Mn Ferrites Research Articles

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.

Synthesis, structural and magnetic properties of different metal ion substituted nanocrystalline zinc ferrite

The nanocrystalline ZnMFeO4 (M=Fe, Mn, Cr and Ti) ferrites were synthesized by sol–gel autocombustion route. XRD studies on these compositions revealed the formation of cubic phase for Cr and Ti substituted zinc ferrite, while tetragonal for phase for Mn substituted samples. The FT-IR data revealed two absorption bands in the range 400–800cm−1 arising due to tetrahedral (A) and octahedral (B) stretching vibrations. Surface morphology of all the samples studied by scanning electron microscopy technique revealed nearly spherical particles and agglomerates. The elemental analysis as obtained from EDAX is in close agreement with the starting composition used for the synthesis. The ferromagnetic properties studied by VSM indicate a significant role on the magnetic properties of the samples. The detailed results of XRD, infrared spectroscopy, SEM and magnetic properties indicating the role of substitution of different metal ions on the structural and magnetic properties of zinc ferrites are presented in the manuscript.

Low-temperature synthesis of MnxMg1−xFe2O4(x = 0–1) nanoparticles: cation distribution, structural and magnetic properties

Nanoferrites having composition MnxMg1−xFe2O4(x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) are synthesized by a low-temperature combustion method. The particle size measured from transmission electron microscopy and x-ray diffraction (XRD) patterns confirms the nanosized dimension of the as-prepared powder. From the analysis of XRD data with Scherrer's formula, the average crystallite size ranges from 23 to 33 nm and the lattice parameter ranges from 8.385 to 8.468 Å. Substitution of Mn2+ in MgFe2O4 causes an increase in the lattice constant, and this moderately distorts the lattice. Magnetic properties such as magnetization (Ms), coercivity (Hc) and remanence (Mr) with increasing Mn2+ concentration are studied at room temperature by a vibrating sample magnetometer. Substitution of Mn2+ for Mg2+ increases Ms from 34.5 to 54.5 emu g−1 and decreases Hc from 51.0 to 45.0 Oe. The results imply that the low-temperature combustion method is an efficient route for synthesis of nanoferrites without any extra calcination step. The as-prepared Mg–Mn ferrites are suitable for memory and switching circuits in digital computers.

IR Spectra, Elastic and Dielectric Properties of Li–Mn Ferrite

Polycrystalline ferrites, , (where and ), were prepared by using ceramic method. Single phase cubic structure was confirmed by X-ray diffractometer. The lattice parameter “a” was found to increase with increasing ion substitution. IR spectra of the samples were recorded from 200 to 1000 cm−1. The two primary bands corresponding to tetrahedral and octahedral were observed at about 575 cm−1 and 370 cm−1, respectively. Elastic properties of these mixed ferrites were estimated as a function of composition. Young's modulus , rigidity modulus , bulk modulus , Debye temperature (), and mean sound velocity () were calculated from the transverse () and longitudinal () wave velocities. The variation of elastic moduli with composition was interpreted in terms of binding forces between the atoms of spinel lattice. AC conductivity and dielectric properties of the samples were measured at room temperature over 100 Hz–1 MHz. The electrical conduction mechanism could be explained with the electron hopping model. Frequency exponential factor was calculated and it was found between 0.4 and 0.8.

Substitution effect of manganese for iron in “114” YBaFe4O7 ferrite: structure, magnetism and oxygen hyperstoichiometry

The study of the ferrites YBaFe4−xMnxO7 shows that the substitution of Mn2+ for Fe2+ in YBaFe4O7 stabilizes the hexagonal symmetry at the expense of the cubic one for 1 ≤ x ≤ 2. Using combined measurements of a.c. and d.c. magnetization, we establish that Mn substitution for Fe in YBaFe4O7 leading to a cationic disorder induces a spin glass behaviour. An important characteristic of these Mn substituted ferrites deals with their ability to absorb and desorb reversibly oxygen, leading to the oxides YBaFe4−xMnxO7+δ, with the highest δ values 2–2.25 that have been observed to date in this “114” family. These oxidized “Mn ferrites” keep the hexagonal symmetry and the spin glass characteristic temperature, Tsg, is varying with the oxygen content δ.

Controlled Synthesis, Physicochemical and Magnetic Properties of Nano-Crystalline Mn Ferrite System

Controlled Synthesis, Physicochemical and Magnetic Properties of Nano-Crystalline Mn Ferrite System

Study on the Absorption Properties of Spinel Type Ferrite Composite Coatings in the Low Frequency

In the present study magneto-polymer composite coatings are fabricated using nano Zn ferrite, Mn ferrite, Ni ferrite, Zn-Mn ferrite and Zn-Ni ferrite by spraying method. The complex permeabilities, Complex permittivities and microwave absorbing properties within the low frequency of these composites were characterized and investigated. The results showed that the magnetism of the mixed spinel ferrites ( Mn ferrite, Zn-Ni ferrite, Zn-Mn ferrite) are strong but the dielectric properties are weaker, while the magnetism of the normal spinel ferrites (Zn ferrite) is the weakest but provide with a big storage capability of electric energy. The absorbing characteristics of the spinel ferrites are better at 300 kHz-1.5GHz, with minimum absorption of 12.5 dB and the maximum absorption at 480MHz, 1050 MHz and 1400 MHz. The microwave absorbing property of the mixed spinel ferrite Zn-Mn ferrite is best having the RL value being -42.5 dB at 1400GHz.

Magnetic, dielectric, and complex impedance properties of nanocrystalline Mn–Zn ferrites prepared by novel combustion method

The electromagnetic and micro-structural properties of nanocrystalline spinel ferrite Mn xZn 1 − x Fe 2O 4 (x = 0.0–1.0) prepared by the novel route of combustion method were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively. The magnetic properties were measured using vibrating sample magnetometer. The analysis indicates that the permittivity, saturated magnetization and coercivity increase as the content of manganese rises. Further, the analysis of complex impedance spectra by an equivalent circuit model was used to investigate the AC electrical conduction mechanism. The results show that as-synthesized Mn–Zn ferrites with low conductivity and good magnetic properties have excellent potential for applications in electromagnetic devices.

Structure, electric and dielectric studies of indium-substituted magnesium copper manganese ferrites

The structure, electric and dielectric properties of In-substituted Mg–Cu–Mn ferrites having the general formula of Mg 0.9Cu 0.1Mn 0.1In x Fe 1.9− x O 4 with 0.0≤ x≤0.4 have been studied. X-ray diffraction (XRD) patterns of the samples indicated the formation of single-phase cubic spinel structure up to 0.2 and mixed phase (cubic and tetragonal phase) for samples x≥0.3. The relation of conductivity with temperature revealed a semiconductor to semimetal behavior as In +3 concentration increases. Variation in the universal exponent s with temperature indicates the presence of two hopping conduction mechanisms: the correlated barrier hopping (CHB) at low In +3 content x≤0.1 and small-polaron (SP) hopping at In +3 content x≥0.2. The variation in dielectric permittivity ( ε′, ε″) with temperature at different frequencies shows a normal behavior for the studied compounds, while the variation in dielectric loss tangent with frequency at different temperatures shows abnormal behavior with more than relaxation peak. The conduction mechanism used in the present study has been discussed in the light of electron exchange between Fe 3+ and Fe 2+ ions and hole hopping between Mn 2+ and Mn 3+ ions at the octahedral B-sites.

Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn–Mn ferrites

Graphical abstract: Variation of dielectric constant with frequency. Research highlights: {yields} Sol-gel route synthesized spherical crystalline nanoparticles of ZnMn{sub 1-x}Cr{sub x}FeO{sub 4}. {yields} XRD, DTA, FTIR, SEM, dielectric and impedance study. {yields} The ferrites show concentration dependence of ac electrical conductivity. {yields} Impedance response is dominated by grain boundary behavior. -- Abstract: Nanocrystalline ZnMn{sub 1-x}Cr{sub x}FeO{sub 4} (1.0 {>=} x {>=} 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm{sup -1} arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.

Study of dielectric and impedance properties of Mn ferrites

The paper reports on the effect of Al substitution on the structural and electrical properties of bulk ferrite series of basic composition MnFe 2−2 x Al 2 x O 4 (0.0≤ x≤0.5) synthesized using solid state reaction method. XRD analysis confirms that all the samples exhibit single phase cubic spinel structure excluding presence of any secondary phase. The dielectric constant shows a normal behaviour with frequency, whereas the loss tangent exhibits an anomalous behaviour with frequency for all compositions. Variation of dielectric properties and ac conductivity with frequency reveals that the dispersion is due to Maxwell–Wagner type of interfacial polarization in general and hopping of charge between Fe +2 and Fe +3 as well as between Mn +2 and Mn +3 ions at octahedral sites. The complex impedance plane spectra shows the presence of two semicircles up to x=0.2, and only one semicircle for the higher values of x. The analysis of the data shows that the resistive and capacitive properties of the Mn ferrite are mainly due to processes associated with grain and grain boundaries.

Magnetic and high rate adsorption properties of porous Mn1−Zn Fe2O4 (0 ⩽x⩽ 0.8) adsorbents

Porous spinel ferrites Mn(1-x)Zn(x)Fe(2)O(4) (0 ≤ x ≤ 0.8) are synthesized by a simple sol-gel method with egg white. All samples exhibit porous morphologies and large BET surface area (S(BET)). The substitution of Zn(2+) affects the magnetic properties of ferrites and the adsorption properties of methylene blue (MB) on ferrites, obviously. The saturation magnetization (Ms) of Mn(1-x)Zn(x)Fe(2)O(4) increases before x=0.4, and decreases with further increase of Zn(2+) substitution. This can be ascribed to the changes of the cationic distribution and the variation of spin arrangement in A-site and B-site of spinel structure. All samples show high adsorption capacity and the removal efficiencies of MB reach up to >90% within 3 h. The Zn(2+) substitution accelerates the adsorption rate and capacity of MB on Mn(1-x)Zn(x)Fe(2)O(4). The quickest adsorption occurred at x=0.2 and the largest adsorption capacity occurred at x=0.8.

Synthesis and morphological study of chromium substituted Zn–Mn ferrites nanostructures via sol–gel method

Nanocrystalline ZnMn 1− x Cr x FeO 4 (1.0 ≥ x ≥ 0) ferrites were prepared by sol–gel route. X-ray diffraction (XRD) method was used to confirm the formation of single phase cubic spinel lattice for all the composition. The lattice parameter ( a) shows a decreasing trend with the increase in Cr content. In all the studied compositions, spherical crystalline nanoparticles of about 30 nm size were observed by transmission electron microscopy (TEM) technique. The elemental analysis as obtained from EDAX is in close agreement with the expected composition from the stoichiometry of reactant solutions used. Infrared spectroscopic studies revealed two main absorption bands in the range of 400–800 cm −1 arising due to tetrahedral (A) and octahedral (B) stretching vibrations. On substitution of Cr 3+ in Mn 3+ site, the stretching frequency of the octahedral site increases smoothly but that of the tetrahedral site is seen to be unaltered. The detailed results of XRD, SAED and infrared spectroscopy have been discussed so as to bring out the role of chromium substitution in determining structural properties of Zn–Mn ferrites.

Inverse Magnetoelectric Effect in Two-Layer PbZr0.53Ti0.47O3–Mn0.4Zn0.6Fe2O4 Composite

The inverse magnetoelectric effect in two-layer composite consisting of piezoelectric PbZr0.53Ti0.47O3 (PZT) and ferrite Mn0.4Zn0.6Fe2O4 (MZF) plates has been studied. Dependences of the magnetic induction variation Bm on amplitude and frequency of ac electric field as well as on magnetic field strength, temperature, and composite composition for layered PZT–MZF composite have been determined.

Microwave electromagnetic and absorbing properties of Dy 3+ doped MnZn ferrites

Dy 3+ doped Mn-Zn ferrites Mn 0.3Zn 0.7Fe 2– x Dy x O 4 x=0, 0.01, 0.02, 0.03, 0.04were prepared by the conventional solid-state reaction. The crystal structure, surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction analysis(XRD), scanning electron microscopy(SEM) and network analyzer (Agilent 8722ET). All the XRD patterns showed the single phase of the spinel-type ferrite without other intermediate when x≤0.03. The average crystallite size was about 44–56 nm. The microwave electromagnetic properties of the samples were studied at the frequency range from 2 GHz to 18 GHz. It was shown that small amounts of Dy 3+ substitution could adjust microwave electromagnetic parameters magically. The tan δ exhibited a maximal peak when x=0.03, and the peak value was 0.56. It indicated that the microwave electromagnetic loss properties were excellent when x=0.03. Furthermore, the reasons were also discussed using electromagnetic theory. The reflection loss (RL) increased with the Dy 3+ content when x<0.04. The Mn 0.3Zn 0.7Fe 1.97Dy 0.03O 4 ferrite displayed excellent microwave absorption properties. The frequency (with respect to −10 dB) started from 11.9 GHz, and the bandwidth reached about 3.5 GHz. The peak value of RL was about −20.5 dB at a matching thickness of 2.7 mm.

Structural, magnetic and electrical properties of Co–Ni–Mn ferrites synthesized by co-precipitation method

Abstract In present work, fine particles of Co1−xNixFe1.9Mn0.1O4 (x = 0.2, 0.4, 0.6 and 0.8) system were prepared by co-precipitation method. X-ray diffraction (XRD) study of prepared sample confirms the cubic spinel phase formation. The microstructural features were examined by SEM images. Infrared absorption (IR) spectra shows two vibrational bands, one around 600 cm−1 ( v 1 ) and second around 400 cm−1 ( v 2 ) were attributed to the tetrahedral and octahedral group complexes of the spinel lattice respectively. The magnetic parameters viz. magnetization at 6 kOe (M6 kOe) and coercivity (Hc) were measured at room temperature under the field of 6 kOe. It is observed that, both M6 kOe and Hc decrease with increase of Ni content. The DC resistivity measurement with temperature indicates a semiconducting behavior of the samples. Frequency dependent dielectric constant (ɛ′) shows the usual dispersion behavior, while linear variation of AC conductivity (σAC) with frequency confirms the conduction due to small polaron.

Magnetoelectrical effect in layered composites PbZr0.53Ti0.47O3-Mn0.4Zn0.6Fe2O4

The magnetoelectric (ME) effect in two- and three-layered composites made up of polarized ceramic plates of lead zirconate-titanate PbZr0.53Ti0.47O3 (PZT) and manganese-zinc ferrite Mn0.4Zn0.6Fe2O4 (MZF) has been studied. Dependences of the transverse ME voltage coefficient (α31) on the magnetostrictive layer thickness and the magnetic field intensity and frequency have been established. The mechanical coupling coefficient of the composite plates has been estimated. Results obtained for two-layered PZT-MZF structures have been analyzed using the method of efficient medium parameters.

Mixed Mg–Mn ferrites for high frequency applications processed by citrate precursor technique

Mg0.9Mn0.1InxFe2−x O4 (x = 0.1 and 0.2) and Mg0.9Mn0.1AlyFe2−y O4 (y = 0.1, 0.5 and 0.7) ferrites, with improved initial permeability and extremely low relative loss factor (RLF), were synthesized by the citrate precursor technique. Structural studies were made by using the x-ray diffraction technique and scanning electron microscopy (SEM), which confirm the formation of single-phase spinel structure. The size of the particle was of the order of ∼0.5 µm for the samples sintered at 1200 °C, which is smaller than that obtained for ferrite powders by the conventional ceramic method. The magnetic properties such as initial permeability and RLF with frequency, in the range 0.1–20 MHz, at different temperatures have been investigated. Initial permeability (μi) attains a very high value, 17342, for the In3+ doped ferrite series and for the Al3+ doped ferrite series the maximum value is 3785. The RLF was found to have low values and is of the order of 10−5–10−4 in the frequency range 0.1–20 MHz. In addition to this, an increase in the value of μi was observed with the rise in the temperature for all the series of ferrites.

Optimization of catalytic, surface and magnetic properties of nanocrystalline manganese ferrite

Single-domain manganese ferrite nanoparticles have been synthesized with narrow particle size distribution using the combustion technique. Influence of fuel ratios on the as-prepared powders were characterized by XRD, SEM, VSM, N 2 adsorption at −196 °C and conversion of cyclohexene at 200–400 °C. Ratios of fuel to cations were maintained variously at 0.0, 0.67, 1.33 and 2.67. The fuel to cations ratio of 2.67 gives better yield in the formation of nanocrystalline Mn ferrite and single-domain particles with a narrow range of size distribution. Maximum magnetization and coercivity values of the investigated ferrite are also greater for the ratio of 2.67. These values measured at room temperature are found to be 68.58 emu/g and 62.57 Oe, respectively. The BET surface area of the investigated solids was found to decrease by increasing the ratio between fuel and cations due to increasing the flame temperature. However, this treatment resulted in a significant increase in catalytic activity of the as-synthesized solids. All solids investigated behaved as dehydrogenation catalysts. The change in fuel/cations ratios did not alter the mechanism of dehydrogenation of cyclohexene, but increased the concentration of active sites involved in the catalyzed reaction.

Enhanced Néel temperature in Mn ferrite nanoparticles linked to growth-rate-induced cationinversion

Mn ferrite (MnFe2O4) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a modifiedco-precipitation technique in which mixed metal chloride solutions were added todifferent concentrations of boiling NaOH solutions to control particle growth rate.Thermomagnetization measurements indicated an increase in Néel temperaturecorresponding to increased particle growth rate and particle size. The Néel temperature isalso found to increase inversely proportionally to the cation inversion parameter,δ, appearing inthe formula (Mn1−δFeδ)tet[MnδFe2−δ]octO4. These results contradict previously published reports of trends between Néel temperatureand particle size, and demonstrate the dominance of cation inversion in determining thestrength of superexchange interactions and subsequently Néel temperature in ferritesystems. The particle surface chemistry, structure, and magnetic spin configuration playsecondary roles.