Synthesis and magnetic properties of Mn–Zn ferrite nanoparticles

Mn–Zn ferrite nanoparticles (Mn_1−xZn_xFe₂O₄) are synthesized by a hydrothermal precipitation approach using metal sulfate solution and aqueous ammonia. The analysis methods of XRPD, TEM, TGA, and VSM are used to characterize the magnetic nanoparticles. Through the characterization of the precipitated nanoparticles, the effects of the reacting component proportions and preparation techniques on the Curie temperature, the magnetization, and the size distribution of Mn–Zn ferrite nanoparticles are discussed. Furthermore, the Mn–Zn ferrite nanoparticles are used to prepare ferrofluid. Variation of the magnetic properties of the ferrite nanoparticles with the composition content x of Zn and the magnetic moment of the nanoparticles are discussed.     

Micro Raman,Mossbauer and magnetic studies of manganese substituted zinc ferrite nanoparticles: Role of Mn

A series of Mn–Zn Ferrite nanoparticles (<15 nm) with formula Mn_xZn_1−xFe₂O₄ (where x=0.00, 0.35, 0.50, 0.65) were successfully prepared by citrate-gel method at low temperature (400 °C). X-ray diffraction analysis confirmed the formation of single cubic spinel phase in these nanoparticles. The FESEM and TEM micrographs revealed the nanoparticles to be nearly spherical in shape and of fairly uniform size. The fractions of Mn²⁺, Zn²⁺ and Fe³⁺ cations occupying tetrahedral sites along with Fe occupying octahedral sites within the unit cell of different ferrite samples are estimated by room temperature micro-Raman spectroscopy. Low temperature Mossbauer measurement on Mn_0.5Zn_0.5Fe₂O₄ has reconfirmed the mixed spinel phase of these nanoparticles. Room temperature magnetization studies (PPMS) of Mn substituted samples showed superparamagnetic behavior. Manganese substitution for Zn in the ferrite caused the magnetization to increase from 04 to18 emu/g and Lande's g factor (estimated from ferromagnetic resonance measurement) from 2.02 to 2.12 when x was increased up to 0.50. The FMR has shown that higher Mn cationic substitution leads to increase in dipolar interaction and decrease in super exchange interaction. Thermomagnetic (M–T) and magnetization (M–H) measurements have shown that the increase in Mn concentration (up to x=0.50) enhances the spin ordering temperature up to 150 K (blocking temperature). Magnetocrystalline anisotropy in the nanoparticles was established by Mossbauer, ferromagnetic resonance and thermomagnetic measurements. The optimized substitution of manganese for zinc improves the magnetic properties and makes these nanoparticles a potential candidate for their applications in microwave region and biomedical field.     

Effect of cation distribution on the properties of Mn0.2ZnxNi0.8−xFe2O4

Mn_0.2Zn_xNi_0.8−xFe₂O₄ (x=0.2, 0.3, 0.4, 0.5, 0.6) are synthesized by the citrate precursor method. Effects of zinc substitution on DC resistivity, dielectric relaxation intensity, initial permeability, saturation magnetization and Curie temperature have been investigated. It is observed that resistivity increases with increase in zinc concentration up to x=0.5 and then decreases. The observed behaviour is explained in terms of hopping and site preference of ions in the lattice. The main contribution to dielectric relaxation intensity is observed to be due to space charge polarization. Initial permeability is observed to increase with increase in zinc concentration. Saturation magnetization increases up to x=0.4 and then starts decreasing. Canting effect is observed for higher zinc concentrations.     

Fabrication and magnetic property analysis of monodisperse manganese-zinc ferrite nanospheres

Monodisperse Mn-Zn ferrite (Mn_1−xZn_xFe₂O₄) nanospheres have been prepared via a simple solvothermal method. The as-synthesized samples were characterized in detail by X-ray diffraction pattern (XRD), transmission electron microscope (TEM), high-solution transmission electron microscope (HRTEM), select area electron diffraction pattern (SAED), scanning electron microscope (SEM), and vibrating sample magnetometer (VSM). The results show that a large number of the high-purity Mn_1−xZn_xFe₂O₄ nanocrystallites were synthesized and these nanocrystallites oriented aggregated to nanospheres. The dependence of magnetic properties of Mn_1−xZn_xFe₂O₄ nanospheres on the composition content x of Zn was studied. The maximum saturation magnetization value of the as-prepared sample (Mn_0.6Zn_0.4Fe₂O₄) reached 52.4 emu g⁻¹.     

Magnetic properties of bio-synthesized zinc ferrite nanoparticles

The magnetic properties of zinc ferrite (Zn-substituted magnetite, Zn_yFe_1-yFe₂O₄) formed by a microbial process compared favorably with chemically synthesized materials. A metal reducing bacterium, Thermoanaerobacter, strain TOR-39 was incubated with Zn_xFe_1−xOOH (x=0.01, 0.1, and 0.15) precursors and produced nanoparticulate zinc ferrites. Composition and crystalline structure of the resulting zinc ferrites were verified using X-ray fluorescence, X-ray diffraction, transmission electron microscopy, and neutron diffraction. The average composition from triplicates gave a value for y of 0.02, 0.23, and 0.30 with the greatest standard deviation of 0.02. Average crystallite sizes were determined to be 67, 49, and 25 nm, respectively. While crystallite size decreased with more Zn substitution, the lattice parameter and the unit cell volume showed a gradual increase in agreement with previous literature values. The magnetic properties were characterized using a superconducting quantum interference device magnetometer and were compared with values for the saturation magnetization (M_s) reported in the literature. The averaged M_s values for the triplicates with the largest amount of zinc (y=0.30) gave values of 100.1, 96.5, and 69.7 emu/g at temperatures of 5, 80, and 300 K, respectively indicating increased magnetic properties of the bacterially synthesized zinc ferrites.     

Structural and magnetic properties of Co1−xZnxFe2O4 nanoparticles by co-precipitation method

Co_1−xZn_xFe₂O₄ nanoparticles were prepared by co-precipitation method with x varying from 0 to 1.0. The powder samples were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR). The average crystallite sizes of the particles were determined from XRD. X-ray analysis showed that the samples were cubic spinel. The average crystallite size (D_aveXR) of the particles precipitated was found to vary from 6.92 to 12.02 nm decreasing with the increase in zinc substitution. The lattice constant (a_o) increased with the increase in zinc substitution. The specific saturation magnetization (M_S) of the particles was measured at room temperature. The magnetic parameters such as M_S, H_c, and M_r were found to decrease with the increase in zinc substitution. FTIR spectra of the Co_1−xZn_xFe₂O₄ with x varying from 0 to 1.0 in the range 400–4000 cm⁻¹ were reported. The spinel structure and the crystalline water adsorption of Co_1−xZn_xFe₂O₄ nanoparticles were studied by using FTIR.     

Synthesis and magnetic properties of Co–Zn magnetic fluid

Co_1−xZn_xFe₂O₄ (with x varying from 0 to 0.7) nanoparticles to be used for ferrofluid preparation were prepared by chemical co-precipitation method. The fine particles were suitably dispersed in transformer oil using oleic acid as the surfactant. The magnetization (M_s) and the size of the particles were measured at room temperature. The magnetization (M_s) was found to decrease with the increase in zinc substitution. The magnetic particle size (D_m) of the fluid was found to vary from 11.19 to 4.25 nm decreasing with the increase in zinc substitution.     

Nanostructural,magnetic and Mössbauer studies of nanosized Co1−xZnxFe2O4 synthesized by co-precipitation

This work presents a systematic investigation on the structural and magnetic properties of Co_1−xZn_xFe₂O₄ (0.5<x<0.75) nanoparticles synthesized by the chemical co-precipitation method. The X-ray diffraction analysis, the Fourier Transform Infrared (FTIR) and the Vibrating Sample Magnetometer were carried out at room temperature to study the micro-structural and magnetic properties. The X-ray measurements revealed the production of a broad single cubic phase with the crystallite size within the range of 6–10 nm. The FTIR measurements between 400 and 4000 cm⁻¹ confirmed the intrinsic cation vibrations of the spinel structure. The magnetic measurements show that the saturation magnetization and coercivity decrease by increasing the zinc content. Furthermore, the results reveal that the sample with a chemical composition of Co_0.3Zn_0.7Fe₂O₄ exhibits the super-paramagnetic behavior and the Curie point of 97 °C.     

Y-type hexagonal ferrites containing zinc,copper and cadmium: Magnetic properties and cation distribution

A complete magnetic and Mössbauer characterization has been worked out for the Y-type hexaferrites series with (Ba, Sr)₂Me₂Fe₁₂O₂₂ (Me = Zn, Cu, Cd) composition. The data relative to the dependence of the saturation magnetization, anisotropy, Curie temperature and cation distribution on composition and temperature could be logically interpreted as leading to the following conclusions. The magnetic order in Zn₂-Y is characterized by the presence of a “random flip” for which a quantitative model has been developed. The substitution of zinc with cadmium increases the spin flip, which, on the other hand, is reduced or eliminated by substitution of zinc with copper or of barium with strontium: the possibility of partially controlling the value of the saturation magnetization will follow. Also the planar anisotropy of Zn₂-Y can be controlled and finally turned into an axial one by substituting zinc with copper.     

Influence of manganese substitution and annealing temperature on the formation,microstructure and magnetic properties of Mn–Zn ferrites

The effects of annealing temperature and manganese substitution on the formation, microstructure and magnetic properties of Mn_xZn_1−xFe₂O₄ (with x varying from 0.3 to 0.9) through a solid-state method have been investigated. The correlation of the microstructure and the grain size with the magnetic properties of Mn–Zn ferrite powders was also reported. X-ray diffraction (XRD), a scanning electron microscope (SEM) and a vibrating sample magnetometer (VSM) were utilized in order to study the effect of variation of manganese substitution and its impact on crystal structure, crystalline size, microstructure and magnetic properties of the ferrite powders formed. The XRD analysis showed that pure single phases of Mn–Zn ferrites were obtained by increasing the annealing temperature to 1200–1300 °C. Increasing the annealing temperature to ?1300 °C led to abnormal grain growth with inter-granular pores and this led to a decrease in the saturation magnetization. Moreover, an increase in the Mn²⁺ ion substitution up to x=0.8 increased the lattice parameter of the formed powders due to the high ionic radii of the Mn²⁺ ion. Mn–Zn ferrites phases were formed and the positions of peaks were shifted by substituting manganese. The average crystalline size was increased by increasing the annealing temperature and decreased by increasing the substitution by manganese up to 0.8. The average crystalline size was in the range 95–137.3 nm. The saturation magnetization of the Mn–Zn-substituted ferrite powders increased continuously with an increase in the Mn concentration up to 0.8 at annealing temperatures of 1200–1300 °C. Further increase of Mn substitution up to 0.9 led to a decrease of saturation magnetization. The saturation magnetization increased from 17.3 emu/g for the Mn_0.3Zn_0.7Fe₂O₄ phase particles produced to 59.08 emu/g for Mn_0.8Mn_0.2Fe₂O₄ particles.     

Enhancement of initial permeability due to Mn substitution in polycrystalline Ni0.50−xMnxZn0.50Fe2O4

The structural and magnetic properties of Mn substituted Ni_0.50−xMn_xZn_0.50Fe₂O₄ (where x=0.00, 0.10 and 0.20) sintered at various temperatures have been investigated thoroughly. The lattice parameter, average grain size and initial permeability increase with Mn substitution. Both bulk density and initial permeability increase with increasing sintering temperature from 1250 to 1300 °C and above 1300 °C they decrease. The Ni_0.30Mn_0.20Zn_0.50Fe₂O₄ sintered at 1300 °C shows the highest relative quality factor and highest initial permeability among the studied samples. The initial permeability strongly depends on average grain size and intragranular porosity. From the magnetization as a function of applied magnetic field, M(H), it is clear that at room temperature all samples are in ferrimagnetic state. The number of Bohr magneton, n(μ_B), and Neel temperature, T_N, decrease with increasing Mn substitution. It is found that Mn substitution in Ni_0.50−xMn_xZn_0.50Fe₂O₄ (where x=0.20) decreases the Neel temperature by 25% but increases the initial permeability by 76%. Possible explanation for the observed characteristics of microstructure, initial permeability, DC magnetization and Neel temperature of the studied samples are discussed.     

Synthesis and characterization of Ni-Zn ferrite nanoparticles

Nickel zinc ferrite nanoparticles Ni_xZn_1−xFe₂O₄ (x=0.1, 0.3, 0.5) have been synthesized by a chemical co-precipitation method. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, electron paramagnetic resonance, dc magnetization and ac susceptibility measurements. The X-ray diffraction patterns confirm the synthesis of single crystalline Ni_xZn_1−xFe₂O₄ nanoparticles. The lattice parameter decreases with increase in Ni content resulting in a reduction in lattice strain. Similarly crystallite size increases with the concentration of Ni. The magnetic measurements show the superparamagnetic nature of the samples for x=0.1 and 0.3 whereas for x=0.5 the material is ferromagnetic. The saturation magnetization is 23.95 emu/g and increases with increase in Ni content. The superparamagnetic nature of the samples is supported by the EPR and ac susceptibility measurement studies. The blocking temperature increases with Ni concentration. The increase in blocking temperature is explained by the redistribution of the cations on tetrahedral (A) and octahedral (B) sites.     

Mn–Zn ferrite nanoparticles for ferrofluid preparation: Study on thermal–magnetic properties

Mn_1−xZn_xFe₂O₄ (with x   varying from 0.1 to 0.5) ferrite nanoparticles used for ferrofluid preparation have been prepared by chemical co-precipitation method and characterized. Characterization techniques like elemental analysis by atomic absorption spectroscopy and spectrophotometry, thermal analysis using simultaneous TG-DTA, XRD, TEM, VSM and Mossbauer spectroscopy have been utilized. The final cation contents estimated agree with the initial degree of substitution. The Curie temperature (_Tc$T_{\mathrm{c}}$) and particle size decrease with the increase in zinc substitution. In the case of particles with higher zinc concentration, both ferrimagnetic nanoparticles and particles exhibiting superparamagnetic behavior at room temperature are present. In addition, some of the results obtained by slightly altering the preparation condition are also discussed. The precipitated particles were used for ferrofluid preparation. The fine particles were suitably dispersed in heptane using oleic acid as the surfactant. The volatile nature of the carrier chosen helps in altering the number concentration of the magnetic particles in a ferrofluid. Magnetic properties of the fine particles and ferrofluids are discussed. Ferrofluids having Mn_0.5Zn_0.5Fe₂O₄ particles can be used for the energy conversion application utilizing the magnetically induced convection for thermal dissipation.     

Structural, thermal and magnetic properties of Ni1−xMnxFe2O4 nanoferrites

In this paper, the structural, thermal and magnetic properties of Ni_1−xMn_xFe₂O₄ are presented. It is observed that high concentration of Mn²⁺ ions into NiFe₂O₄ tends to reduce the particle size. Calcination at 500 °C has resulted in the growth of Ni_1−xMn_xFe₂O₄ nanoparticles, but the calcination at 900 °C has led to the evaporation of the majorities of the polyvinyl alcohol. After calcination at 900 °C, crystallographically oriented NiMnFe₂O₄ nanoparticles are formed. These Ni_1−xMn_xFe₂O₄ nanoparticles show hysteresis behaviour upon magnetization. On the other hand, saturation magnetization (Ms) values decreases with increasing Mn content in ferrite due to the influence of Mn²⁺ ion in the sub lattice.     

Magnetic interactions in Cu-substituted manganese ferrites

A series of Mn_1−xCu_xFe₂O₄, with x=0, 0.25, 0.50, 0.75 and 1.0, spinel ferrites were prepared by standard ceramic method, to study the effect of compositional variation on magnetic susceptibility, saturation magnetization (M_s), Curie temperature (T_c) and magnetic moments (μ_B). The Curie temperatures have been evaluated by measuring the ac susceptibility using the mutual inductance technique. On increasing Cu contents from 0.0 to 0.50, the saturation magnetization increases while the Curie temperature decreases. On further increase in Cu contents, x>0.50 a decreasing trend in M_s is exhibited while T_c continues to decrease. This effect can be partially related to the low magnetic moments of Cu⁺² ions. The dominant interaction in all ferrite samples is A-B interaction which is due to the negative values of the characteristic temperature θ(K) showing that the magnetic ordering is antiferromagnetic. The Y-K angle increases gradually with increasing copper contents and extrapolates to 90° for CuFe₂O₄. From the computation of Y-K angles for Mn_1−xCu_xFe₂O₄, it can be concluded that the mixed copper ferrites exhibit a non-collinearity of the Y-K type while MnFe₂O₄ shows a Neel type of ordering.     

Influence of copper cations on the magnetic properties of NiCuZn ferrite nanoparticles

Ni_0.6−xCu_xZn_0.4Fe₂O₄ (x=0-0.5) ferrite nanoparticles were prepared, employing a reverse micelle process. X-ray diffraction and transmission electron microscopy evaluations demonstrated that single phase spinel ferrites with narrow size distribution were obtained. Vibrating sample magnetometer was employed to probe the magnetic properties of the samples. It was found that with an increase in copper content, the saturation magnetization decreases. Magnetic dynamics of the samples was studied by measuring a.c. magnetic susceptibility versus temperature at different frequencies. The phenomenological Néel-Brown and Vogel-Fulcher models were employed to distinguish between the interacting or non-interacting systems. The system exhibits that there is strong interaction among fine particles.     

Magnetic properties of nanostructured MnZn ferrite

Mn_0.5Zn_0.5Fe₂O₄ nanoparticles (10-30 nm) have been prepared via mechanochemical processing, using a mixture of two single-phase ferrites, MnFe₂O₄ and ZnFe₂O₄. SQUID measurements (field-cooled magnetization curves and hysteresis loops) were performed to follow the mechanically induced evolution of the MnFe₂O₄/ZnFe₂O₄ mixture submitted to the high-energy milling process. The resulting single MnZn nanoferrite phase was characterized by SQUID (M-H curve), Faraday balance (M-T curve) and transmission electron microscopy. The magnetic characteristics of the mechanosynthesized material were compared with those of bulk Mn_0.5Zn_0.5Fe₂O₄. It was found that the saturation magnetization of nanostructured Mn_0.5Zn_0.5Fe₂O₄ (87.2 emu/g) is lower than that of the bulk Mn_0.5Zn_0.5Fe₂O₄, but, the Néel temperature of the sample (583 K) is higher than that of the bulk Mn_0.5Zn_0.5Fe₂O₄.     

Magnetic,electronic and structural properties of ZnxFe3−xO4

A series of samples Zn_xFe_3−xO₄ have been prepared by the chemical coprecipitation technique and characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS). XRD demonstrates all the samples of Zn_xFe_3−xO₄ have a spinel structure same as Fe₃O₄. The magnetic hysteresis loops of Zn_xFe_3−xO₄ obtained from VSM indicate that the saturation magnetization has a maximum when x is ∼1/3. The chemical states of Fe atoms and Zn atoms in zinc ferrites have been measured using XPS and Auger electron spectroscopy (AES). The Fe 2p core-level XPS spectra and Zn L₃M₄₅M₄₅ Auger peaks have been analyzed and the results have been discussed in correlation with the samples’ magnetic properties. These results suggest most of Zn atoms occupy the tetrahedral sites and a small amount of them occupy the octahedral sites.     

Li0.5Fe2.5−xMnxO4 ferrite sintered from microwave-induced combustion

Li_0.5Fe_2.5−xMn_xO₄ (0≦x≦1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion, using lithium nitrate, ferric nitrate, manganese nitrate and carbohydrazide as the starting materials. The process takes only a few minutes to obtain as-received Mn-substituted lithium ferrite powders. The resultant powders annealed at 650 ^°C for 2 h and were investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermomagnetic analysis (TMA). The results revealed that the Mn content were strongly influenced the magnetic properties and Curie temperature of Mn-substituted lithium ferrite powder. As for sintered Li_0.5Fe_2.5−xMn_xO₄ specimens, substituting an appropriate amount of Mn for Fe in the Li_0.5Fe_2.5−xMn_xO₄ specimens markedly improved the complex permeability and loss tangent.     

Magnetic and Mössbauer studies of Ni substituted Li-Zn ferrite

Li-Zn ferrites substituted with Ni having the compositional formula Li_0.4−0.5xZn_0.2Ni_xFe_2.4−0.5xO₄ where x=0.02?x?0.1 in steps of 0.02 were fabricated by the citrate precursor method. This method has been employed to get nanosized particles and good magnetic properties. The spinel phase structure of the prepared ferrites was confirmed by XRD analysis. The effect of Ni concentration on magnetic properties such as saturation magnetization and Curie temperature were investigated. A good knowledge of these magnetic properties is desirable from application point of view. The values observed are large and both quantities were found to decrease with substitution. The saturation magnetizations were found to vary from 78 to 94 emu/gm while the Curie temperature which limits the operating temperature of the system ranges between 563 and 584 °C. Mössbauer data were also recorded at room temperature and the hyperfine parameters like isomer shift, quadrupole splitting and internal magnetic field estimated. The results obtained and mechanisms involved are discussed.