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Study on Structure and Magnetic Properties of Ferrite/SiO2 Composite Films

Author: LiuYu
Tutor: LiHaiBo
School: Jilin Normal University
Course: Condensed Matter Physics
Keywords: Sol - gel spin coating method Ferrite / SiO2 Nanocomposite Films Structure Magnetic
CLC: TB383.2
Type: Master's thesis
Year: 2011
Downloads: 42
Quote: 0
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Abstract


The advantage of the spinel ferrite thin films in perpendicular magnetic recording and magneto-optical recording, electronic devices, more and more people's attention. In the ferrite, cobalt ferrite is a ferrous magnetic oxide, has the proper saturation magnetization, high magnetic anisotropy and coercive force, and good chemical stability and mechanical abrasion; Ni-Zn ferrite its biggest advantage as compared with the metal or metal alloy is a high resistivity, and therefore the eddy current loss and skin effect can be almost ignored. In this paper, the sol - gel spin coating prepared by ferrite / SiO 2 nanocomposite films. The use of X-ray diffraction (XRD), X-ray fluorescence spectroscopy analyzer (XRF), atomic force microscopy (AFM), scanning electric microscopy (SEM), vibrating sample magneto strong meter (VSM) sample surface morphology, structure and magnetic studies to discuss the impact of the sol pH value, doping and annealing temperature on the structure, grain size, morphology, magnetic. The results show that: (1) of CoFe 2 O 4 / SiO 2 samples, as sol pH value decreases, CoFe 2 O 4 grain size and lattice constant decreases of CoFe 2 O 4 grains exist obvious ( 111) preferred orientation of the crystal surface growth. As of CoFe 2 O 4 the grain size decreases, the coercive force of the sample becomes larger, the coercive force with the change of the grain size is due to the sample of the magnetic caused by the change of the domain structure. Samples obvious perpendicular magnetic anisotropy related to the growth of CoFe 2 O 4 preferred orientation. The stress anisotropy is present in the film sample, the result in the coercive force of the film sample was significantly higher than the powder sample. (2) Co 1-x Mg x Fe 2 O 4 / SiO 2 samples As of Mg 2 increase in the content of the the Co. 1-x the Mg x Fe 2 O < sub> 4 lattice constant decreases the saturation magnetization of the sample decreases, the coercivity first increases and then decreases. (3) With the improvement of the annealing temperature, the sample Co 0.8 Mg 0.2 Fe 2 O 4 crystal increase the degree, the grain size becomes large, the lattice constant decreases. The higher temperature annealing samples Co 0.8 Mg 0.2 the Fe 2 O 4 exist along the (111) direction The oriented growth trends. With the Co 0.8 Mg 0.2 Fe 2 O 4 increase in grain size, the magnetization of the sample becomes larger magnetization changes from the sample Co 0.8 Mg 0.2 the Fe 2 O 4 grain size effect and surface effects. Coercivity of the sample with the Co 0.8 Mg 0.2 Fe 2 O 4 increase in grain size increased first large and then decreases the coercivity changes with sample Co 0.8 Mg 0.2 Fe 2 O 4 crystal The grains of the magnetic domain structure associated with the changes in the grain size. (4) for-x the Ni 1 the Zn x the Fe 2 the O 4 / SiO 2 samples, with Zn 2 content increases, NiFe 2 O 4 sample saturation magnetization first increases and then decreases. When x = 0.6, maximum saturation magnetization of 630.3 kA · m -1 , the value of the coercive force is 5.7 kA · m -1 , a saturation magnetization of the sample. high coercive force is small, has good soft magnetic properties. (5) With the heat treatment temperature, the sample Ni 0.4 Zn 0.6 Fe 2 O 4 The crystallization degree increased, the grain size becomes large. A saturation magnetization of the sample is increased as the temperature increases, which is caused due to the nanoparticle surface effect and the small size effect. The coercive force of the sample increases as the annealing temperature increases, which is due to the difference in thermal expansion coefficient between the film and the substrate, leading to the film stress, the stress becomes larger as the temperature increases, so coercivity improved. (6) With the different dopant ions, the magnetic properties of the samples changed. Co 0.8 Mg 0.2 Fe 2 O 4 / SiO 2 2 O 4 / SiO 2 compared to the coercive force is increased, the saturation magnetization is decreased. Samples Co. 0.8 Zn 0.2 the Fe 2 O 4 / SiO 2 sample CoFe 2 O 4 / SiO 2 compared to the coercive force has been reduced, but the increase in saturation magnetization. Samples Co. 0.8 Ni 0.2 the Fe 2 O 4 / SiO 2 sample CoFe 2 O 4 / SiO 2 compared to the coercive force is decreased, the saturation magnetization is also decreased.

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CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Special structural materials
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