Preparation And Magnetoelectric Properties Of BSZT/NZFO Magnetoelectric Thin Films

The magnetoelectric composite materials possess not only the properties of ferroelectric and ferromagnetic, but also magnetoelectric coupling properties. Therefore,they have been widely used in the field of electronic components, information storage,magnetic sensor etc. Up to date, the widely used magnetoelectric composite films contain lead-based films, which tend to cause environmental pollution and harm to human health, so that the applications of such composite films are strictly limited. In this paper,lead-free ferroelectric films of Ba_xSr_1-xTi₀.9Zr₀.1O₃?BSTZ? and ferromagnet films of Ni_1-xZn_xFe₂O₄?NZFO? were prepared on Pt/Ti/SiO₂/Si substrate by the method of sol-gel. And, lead-free magnetoelectric composite films of NZFO/BSTZ and BSTZ/NZFO were prepared through different deposition sequences. This paper also investigates the microstructure and properties of ferroelectric films, ferromagnetic films and magnetoelectric composite films.Firstly, BSTZ films with different doping contents of Sr and Zr were prepared by Sol-gel method. The results show that the BSTZ film is composed of main phase-BaTiO₃ ?BTO?, when annealed at 700 ? and no impurity phase can be found. In addition, the BSTZ films are dense and free of porosity. The interface between the film and the substrate is smooth and distinct. Actually, the different doping contents of Sr and Zr can infuence the ferroelectric properties of BTO films. Though the ferroelectric properties of BSTZ films decrease with the increasing of the doping contents of Sr, the value of the dielectric constant ??r? increases and the value of the dielectric loss ?tan ??reduces. When the doping amount of Sr is 20%, the BSTZ films exhibit good ferroelectric properties and dielectric properties, relatively.Then, NZFO films with different doping contents of Zn were prepared by Sol-gel method. The results show that when annealed at 650?, NZFO films are composed of main phase-NiFe₂O₄ ?NFO? and have no other impurity-phase. In addition, the surface of NZFO films is dense and smooth. The interface between the film and the substrate is smooth and distinct. The value of the saturation magnetization and coercive field of films are improved with different doping contents of Zn. This shows that the doping of Zn can effectively improve the magnetic properties of the ferromagnet film. When Zn doping amount is 20%, the NZFO films have the best magnetic properties.Finally, the ferroelectric film of BSTZ and ferromagnetic film of NZFO were deposited on Pt/Ti/SiO₂/Si substrates through different deposition sequences by Sol-gel method to prepare two kind of lead-free magnetoelectric composite film. This paper also focuses on the influence of the different deposition sequences on microstructure and magnetoelectric coupling properties of the obtained composite films. The results show that the two kinds of composite films have not only ferroelectric,ferromagnetic,but also obvious magnetoelectric coupling performance. The values of the ferroelectric properties of BSTZ/NZFO films are better than that of NZFO/BSTZ film. The values of the saturation magnetization of NZFO/BSTZ films are better than that of BSTZ/NZFO films. The values of the magnetoelectric coupling coefficient of NZFO/BSTZ films are higher than that of the BSTZ/NZFO films.