Manganese Substituted Cobalt Ferrites Research Articles

Structural, Optical, and Morphological Study of Manganese Substituted Cobalt Ferrite and Its Effect on the Magnetic and Dielectric Properties of PVA Composites

Nanopowders of Mn-substituted CoFe2O4 were prepared in different proportions using the sol-gel auto-combustion method and were structurally and morphologically studied. In another step, composites based on polyvinyl alcohol (PVA) with Mn-substituted CoFe2O4 fillers were prepared, and the effect of the Mn-substituted CoFe2O4 on the optical, magnetic, and dielectric properties was studied. X-ray analysis revealed the formation of polycrystalline Mn-substituted CoFe2O4. The results showed a decrease in the lattice constant with Mn2+ substituted and incorporated into the crystal structure of CoFe2O4. The Fourier confirmed the spinel structure of the Mn-substituted CoFe2O4 transform infrared spectrum where absorption bands appeared at 569–561 and 446–407 cm-1, which are attributed to tetrahedral and octahedral groups. The magnetic properties were affected when Mn ions were substituted with CoFe2O4, as shown by the results of VSM. It was observed that the saturation magnetization, remnant magnetization, and coercivity decreased with increasing Mn content. The dielectric constant and loss tangent of PVA/MnxCo1−xFe2O4 were also studied. The difference in the diameters of the substituted and host ions causes the dielectric constant to increase following the substitution of Mn ions.

Selective recovery of cerium (III) and iron (III) from nitrate medium by manganese substituted Cobalt Ferrite Magnetic Nanoparticles as low cost synthesized sorbent

ABSTRACT The facile synthesis of manganese-substituted cobalt ferrite (MCFO) nanoparticles (NPs) as a potential effective adsorbent for the adsorption of cerium(III) and iron(III) from the aqueous nitric acid medium is carried out in this work. The characterisation of the MCFO NPs was done using different spectroscopic tools such as Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, and vibrating sample magnetometry. The effecting parameters for the adsorption of cerium(III) and iron(III) ions from HNO3 acid using MCFO NPs were investigated using the batch technique. The obtained results indicate the effectiveness of MCFO NPs for recovery of cerium(III) and iron(III) ions from the nitric medium. The isotherm study showed that the adsorption process obeys the Langmuir model. In contrast, the kinetic study indicated that cerium(III) and iron(III) adsorption from an aqueous nitric acid medium was fitted to a pseudo-second-order model. The adsorption capacities were found to be 130 and 161 mg/g for cerium(III) and iron(III), respectively. The separation feasibilities of cerium(III) and iron(III) from an aqueous nitric acid solution were also discussed.

Observation of intrinsic fluorescence in cobalt ferrite magnetic nanoparticles by Mn2+substitution and tuning the spin dynamics by cation distribution

In this work, we report the synthesis and detailed characterization of single-domain, optically active, manganese-substituted cobalt ferrite (CoFe2O4) magnetic nanoparticles without any surface functionalization as prospective fluorescent probes for bio-imaging.

Study of the Suitability of Manganese-Substituted Cobalt Ferrites Nanoparticles for the Diagnosis of Malignant Cells by MRI and Treatment by Employing Hyperthermia Temperature

Study of the Suitability of Manganese-Substituted Cobalt Ferrites Nanoparticles for the Diagnosis of Malignant Cells by MRI and Treatment by Employing Hyperthermia Temperature

Thermal, microstructural and magnetic properties of manganese substitution cobalt ferrite prepared via co-precipitation method

Manganese-substituted cobalt nano-ferrites, Co(1−x)Mn(x)Fe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized using chemical co-precipitation method. Physical properties of Co(1−x)Mn(x)Fe2O4 nano-ferrites were then characterized using thermal gravimetric—differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrometer, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). TGA/DTA study indicates that the thermal stability of the prepared manganese doped cobalt ferrite nanoparticles. X-ray diffraction patterns of all the prepared ferrite samples show good in quality, pure nanosized, single-phased cubical spinel structures, with ferromagnetic behavior. We demonstrated that the expansion of lattice constant (a) and crystallite size (D) induced by manganese substituted of cobalt ferrites exerted remarkable effects on its structural and magnetic properties. The lattice constant (a) and crystallite size (D) increase with increasing manganese substituted cobalt ferrites. Williamson–Hall (W–H) method was used to evaluate the crystallite size and lattice strain of the Co(1−x) Mn(x)Fe2O4 nanoparticles samples by peak broadening. The calculated crystal size of Co(1−x) Mn(x)Fe2O4 nanoparticles on the W–H plots were highly intercorrelated with the HR-TEM and results of Scherrer Deby equation. The other physical parameters, such as X-ray density, hopping length, ionic radius, bond length, tetrahedral edge, octahedral edge, and unshared octahedral edge values were estimated from the highest intensity peak (311) of X-ray diffraction. The Fourier transform infrared (FT-IR) spectrometer of the Co–Mn ferrite nanoparticles systems were recorded in the frequency range of 200–1000 cm−1. FT-IR spectra show the two fundamental absorption bands of interstitial sub-lattice sites (M–O). The high absorption band (ν1) and the low absorption band (ν2) corresponds to the tetrahedral [A] and octahedral (B) sites, respectively, confirming the formation of single cubic spinel ferrite lattice system. The TEM results show that the ferrite nanoparticles have a nearly spherical shape with some agglomerations. From the analysis of VSM, the values of saturation magnetization (Ms) increases from 31.46 to 37.16 emu/g, then decreases with increasing Mn2+ ions substitution in the Co-ferrite system. The coercivity of the Mn2+ ions substituted cobalt ferrites increases up to x = 0.6 followed by a decrease. The optimized magnetic parameters suggest that the material with composition Co0.6Mn0.4Fe2O4 may be suitable for longitudinal magnetic recording media and other various technological applications.

Effect of cation distribution and temperature variation on magnetic and dielectric properties of manganese substituted cobalt ferrites

Bulk samples of Co1-xMnxFe2O4 (x = 0, 0.05 and 0.10) were synthesized in single phase form by using sol-gel technique. All samples undergo ferrimagnetic transition which decrease from 778 K to 766 K with increase in Mn substitution. The initial magnetization data measured at room temperature were interpreted using the Law of Approach to Saturation. The magnetocrystalline anisotropy constant and saturation magnetization showed increase in value for 5 at.% of Mn concentration.The variation of coercive field was interpreted in terms of microstructural parameter. The complex impedance spectroscopic data showed the charge carrier relaxes over the grains and grain boundaries with relaxation energy of the order of 10−1 eV. Equivalent circuits corresponding to the Nyquist plots were obtained from Zsimpwin software. The ac conductivity was studied by using Jonscher Power Law and it was established that small polaron model governs the mechanism of electrical conductivity.

The effect of MnxCo(1-x)Fe2O4 with x = 0, 0.25 and 0.5 as nanoparticles additives in magnethorheological fluid

This study focused on the effect of manganese substituted cobalt ferrite (Mn x Co1–x Fe2O4) nanoparticles with different mole ratios (x = 0, 0.25 and 0.5) in magnetorheological fluids (MRF). The nanoparticles were synthesized using co-precipitation method. The irregularly–spherical form of the nanoparticles was observed/confirmed using a field emission scanning (FESEM) microscope. The vibrating sample magnetometer (VSM) was performed to analyze the effect of nanoparticles in MRF on their magnetic properties. The VSM test results show that the nanoparticles have a negative effect on the magnetic properties of MRF. The higher magnetic saturation of nanoparticles will reduce more magnetic saturation in MRF. This phenomenon shows that the direction of the magnetic field from the cobalt manganese ferrite has the opposite direction to MRF. It is also identified that the field-dependent rheological properties of MRF show that the addition of nanoparticles increases the yield stress of MRF results except for Mn0.5Co0.5Fe2O4 which leads to the reduction of the yield stress of MRF.

Observation and manipulation of magnetic domains in sol gel derived thin films of spinel ferrites

Thin films of spinel ferrites, namely zinc substituted nickel, cobalt ferrite, and manganese substituted cobalt ferrite, were synthesized using sol-gel derived spin-coating techniques. The films were characterized using x-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy techniques for the analysis of structural, morphological and vibrational band transition properties, which confirm the spinel phase formation of the films. The magnetic force microscopy (MFM) technique was used to observe the magnetic domain structure present in the synthesized films. Further, the films were subjected to an external DC magnetic field of 2 kG to orient the magnetic domains and analyzed using an ex situ MFM technique.

Impact of metal ions (Cr3+, Co2+, Ni2+, Cu2+ and Zn2+) substitution on the structural, magnetic and catalytic properties of substituted Co–Mn ferrites synthesized by sol–gel route

Manganese substituted cobalt ferrites (CoMn x Fe2−x O4, x = 0.2, 0.4, 0.6, 0.8 and 1.0) synthesized using sol gel autocombustion method were used as photocatalysts for the degradation of both cationic and anionic dyes i.e Safranine-O and Remazol Brilliant yellow. CoMn0.4Fe1.6O4 exhibited maximum photocatalytic activity among all the synthesized ferrites. To further study the effect of metal ion doping on catalytic performance, substitution with different metal ions (Cr3+, Co2+, Ni2+, Cu2+ and Zn2+) was done in CoMn0.4Fe1.6O4 lattice. The structural and magnetic properties of prepared samples were investigated using powder X-ray diffraction, Fourier transform infrared spectroscopy and vibrating sample magnetometer. The average crystallite size of the synthesized nanoparticles was observed to be in the range of 39–52 nm. The saturation magnetization of the samples was found to decrease with the introduction of all metal cations (except Co2+) in the Co–Mn lattice. The changes in the catalytic activity were tested for degradation of Safranine-O and Remazol Brilliant yellow. Amongst the synthesized CoMn0.4M x Fe1.6−x O4, Cu substituted Co–Mn ferrite exhibited maximum photocatalytic efficiency. All the magnetic nanoferrites were easily recovered by using an external magnet and could be reused without any remarkable change in catalytic efficiency.

Magnetic Properties of Spinel Cobalt–Manganese Ferrites

Cobalt ferrite (CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) and manganese substituted cobalt ferrite (Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) were synthesized by coprecipitation and sol-gel methods. X-ray diffraction revealed that manganese ions slightly enlarged the crystal lattice with respect to pure cobalt ferrite. Magnetization, linear magnetostriction, and piezomagnetic coefficient values tended to decrease with the ion substitution. Linear magnetostriction dropped from a value of -111.5 ppm for cobalt ferrite to values of -22.6 and -30.6 ppm for the substituted samples obtained from coprecipitation and sol-gel, respectively. The sample prepared by sol-gel technique resulted in a higher magnetization, magnetostriction, and piezomagnetic coefficient than that synthesized by coprecipitation method.

Magnetic, magnetostrictive, and AC impedance properties of manganese substituted cobalt ferrites

In this study, we investigated the effects of substituting Mn3+ for some Fe3+ in spinel lattice on the structure, magnetic properties, magnetostriction behavior, and AC impedance characteristics of cobalt ferrites. The manganese substituted cobalt ferrites (Co–Mn ferrites), CoMnxFe2−xO4, with x varied from 0 to 0.3 in 0.1 increments, were prepared by solid-state reaction. XRD examination confirmed that all sintered Co-based ferrites had a single-phase spinel structure. The average grain size, obtained from SEM micrographs, increased from 8.2μm to 12.5μm as the Mn content (x) increased from 0 to 0.3. Both the Curie temperature and coercivity of Co-based ferrites decreased with greater amounts of Mn, while the maximum magnetization (at H=6kOe) of Mn-substituted cobalt ferrites was larger than that of the pure Co-ferrite. Magnetostrictive properties revealed that the pure Co-ferrite had the largest saturation magnetostriction (λS), about −167ppm, and the CoMn0.2Fe1.8O4 sample exhibited the highest strain sensitivity (|dλ⊥/dH|m) of 2.23×10−9A−1m among all as-prepared Co-based ferrites. In addition, AC impedance spectra analysis revealed that the real part (Z′) of the complex impedance of Co–Mn ferrites was lower than that of pure Co-ferrite in the low frequency region, and the Co-based ferrites exhibited semiconductor-like behavior.

Manganese substituted cobalt ferrites as efficient catalysts for H2O2 assisted degradation of cationic and anionic dyes: Their synthesis and characterization

Manganese substituted cobalt ferrites of the formula CoMnxFe2−xO4 (x=0.2, 0.4, 0.6, 0.8 and 1.0), were synthesized by means of sol–gel auto combustion method and were annealed at different temperatures. The annealed ferrite compositions were characterized using FT-IR spectroscopy, Transmission Electron Microscopy (TEM) and powder X-Ray Diffraction techniques, substantiating the formation of pure phase ferrites. The saturation magnetization values of the entire ferrite compositions displayed a decreasing trend with increasing concentration of manganese ion, implying substitution of iron ions by manganese ions in the octahedral sites of the ferrite lattice. Additionally, the catalytic properties of these ferrites were studied. For this purpose, the ferrites were employed as heterogeneous catalysts in H2O2 assisted degradation of cationic and anionic dyes. The dyes chosen were Methylene Blue (cationic dye) and Remazol Turquoise Blue (anionic dye). The catalytic degradation of both the dyes was performed in dark as well as under visible light irradiation. Over 90% of dye degradation was achieved in a time period of 40–90min in dark and within 20–30min under visible light irradiation. In all the reactions, it was observed that the presence of Mn3+ ions in the cobalt ferrite lattice significantly augmented the degradation of dyes. Further, an increase in dye degradation was observed with increase in manganese content. The increase in the catalytic efficiency of the ferrites was correlated with their cation distribution, deduced from the saturation magnetization values on the basis of Neel's two sub-lattice model.

Dielectric relaxations and alternating current conductivity in manganese substituted cobalt ferrite

Manganese (Mn) substituted cobalt ferrites (CoFe2-xMnxO4, referred to CFMO) have been synthesized by the solid state reaction method and their dielectric properties and ac conductivity have been evaluated as a function of applied frequency and temperature. X-ray diffraction measurements indicate that CFMO crystallize in the inverse cubic spinel phase with a lattice constant ∼8.38 Å. Frequency dependent dielectric measurements at room temperature obey the modified Debye model with relaxation time of 10−4 s and spreading factor of 0.35(±0.05). The frequency (20 Hz–1 MHz) and temperature (T = 300–900 K) dependent dielectric constant analyses indicate that CFMO exhibit two dielectric relaxations at lower frequencies (1–10 kHz), while completely single dielectric relaxation for higher frequencies (100 kHz–1 MHz). The dielectric constant of CFMO is T-independent up to ∼400 K, at which point increasing trend prevails. The dielectric constant increase with T &amp;gt; 400 K is explained through impedance spectroscopy assuming a two-layer model, where low-resistive grains separated from each other by high-resistive grain boundaries. Following this model, the two electrical responses in impedance formalism are attributed to the grain and grain-boundary effects, respectively, which also satisfactorily accounts for the two dielectric relaxations. The capacitance of the bulk of the grain determined from impedance analyses is ∼10 pF, which remains constant with T, while the grain-boundary capacitance increases up to ∼3.5 nF with increasing T. The tan δ (loss tangent)-T also reveals the typical behavior of relaxation losses in CFMO.

Correlation between structural, magnetic, and dielectric properties of manganese substituted cobalt ferrite

Manganese (Mn) substituted cobalt ferrites (CoFe2−xMnxO4, referred to CFMO) were synthesized and their structural, magnetic, and dielectric properties were evaluated. X-ray diffraction measurements coupled with Rietveld refinement indicate that the CFMO materials crystallize in the inverse cubic spinel phase. Temperature (T = 300 K and 10 K) dependent magnetization (M(H)) measurements indicate the long range ferromagnetic ordering in CoFe2−xMnxO4 (x = 0.00–0.15) ferrites. The cubic anisotropy constant (K1(T)) and saturation magnetization (Ms(T)) were derived by using the “law of approach” to saturation that describes the field dependence of M(H) for magnetic fields much higher than the coercive field (Hc). Saturation magnetization (Ms), obtained from the model, decreases with increasing temperature. For CoFe2O4, Ms decreases from 3.63 μB per formula unit (f.u.) to 3.47 μB/f.u. with increasing temperature from 10 to 300 K. CFMO (0.00–0.15) exhibit the similar trend while the magnitude of Ms is dependent on Mn-concentration. Ms-T functional relationship obeys the Bloch's law. The lattice parameter and magnetic moment calculated for CFMO reveals that Mn ions occupying the Fe and Co position at the octahedral site in the inverse cubic spinel phase. The structure and magnetism in CFMO are further corroborated by bond length and bond angle calculations. The dielectric constant dispersion of CFMO in the frequency range of 20 Hz–1 MHz fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived from modeling the experimental data are ∼10−4 s and ∼0.35(±0.05), respectively.

Influence of manganese substitution on the microstructure and magnetostrictive properties of Co1−xMnxFe2O4 (x = 0.0–0.4) ferrite

Manganese substituted cobalt ferrite, Co1−xMnxFe2O4 (x = 0.0–0.4), was prepared by a ceramic method. The heat-treated powders were pressed at hydrostatic pressure of 167 MPa, and were annealed at 1350 °C for 24 h. These samples present a single-phase cubic spinel structure and the compositional mass ratios are close to the empirical formula. The lattice constant determined from XRD increases with the increase of Mn content, whereas SEM study reveals that Mn substitution changes the microstructure and cause pores within the grains, which reduces the bulk density of the samples. The magnetocrystalline anisotropy constant, coercive field, and magnetostriction were observed to decrease with increasing Mn substitution; however, the strain derivative (dλ/dH) reaches a maximum value for x = 0.3. The observed variation in strain derivative in the Mn substituted cobalt ferrite is correlated to the microstructure whereas the reduced anisotropy of the system plays only a minor role.

Improved magnetostrictive properties of Co–Mn ferrites for automobile torque sensor applications

Strain derivative of local anisotropy, which depends on the magnetostriction, is the figure of merit for the magnetic materials used in automobile torque sensor applications. In order to improve the strain derivative, a series of samples with chemical formulae CoMnxFe2−xO4 (x=0.00–0.60) was prepared by a conventional ceramic technique. X-ray diffraction patterns of the samples confirm cubic spinel crystal structures. The magnetic properties, such as saturation magnetization and coercivity, were measured and the Curie temperature was estimated. Magnetostrictive properties were studied by the tensile strain gauge method. Manganese substituted cobalt ferrites have shown improved strain derivative values as compared to the pure cobalt ferrite. The strain derivative has been observed to increase for larger Mn substituent concentrations in CoMnxFe2−xO4. This behavior has been ascribed to the net decreased anisotropic contribution due to the increased presence of Mn3+ ions in B-sites and a corresponding migration of Co2+ ions to A-sites, and also to the microstructural grain size of the samples. The coercivity and magnetostriction measurements are in support of the strain derivative variations. The results are discussed on the basis of cationic site occupancies, variations in grain size and reduced anisotropy of the system.

Effect of reaction time on particle size and dielectric properties of manganese substituted CoFe2O4 nanoparticles

An auto-combustion route was adopted for preparing nanosize manganese substituted cobalt ferrite. The synthesis of the nanoparticles was carried out using different fuel ratio for combustion process. The prepared samples were characterized using XRD and TEM. The impact of fuel ratio on the formation of Co0.6Mn0.4Fe2O4 nanoparticles was analyzed in terms of particle size. The particle is achieved towards smaller range of size as ∼3–51nm only at the 50% fuel ratio. The 75% and 100% fuel combustion ratio are not supported to attain the particle size on these ranges. The dielectric loss and low value of dielectric constant have been measured in the frequency range of 50Hz–1MHz.

Study of dielectric and magnetic properties of PbZr 0.52Ti 0.48O 3–Mn 0.3Co 0.6Zn 0.4Fe 1.7O 4 composite

Results of detailed structural, dielectric, magnetic and magnetoelectric studies of ( x)PbZr 0.52Ti 0.48O 3–(1 −x)Mn 0.3Co 0.6Zn 0.4Fe 1.7O 4 composites where x=65, 70, 75 and 80 are shown in this work. Manganese substituted cobalt ferrites are known to exhibit large strain derivative ( dx/ dH) and on the other hand substitution of Zn in pure cobalt ferrite is known to enhance its permeability μ and permittivity ε. The choice of ferrite as Mn, Zn simultaneously substituted cobalt ferrite (MCZFO) is made keeping in view that for good magnetoelectric (ME) voltage coefficient the magnetostrictive constituent phase of the composite should have large strain derivative ( dx/ dH) along with large permittivity and permeability. It is shown here that although the dielectric transition temperature changes significantly with change in the mole ratio of the two component phases, magnetic transition temperature (much less compared to the bulk cobalt ferrite) is relatively non-responsive to the changing molar ratio of the two component phases. In the vicinity of the magnetic transition temperature we observed an anomaly in tan δ vs. T plots, which indicates a possible magnetoelectric coupling in the samples. Magnetoelectric voltage coefficient ( α E ) has been measured using static magnetoelectric method. Highest magnetoelectric voltage coefficient ( α E =0.312 mV/cmOe) is obtained for sample 80:20 at H DC =1000 Oe.

Substituted cobalt ferrites for sensors applications

The aim of this work was to study the influence of the sintering temperature and of the substitution level on the Curie temperature and on the magnetostriction coefficients for four series of cobalt ferrites sintered by conventional ceramic method. The microstructure of the samples was characterized using X-ray diffractometry and scanning surface electron microscopy. Vibrating sample magnetometry and strain gauge measurements were used to characterize the magnetic and magnetostriction properties. The study proves that a small amount of manganese substitution for iron decrease drastically the Curie temperature but in the same time decrease the specific magnetization and magnetostriction coefficient. Despite this drawback, the manganese substituted cobalt ferrites present the largest strain derivative. The maximum of the magnetostriction coefficient is also influenced by the stoichiometry of the cobalt ferrites. The magnetostriction coefficient of cobalt ferrite can be enhanced by substitution of small fraction of iron or cobalt by silicon or manganese, this implying the modification of the strain derivative as well as magnetostriction at lower magnetic fields. The maximum magnetostriction can be tuned by substitution levels and sintering parameters.

Magnetic and magnetostrictive properties of manganese substituted cobalt ferrite

The magnetic and magnetostrictive properties of polycrystalline Co1−xMnxFe2O4 (0 ⩽ x ⩽ 0.4) have been studied. Although the Curie temperature decreases continuously with increasing concentration of Mn, the magnetization remains high up to x = 0.3 and unexpectedly low coercivity is observed for this composition showing an unusual magnetostrictive behaviour. This composition shows a relatively larger magnetostriction at low fields. Moreover, the strain derivative which is the slope of the magnetostriction curve at low magnetic fields is almost doubled and the field at which maximum magnetostriction is observed is reduced to almost half for 30% of Mn substitution. The results show that x ≈ 0.3 in Co1−xMnxFe2O4 is an optimum composition with superior magnetostrictive properties for many applications.