Influence of cobalt ferrite on the magnetoelectric properties of thin films of bismuth ferrite deposited by spin coating

ABSTRACT The films composed of (1-x) BiFeO3- (x) CoFe2O4 varying the concentration (x = 0, 0.1, 0.2 and 0.3) were deposited by spin coating on Pt substrate (Pt / TiO2 / SiO2 / Si) from of 0.05 molar concentration precursors solutions, which were obtained by sol-gel method. Thin films characterization was made, the structure and the magnetoelectric properties were studied using X-ray diffraction, leakage current, dielectric constant, ferroelectric and ferromagnetic hysteresis curve. The XRD results show characteristic peaks with the formation of BiFeO3 and the growth of peaks belonging to CoFe2O4 with the increase of x. All samples reveal little leakage current, being the lowest of 10-10 A/cm2 for (0.8) BiFeO3- (0.2) CoFe2O4. The dielectric constant increased in the range from 102Hz to 105Hz then decreased due to dielectric relaxation, for all samples the dielectric loss is less than 4%. All fabricated films show remnants polarization and magnetization greater than 60 μC/cm2 and 30 emu/gr respectively.

摘要 由(1-x)铁酸铋(BiFeO3)-(x)钴铁氧体(CoFe2O4)构成的薄膜，其组分掺杂浓度x取值为0、0.1、0.2与0.3，采用旋涂法（spin coating）沉积于铂(Pt)/二氧化钛(TiO2)/二氧化硅(SiO2)/硅(Si)复合基底上；前驱体溶液通过溶胶-凝胶法（sol-gel method）制备，摩尔浓度为0.05。本研究对所制备的薄膜开展了全面表征，通过X射线衍射（X-ray diffraction）、漏电流测试、介电常数测试、铁电滞回线与铁磁滞回线分析，对其微观结构与磁电性能进行了系统研究。X射线衍射结果显示，随着x值升高，薄膜中出现铁酸铋的特征衍射峰，且钴铁氧体的特征峰强度逐步提升。所有样品均表现出极低的漏电流，其中(0.8)BiFeO3-(0.2)CoFe2O4样品的漏电流最低，仅为10⁻¹⁰ A/cm²。在10²Hz至10⁵Hz的频率区间内，薄膜的介电常数呈上升趋势，随后因介电弛豫出现下降；所有样品的介电损耗均低于4%。所制备的全部薄膜均展现出大于60 μC/cm²的剩余极化强度，以及大于30 emu/gr的磁化强度。