Mixed Ferrite System Research Articles

Physico-chemical properties of pure and zinc incorporated cobalt nickel mixed ferrite (ZnxCo0.005−xNi0.005Fe2O4, where x = 0, 0.002, 0.004 M) nanoparticles

Pure and zinc substituted Co–Ni mixed ferrites (ZnxCo0.005−xNi0.005Fe2O4, where x = 0, 0.002, 0.004 M) were effectively prepared by employing co-precipitation method and their physico-chemical properties were investigated. XRD results confirmed face centered cubic cobalt nickel spinel ferrite formation. The noticeable variations were found in peaks corresponding to planes (220) and (440) as well as in crystallite size with Zn2+ ion incorporation. SEM images revealed rock like ferrite particles with agglomerated nature. Raman spectra revealed typical phonon vibration modes T2g(1), T2g(2) and Eg of cubic ferrite system. The Raman stoke shift and line broadening effect was revealed with foreign cation substitution in Co–Ni mixed ferrite system. Transition mechanism of spinel ferrites as 3A2(3F) → 1T2(1D) and 3d5 → 3d4 4 s observed at 493 and 521 nm was confirmed by photoluminescence studies. The emission and luminescent property of prepared ferrite was strongly depending on substituted cations into the spinel structure. FTIR bands in finger print region located at 584 (υ1) and 432 (υ2) cm−1 could be attributed to the cationic vibration preferred in tetrahedral A site and octahedral B site. The electrochemical behavior strongly reflected the cationic incorporation by means of possessing specific capacitance value of about 183 F/g for the sample Zn0.002Co0.003Ni0.005Fe2O4 at the scan rate of 5 mV/s. The substitution of foreign cations into the spinel lattice is one of the effective processes for tailoring the physico-chemical properties of nanoferrites.

Investigation of structural, optical and magnetic properties of thermal plasma synthesized Ni-Co spinel ferrite nanoparticles

Magnetic nanoparticles of nickel substituted cobalt ferrites, NixCo1−xFe2O4, (x=0 to 1 in the step of 0.2) were successfully synthesized by gas phase nucleation and growth process. For the first time, we report feasibility of synthesizing such mixed ferrite system using thermal plasma route. Further, effect of change in molar ratio of Co:Ni on the structural, optical and magnetic properties has been investigated in detail. The structural and phase formation analysis of the samples under investigation have been carried out using powder X-ray diffraction and Raman spectroscopy. The surface morphology of these particles has been studied using scanning electron microscopy and the micrographs so obtained were used to find out average gain size and size distribution. The optical and magnetic properties of the as synthesized samples were finally correlated with the magnetic moment of substituted species such as Ni for Co and cation distribution, analyzed using Mössbauer spectroscopy. Special modification in Thermo Gravimetric Analyzer was used to determine magnetic transition temperature.

Characterization and Transport Properties of Mixed Ferrite System Mn1-xCuxFe2O4; 0.0 ≤ x ≤ 0.7

A series of Cu-doped Mn ferrites with the formula Mn1-xCuxFe2O4 (0.0 ≤ x ≤ 0.7) were synthesized by citrate auto combustion method. The structural characterization and morphology of the samples were examined by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM). XRD and EDX confirmed the formation of single-phase cubic spinel structure. The electrical conductivity (σ), dielectric constant (ϵ′), and dielectric loss factor (ϵ′′) were studied as a function of temperature at different frequencies ranged from 100 kHz to 5 MHz. Increasing is observed in the values of σ, ϵ′, and ϵ′′ with substitution of copper up to x = 0.3. Above this value, a decrease in σ, ϵ′, and ϵ′′ was detected.

Microstructure and magnetic properties of substituted (Cr, Mn) - cobalt ferrite nanoparticles

Three mixed ferrite systems CoFe2O4, CoCr0.2Fe1.8O4 and CoMn0.2Fe1.8O4 were prepared by the co-precipitation method. X-ray diffraction (XRD) of the calcined powders at 900 °C confirms the accomplishment of the cubic spinel phase formation without any secondary phase. The cation distribution was determined from XRD data and suggested a mixed spinel structure. The higher value of the lattice parameter for Mn comparing with Cr substituted cobalt ferrite could be explained by migration of Co2+ cation from octahedral to tetrahedral sites. Infrared spectroscopy (FTIR) showed two absorption bands attributed to intrinsic vibrations of tetrahedral and octahedral complexes. The bands shifted toward lower frequency for doped samples comparing with corresponding Co-host ferrite frequencies. The microstructure was investigated by scanning electron microscopy (SEM) and suggested that the nanoparticles are agglomerated and have polygonal faced surfaces. The effect of Mn3+ and Cr3+ cation distribution among the tetrahedral (A) - and octahedral [B] - sites of Co substituted ferrite on magnetization and coercive field was investigated by vibrating sample magnetometer technique. Higher values of the coercive field of manganese and chromium substituted cobalt ferrite was explained by lower value of the average particle size. The small increase of saturation magnetization for doped ferrites was explained considering the oxidation state of the substituting ions.

Synthesis, characterisation and magnetic/electrical properties of the magnesium-doped Li–Zn nanoferrites

Nano-sized magnesium-doped Li-Zn mixed ferrite system, Li 0.25 Mg 0.5-x Zn x Fe 2.25 O 4 where X varies from 0 to 0.5 in steps of 0.1 has been prepared by novel solution combustion method using oxalyl-dihydrazide as capping agent and were characterised by X-ray diffraction, infrared, Mossbauer studies and transmission electron microscopy (TEM). The magnetic and electrical properties of the nanoparticles have been investigated by vibrating sample magnetometer and two-probe method, respectively, and results are compared with bulk materials. TEM and electrical studies reveal the formation of one-dimensional semiconducting nanorods that find an extensive application in lithium batteries and in the fast-paced miniaturisation of modern electronic devices. The variation in dielectric constant with frequency has been studied.

Preparation and magnetic studies of nickel ferrite nanoparticles substituted by Sn 4+ and Cu 2+

The mixed ferrite systems, namely NiFe 2−2 x Sn x Cu x O 4 ( x=0, 0.1, 0.2, and 0.3) nanoparticles have been studied to understand their structural and magnetic parameters. The NiFe 2−2 x Sn x Cu x O 4 nanoparticles were prepared by high energy ball milling (HEBM). The samples were characterized by the X-ray diffraction technique. All samples exhibited spinel structures. The crystalline size and internal strain were evaluated by XRD patterns using Williamson–Hall and Scherrer methods. Magnetic properties of the nanoparticles ferrite were studied by means of alternating gradient force magnetometry (AGFM) and Faraday balance.

Synthesis and characterization of mixed ferrite nanoparticles

Three mixed ferrite systems, namely Mn 0.75 Zn 0.18 Fe 2.07 O 4 (Mn–Zn), Ni 0.65 Zn 0.375 In 0.25 Ti 0.025 Fe 1.70 O 4 (Ni–Zn–In–Ti), and Ni 0.65 Zn 0.35 Fe 2 O 4 (Ni–Zn), have been studied to understand their structural and magnetic parameters under different nano-preparation routes. The Ni–Zn–In–Ti ferrite nanoparticles were prepared by ball milling while the Ni–Zn and Mn–Zn ferrite nanoparticles were prepared by coprecipitation. The samples were characterized by X-ray diffraction and VSM techniques. All the three systems exhibited spinel structures and displayed hysteresis. The estimated average ferrite particle sizes of Mn–Zn, Ni–Zn–In–Ti, and Ni–Zn ferrites using the Scherrer equation are 2.4, 6.9, and 9.9 nm, respectively. The observed corresponding magnetization values of these three systems are 7.9, 26, and 9.1 emu/g, respectively. The results are analyzed by attempting to correlate the magnetic performance of the samples under similar synthesis conditions and the particle size.

Structural and Magnetic Characterizations of Coprecipitated Ni–Zn and Mn–Zn Ferrite Nanoparticles

Two mixed ferrite systems, namely Ni0.65Zn0.35 Fe2O4 (Ni-Zn) and Mn0.75 Zn0.18 Fe2.07 O4 (Mn-Zn) have been prepared by coprecipitation method, and then the resulting ultrafine powders were heat treated at different temperatures from 200 to 800degC for improved crystallinity and magnetic properties. The samples were characterized by X-ray diffraction, vibrating sample magnetometry, and ferromagnetic resonance spectrometry. As a result of the heat treatment, the average particle size has been found to increase from 9.9 to 15.7 nm for Ni-Zn ferrites and from 2.4 to 10.2 nm for Mn-Zn ferrites, and the corresponding magnetization values have increased from 9.1 to 23 emu/g for Ni-Zn ferrites and from 7.9 to 11.7 emu/g for Mn-Zn ferrites, respectively. The results are discussed in the light of changes in particle size and inversion degree parameter for cationic distribution at nanoscales

Electrical conductivity of Mn–Zn ferrites

The electrical conductivity of polycrystalline mixed ferrite system having the chemical formula MnxZn1−xFe2O4 (where x=0.0, 0.2, 0.4, 0.6, and 0.8) was investigated from room temperature to the neighborhood of the Curie temperature by the two-probe method. The electrical conduction in these ferrites is explained on the basis of the hopping mechanism. Plots of log (σT) versus 103/T are almost linear and show a transition near the Curie temperature. The activation energy in the ferrimagnetic region is in general less than that in the paramagnetic region.

Investigation of Ferrimagnetism in Some Compounds using Polarized Neutrons

Polarized neutrons offer a very useful method of studying ferrimagnetic materials such as ferrites, in which the multiplicity of cations and their valence states prevent a unique determination of the spin structure when only polycrystalline material is available. This paper presents the first extensive use of polarized neutron powder-diffraction patterns for determining the structure of a carbide of Mn and Co and of a number of mixed ferrites having the spinel structure. The ferrimagnetic carbide with composition (Mn,Co)4C is found to have a cubic structure of the Mn4N type, with one of the Mn atoms at the cube corner and the face centers being occupied by one Mn and two Co atoms in a statistical distribution. The two Mn atoms are antiferromagnetically aligned with respect to each other, the corner atom having a moment of 4.0 μB while the face center moment is 3.0 μB. The two Co atoms have a moment of 0.8 μB each and are aligned parallel to the corner Mn moment along the cube edges. The material has a Néel temperature of 810°K and saturates at a field of 4.5 kOe. Polarized neutrons were used to choose a structure of cubic symmetry in preference to one of tetragonal symmetry. Two mixed ferrite systems of the general formula MxM′1−xFe2O4 where M = Mg, Zn and M′ = Mn, Ni have been studied for various values of x. Their Néel temperatures and cation distributions have been determined.