Layered Magnetoelectric Composite Magnetic Capacitance Effects

Magnetocapacitance(MC) is a property of some materials that exhibit a change in the value of their capacitance or permittivity when an external magnetic field is applied to them.It has important application values in magnetic detection, intelligent filter, storage devices and etc.But the single single phase material has not gained the actural application bacause its magneto-capacitance usually needs low temperature. As a result,the research of room-temperature MC effects in laminate composites has attracted much more interest, Which is not only because the material features simple structure,easy preparation,but also because it has no dilution nor mix between its piezoelectric phase and magnetostrictive phase.It can gain ideal MC effects,thus,this kind of material has been widely used.The present work is focused on the giant room temperature magneto-capacitance effect in laminate of Terfenol-D (TDF)/Pb(Zr,Ti)O3 (PZT) composites. Such magneto-capacitance relates to the magnetic-elastic coupling of interfaces. The maximum negative magneto-capacitance is as large as 65% and 85% at the resonant frequencies of 46.15 kHz and160.00 kHz, respectively, under the bias magnetic field of 1600 Oe.A negative magneto-capacitance of 5% has been observed at sub-resonant frequencies under the same magnetic field。It is also shown that the resonance frequency shifts with increasing applied magnetic field. To investigate the influence of H on the resonant frequencies and capacitance, elasticity theory model is applied, based on piezoelectric and magnetostrictive constitutive equations. The calculation showed that the resonant frequencies change predicted by the model is consistent with experimental results,suggesting that the resonant frequencies change of the layered composite of magnetostriction/piezoelectric originates from the magnetic field-controlled compliances of the magnetostrictive phase.