Structural and magnetic properties of MgxSrxMnxCo1-3xFe2O4 nanoparticle ferrites (original) (raw)
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International Journal of Nanoparticles, 2016
Nanoferrite powders having composition Mn x Mg 1-x Fe 2 O 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8) were synthesised by the chemical co-precipitation method and then sintered as the pellets. The X-ray diffraction (XRD), Alternating Gradient Force Magnetometer (AGFM) techniques and Curie temperature measurement were used to carry out this study. The XRD patterns confirm the nanosized dimension of the samples and showed that the samples are single phase cubic spinel nanoferrites. From the analysis of XRD data using Scherrer's formula, the average crystallite size (D XRD) of the particles was found to decrease from 81 to 55 nm with increasing manganese substitution. Substitution of Mn 2+ in MgFe 2 O 4 causes an increase in the lattice constant (a) from 8.35 to 8.43 Å. The magnetic parameters such as saturation magnetisation (M S), coercivity (H C) and remanence (M r) with increasing Mn 2+ concentration are studied at room temperature by an AGFM. Substitution of Mn 2+ for Mg 2+ increased M S from 21.2 to 74.7 emu g-1 and decreased H C from 23 to 10 Oe and decreased Curie temperature from 392 to 294°C.
Structural and magnetic properties of MnxCo1−xFe2O4 ferrite nanoparticles
2011
We report on the structural and magnetic properties of nanoparticles of Mn x Co 1 À x Fe 2 O 4 (x ¼0.1, 0.5) ferrites produced by the glycothermal reaction. From the analysis of XRD spectra and TEM micrographs, particle sizes of the samples have been found to be about 8 nm (for x ¼ 0.1) and 13 nm (for x ¼ 0.5). The samples were characterized by DC magnetization in the temperature range 5-380 K and in magnetic fields of up to 40 kOe using a SQUID magnetometer. Mössbauer spectroscopy results show that the sample with higher Mn content has enhanced hyperfine fields after thermal annealing at 700 1C. There is a corresponding small reduction in hyperfine fields for the sample with lower Mn content. The variations of saturation magnetization, remnant magnetization and coercive fields as functions of temperature are also presented. Our results show evidence of superparamagnetic behaviour associated with the nanosized particles. Particle sizes appear to be critical in explaining the observed properties.
Structural and magnetic properties have been investigated for Co x Fe 3 À x O 4 nanoferrites (x ¼0.5-1.2, with a step increment of 0.1) prepared by a citrate-precursor autocombustion method. X-ray diffraction patterns (XRD) and Fourier-transform infrared (FTIR) spectra prove the formation of a cubic spinel phase of CoFe 2 O 4 , besides x-dependent FeCo 2 O 4 spinel for samples with x Z 0.7. Size of the formed nano-crystals ranges from 34 to 45 nm, which is further confirmed with a TEM micrograph. Investigating magnetic parameters such as saturation magnetization, coercivity, and remanence field, through vibrating sample magnetometry (VSM) data, revealed a strong dependence of the magnetic properties of each sample on its own cation distribution being suggested according to the experimental results of XRD, VSM, and IR data.
A B S T R A C T Polycrystalline nanoferrites with chemical formula Mg x Zn 1−x Fe 2 O 4 (x=0.5, 0.6, 0.7) have been synthesized by co-precipitation technique and then subsequently heated to 800 °C in order to investigate structural, thermal and magnetic properties. The samples are characterized by using XRD, FTIR, TGA-DSC, SQUID and Mössbauer spectroscopy techniques. The synergic effect of heat treatment with substitution of Mg 2+ , results in random variation of lattice parameter (a) and crystallite size (D). FTIR studies revealed the formation of cubic spinel structure. The broadening at octahedral bands for compositions x=0.6 and 0.7 attributes to distribution of ferrite particles of different sizes in these samples. The characteristic feature of hysteresis loops reflects the nature of ferrite particles in the state of superparamagnetism. The saturation magnetization at room temperature has been reported for composition x=0.7 is 44.03 emu/g. The variation of coercivity is due to variation in magnetic anisotropy which is predominately affected by the exchange interactions arising from the nature of nanoparticles. The blocking temperatures are in the range of 10–30 K and their variation is in the line of change in magnetocrystalline anisotropy but not due to variation in crystallite sizes. The Zeeman splitting at tetrahedral (A) and octahedral (B) sites for composition x=0.6 is expected due to increase in size of core of the nanoparticles/or increasing of magnetocrystalline anisotropy. The range of isomer shift values and quadruple splitting values are evident for the presence of Fe 3+ ions and the absence of Fe 2+ ions in the present systems. The present ferrite nanoparticles in the superparamagnetic state are the potential candidates for biomedical applications like cancer treatment through hyperthermia. The results are interpreted in terms of cation redistribution presuming exchange coupling energy variation on magnetocrystalline anisotropy.
Hyperfine Interactions, 2008
Nano size Mg x Co 1−x Fe 2 O 4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) ferrites have been prepared using sol gel method and characterized using i.r., TEM, XRD, magnetic and Mössbauer spectral studies. The particle size of as obtained samples was found to be ∼6 nm, which increases up to ∼80 nm after annealing at 1,000 • C. The saturation magnetization decreases from 80.0-27.5 emu/g on increasing the Mg 2+ ions after annealing at 1,000 • C due to the diamagnetic behaviour of the Mg 2+ ions. Room temperature (RT) Mössbauer spectra (MS) of as obtained samples exhibit a broad doublet, suggesting super paramagnetic nature of the sample. However, annealed samples exhibited a broad sextet, resolved into two sextets, corresponding to tetrahedrally and octahedrally coordinated Fe cations.
Structural and magnetic properties of CoFe2−xMoxO4 nanocrystalline ferrites
Materials Science and Engineering: B, 2014
Structural and magnetic properties of CoFe 2−x Mo x O 4 (x ----0, 0.04, 0.08, 0.12, 0.16, 0.2, and 0.3) nano ferrites synthesized by autocombustion method were investigated. X-ray powder diffraction patterns have confirmed the pure cubic crystalline phase of the synthesized nanoparticles. Magnetic properties were explored using vibrating sample magnetometry and Mössbauer spectroscopy. Both the crystallite size (D) and the saturation magnetization (M s ) decreased continuously with increasing Mo content. Bertaut method based on X-ray diffraction, infrared spectroscopy (IR) data, saturation magnetization and Mössbauer spectroscopy were used to suggest the cation distribution in tetrahedral (A) and octahedral [B] sites for the whole samples. address: a m wahba@yahoo.co.uk (A.M. Wahba).
Structural and Magnetic Properties of Nanocrystalline Mg–Co Ferrites
Journal of Superconductivity and Novel Magnetism
Mg–Co nano crystalline ferrites having the general formula Mg1−x Cox Fe2O4 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25) were prepared by the sol–gel method. X-ray powder diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR) were carried out to investigate the structural properties of the samples. X-ray powder diffraction patterns indicated the formation of a spinel structure of the prepared compounds. Fourier Transform Infrared (FTIR) spectroscopy of the samples confirmed the XRD results. The crystallite size, lattice parameters and porosity of samples were calculated by XRD data analysis as a function of cobalt concentration. The dielectric constant (ε r ), dielectric loss tangent (tan δ) and ac electrical conductivity (σ ac) of nanocrystalline Mg–Co ferrites were investigated as a function of frequency and Co concentration. The frequency dependence of ε r , tan δ and σ ac is in accordance with the Maxwell–Wagner model. The effect of Co doping on dielectric and electric properties was explained on the basis of cations distribution in the crystal structure. The saturation magnetization MS, remanent magnetization Mr and coercivity HC of all samples were explained as a function of cobalt concentration on the basis of Néel’s two-lattice model.
ACS Omega
This study reports the formation of Er-doped nanocrystalline cobalt ferrite with the formula CoFe 2−x Er x O 4 (0.0 ≤ x ≤ 0.10) from nontoxic metal precursors Co(NO 3) 2 •6H 2 O, Fe(NO 3) 3 •9H 2 O, and Er(NO 3) 3 •5H 2 O through an easy and economical sol−gel route in which citric acid is served as the chelating agent. The as-prepared powder was annealed at 700°C for 3 h in ambient air to get the required spinel structure. The annealed samples were subjected to structural and magnetic characterization. The X-ray diffraction (XRD) data of the samples confirmed the cubic spinel structure formation. The average crystallite size evaluated from XRD data increased from 21 to 34 nm with the substitution of Er due to the larger atomic size of Er 3+ than Fe 3+. Moreover, the crystallite size obtained from XRD data are well matched with the particle size measured from transmission electron microscopy images. The lattice parameters obtained from XRD data agree well with the values estimated from theoretical cation distribution and Rietveld refinement calculation. The hysteresis curve exhibits the particles are soft ferromagnetic and the coercivity increased from 54.7 to 76.6 kA/m with maximum saturation magnetization, M s = 61 emug −1 for 0.10 Er content. The squareness ratios were found to be less than 0.5, which indicates the single-domain nature of our particles. The blocking temperature measured from field cooled-zero field cooled curves is T B > 350 K for all the samples, which is much higher than the room temperature (300 K). The enhancement of saturation magnetization and coercivity has been explained based on the crystallite size, anisotropy constant, and cation distribution. Thus, the structural and magnetic properties of CoFe 2 O 4 nanoparticles (NPs) can be tuned by Er incorporation and these NPs can be applied in different soft magnetic devices.
The structural and magnetic behaviour of the MgFe2 − xCrxO4 spinel ferrite
Hyperfine Interactions, 2012
The crystal structure and magnetic properties of the spinel system MgFe 2−x Cr x O 4 (with x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) have been investigated by means of X-ray diffraction (XRD), and Mössbauer spectroscopy. The XRD patterns showed the samples were single-phase cubic spinels. The 295 K Mössbauer spectra of the studied samples showed a continuous collapse of the internal magnetic field for both tetrahedral (A) and octahedral [B] sites with increasing Cr contents. Their 78 K Mössbauer spectra showed an ordered magnetic structure for both sites with the internal magnetic fields decreasing with increasing Cr contents. The continuous decrease in the internal magnetic field is interpreted in terms of the weakening of A-B exchange interaction. The cation distribution at tetrahedral (A) and octahedral [B] sites and its effect on Mössbauer parameters is studied. Mg 2+ ions are found to occupy both sites A and B, while Cr 3+ ions occupy site B only.
Chinese Physics B, 2016
Sol-gel auto-combustion is a method of preparing ferrite by combining combustion with chemical gel. In this study, Ni-Mg-Co ferrite powders are prepared by coprecipitation method, and the nanocrystals of Ni 0.2 Mg x Co 0.8−x Fe 2 O 4 are successfully synthesized. The structure and magnetic properties of undoped and Mg-substituted Ni-Co ferrite nanoparticles are systematically investigated. The methods used to characterize the prepared samples are X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and Vibrating sample magnetometry (VSM). The synthesized samples are confirmed by XRD analysis to form a single-phase cubic spinel structure with crystals between 48 and 50 nm. With the increase of Mg ion concentration, the lattice constant decreases. The results of FTIR spectroscopy indicated that a spinel structure was formed. Transmission electron microscopy (TEM) images show spherical cubic microcrystals in the samples. EDX analysis confirms that the synthesized ferrite is pure phase structure, and Mg 2+ is successfully replaced. With the increase of Mg 2+ ion content, the saturation magnetization and remanent magnetization decreased from 70.16 to 39.77 emu/g and 36.40 to 20.20 emu/g at room temperature, respectively. Meanwhile, the coercivity decreases from 1032.16 to 378.50 Oe by increasing Mg 2+ concentration. This also indicates that the Mg-substituted Ni-Co nano-ferrite has a low magnetic of multi-ferric material. The increasing of peak height of dM/dH at H m indicates that the cubic spinel structure sample has good crystallinity and magnetic stability.