mg1/3Nb2/3)O-3-PbTiO3 heterostructure
    Wang, Yaojin; Gao, Junqi; Li, Menghui; Hasanyan, Davresh J.; Shen, Ying; Li, Jiefang; Viehland, Dwight D.; Luo, Haosu (AIP Publishing, 2012-07-01)
    An ultralow equivalent magnetic noise of 6.2 pT/root 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)O-3-29PbTiO(3) (PMN-PT) single crystal. Furthermore, the equivalent magnetic noise was <= 1 pT/root 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 x 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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733963]