Reserch On Dual-peak Magnetoelectric Effect In Magnetoelectric Laminate And Applications In Microwave Devices

Abstract:Recently, the magnetoelectric (ME) laminated composite composed of giant magnetostrictive material Terfenol-D and piezoelectric material PZT has become a research hotspot due to its strong ME coupling effect. At low frequency, when the laminated composite is under resonance drive, its ME coupling effect will be greatly enhanced. For the nonlinear magnetic-mechanical-electric coupling effect, a novel dual-peak phenomenon of ME effect in the laminate is reported, but yet there is no perfect theoretical model can explain it. In addition, magnetic loss, dielectric loss, the mechanical loss, etc. existing in resonance ME coupling process greatly reduce the strength of ME coupling, especially the mechanical loss of the laminate. At microwave frequency, the applications of laminate mainly focus on the production of ME tunable microwave devices.To solve the above problems, this paper carries out the following tasks:First, for the experimental phenomenon of the mechanical loss of the L-T mode Terfenol-D/PZT/Terfenol-D ME laminate at resonant state nonlinearly varies with the magnetic field, we adopted the magnetostrictive constitutive relations, which can completely describe characteristics of the complex magnetic-mechanical coupling in giant magnetostrictive material, then established a nonlinear mechanical loss model taken full consideration of the static magnetic field and pre-stress. The proposed model effectively predicts the resonance frequency fr and anti-resonance frequency fa, and tanδm of the composite dependencies of magnetic bias, which fit well with the experimental results quantitatively and qualitatively. Through the model we can find that tanδm can be effectively reduced by choosing the bias magnetic field below the critical resonance magnetic field when f<f0f (f0f is the resonance frequency at H=0), i.e. tanδm reduces62.1%at fr=98.9kHz. While if fr>f0r, tanδm also can be effectively reduced through applying compressive stress, i.e. tanδm reduces51.2%at fr=103kHz under prestress σ=-18MPa.Secondly, for the experiment phenomenon of dual-peak ME effect at resonant state in L-T mode ME laminate, on the basis of the established magnetic-mechanical-electric equivalent circuit under resonance drive, according to Ohm’s law, a specific expression of ME coefficient considering the pre-stress, staticmagnetic field, frequency of AC magnetic field and nonlinear mechanical loss hasbeen given. The theoretical model predicts the curves of ME coefficient vs staticmagnetic field under different resonance frequencies and the curves of MEcoefficient vs resonance frequency under different static magnetic fields. We find theprediction results at the resonance frequency of100~125kHz both quantitatively andqualitatively fit well with the experimental results, which proves the validity andreliability of the theoretical model. Then we further predict the impact of pre-stresson ME dual-peak effect, and find that: with the increase of pre-stress, the first peakcontrolled by piezomagnetic coefficient will meet the second peak controlled byYoung’s modulus at some magnetic field, dual-peak ME effect disappears, the entiregroup curves of ME coefficient show "flip" phenomenon. In particular, applying thecompressive/tensile stress can increase the first peak, in which the effect of tensilestress is more significant.Finally, according to the outstanding advantages of ME laminated materialapplying at microwave frequencies, we designed a ME dual-tunable band-pass filterbased on YIG/PZT ME laminated material, and used Ansoft HFSS electromagneticsimulation software to establish a numerical model. Simulation results show that iftaking microwave signal band3GHz for example, the magnetic adjustable offsetband rejections of the filter at the operating frequency2.9-4.2GHz reach a maximumof-20dB. When set the magnetic field of100Oe, the electric field tunability isapproximately linear when the electric field ranges in-10kV/cm~10kV/cm.