兰州大学机构库 >物理科学与技术学院
纳米镍铁氧体及其与铁电材料复合的性能研究
Alternative TitleInvestigation of Properties for Nickel Ferrite and Its Composites with Ferroelectric in Nanoscale
史振华
Thesis Advisor薛德胜
2014-05-23
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
KeywordNiFe2O4 铁电材料 磁电效应
Abstract最近几十年来,由铁电材料和铁磁材料组合构成的磁电复合材料因其性能可实现多场调制而受到广泛研究。最近的研究显示,纳米尺度下的磁电复合材料表现出电荷、交换偏执等新效应。本论文选取了具有高的饱和磁化强度、高电阻率、良好的机械性能和化学稳定性的NiFe2O4作为磁电复合材料中的磁性材料,在纳米尺度下研究了NiFe2O4颗粒的磁性以及其与铁电材料组成的纳米复合材料的性能。主要结果如下: 随着NiFe2O4纳米颗粒尺寸的减小,磁谱的结果显示磁共振频率从1.4 GHz增加至2.5 GHz,明显高于之前的报道。其原因在于NiFe2O4纳米颗粒表面存在大量的氧缺陷,氧离子的缺少使得超交换相互作用被破坏,使得颗粒表面产生了强表面各向异性。 在NiFe2O4-BaTiO3体系当中,利用穆斯堡尔谱证明了BaTiO3与NiFe2O4之间存在特殊的界面相。同时在没有恒定外磁场的作用下,样品的磁电耦合电压系数最大达到5 V/cm Oe。在NiFe2O4-PbZr0.52Ti0.48O3体系当中,没有实现静磁场对样品的电极化进行调制,这归因于体系当中没有形成与上个体系类似的界面相。由此得到在纳米磁电复合材料当中界面的性质与磁电效应有紧密联系。 在NiFe2O4/BaTiO3磁电复合薄膜中,发现复合薄膜的磁电阻与BaTiO3的电极化强度紧密相关。BaTiO3电极化的方向以及其铁电性都决定了薄膜的磁电阻效应,说明复合薄膜存在明显的磁电效应。
Other AbstractIn recent decades, magnetoelectric composites which are composed of ferroelectric material and ferromagnetic material have attracted much attention. The magnetoelectric composites show charge effect, exchange-bias mediated effect, and so on, in nanoscale. In this thesis, NiFe2O4 which shows high saturation magnetization, high resistivity, excellent mechanical performance and chemical stability is used as ferromagnetic phase in magnetoelectric composites. We have studied the magnetic of NiFe2O4 nanoparticles and the properties of magnetoelectric nanocomposites composed of a ferroelectric material and NiFe2O4. The main results are as follows: The magnetic resonance frequency of NiFe2O4 nanoparticles increase from 1.4 GHz to 2.5 GHz with the nanoparticles size decreasing, which is much higher than that previously reported. This is because, the presence of oxygen defects in the NiFe2O4 nanoparticles surface can be deduced, and the oxygen defects can destroy superexchange interaction. This leads to the presence of strong surface anisotropic field for NiFe2O4 nanoparticles. The NiFe2O4-BaTiO3 nanocomposites exhibit large magnetoelectric voltage coupling coefficient (5 V/cm Oe) without dc magnetic field. Results of Mössbauer spectra demonstrated the presence of interface phase in particulate nanocomposite. However, the polarization of NiFe2O4-PbZr0.52Ti0.48O3 nanocomposits can not be modulated by a static magnetic field. This is because, there is no special interface which is similar to the interface in NiFe2O4-BaTiO3 nanocomposites between NiFe2O4 and PbZr0.52Ti0.48O3 nanoparticles. For NiFe2O4/BaTiO3 heterostructure, the magnetoresistance of multilayer film is closely related to the polarization of BaTiO3, at the room temperature. The magnetoresistance of multilayer film depends on the direction of the ferroelectric polarization. A magnetoresistance ~50% can be observed when the direction of the ferroelectric polarization point to the substrate. When the ferroelectric polarization point to the surface, the multilayer films show no magnetoresistance effect. This indicate the multilayer show obvious magnetoelectric effect.
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229525
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
史振华. 纳米镍铁氧体及其与铁电材料复合的性能研究[D]. 兰州. 兰州大学,2014.
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