Consequences of electronic excitations in CoFe1.90Dy0.10O4 (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, optical, elastic and magnetic properties of Ce and Dy doped cobalt ferrites
Journal of Alloys and Compounds 834 (2020) 155089, 2020
The CoCe x Dy x Fe 2-2x O 4 (x ¼ 0.0, 0.01, 0.02, 0.03, 0.04, 0.05) have been prepared by sol-gel auto-combustion technique. The structural result confirmed the formation of single phase cubic spinel structure showed by XRD. Crystallite size obtained from the XRD is in the range of 24e28 nm, whereas particle size obtained from the transmission electron microscopy is in the range of 20e30 nm. It is also found that the cation distribution of CoCe x Dy x Fe 2-2x O 4 resulted in the Fe 3þ and Co ions occupy both tetrahedral A-site and octahedral B-site, whereas Ce and Dy cation distributed in both of them. The photoluminescence (PL) analysis reveals that all prepared samples contain four bands; (i) peak centered at 412 nm corresponding to ultraviolet (UV) band i.e. near band edge emission, (ii) a high intensity peak centered at 434 nm belonging to violet band, (iii) a low intensity and sharpness peak positioned at 466 nm refers to blue band, and (iv) a broad and very low intensity peak observed at 502 nm assigned to green band. FTIR results of the prepared samples showed that two vibration bands between 600 cm À1 and 400 cm À1 belonging to the stretching vibration of tetrahedral metal-oxygen bond (v A) and stretching vibration of octahedral site (v B) respectively. M€ ossbauer spectroscopy has also been performed to investigate the hyperfine structure of undoped, Ce and Dy co-doped cobalt nano ferrites. The higher values of M S and H hf for x ¼ 0.01 composition can be attributed to the occupation of Dy 3þ ions in octahedral site whereas the Ce 3þ ions occupied to tetrahedral site.
Magnetic and electrical properties of In doped cobalt ferrite nanoparticles
Journal of Applied Physics, 2012
Dielectric relaxation study of amorphous TiTaO thin films in a large operating temperature range J. Appl. Phys. 112, 094104 (2012) Gate stack dielectric degradation of rare-earth oxides grown on high mobility Ge substrates J. Appl. Phys. 112, 094501 (2012) Solvated dissipative electro-elastic network model of hydrated proteins JCP: BioChem. Phys. 6, 10B620 Solvated dissipative electro-elastic network model of hydrated proteins J. Chem. Phys. 137, 165101 (2012) Experimental studies of Debye-like process and structural relaxation in mixtures of 2-ethyl-1-hexanol and 2-ethyl-1-hexyl bromide Nanoparticles of CoFe 2 O 4 and CoIn 0.15 Fe 1.85 O 4 ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In 3þ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric constant (e 0 ) and dielectric loss (tan d) are also studied as a function of frequency and temperature. The variation of dielectric properties e 0 , tan d, and ac conductivity (r ac ) with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe 2þ and Fe 3þ as well as between Co 2þ and Co 3þ ions at B-sites. Magnetization and electrical property study showed its dominant dependence on the grain size. V C 2012 American Institute of Physics.
Applied Surface Science, 2011
In the present paper we report our results on the effect of Nd:YAG laser irradiation on the structural and magnetic properties of Li 0.5 Fe 2.5 O 4 spinel ferrite prepared by solid-state reaction technique. X-ray diffraction analysis was carried out to confirm the formation of the single phase cubic spinel structure. The lattice constant calculated from X-ray diffraction data (XRD) goes on increasing with non irradiated phase to exceeding higher doses of irradiation. The distribution of the substituted ions over the different lattice sites is determined from XRD and infrared spectra. The damage structure and morphological investigations were carried out by using scanning electron microscopy and transmission electron microscopy techniques. It has been observed from our data on magnetic properties that laser irradiation severely affects the magnetization. From the magnetization measurements it has been observed that the saturation magnetization decreases with increase in the laser dose rate. The observed reduction in the saturation magnetization after irradiation is understood on the basis of the partial formation of paramagnetic centers and rearrangement of cations in the lattice.
International Journal for Innovation Education and Research, 2021
In this study we report on the synthesis and characterization of cobalt ferrite (CoFe2O4) nanoparticles (NPs), synthesized by chemical co-precipitation in alkaline medium. Two samples were synthesized at two different temperatures, 35 and 90 oC. Both samples were characterized by Transmission Electron Microscopy (TEM), x-ray diffraction (XRD), and room-temperature (RT) magnetization. Two samples showed superparamagnetic behavior (SPM) at RT. TEM reveals morphological mean diameter increasing 5.8 nm to 10.4 nm, with the increase of the co-precipitation temperature. XRD confirm the inverse cubic spinel structure. The RT magnetization curves were analyzed by the first-order Langevin function averaged out by a lognormal distribution function of magnetic moments. This analysis showed saturation magnetization and magnetic moment increases from 60.2 to 74.8 emu/g and from 3.9 x 103 to 8.2 x 103 mB, respectively.
Superparamagnetic cobalt ferrite nanoparticles synthesized by gamma irradiation
New Journal of Chemistry, 2023
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Journal of Magnetism and Magnetic Materials, 2014
Mo-substituted cobalt ferrite nanoparticles; CoFe 2 À 2x Mo x O 4 (0.0 rx r 0.3) were prepared by a one-step solution combustion synthesis technique. The reactants were metal nitrates and glycine as a fuel. The samples were characterized using an X-ray diffraction (XRD), a transmission electron microscope (TEM) and a vibrating sample magnetometer (VSM). XRD analysis revealed a pure single phase of cubic spinel ferrites for all samples with x up to 0.3. The lattice parameter decreases with Mo 6 þ substitution linearly up to x ¼0.15, then nonlinearly for x Z0.2. Rietveld analysis and saturation magnetization (M s ) revealed that Mo 6 þ replaced Fe 3 þ in the tetrahedral A-sites up to x ¼0.15, then it replaced Fe 3 þ in both A-sites and B-sites for x Z 0.2. The saturation magnetization (M s ) increases with increasing Mo 6 þ substitution up to x ¼ 0.15 then decreases. The crystallite size decreased while the microstrain increased with increasing Mo 6 þ substitution. Inserting Mo 6 þ produces large residents of defects and cation vacancies.
International Journal of Spectroscopy, 2013
Positron lifetime and Doppler broadening measurements were carried out on nanocrystalline (grain size ~60–65 nm) samples of the Cr3+-substituted cobalt ferrite system with general chemical formula CoCrxFe2−xO4 (x=0.0−2.0) synthesized by the coprecipitation technique. The results indicated selective trapping of positrons in large vacancy clusters initially at the tetrahedral (A-) sites and then with Cr3+-substitution up to concentration (x)=0.7, at the octahedral (B-) sites. The results are consistent with the cation distribution determined from X-ray diffraction line intensity calculations, which indicated partial inversion of the inverse spinel ferrite, subsequent stabilization over a range of substitution (x=0.7 to 1.7), and finally the full inversion to the normal spinel chromite (CoCr2O4, x=2.0). In the intermediate range of substitution, lattice contraction prevented a fraction of Co2+ ions released from the (B-) sites from entering the tetrahedral sites, and these vacancies at...
Enhanced magnetic properties of doped cobalt ferrite nanoparticles by virtue of cation distribution
Journal of Alloys and Compounds, 2015
Enhancement of magnetic moment as well as magnetocrystalline anisotropy constants is very much required for the device application of cobalt ferrites. We are able to achieve enhanced magnetic properties of nanocrystalline cobalt ferrite by virtue of suitable doping. Pure, Mn and Ni doped cobalt ferrite nanoparticles have been synthesized using facile soft chemical route. XRD analysis using Rietveld refinement technique confirms the growth of pure, single phase cobalt ferrite nanoparticles, corroborates with TEM study. The observed increase in saturation magnetization for the doped samples can be attributed to the migration of Co 2+ ions from B site to A site and hence Fe 3+ ions from A site to B site. Detailed magnetic analysis using Law of Approach shows an increase of different magnetic properties like anisotropy constant, anisotropy field, coercivity for the doped samples, could be due to the increase in magnetic interaction between two sites due to different cation distribution. A structure property correlation has been established by proposing a cation distribution which enables us to explain the enhancement of magnetic properties.