Studies On The Converse Magnetoelectric Coupling Eeffect Of Mn/Mg/Zn Doped Ni/CoFe₂O₄-PbTiO₃Composites

A series of x CoFe2O4–(1)5b9i43(x=0.3,0.4,0.5,0.6)， xCo0.6Mg0.2Mn0.2Fe2O4-(1-x)PbTiO3(x=0.4,0.5,0.6,0.7) and xNi0.6Zn0.4Fe1.8Mn0.2O4-(1-x）PbTiO3(x=0.3,0.4,0.5,0.6,0.7) composites that are0-3connectivity of phaseswere prepared by sol-gel method and the magnetic, dielectric and conversemagnetoelectric properties of the composites were investigated by the technology ofX-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating samplemagnetometer (VSM) and Agilent E4991Impedance Analyzer and Magnetoelectriccoupling test system.The characteristic peaks of the PbTiO3and CoFe2O4phases have been observedby XRD.9he8*2reveal that the composites are densifed and homogeneous. Thecomposite that contain high concentration of ferrite disperse in the piezoelectricmatrix. Agilent E4991Impedance Analyzer reveal that permittivity and magneticpermeability increase with increasing frequency. In the magnetic hysteresis loops, thelowest coercivity (Hc) was found in0.6PbTiO3-0.4CoFe2O4composite. Saturationmagnetization (Ms) decreases with the increase of PbTiO3content as expected. CMEcoupling effect was obtained at resonance frequency of13kHz for all the investigatedsamples under an bias magnetic feld-of300,auss and an small ac electric feld of3V/cm. The composite of0.6PbTiO3-0.4CoFe2O4exhibits a maximum CMEcoeffcient.The average grain size of the ferrite phase Co0.6Mg0.2Mn0.2Fe2O4was estimatedfrom the full width at half maximum (FWHM) of the (311) peak by means of theScherrer formula. Grain size increase and then decrease with the increase ofCo0.6Mg0.2Mn0.2Fe2O4content.0.6Co0.6Mg0.2Mn0.2Fe2O4-0.4PbTiO3sample exhibitsthe maximum grain size. It is observed that the magnitude ofCMEincreases withferrite content (except for x=0.6). This is ascribed to the increase of grain size forferrite phase, which affects the resistivity of composites that is favorable to reduce theleakage of piezoelectric charge during electric poling process. Higher CME voltagecoeffcient is obtained in o0.6Mg0.2Mn0.2Fe2O4-(1-x)PbTiO3other than inxCoFe2O4-(1-x)PbTiO3, which is due to doping Mn and Mg into CoFe2O4canenhance2*coeffcients and resistivit of composite. oping Mn and Mg intoCoFe2O4reduced coercivity of Co0.6Mg0.2Mn0.2Fe2O4.The low coercivity means the low magnetic anisotropy which is beneficial to magnetoelectric mechanical couplingbecause the low magnetic anisotropy is in favor of the magnetization in the crystal.The initial permeability of Ni0.6Zn0.4Fe1.8Mn0.2O4decreases with increasingtemperature and then quickly drops to zero at Curie temperature, TC. Compared withxCo0.6Mg0.2Mn0.2Fe2O4-(1-x)PbTiO3(x=0.4,0.5,0.6,0.7) and xCoFe2O4-(1-x)PbTiO3(x=0.3,0.4,0.5,0.6), xNi0.6Zn0.4Fe1.8Mn0.2O4-（1-x）PbTiO3(x=0.3,0.4,0.5,0.6,0.7)have the highest2*voltage coeffcient. ecause3i0.6Zn0.4Fe1.8Mn0.2O4asferromagnetic phase has higher permeability, higher higher magnetic inductionintensity and lower anisotropy.