Preparation And Performance Study Of Composite Multiferroic Thin Film

Multiferroic materials are receiving particular attention due to the additional functionality results from the interaction of ferroelectrics and magnetics.Various lead-free magnetoelectric(ME)material with notable magnetoelectric coupling effect has been applied in environmental friendly multifunctional devices.When a magnetic field applied on a ME compound material,the sharp magnetostriction of the ferromagnetic phase would change,so as to the strain of the material will transmit to the piezoelectric phase,which lead to the generation of electric polarization.The ME effect was observed in the ME compound material above room temperature previously.In recent years,lots of jobs have been done on various ME compound material system,among them multiferroic thin film materials offers a huge potential application prospect for developing the new information processor and ME device based ferroelectric-ferromagnetic integration effect.In this thesis,combining the sol-gel method with rapid heat treatment to prepare Ba0.8Ca0.2Zr0.05Ti0.95O3(BCZT)ferroelectric thin film and Ni0.9Zn0.1Fe2O4(NZF)ferromagnetic thin films and the BCZT/NZF composite film,respectively.After exploring the optimal process parameters of preparing the single ferroelectric and ferromagnetic thin films,the parameters were applied to prepare the composite thin film,and then representing its microstructure and performance.Firstly,after preparing BCZT thin films,we investigated the influence of annealing temperature,annealing time and film thickness on the phase texture,electrical properties and surface topography,respectively.The experimental results show that the film is under optimal condition when the annealing temperature was700℃,thickness is four layers and the annealing time is 11 min.The value of Rq is only 2.33 nm,exhibiting an excellent ferroelectric performance.Secondly,after preparing the NZF thin film,we investigated the influences thatdifferent annealing temperature and annealing time on the phase texture,surface topography,electrical properties and leakage current characteristic of the NZF thin films,respectively.The experimental results show that annealing temperature at600℃,and the annealing time of 600 s are the best condition to present a sounding ferromagnetic property.Finally,we successfully synthesized BCZT-NZF composite films.Phase texture,surface morphology,ferroelectric properties,ferromagnetic properties and magnetoelectric coupling effect were characterized.The results show that the composite film crystallize well with uniform grain size with low surface roughness.comparing with single phase BCZT ferroelectric thin film and NZF ferromagnetic thin film,the ferroelectric and ferromagnetic properties were weakened slightly for the existence of a part of voltage was leaking by ferromagnetic layer and lattice mismatch.The magnetoelectric coupling coefficient of composite thin film was measured by magnetoelectric coupling test device with a valuE? of39.4mv/cm-1Oe-1.