Satish Verma

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??m 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 (?i) 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 ?i was observed with the rise in the temperature for all the series of ferrites.

Electrical and magnetic properties of nanosized Mg0.2Mn0.5Ni0.3AlyFe2-yO4 ferrites

Electrical and magnetic behavior of Mg0.2Mn0.5Ni0.3AlyFe2-yO4(y=0.0-0.3) spinel ferrites synthesized by citrate precursor method sintered at 1200°C are reported. Samples were characterized by X-ray diffraction technique at room temperature. Lattice parameter ‘a’, saturation magnetization Ms, retentivity Mr, Bohr magneton nB and remnant ratio R=Mr/Ms are seen to decrease whereas coercivity Hc shows increasing trend with increasing Al3+ content. Anisotropy field HKA increases with aluminium content, which along with Ms enable calculation of magneto-crystalline anisotopy constant K1, which increases with increasing Al3+ content. The compositional variations of hysteresis parameters like Ms, Hc, Mr and R reveals that grains in composition studied are of multidomain type. A significant reduction in value of initial permeability and relative loss factor (RLF) was observed with increase of Al3+ ions. DC electrical resistivity decreases with increase in temperature exhibiting semiconductor like behavior. Activati...

Study of Structural, electrical and magnetic properties of Al3+ ions doped Mg0.2Mn0.5Ni0.3AlyFe2−yO4 spinel ferrites for high frequency applications

Structural, electrical and bulk magnetic properties of spinel system Mg0.2Mn0.5Ni0.3AlyFe2−yO4 with y varying from 0.0–0.3 in step of 0.1, synthesized by citrate precursor technique at 1200 °C, have been investigated. Variations of initial permeability, and RLF (relative loss factor) with frequency, in range of 0.075–20 MHz at different temperatures have been studied. Initial permeability (μi) attains very high value i.e. 59487 and RLF has very low values of 10−6–10−5 which is three orders of magnitude less than the samples prepared by conventional method. There is significant reduction in initial permeability, Curie temperature, RLF and dielectric loss with Al3+ ions. Therefore, very high μi and very low values of RLF and dielectric loss are attributed to better compositional stoichiometery and uniform microstructure, making these ferrites attractive for use in high frequency applications.

Study of Mössbauer and magnetic properties of Al3+ ions doped superparamagnetic nano ferrites

Nanocrystalline Al3+ ions doped Mg0.2Mn0.5Ni0.3AlyFe2-yO4 compositions, where y=0.0 and 0.10 have been synthesized by citrate precursor method. Crystal structure and magnetic properties have been investigated at room temperature by means of X-ray diffraction, TEM, LCR meter, VSM and Mossbauer spectroscopy. Particle size and lattice parameter has been found to decrease as non-magnetic Al content increased. Relative loss factor has very low value in range of 10−6–10−5 which is three orders of magnitude less than samples prepared by conventional method. The Mossbauer spectroscopy results shows superparamagnetism. The isomer shift corresponding to Fe3+ ions do not show any significant variation which indicates that replacement of Fe3+ ions do not affect significantly the d-electrons density which in turn affects the s-electrons density around Fe3+ nuclei. The nuclear hyperfine magnetic fields have been found to decrease at A-site and B-site with increasing substitution of Al3+ ions in Mg-Mn-Ni ferrite.

The microstuctural, Mössbauer and magnetic properties of MgGd0⋅1Fe1⋅9O4 ferrite processed by solid state reaction technique

The excellent combination of magnetic, electric and dielectric properties of Gd-Mg ferrites can be used to fulfill the future demand for high-frequency applications. MgGdxFe2−xO4 (x=0.0 and =0.1) ferrites, with improved initial permeability and extremely low relative loss factor (RLF), are prepared by solid state reaction technique. The structural studies were made by using XRD which confirm the single-phase spinel structure. The magnetic properties such as initial permeability and relative loss factor with frequency, in the range 0.075-30 MHz, at room temperature have been investigated. Mossbauer spectra of all the samples exhibit normal Zeeman split sextets due to the ferromagnetic behavior of the ferrites. The values of RLF in the presently studied ferrites at room temperature are of the order of 10−4 - 10−5. Low values of RLF exhibited by these ferrites suggest its utility in inductor and transformer applications. The mechanisms responsible to these results have been discussed in detail in this paper.

Study of Non‐Magnetic Al3+ Substituted Mixed Mg‐Mn‐Ni Ferrites for High Frequency Applications

Structural, magnetic and electrical studies have been carried out on Mg0.2Mn0.5Ni0.3AlyFe2−yO4 (y = 0.0, 0.1, 0.2, 0.3) prepared through citrate precursor technique sintered at 1200° C. Structural studies were made by X‐ray diffraction and TEM, which confirm the formation of single phase cubic spinel structure. Substitution of non‐magnetic Al3+ ion in Mg‐Mn‐Ni ferrite results in the decrease in particle size which was around 41.5 nm for y = 0.1. Variations of initial permeability, magnetic loss and RLF with frequency at different temperatures have been studied. RLF has very low values of the order 10−6−10−5. Magnetic loss has value of 11×10−3 at 10MHz. There is significant reduction in initial permeability, Curie temperature, RLF and lattice parameter with the incorporation of Al3+ ions in place of Fe3+ ions. Saturation magnetization (Ms) and retentivity decreases while coercivity (Hc) increases with increasing substitution of aluminum ion. DC resistivity increases and is of the order of 108 ohm‐cm making...

Study of Structural and Magnetic Properties of In3+ Substituted Mg‐Mn‐Ni Spinel Ferrites

Effect of substitution of trivalent indium ions in stoichiometric magnesium‐manganese‐nickel ferrites has been studied with composition Mg0.2Mn0.5Ni0.3InxFe2−xO4 with x varying from 0.1 to 0.3 in steps of 0.1 using citrate precursor technique Single‐phase cubic spinel structure of these samples has been confirmed from X‐ray analyses. Ferrites have been investigated for their electric and magnetic properties such as dc resistivity, saturation magnetization, initial permeability and relative loss factor (RLF). DC electrical resistivity (ρ) decreases with increase in temperature exhibiting semiconductor like behavior Bulk density increases and initial permeability (μi) decrease with increasing In3+ substitution. But μi increase with increasing sintering temperature for all composition. Fairly constant value of initial permeability over a wide frequency range (0.1–15 MHz) and low values of relative loss factor of order of 10;−6−10−5 are main achievements of present investigation. Saturation magnetization (Ms)...

Room Temperature Ferromagnetic Ordering in Lanthanum Substituted Nano‐Cobalt Ferrite

The effect of Fe3+ ions substitution by rare earth La3+ ions on magnetic properties of nanocrystalline cobalt ferrite is investigated in this paper. Co‐precipitation method was used to prepare ultrafine particles of CoFe2−xLaxO4 (x = 0,0.10,0.15). The samples have cubic spinel structure. Structure has been investigated by XRD while magnetic properties have been studied using VSM and Mossbauer spectrometer. La3+ ions modulate significantly the magnetic properties of cobalt ferrites.

Improvement in Electric, Dielectric and Magnetic Properties of MgGd0.05Fe1.95O4 Ferrites Processed by Solid State Reaction Technique

MgGd0.05Fe1.95O4 (MGFO) ferrite with improved magnetic, electrical and dielectric properties has been synthesized by solid state reaction technique and has been investigated for microstructures, magnetic, electric and dielectric properties. The dc electrical resistivity of MGFO ferrite was found to increase up to 40 times more as compared to MgFe2O4 (MFO) ferrite. The value of saturation magnetization (Ms) and remnant magnetization (Mr) has been increased due to the doping of Gd3+ ions in MFO ferrite. High resistivity, low value of dielectric loss and improved magnetic properties (Ms, Mr) can be correlated with better compositional stoichiometry and the replacement of Fe3+ ions by Gd3+ ions. The mechanisms responsible to these results have been discussed in this paper.MgGd0.05Fe1.95O4 (MGFO) ferrite with improved magnetic, electrical and dielectric properties has been synthesized by solid state reaction technique and has been investigated for microstructures, magnetic, electric and dielectric properties. The dc electrical resistivity of MGFO ferrite was found to increase up to 40 times more as compared to MgFe2O4 (MFO) ferrite. The value of saturation magnetization (Ms) and remnant magnetization (Mr) has been increased due to the doping of Gd3+ ions in MFO ferrite. High resistivity, low value of dielectric loss and improved magnetic properties (Ms, Mr) can be correlated with better compositional stoichiometry and the replacement of Fe3+ ions by Gd3+ ions. The mechanisms responsible to these results have been discussed in this paper.