Structural, optical, elastic and magnetic properties of Ce and Dy doped cobalt ferrites (original) (raw)
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FTIR and Electrical Study of Dysprosium Doped Cobalt Ferrite Nanoparticles
Journal of Nanoscience, 2014
We have studied the role of Dy 3+ doping on the XRD, TEM, FTIR, and dielectric and electrical properties of CoFe 2 O 4 at room temperature. Cubic spinel phase of CoFe 2−x Dy x O 4 ( = 0.00, 0.05, 0.10, and 0.15) was synthesized by using different sintering temperatures (300, 500, 700, and 900 ∘ C). The two absorption bands ] 1 and ] 2 are observed in Fourier transform infrared spectroscopy (FTIR) spectra corresponding to the tetrahedral and octahedral sites, which show signature of spinel structure of the sample. For the sample sintered at 300 ∘ C, the dielectric constant is almost unchanged with the frequency at the particular concentrations of = 0.00 and 0.05. Similar result is obtained for the sample sintered at 500 ∘ C ( = 0.10, 0.15), 700 ∘ C ( = 0.05, 0.10, and 0.15), and 900 ∘ C ( = 0.05, 0.10). An increase in the dielectric constant was observed for the undoped cobalt ferrite sintered at 500, 700, and 900 ∘ C. The values of electrical resistivity of the materials vary from ∼10 5 to 10 9 Ω-cm.
Structural, magnetic and electrical properties of cobalt ferrites prepared by the sol-gel route
Nanosized cobalt ferrites having the general formula CoFe 2−x Al x O 4 (for x = 0.00, 0.25, 0.50) have been synthesized by the sol-gel route. The effect of Al 3+ ions on structural, Curie temperature, DC electrical resistivity and dielecltric properties are presented in this paper. From the analysis of powder X-ray diffraction patterns, the nanocrystallite size was calculated by the most intense peak (3 1 1) using Scherrer formula. The crystallite size decreases with increase in aluminium concentartion. The lattice parameter 'a' also decreased with increase in aluminum concentration. The magnetic and electrical properties have been studied as a function of temperature. The Curie temperature was determined from AC magnetic susceptibility measurement. It is observed that Curie temperature decreases and DC electrical resistivity increases with increasing concentration of Al 3+ ions. The observed variations in DC electrical resistivity have been explained by Verwey's hopping mechanism. The activation energy was found to increase with increasing Al 3+ ions. The variations of dielectric constant for all the samples have been studied as a function of frequency in the range 500 Hz to 1 MHz at room temperature. The room temperature dielectric constant decreases with increase of trivalent Al 3+ ions. The observed variation in dielectric constant has been explained on the basis of space charge polarization.
Journal of Experimental Nanoscience, 2014
Ho 3þ ion-substituted nanocrystalline cobalt ferrite materials with the chemical formula CoFe 2Àx Ho x O 4 for x ¼ 0.0, 0.025, 0.05, 0.075 and 0.1 have been synthesised by standard citrate precursor method. Crystal structure and phase purity have been studied by powder X-ray diffraction (XRD) method by employing Rietveld refinement technique. The distribution of cations between the tetrahedral site (A-site) and octahedral site (B-site) has been estimated by Rietveld analysis. The refinement result shows that Ho 3þ ion has a strong preference for octahedral sites (B-sites). The lattice constants decrease with the Ho 3þ concentration up to x ¼ 0.05. Crystallite size decreases with the Ho 3þ concentration. The magnetic hysteresis loop measurements have been carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of AE2 T. The magnetisations in saturation have been analysed by employing the 'law of approach (LA)' technique. The magnetocrystalline anisotropy constant and saturation magnetisation are found to decrease with the Ho 3þ concentration up to x ¼ 0.05. The coercivity decreases with the Ho 3þ concentration. The vibrational modes of the octahedral and tetrahedral metal complex in the sample have been carried out using Fourier transform infrared spectroscopy (FT-IR). The FT-IR spectra of the samples have been analysed in the wave number range of 350-1000 cm À1. We have observed two prominent absorption bands which are assigned to tetrahedral and octahedral metal complexes. The elemental analysis has been carried out using energy dispersive spectroscopy (EDS) with the help of field emission scanning electron microscope (FE-SEM) and the results reveal that, elements are as per the stoichiometric ratio in all the samples.
Superparamagnetic properties of the cobalt ferrite nanocrystals have been demonstrated. The significance of the solgel autocombustion method in preparation of cobalt ferrite oxide in the nano range (30-40 nm) has been very well complimented with the structural, dimensional and morphological techniques, such as X-ray diffraction technique, Transmission Electron Microscopy and Scanning Electron Microscopy. The valence states of the metal ions and single phase formation of the polycrystalline oxide have been confirmed with the help of X-ray photoelectron spectroscopy and Raman spectroscopy. The distribution of the Fe 3+ ions in the tetrahedral and octahedral lattice sites has been illustrated with the help of the Mössbauer spectroscopy that shows five sextets, indicating occupancies of one tetrahedral and four octahedral sites by Fe 3+ ions. Hyperfine fields of 51. 29, 48.74, 46.78, 43.58 and 48.59 Tesla, respectively in CoFe 2 O 4 have been found for four octahedral and one tetrahedral site respectively, at ambient temperature. The magnetic measurements M-H and M-T demonstrate a change in the magnetic moment and a superparamagnetic-ferrimagnetic transition at 235 K in the ferrite system.
Journal of Superconductivity and Novel Magnetism, 2015
Dysprosium-substituted cobalt ferrite nanoparticles with composition of CoFe 2−x Dy x O 4 (x = 0 − 0.1 in a step of 0.025) were synthesized by starch-assisted sol-gel auto-combustion method. The effect of Dy 3+ cation substitution on structural and magnetic properties of cobalt ferrite nanoparticles was investigated. Powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, infrared spectroscopy (IR), X-ray photoelectron spectroscopy and vibrating sample magnetometer (VSM) were employed to characterize the physical properties of these ferrite nanoparticles. XRD pattern reveals the formation of cubic spinel ferrite with the signature of DyFeO 3 phases for x ≥ 0.05. An infrared spectroscopy study shows the presence of two absorption bands in the frequency range around 560 cm −1 (ν 1) and around 380 cm −1 (ν 2), which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. FE-SEM analysis indicated the formation of nanosized particles (5−15 nm) with spherical morphology. Vibrating sample magnetometer was employed to probe the magnetic properties of the samples at room temperature. It was observed that rare earth ion dopant, crystallite size and foreign phase DyFeO 3 affect the magnetic properties of cobalt ferrite nanoparticles.
Structural and Magnetic Properties of Cerium Doped Cobalt Ferrite Nanoparticles
2014
1 Deptt. of Physics, D.S.B. Campus, Kumaun University, Nainital, Uttarakhand, India. 2 G. B. Pant University of Ag. & Technology, Pantnagar 263145, Uttarakhand, India 3 Inter University Accelerator Centre, Aruna Ali Asaf Marg, New Delhi 110067, India. Abstract. A series of cerium doped cobalt ferrites were synthesized using the nitrate method. The effects of Fe 3+ ions substitution by Ce 3+ ions on structural and magnetic properties of cobalt ferrite nanoparticles were investigated. Crystallite size of the nanoparticles of cobalt ferrite depends directly on the thermal treatment and their compositions. Specific surface area varies from 108 to 28 m 2 /g as the crystallite size increases from 10nm to 40nm. X-ray density is found to be maximum for the lowest sintering temperature and it becomes almost constant above the sintering temperature of 500 o C. Variation of lattice parameter is complex with sintering temperature. The value of saturation magnetization is increased gradually wit...
Synthesis and characterization of ultrafine and mesoporous structure of cobalt ferrite
Journal of Industrial and Engineering Chemistry, 2014
A B S T R A C T Ultrafine nanoparticles of cobalt ferrite (CoFe 2 O 4 ) were synthesized under microwave irradiation in polyol media and then were applied for the synthesis of mesoporous structures of cobalt ferrite. The effect of reaction parameters on products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FT-IR) spectra, vibrating sample magnetometer (VSM), and volumetric nitrogen adsorption. TEM and BET analysis showed presence of mesoporus structures with pore sizes less than 10 nm in the final product.