The Study Of Output Signal In A Magnetoelectric Unimorph

Magnetoelectric(ME) laminate material has recently became an extremely hot and competitive field in physics and materials science because it contains a wealth of physical phenomena. Its unique characteristics and prospects of multi-functional electronic devices application have drawn considerable interests from scientists. As more and more research on this materials being done, its applications potential, like high sensitivity magnetic field sensors, transducers, filters, resonators, commutations,and information storage devices, is gradually being discovered. High-performance electronic devices made of this material has many advantages compared to other materials. Thus, research about novel physical characteristics of ME laminate composites will have some practical significance. This article is mainly about some special output signal of ME laminate composites and its relationship with external magnetic field conditions. Specific research work and conclusions as follows;(1) Based on a ME measurement system, we investigated output signal of metglas/PZT L-T ME unimorph under different direct current (DC) magnetic field.The amplitude of Output signal increases at first and then decreases with the increase of DC magnetic field, which is consistent with the magnetostrictive material-metglas’permeabiiity trends. The result on the frequency of the output signal obtained is:the output frequency is two times of the input when the amplitude of alternative current (AC) magnetic field is not high; with the increase of DC magnetic field, the output signal waveform changes, and its frequency gradually shifted to the input frequency. The fast Fourier transform of output signal shows that the output of the ME unimorph consists of a series of harmonic signals, and amplitude of these harmonics change when the external DC magnetic field increases.(2) when the AC magnetic field amplitude increases, in the case of no DC field, four different output multiplying relationship were found in the samples with different dimension. Then we investigated the relationship between output signal and AC magnetic field amplitude in a chosen sample. Fast Fourier transform shows that the amplitude of harmonic signals increase with increasing AC magnetic field amplitude, and so the number of harmonics.(3) A series of output frequency multiplying phenomenon were observed in a ME laminate sample, as the amplitude of the AC field was increased up to34.3Oe. These multiplying signal are all around a same frequency, which is consisting with the mechanical resonance frequency fr.And fr was obtained from the impedance and phase angle of sample. The multiplying output phenomenon is only odd times of the input frequency when there is only AC field input. With the superimposition of DC field, odd and even-order multiplying output are both observed. Fast Fourier transform of output signal shows; as AC field inputs, output of ME unimorph contain only odd harmonics of input; when there is DC field applied,both odd and even harmonics of input present in output signal.(4) ME coefficient curves were obtained from the measurement result as sample were exposed to high-amplitude AC magnetic field. With different measurement condition, four ME coefficient curve all demonstrate a phenomenon that there are more than one mechanic resonance peak in four curves. Positions of these peaks Coincide with places we observed frequency multiply phenomenons before, all of these peaks’frequency are all around1/n of fr.(5) By analyzing the multiplying output behavior and multi-peaks phenomenon in ME coefficient above,we get following conclusions; under high-amplitude AC magnetic field, magnetostrictive layer in L-T ME unimorph presents AC magnetostriction, its AC magnetostrictive signal and nonlinear harmonics result in the the electromechanical resonance of sample. Magnetostrictive signal or harmonics with frequency around the fr, caused the resonance of sample. Electromechanical resonance make these signal occupy the entire output of sample. It also make the ME coefficient increase as input frequency is around1/n of fr, and there are also peaks presented in ME coefficient curves Correspondingly.