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Summary Ni1-xZnxFe2O4 (0≤x≤1) mixed ferrite nanoparticles encapsulated with amorphous-SiO2 were prepared by a wet chemical method. Particle sizes were controlled to range from 2.6 to 33.7 nm by heat treatment, and the particle size dependence of saturation magnetization Ms was investigated for the x=0.5 region. The Ms value decreased abruptly for particle sizes below about 6 nm. From the temperature dependence of the magnetization under field-cooled and zero-field-cooled conditions, blocking temperatures Tb were observed to be between 28 and 245 K depending on the particle size. At the blocking temperature, the superparamagnetic spins in the particle are supposed to be blocked against the thermal fluctuation energy. A smaller particle volume causes a lower blocking temperature; so an extremely small particle would be strongly affected by thermal fluctuation.

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decomposition of these precursors, depending on the systems composition and thermal treatment, magnetic materials, catalysts, pigments and luminophores may be obtained [ 5 – 9 ]. The Ni–Zn ferrite represents a material of high technological importance

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Nano-crystalline Mn0.3Ni0.3Zn0.4Fe2O4 obtained by novel fumarato-hydrazinate precursor method

Synthesis, characterization and studies of magnetic and electrical properties

Journal of Thermal Analysis and Calorimetry
Authors: U. B. Gawas, V. M. S. Verenkar, and S. C. Mojumdar

their high permeability and high magnetization [ 2 ]. Ni–Zn ferrites on the other hand possess high resistivity, but relatively low permeability at high frequencies [ 3 ]. For high frequency magnetic application ferrites with high permeability as well as

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Abstract  

This article presents the results of our investigation on the obtaining of Ni0.65Zn0.35Fe2O4 ferrite nanoparticles embedded in a SiO2 matrix using a modified sol–gel synthesis method, starting from tetraethylorthosilicate (TEOS), metal (FeIII,NiII,ZnII) nitrates and ethylene glycol (EG). This method consists in the formation of carboxylate type complexes, inside the silica matrix, used as forerunners for the ferrite/silica nanocomposites. We prepared gels with different compositions, in order to obtain, through a suitable thermal treatment, the nanocomposites (Ni0.65Zn0.35Fe2O4)x–(SiO2)100–x (where x=10, 20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy. The formation of Ni–Zn ferrite in the silica matrix and the behavior in an external magnetic field were studied by X-ray diffraction (XRD) and quasi-static magnetic measurements (50 Hz).

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view [ 1 ]. Ni–Zn ferrites are soft ferrimagnetic materials with low magnetic coercivity and high resistivity [ 2 ]. The eddy current loses are also low for this materials in high frequency operations [ 3 ]. Because of these properties, Ni–Zn ferrites

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Nanocrystalline Zn0.5Ni0.5Fe2O4

Preparation and kinetics of thermal process of precursor

Journal of Thermal Analysis and Calorimetry
Authors: Wenwei Wu, Yongni Li, Kaiwen Zhou, Xuehang Wu, Sen Liao, and Qing Wang

sensor [ 1 – 6 ], etc. Within this group, Ni–Zn ferrites are very important soft magnetic materials. Its properties were highly dependent on the molar ratio of Ni to Zn, and crystallite diameter. Compared with other composition Ni 1− x Zn x Fe 2 O 4 , Zn

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size of nanocrystalline materials is attributed to surface effect, spin canting, and broken exchange bonds [ 32 , 33 ]. In case of nanocrystalline Ni–Zn ferrite, the magnetization has been found to be increasing from 28.3 to 58.3 emu/g when the

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, S , Murakami , R , Yoshimura , M . Synthesis of Co-, Co–Zn and Ni–Zn ferrite powders by the microwave-hydrothermal method . Mater Res Bull . 2001 ; 36 : 2241 – 2250 . 10.1016/S0025-5408(01)00703-6 . 5

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. Macromolecules 34 : 5910 – 5915 10.1021/ma001576b . 23. Rao , BP , Rao , KH , Trinadha , K , Caltunb , OF 2004 Dielectric behaviour of niobium doped Ni-Zn ferrites . J Optoelectron Adv Mater

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. J Magn Magn Mater 171 : 309 – 314 10.1016/S0304-8853(97)00093-0 . 13. Bid , S , Pradhan , SK 2004 Characterization of crystalline structure of ball-milled nano-Ni–Zn-ferrite by

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