Preparation And Magnetoelectric Properties Of BNTO/LSMO Magnetoelectric Thin Films

Magnetoelectric composites exhibit ferromagnetic properties,ferroelectric properties as well as magnetoelectric coulping effect,which can achieve the mutual conversion between magnetic signal and electric signal.They possess potential application in logic memories,filters,magnetoelectric transducers.Nevertheless,the pollution to environment and harm to human's body limites their application.Thus,it is necessary to develop lead-free magnetoelectric composite films.Neodymium(Nd)doped Bi_4-xNd_xTi₃O₁₂(BNTO)ferroelectric film and strontium(Sr)doped La_1-ySr_yMn O₃(LSMO)ferromagnetic film were deposited on the Pt/Ti/Si O₂/Si substrate via the spin-coating method,respectively.Then,two composite films with the structurs of BNTO/LSMO/substrate(BL)and LSMO/BNTO/substrate(LB)were deposited on the Pt/Ti/Si O₂/Si.The phase compositions,morphology and materials properties of ferroelectric films,ferromagnetic films and magnetoelectric composite films are also investigated.The main results are as follows:Firstly,the films of Bi₄Ti₃O₁₂(BIT)are composed of main phase,Bi₄Ti₃O₁₂without impurity phases when annealed at 700°C.The films of BIT and BNTO possess uniform microstructure without pores or cracks.And the interface between the film and the substrate is distinct.The doping of Nd to the film of BIT is beneficial to improving the ferroelectric properties,the residual polarization and dielectric propertiues.The films of BNTO exhibit the best ferroelectric properties and dielectric properties when the doping content of Nd is 0.45,the value of P_r of the BNTO film is 16.86?c/cm².Secondly,the films of LMO are composed of main phase,LaMnO₃,without impurity phases when annealed at 680°C.The films of LMO and LSMO also possess uniform microstructure without pores or cracks.The doping of Sr to LMO film helps to improve the ferromagnetic properties and to enhance residual magnetization and saturation magnetization.The film of LSMO exhibits the best ferromagnetic properties when the doping content of Sr reaches 0.3,the Ms of the LSMO film is 56.14 emu/cm³.Thirdly,there is no obvious change of the phase compositions and morphology of the magnetoelectric composite films for the two composite films.Ferroelectric effect and ferromagnetic effect,as well as magnetoelectric coupling effect can be observed in both LB and BL magnetoelectric composite films.The ferroelectric properties and ferromagnetic properties of two magnetoelectric composite films is inferior to single phase film of LSMO or BNTO.The coefficients of magnetoelectric coupling of LB composite films are greater than those of BL composite films,the value of?_Eof LB composite film is 67.75 m V/(cm·Oe).