Remenant Magnetization Research Articles

Structure and magnetic properties of Ba1−xDyxFe12−yZnyO19 synthesized by Sol–Gel auto-combustion technique

Ba1-xDyxFe12-yZnyO19 (x ​= ​0–0.1 and y ​= ​0–1) hexaferrites were produced by the sol-gel auto-combustion technique.In the XRD analyses of all samples, BaFe12O19 phase was observed as the pure state. ZnFe2O4 begins to form at x ​= ​0.02 and y ​= ​0.2 and peak intensities increases with the substution of Dy3+ and Zn2+ cations for the samples sintered at 900 ​°C and 1100 ​°C. As the temperature increases to 1300 ​°C, peaks belonging to BaFe12O19 phase were disappeared and transformed into Ba3Fe26O41 and BaZn1.2Fe16.8O27 phases at x ​= ​0.06 and y ​= ​0.6.Crystallite size decreased with increasing Dy3+ and Zn2+ substitutions for the samples sintered at 900 ​°C and 1100 ​°C. The smallest crystallite size obtained at 900 ​°C, x ​= ​0.06 and y ​= ​0.6.As the amount of substitution elements increase, saturation magnetization (Ms) and remenance magnetization (Mr) values decreased due to the formation of paramagnetic spinel ZnFe2O4 phase for the samples sintered at 900 ​°C and 1100 ​°C.The highest Mr value of 36.1 emu/g was obtained for the pure samples sintered at 1300 ​°C. It decreased sharply to 18.9 emu/g (about 50%) with the substitution of Dy3+ and Zn2+ cations at x ​= ​0.02 and y ​= ​0.2.Dy3+ and Zn2+ substituted hexaferrites sintered at 900 ​°C (x ​= ​0.06 and y ​= ​0.6) exhibited the highest Hc value of 4.84 ​kOe.

Structural, Electrical and Magnetic Studies on Cu(1-x)ZnxFe2O4 Nanoparticles Synthesized by Co-Precipitation method

Magnetic Nano particles of Cu(1-x)ZnxFe2O4 have been synthesized using Coprecipitation technique. During the experimental investigation, CuZn ferrites exhibited interesting structural, electrical and magnetic properties. Formation of spinel phase was identified using X-Ray diffraction (XRD) technique. The ferrite compounds prepared in the laboratory exhibited cubic spinal symmetry. The Lattice constants of the compounds were determined. The morphology and size of the crystallite was found by Transmission Electron Microscopy (TEM). The magnetic properties were studied using Vibration Sample Magnetometer (VSM) and the saturation magnetization (Ms), remenant magnetization (Mr) and the Coercivity force (Hc) values were evaluated. Electrical properties of the samples were quantified using standard two-probe method

Green synthesis approach for nano sized CoFe2O4 through aloe vera mediated sol-gel auto combustion method for high frequency devices

Abstract Nanosized CoFe2O4 was synthesized by Aloe vera-mediated sol-gel auto-combustion method. The yielded nanoparticles were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) to investigate the phase formation and morphology of the obtained powders. FTIR, XRD and Raman spectra revealed the formation of single phase CoFe2O4. FESEM micrographs showed the formation of some bud like structure and the particle size obtained is around 50–65 nm. Investigation of magnetic properties viz. saturation magnetization (Ms), remenant magnetization (Mr) and coercivity (Hc) were studied from the M-H loop and were found to be 72.23 emu/gm, 31.29 emu/gm, 1519 Oe respectively. In addition, the massive dielectric constant, low dielectric loss, and AC conductivity of the CoFe2O4 nanoparticles were dependent on the frequency (100 Hz-1 MHz), method of preparation and grain size. Room temperature ferroelectric measurement reveals a partially unsaturated P-E loop due to the high coercive field and influence of leakage current.

Effect of Nd3+ doping on structural and magnetic properties of Ni0.5Co0.5Fe2O4 nanocrystalline ferrites synthesized by sol-gel auto combustion method

Rare earth Neodymium (Nd3+) doped nanocrystalline Ni-Co mixed spinel ferrites which are chemically represented as Ni0.5Co0.5NdxFe2-xO4 (x = 0.025 to 0.125, in the step of 0.025) were synthesized by sol-gel auto-combustion method. The structural, morphological, infrared and magnetic properties were studied in detail in the light of Nd3+ doping using standard techniques. X-ray analysis reveals the formation of single phase cubic spinel structure for all the prepared samples without any impurity phase. The crystallite size calculated from Scherrer's formula was observed to be decreasing with increasing Nd3+ content. The lattice parameter calculated using XRD data was found to be decreasing upto x = 0.100 and then increases for x = 0.125. X-ray density was observed to be increasing from 5.327 to 5.630 gm/cm3. Surface morphology was studied through scanning electron microscopy technique. Grain size calculated from SEM analysis was found to be in the range of 30–59 nm. From transmission electron microscopy study, the average particle size was observed to be in the range of 35–45 nm. FTIR results exhibit the characteristics cubic spinel ferrite nature of the samples with two prominent absorption bands near 400 cm−1 and 600 cm−1. FTIR also confirms the incorporation of Nd3+in the crystal structure. The magnetic behavior shows strong influence of substitution of Nd3+ions. The saturation magnetization, coercivity and remenance magnetization all decrease with substitution of Nd3+ ions up to x = 0.100. For further increase in Nd3+ concentration (x = 0.125), the saturation magnetization found to be increased.

Deposition, characterization, magnetic and optical properties of Zn doped CuFe2O4 thin films

Nanocrystalline Zn doped Cu spinel ferrite thin films having compositional formula Cu1−xZnxFe2O4 (where x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) were deposited on glass substrate by spray pyrolysis deposition technique using nitrates of copper, zinc and ferric metals as raw materials. The deposited thin films were characterized by X-ray diffraction, infrared, field emission scanning electron microscope, energy dispersive spectra, atomic force microscope, vibrating sample magnetometer and ultra violet visible spectroscopy at room temperature. X-ray diffraction studies revealed the formation of single phase cubic spinel structure of CuZn spinel ferrite thin films. The crystallite size was determined using Debye-Scherrer's formula and found in the range of 9–20 nm. The thickness of the deposited thin films measured by spectroscopy reflectometer was found in the range of 267–247 nm. The surface morphology of the prepared thin films studied by FESEM technique exhibits the dense structure. The analysis of AFM images showed the columnar structure of the deposited thin films. The magnetic measurements showed the soft ferromagnetic behaviour except for x = 1.0; for this it shows anti-ferromagnetic behaviour. The magnetic parameters like saturation magnetization, remenance magnetization, coercivity, initial permeability and magnetic domain size were obtained from the M − H loops. The value of saturation magnetization of thin film samples increases with zinc up to x = 0.6 and decreases for further x values. The optical properties as a function of Zn content ‘x’ were investigated in order to get the both direct and indirect band gaps of thin films. The values of direct and indirect band gap increased with zinc content x except for x = 0.8 and varies from 2.04 to 2.26eV and 1.74–1.96eV respectively.

Effects of Calcination Temperature on the Structural and Magnetic Properties of NiFe2O4 Nanoparticles

NiFe2O4 nanoparticles have been synthesized by water-in-oil microemulsion method. Effects of calcination temperature varying from 600 to 1200°C on the structural and magnetic properties of NiFe2O4 nanoparticles have been investigated. Studies carried out using XRD, SEM and VSM techniques. Results indicated that magnetic properties of NiFe2O4 nanoparticles showed great dependence on the variation of the crystallinity and particle sizes caused by the calcination temperature. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc was not determined only by the crystallinity and size of NiFe2O4 nanoparticles.

Magnetic and dielectric interactions in nano zinc ferrite powder: Prepared by self-sustainable propellant chemistry technique

The structural, magnetic and dielectric properties of nano zinc ferrite prepared by the propellant chemistry technique are studied. The PXRD measurement at room temperature reveal that the compound is in cubic spinel phase, belong to the space group Fd−3m. The unit cell parameters have been estimated from Rietveld refinement. The calculated force constants from FTIR spectrum corresponding to octahedral and tetrahedral sites at 375 and 542cm−1 are 6.61×102 and 3.77×102Nm−1 respectively; these values are slightly higher compared to the other ferrite systems. Magnetic hysteresis and EPR spectra show superparamagnetic property nearly to room temperature due to comparison values between magnetic anisotropy energy and the thermal energy. The calculated values of saturation magnetization, remenant magnetization, coercive field and magnetic moment supports for the existence of multi domain particles in the sample. The temperature dependent magnetic field shows the spin freezing state at 30K and the blocking temperature at above room temperature. The frequency dependent dielectric interactions show the variation of dielectric constant, dielectric loss and impedance as similar to other ferrite systems. The AC conductivity in the prepared sample is due to the presence of electrons, holes and polarons. The synthesized material is suitable for nano-electronics and biomedical applications.

Structural and magnetic studies of Mg(1−x)ZnxFe2O4 nanoparticles prepared by a solution combustion method

Abstract Nanocrystalline Mg(1−x)ZnxFe2O4 (x = 0.0, 0.25, 0.5, 0.75 and 1) ferrites were prepared by a solution combustion method using a mixture of fuels. The structural and magnetic properties of the as-prepared samples were studied using powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis absorption spectra and vibrating sample magnetometer (VSM) measurements. The PXRD analysis of all the samples revealed the single phase cubic structure with the space group Fd 3 ¯ m . The average crystallite size determined from the PXRD data was found to increase from 12 nm to 25 nm with an increase in the Zn content from x = 0 to x = 1. The IR absorption spectra exhibited two prominent peaks, which are assigned to tetrahedral and octahedral vibrations. The saturation magnetization, magnetic moment and remenant magnetization increases with an increase in the zinc content up to x = 0.5 and decrease thereafter. The observed behavior is consistent with Yaffet–Kittel magnetic ordering. The ZFC (zero field cooled) and FC (field cooled) measurements of magnetization revealed that the blocking temperature is well below room temperature.

Synthesis and characterization of Pd-doped Co nanofibers as a multifunctional nanostructure

Due to the axial ratio feature, bimetallic nanofibers are expected to have novel characteristics. In this study, Pd-doped Co nanofibers could be successfully prepared using simple, low cost, high yield and effective technique; electrospinning. The introduced nanofibers have been synthesized by calcination of electrospun nanofibers composed of Pd NPs/cobalt acetate tetrahydrate/poly(vinyl alcohol) in a vacuum atmosphere. The introduced Pd–Co nanofibers revealed distinct photocatalytic activity as an almost 90% from the methylene blue dye has been oxidized within 30min. As an active layer in a diode, the introduced nanofibers showed good performance. Magnetic properties study indicated that Pd nanoparticles negatively affected the saturation magnetization of the cobalt nanofibers, however very low remenant magnetization was obtained (7.7emu/g) compared to the un-doped Co nanofibers (69.22emu/g) which concludes that Pd modified Co to be magnetically clean material.

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor.

Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the crystallinity and size of CoFe2O4 nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results showed that the well-established silica network provided nucleation locations for CoFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an ideal nucleation environment to disperse CoFe2O4 nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even more versatile.

Study on the influence of annealing temperature and ferrite content on the structural and magnetic properties of x(NiFe 2O 4)/(100 − x)SiO 2 nanocomposites

Magnetic nanocomposites of nickel ferrite nanoparticles uniformly dispersed in the silica matrix have been synthesized successfully by a sol–gel process using tetraethylorthosilicate (TEOS) and metallic nitrates as precursors. In addition, the influence of the annealing temperatures, varying from 400 to 900 °C, and NiFe 2O 4 contents, x(NiFe 2O 4)/(100 − x)SiO 2 (10 ≤ x ≤ 60 wt.%), on the structural and magnetic properties of the nanocomposite samples have been investigated. The studies carried out using XRD, FT-IR, TEM, STA (TG–DTG–DTA) and VSM techniques. The results indicated that the structural and magnetic properties of the samples showed great dependence on the variation of the particle size caused by the annealing temperature and NiFe 2O 4 content. The crystallization, saturation magnetization M s and remenant magnetization M r increased as the annealing temperature and NiFe 2O 4 content increase. But the variation of coercivity H c was not in accordance with that of M s and M r, indicating that H c is not determined only by the size of NiFe 2O 4 nanoparticles. TEM images showed spherical nanoparticles homogeneously dispersed in the silica network and were uniform in both morphology and particle size distribution with sizes of 10–15 nm. The results showed that the well-established silica network provided nucleation locations for NiFe 2O 4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. The synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of nickel ferrite even more versatile.

Enhancement of magnetization in Eu doped BiFeO3 nanoparticles

Bi 1 − x Eu x FeO 3 (BEFOx) nanoparticles have been synthesized by a sol-gel method. The samples maintain the pure rhombohedral structure up to x=0.1, while an impure phase of EuFeO3 is observed at x=0.15. The remenant magnetization of the BEFOx, which is significantly higher than those in nonmagnetically rare-earth doped BiFeO3, is found to increase with the increase of Eu concentration. Ferromagnetic coupling between Eu3+ and Fe3+ ions, evidenced by our first-principles calculations, is found to be the main reason for such a magnetization enhancement. In the mean time, the appearance of EuFeO3 phase is demonstrated to be another factor for the further magnetization enhancement in BEFOx=0.15.

Studies on structural, electrical and magnetic properties of y(Ni 0.5Zn 0.3Co 0.2Fe 2O 4) + (1 − y)(BaTiO 3) composites

The polycrystalline Ni 0.5Zn 0.3Co 0.2Fe 2O 4 ferrite and barium titanate were prepared by standard ceramic technique. The ME composites having the general formula y(Ni 0.5Zn 0.3Co 0.2Fe 2O 4) + (1 − y)(BaTiO 3) were prepared using these as basic materials. The confirmation of cubic spinel structure of the ferrite phase and tetragonal pervoskite of the ferroelectric phase was confirmed by XRD. The microstructure of the composites was studied by scanning electron microscopy (SEM). The dc resistivity of the samples was measured as a function of temperature. The ac conductivity was derived from dielectric constant ( έ) and loss tangent (tan δ) values. It is concluded that the conduction in the present composites is due to small polaron hopping. The hysteresis measurements carried out to determine saturation magnetization ( M s), remenance magnetization ( M r) and coersivity ( H c) of the samples.

Studies on magnetic and magnetoelectric properties of the NiFe2O4–Ba0.7Sr0.3TiO3 composites

The magnetic and magnetoelectric properties of magnetoelectric (ME) composites consisting of with nickel ferrite (NiFe2O4) and barium strontium titanate (Ba0.7Sr0.3TiO3) were investigated. The composites were prepared by standard double sintering ceramic method. The X-ray diffraction analysis was carried out to confirm the phases formed during sintering and also to calculate the lattice parameters. The hysteresis measurements were done to determine saturation magnetization (Ms), remenance magnetization (Mr) and coercivity (Hc) of the samples. The magnetoelectric voltage coefficient (dE/dH)H was studied as a function of intensity of the magnetic field. The measured magnetoelectric (ME) response demonstrated strong dependence on the volume fraction of NiFe2O4 and the applied magnetic field. A large ME voltage coefficient of about 560 μVcm−1Oe−1 was observed for 15% NiFe2O4 + 85% Ba0.7Sr0.3TiO3 composite.