Preparation And Properties Of YIG Film And BaTiO 3 -YIG Magnetoelectric Composite Film

Yttrium iron garnet(YIG)Y3Fe5O12 is a ferrimagnetic material which has a wide application above room temperature.YIG films has been applied not only in modern electronic industry and information industry in microwave devices like resonators,isolators and circulators,but also in the reciprocal waveguide devices,integrated optics and optical memory areas due to its narrow ferromagnetic resonance(FMR)line width,high resistivity,lower loss at high frequency and better gyromagnetic effect.The performance of the devices is determined by the quality of the ferrite films.Therefore,it has vital significance to research how to prepare high quality of YIG films.In this thesis,the YIG ferromagnet films and BaTiO3ferroelectric films were prepared on Nb-SrTiO3 substrates by a RF-magnetron sputtering.Two kinds of 2-2 type magnetoelectric composite films with different deposition sequence of YB and BY were also prepared.The effect of puttering parameters on the phase,microstructure,ferromagnetics,ferroelectrics and magnetoelectrics were studied.The main research about several aspects are:1.The parameters to affect the quality and property of YIG films are sputtering power,substrate temperature,oxygen/argon ratio and sputtering pressure.The optimal conditions for YIG films have been obtained through a series of experiments:sputtering power of 150 W-180 W,substrate temperature of 500 ?,oxygen argon proportion of 0:10,sputtering pressure of 1 Pa and annealing treatment of 750 ?.2.O2/Ar ratio of 0:10 is the best condition to form the stoichiometric YIG film,with the saturation magnetization(Ms)of 139.3 emu/cm3.3.The optimal conditions of prepared BaTiO3 films by RF-magnetron sputtering were:substrate temperature of 400 ?,oxygen argon proportion of 5:1,annealing temperature of 650 ?.The film presents a typical ferroelectric behavior with a remanent polarization of 5.74 ?C/cm2 and coercive field of 238 kV/cm.4.XRD shows that both BY and YB films can be indexed to BaTiO3 phase and YIG phase without any additional or intermediate phases in addition to the substrate diffraction peak.YIG ferromagnetic layer in YB structure exhibits weak(400)orientation.5.The BY composite film exhibits higher saturation and remanent polarizations than the YB film.In compares with the pure BaTiO3 film,the composite film has lower polarization and higher leakage current density.YB type composite film has higher saturation magnetization than YB type,because YIG ferromagnetic layer in YB structure exhibits weak(400)orientation.6.With the increase in applied magnetic field,the dielectric constant and loss of YB magnetoelectric composite film are decrease and the loss peaks shift toward low frequency.