Author name used in this publication: Siu Wing OrAuthor name used in this publication: Helen Lai Wa Chan2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Chan, HLW

Luo, H

Or, DSW

Wang, Y

Zhao, X

Applied Physics Letters

Author name used in this publication: Siu Wing OrAuthor name used in this publication: Helen Lai Wa Chan2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedVoR allowe

PolyU Institutional Repository

Magnetoelectric effect from mechanically mediated torsional magneticforce effect in NdFeB magnets and shear piezoelectric effectin 0.7Pb„Mg1/3Nb2/3…O3–0.3PbTiO3 single crystalYaojin Wang,1,2,3,a Siu Wing Or,2 Helen Lai Wa Chan,2 Xiangyong Zhao,1 andHaosu Luo11State Key Laboratory of High Performance Ceramics and Superfine Microstructure,Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading,Shanghai 201800, People’s Republic of China2Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, HongKong, People’s Republic of China3Graduate School of the Chinese Academy of Sciences, Beijing 10039, People’s Republic of ChinaReceived 16 January 2008; accepted 28 February 2008; published online 27 March 2008We experimentally and theoretically report the magnetoelectric effect in a composite made bysandwiching one shear mode 0.7PbMg1/3Nb2/3O3–0.3PbTiO3 PMN-PT piezoelectric single crystalplate between two longitudinally magnetized NdFeB permanent magnet bars along the lengthdirection of the PMN-PT plate. The magnetoelectric effect originates from the mechanicallymediated product effect of the torsional magnetic force effect in the NdFeB bars and the shearpiezoelectric effect in the PMN-PT plate. The composite exhibits a magnetoelectric voltagecoefficient of 32.7 mV /cm Oe with a flat frequency response in the measured range of0.1–30 kHz. The induced magnetoelectric voltage shows a good linear relationship to the applied acmagnetic field with amplitude varying from 10−7 to 10−3 T. Other distinct features include no needto have a magnetostrictive phase, low Joule heating loss, and high scale-down capability. Thesesuggest promising applications of the torsional-shear mode composite in power-free magnetic fieldsensors. © 2008 American Institute of Physics. DOI: 10.1063/1.2901162The magnetoelectric ME effect is a polarization re-sponse to an applied magnetic field H or conversely a spinresponse to an applied electric field E.1 This effect hasdrawn increasing attention in advanced materials researchowing to its potential uses in power-free magnetic field sen-sors, current sensors, and ME transducers. In the past de-cades, considerable research efforts have been placed on theME effect, first in single-phase materials, then in two-phasebulk composites, and lately, in two-/three-phase laminatedcomposites.2–9 Due to the existence of a strong product effectof the magnetoelastic and elastoelectric effects, laminatedcomposites of Tb0.3Dy0.7Fe1.92 Terfenol-D magnetostrictivealloy and PbMg1/3Nb2/3O3–PbTiO3 PMN-PT piezoelectricsingle crystal have been the focus of investigations.4 More-over, various ME operating modes have been studied, includ-ing longitudinal-longitudinal L-L, longitudinal-transverseL-T, transverse-longitudinal T-L, transverse-transverseT-T, ring-type, push-pull, and bending modes.4,7–10 To date,no reports have been made on composites utilizing the shearmode of PMN-PT single crystal even though the shear piezo-electric properties of PMN-PT single crystal are much higherthan the transverse-extensional and longitudinal-extensionalpiezoelectric properties, as shown in Table I.In this letter, we demonstrate a torsional-shear modecomposite consisting of a shear mode PMN-PT piezoelectricsingle crystal plate sandwiched between two longitudinallymagnetized NdFeB permanent magnet bars along the lengthdirection of the PMN-PT plate. Figure 1 illustrates the geom-etry and working principle of the proposed composite. Theshear mode PMN-PT piezoelectric single crystal plate, ofdimensions 14 mm long, 7 mm wide, and 1 mm thick, andwith their 111 and 110 crystallographic axes oriented inits length and thickness directions, respectively, were grownin-house using a modified Bridgman technique.13 After beingelectroded with silver and polarized along the length direc-tion in a silicone oil bath, the silver electrodes were removedfrom the PMN-PT samples. The de-electroded samples werethen re-electroded along the thickness direction by sputteringgold near room temperature to avoid the occurrence of de-polarization. The shear piezoelectric voltage coefficientg15=d15 /11T  was determined to be 60.510−3 V m /N byan Agilent 4294A impedance analyzer according to the IEEEresonance method.14 The two longitudinally magnetized Nd-FeB permanent magnet bars were commercially suppliedwith the same dimensions, length of 7 mm, width of 2 mm,and thickness of 2 mm. They were galvanized using nickeland their saturation magnetization Ms was know to be1870 kA /m.The working principle of the proposed torsional-shearmode ME composite is as follows Fig. 1. Under an appliedac magnetic field H3 along the length direction of the com-posite, a torsional ac magnetic force F3 will be inducedabout the geometric central axis of the NdFeB bars. This F3will drive the sandwiched PMN-PT plate into shear modevibrations, thus, producing a shear piezoelectric voltage V3or charges based on the shear piezoelectric effect. In fact,there are two distinct differences between the proposed tor-sional magnetic force-induced shear piezoelectric effect inour ME composite and the magnetostrictive strain-inducedtransverse-extensional or longitudinal-extensional piezoelec-tric effect in the previously reported ME laminatedaAuthor to whom correspondence should be addressed. Electronic mail:wangyaojin@hotmail.com.APPLIED PHYSICS LETTERS 92, 123510 20080003-6951/2008/9212/123510/3/$23.00 © 2008 American Institute of Physics92, 123510-1Downloaded 28 Sep 2008 to 158.132.12.80. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jspcomposites.4,7–10 First, our composite does not require amagnetostrictive phase, thereby minimizing the effect ofJoule heating loss. Second, our composite utilizes the ultra-high shear piezoelectric properties of PMN-PT single crystalin contrast to the transverse-extensional or longitudinal-extensional piezoelectric properties Table I. This meansthat the configuration of ME devices based on the currentcomposite is generally simpler and amenable to the miniatur-ization.Based on the charge model for analyzing solid rectangu-lar bar magnets with uniform axial magnetization,15 the mag-nitude of torsional magnetic force exerted by each magnetF3 isF3 = 0MsAmH3 cos  , 1where 0=410−7 H /m is the magnetic permeability offree space, Ms is the saturation magnetization of the magnetbars, Am is the cross-sectional area of the magnet bars, H3 isthe externally applied ac magnetic field, and  is the resultingtorsional angle, as shown in Fig. 1. In our design, the piezo-electric plate is excited in shear mode vibrations so that thefollowing shear piezoelectric constitutive equations for theplate are adopted:16S5 = s55D T5 + g15D1, 2aE1 = − g15T5 + 11T D1, 2bwhere T5 and S5 are the shear stress and strain, respectively;E1 and D1 are the electric field strength and electric displace-ment along the width direction, respectively; s55D is the elasticcompliance coefficient at constant electric displacement; g15is the shear piezoelectric voltage coefficient; and 11T is thedielectric impermittivity at constant stress. The shear stressin the piezoelectric plate T5 due to the transfer of F3 fromthe two magnet bars can be expressed asT5 =2F3tplp, 3where tp and lp are the thickness and length of the piezoelec-tric plate, respectively. By placing F3 from Eq. 1 and T5from Eq. 3 into Eqs. 2a and 2b, respectively, and con-sidering the strain is extremely small, the ME voltage effi-cient E of the composite can be obtained asE = − 20MsAmg15tplp. 4From Eq. 4, it is clear that E of the composite depends ong15 of the piezoelectric plate, Ms of the magnets, and thegeometric parameters of the composite. Substituting the cor-responding material and geometric parameters of PMN-PTand NdFeB into Eq. 4, E of the proposed composite ispredicted to be 38.2 mV /cm Oe.Figure 2 shows the induced ME voltage V3 over anapplied magnetic field H3 range of 10−7–10−3 T at a drivefrequency of 1 kHz. It is clear that V3 has an excellentlinear response to H3 in the whole range. A higher detectionsensitivity of 10−9–10−11 T could be obtained if shieldingof magnetic noise could be adopted and composite fabrica-tion could be improved. From the slope of the plot, theME voltage coefficient E at 1 kHz is determined to be32.7 mV /cm Oe. This experimental E coincides reasonablywell with the predicted E of 38.2 mV /cm Oe based on Eq.4. Nevertheless, the obtained E is higher than most of theTABLE I. Material parameters of 0.7PbMg1/3Nb2/3O3–0.3PbTiO3 PMN-PT single crystal measured at variousvibration modes.Piezoelectricstrain coefficientd, 10−12 C /NPiezoelectricvoltage coefficientg, 10−3 V m /NElectromechanicalcoupling coefficientk, %Transverse-extentional mode 31a −2517 40.4 95.4Longtudinal-extentional mode 33b 2000 38.8 86.4Shear mode 15c 5980 60.5 97aCited from Ref. 11.bCited from Ref. 12.cMeasured properties.FIG. 1. Color online Schematic diagram and working principle of theproposed torsional-shear mode ME composite. The arrow P denotes thepolarization direction in the PMN-PT plate.FIG. 2. Induced ME voltage V3 over an applied magnetic field H3 rangeof 10−7–10−3 T at a drive frequency of 1 kHz.123510-2 Wang et al. Appl. Phys. Lett. 92, 123510 2008Downloaded 28 Sep 2008 to 158.132.12.80. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jspconventional magnetostrictive-piezoelectric ME compositesoperating at zero bias or dc magnetic field.4,5,7–10Figure 3 shows the waveforms of applied magnetic fieldH3 magnitude of 1 Oe peak and induced ME voltage V3at a frequency of 1 kHz. Stable signal conversion betweenthe applied H3 1 Oe peak and induced V3 3.27 mV peakis evident. Besides, H3 and V3 are of opposite phase, whichagrees with the prediction provided by Eq. 4.Figure 4 shows the ME voltage coefficient E in thefrequency f range of 0.1–30 kHz at a constant magneticfield amplitude of H3=1 Oe. It is obvious that E has anexcellent flat response in measured f range. As a comparison,reluctance coils fall short in providing valid detection at lowfrequencies because of the low rate of change of magneticfluxes.9 Due to the electrical insulation of the magnet bars,the possible eddy-current-induced thermal losses in the mag-net bars are negligible even the composite is exposed to ahigh drive frequency of 30 kHz. Consequently, the currentcomposite can stably work under a wide range of frequency.In summary, we have developed a torsional-shear modecomposite by sandwiching a shear mode PMN-PT plate be-tween two longitudinally magnetized NdFeB bars along thelength direction of the PMN-PT plate. The experimental andtheoretical results have demonstrated the existence of a largeE in excess of 32 mV /cm Oe in the composite. A goodlinear relationship between H3 and V3 in the H3 range of10−7–10−3 T has been observed, besides a flat frequency re-sponse from 0.1 to 30 kHz. The composite does not require amagnetostrictive phase and has low Joule heating loss andhigh scale-down capability, making it a promising ME mate-rial for realizing power-free magnetic field sensors.This work was supported by the Research Grants Coun-cil of the HKSAR Government PolyU 5255/03E and PolyU5122/05E, the Niche Areas Project of The Hong Kong Poly-technic University 1-BB95, the 863 High Technology andDevelopment Project of the People’s Republic of China2006AA03Z107, the Natural Science Foundation of China50432030, 50777065, and 50602047, the Scientific Innova-tion Program of Chinese Academy of Sciences KGCX2-YW-111-7, Shanghai Municipal Government 06DZ05016,and Innovation Funds from Shanghai Institute of Ceramicsof Chinese Academy of Sciences SCX0608.1L. D. Landau and E. Lifshitz, Electrodynamics of Continuous MediaPergamon, Oxford, 1960, p. 119.2V. J. Folen, G. T. Rado, and E. W. Stalder, Phys. Rev. Lett. 6, 607 1961.3J. Ryu, A. V. Carazo, K. Uchino, and H. Kim, J. Electroceram. 7, 242001.4S. X. Dong, J. F. Li, and D. Viehland, Appl. Phys. Lett. 83, 2265 2003.5S. W. Or, T. L. Li, and H. L. W. Chan, J. Appl. Phys. 97, 10M308 2005.6Y. M. Jia, S. W. Or, J. Wang, H. L. W. Chan, X. Y. Zhao, and H. S. Luo,J. Appl. Phys. 101, 104103 2007.7S. X. Dong, J. F. Li, and D. Viehland, Appl. Phys. Lett. 89, 2529042006.8S. X. Dong, J. Y. Zhai, F. M. Bai, J. F. Li, and D. Viehland, Appl. Phys.Lett. 87, 062502 2005.9S. X. Dong, J. F. Li, and D. Viehland, J. Appl. Phys. 96, 3382 2004.10Z. P. Xing, S. X. Dong, J. Y. Zhai, L. Yan, J. F. Li, and D. Viehland, Appl.Phys. Lett. 89, 112911 2006.11J. Peng, H. S. Luo, D. Li, H. Q. Xu, T. H. He, and W. Q. Jin, Appl. Phys.Lett. 85, 6221 2004.12H. S. Luo, G. S. Xu, H. Q. Xu, P. C. Wang, and Z. W. Yin, Jpn. J. Appl.Phys., Part 1 39, 5581 2000.13H. S. Luo, G. S. Xu, H. Q. Xu, P. C. Wang, and Z. W. Yin, Jpn. J. Appl.Phys., Part 1 39, 5581 2000.14IEEE Standard on Piezoelectricity, ANS/IEEE Std 176-1978 IEEE, NewYork, 1978.15E. P. Furlani, Permanent Magnet and Electromechanical Device: Materi-als, Analysis, and Applications Academic, San Diego, 2001.16T. Ikeda, Fundamentals of Piezoelectric Oxford University Press, Oxford,1990.FIG. 3. Color online Waveforms of applied magnetic field H3 magni-tude of 1 Oe peak and induced ME voltage V3 at a frequency of 1 kHz.FIG. 4. ME voltage coefficient E in the frequency f range of0.1–30 kHz at a constant magnetic field amplitude of H3=1 Oe.123510-3 Wang et al. Appl. Phys. Lett. 92, 123510 2008Downloaded 28 Sep 2008 to 158.132.12.80. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jsp

Magnetoelectric effect from mechanically mediated torsional magnetic force effect in NdFeB magnets and shear piezoelectric effect in 0.7Pb(Mg[sub ⅓]Nb[sub ⅔])O₃-0.3PbTiO₃ single crystal

Magnetoelectric effect from mechanically mediated torsional magnetic force effect in NdFeB magnets and shear piezoelectric effect in 0.7Pb(Mg[sub ⅓]Nb[sub ⅔])O₃-0.3PbTiO₃ single crystal

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