Modification of ferroelectric properties of BaTiO3-CoFe2O4 multiferroic composite thin film by application of magnetic field
Modification of ferroelectric properties of BaTiO3-CoFe2O4 multiferroic composite thin film by application of magnetic field
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DOI：
10.1143/jjap.47.7603
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发表时间：
2008-09-01
影响因子：
1.5
通讯作者：
Suzuki, Hisao
中科院分区：
文献类型：
--
作者：
Sawamura, Shigeki;Wakiya, Naoki;Suzuki, Hisao
采用脉冲激光沉积法在(La0.5Sr0.5)CoO_3/CeO_2/YSZ/Si(100)衬底上制备了BaTiO_3-CoFe_2O_4复合薄膜。实现了BaTiO_3和CoFe_2O_4同时外延生长。倒易空间图测量表明，BaTiO_3平行于衬底和垂直于衬底的晶格参数分别为0.4239和0.4060 nm。分别进行了分析。这两个晶格参数都大于体相的晶格参数(a=0.3994，c=0.4038 nm)，这表明BaTiO_3薄膜中含有大量的氧空位，且沿平行于衬底的方向观察到较大的温度应力。这些结果表明BaTiO_3薄膜具有(H00)取向，但我们认为也包含少量的(001)取向成分，尽管X射线衍射检测不到明显的(001)取向成分。磁化强度-磁场(M-H)磁滞回线测量表明，薄膜具有高的垂直矫直力，为7.0kOe。此外，还观察到明显的垂直磁各向异性。用磁力显微镜观察了磁畴的分布。极化-电场(P-E)磁滞测量表明，BaTiO_3-CoFe_2O_4复合薄膜具有较弱的铁电性和较大的漏电流。在0.2T的横向磁场作用下，P-E曲线的形状也发生了变化。这种变化是由两种可能引起的：(1)CoFe_2O_4的磁致伸缩；(2)CoFe(2)O(4)或(La0.5Sr0.5)CoO_3的磁阻。
We prepared BaTiO3-CoFe2O4 composite thin film on (La0.5Sr0.5)CoO3/CeO2/YSZ/Si(100) substrate by pulsed laser deposition. Simultaneous epitaxial growths of BaTiO3 and CoFe2O4 were achiieved. Reciprocal space map measurement revealed that the lattice parameters of BaTiO3 parallel and perpendicular to the substrate are 0.4239 and 0.4060 nm. respectively. The fact that both lattice parameters are larger than those of the bulk (a = 0.3994, c = 0.4038 nm) suggests that the BaTiO3 film contains a considerable amount of oxygen vacancies and a relatively large temsile stressis observed along the direction parallel to the substrate. These results indicate that the BaTiO3 iflm has (h00) orientation however, we consider that the small amount of (001) orientation component is also included although the (001) orientation component is not clearly detected by X-raydiffraction. The magnetization-magnetic field (M-H) hystreresis measurement revealed that the film had a high perpendicular coercivity of 7.0 kOe. In addition, a distinct perpendicular magnetic anisotropy was observed. The distribution of magnetic domains was observed by magnetic force microscopy. Polarization-electric field (P-E) hysteresis measurement revealed that the BaTiO3-CoFe2O4 composite film had weak ferroelectricity with considerable leakage current. It was also found that the shape of the P-E curve was changed by the application of a lateral magnetic field of 0.2T. The change would have been caused by the follwing two possiblities: (1) magnetostriction of CoFe2O4 and (2) magnetic resistivity of Cofe(2)O(4) or (La0.5Sr0.5)CoO3.