| Multiferroic materials not only exhibit electric order and magnetic order simultaneously but also have magnetic/electric coupling effect. They have application prospect in storage fields such as multi-state storage and nonvolatile magnetoelecric storage units, and are research hot point in the field of functional materials. Composite materials provide an effective approach to realizing room temperature multiferroics with strong coupling, and the study of coupling in the interface is a new field in Physics. We adopted electrophoretic deposition method to fabricate 2-2 type ferroelectric/magnetic layered composite multierroic materials, and studied the magnetoelectric coupling and interface properties. It is the first time that this method was used to fabricate layered multiferroics, we studied electrophoretic process such as suspensions (especially magnetic suspensions) and deposition mechanisms in deep.Firstly, we studied the synthesis of nano-particles used in electophoretic deposition. Sol-gel was used to synthesis BaTiO3 and Pb(Zro.52Tio.48)03 particles and co-sedimentation method was used to synthesis CoFe2O4, respectively. BaTiO3 particles with xerogle cancinated at 800℃have complete phase and no adhesion between particles, the average size was -40 nm with narrow distribution range, good ferroelectric properties existed in corresponding ceramics, with Ps 19.0μC/cm2. High concentrate source solutions of Pb, Zr and Ti combined with heating while H2O being added were prerequisite of form of stable gel, the Pb(Zr0.52Ti0.48)O3 particles formed by cancinated at 700℃were with particle size of-30 nm, the corresponding ceramics exhibited good ferroelctrics with Ps 41.2μC/cm2. The crystallization of CoFe2O4 formed at rather low temperature, particles with size of 16, 20,40 and 60 nm could be formed under cancination at 500,600,800 and 900℃.Preparation of suspensions was studied, BaTiO3-ethanol-acetylacetone (1:1 volume fraction), Pb(Zro.52Tio.48)O3-acetylacetone-acetic acid (1:1 volume fraction) and CoFe2O4-acetylacetone (0.20 wt.% PEI) were the stable suspensions, respectively. A stability theory of magnetic suspensions based on DLVO and combined by magnetic dipole interactions was established, and it was proved by experiment of stability analysis of CoFe2O4 suspensions with different particle sizes.On the basis of study of suspensions, BaTiO3 and Pb(Zr0.52Ti0.48)O3 single layer films were fabricated via electrophoretic deposition. BaTiO3 and Pb(Zr0.52Ti0.48)O3 films under heat treated at 1200 and 1500℃respectively showed the most density structure and exhibited highest ferroelectricity, with Ps of 18.8 and 32.2μC/cm2, respectively. Phenomenon in our experiment during deposition was corresponding to the Accumulation Theory, the structure of deposition layer was directly decided by suspensions'stability, i.e., ordered and dense structure was formed by more stable suspensions. While dynamics parameters as time, voltage and concentration only changed the deposition weight (thickness), the process followed Hamaker equation.CoFe2O4 films were fabricated on the basis of CoFe2O4-acetylacetone (0.20 wt.% PEI) suspensions, films under heat treated at 1250℃exhibit dense structure, and Ms was 249.2 emu/cm3. As dispersants took advantage in water, we studied deposition of CoFe2O4 films via aqueous suspensions.0.60 wt.% PAMA-NH4 addition with pH= 10 was the condition of formation of stable suspensions. Films heat treated at 1250℃showed ordered arrangement of grains (SEM), XRD showed preferation orientation in (220) and (511), magnetic hystersis showed the abnormal anisotropy, and proved that oriented growth existed in the films.Fe2O4 bilayer films were fabricated on the basis of single layers. Films on heat treated at 1200℃showed more dense structure and higher ferroelectric and magnetic properties than films on ITO (600℃). The former had polarization changes under 800 Oe magnetic fields both in parallel and normal directions, which indicated the magnetic/electric coupling effect. Under parallel fields, Ps increased from 16.2 to 16.85μC/cm2 (4%), and it decreased from 16.2 to 14.9μC/cm2 (-8%) under normal fields. Under fields with different directions the difference of Ps changes were owed to ferroelectric phase's compression strain. No diffusion layer or passive layer was found at the interface, and space charge exsit but showed little influence and intrisinic elastic coupling was the domiant coupling effects in the composite films. Pb(Zr0.52Ti0.48)O3/ CoFe2O4 bilayer films (sintered at 1150℃) showed evident multiferroic effect as the hysteresis loops changed under 800 Oe magnetic fields. Under parallel fields, Ps increased from 30.1 to 30.9 uC/cm2 (3%), it decreased from 30.1 to 27.1μC/cm2 (-10%) under normal fields.
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