Variation Of Saturation Magnetization Research Articles

Structural, magnetic and elastic properties of Mn0.3−xMgxCu0.2Zn0.5Fe3O4 nanoparticles

In this paper, Mn0.3−xMgxCu0.2Zn0.5Fe3O4 (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30) nanoparticles were prepared by the nitrate-citrate technique at low temperature. The structural, microstructural, magnetic and elastic properties of the samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, Transmission electron microscopy, field emission-scanning electron microscopy and vibrating-sample magnetometer at room temperature. Rietveld refinement of the XRD patterns indicated the formation of the single phase cubic spinel structure (space group Fd-3m) without any detectable impurity phase in all the samples that also was confirmed by FTIR studies. The lattice parameter is found to increase non-monotonically with an increase in Mg ion concentration. Also, the bond lengths and bond angles (A and B sites) of the studied ferrites were calculated by the refining of the XRD data. The values of the crystallite size decrease with increasing micro-strain (and conversely) and both of them reach extremum at x = 0.15. The low remanence and coercivity values confirmed the formation of the superparamagnetic ferrites nanoparticles. The saturation magnetization of the samples gradually grows with Mg substitution and reach extremum at x = 0.15. Variation of saturation magnetization with Mg content can be mainly attributed to change of cation distribution, and Yafet-Kittel angle occurred between magnetic moments on B-site in the samples. The values of Young's modulus, Debye temperature, bulk modulus, rigidity modulus of the samples were determined by the values of elastic constant and wave velocities obtained from the force constants. The improvement of the elastic properties of sample x = 0.05 could be explained regarding the smaller values of the lattice parameter (a), the bond length and angle and the smaller crystallite size.

Structural, Magnetic and Rheological Behavior of Mn–Zn Ferrofluid

Oleic acid coated Mn–Zn ferrite nanoparticles with different compositions have been synthesized by a chemical co-precipitation method to prepare kerosene based ferrofluid. XRD confirms the synthesis of single crystalline phase of Mn–Zn ferrite nanoparticles. The saturation magnetization increases with increase in zinc concentration, reaches maximum at x = 0.4 and decreases for further increase in zinc concentration. The variation in saturation magnetization can be correlated to the modifications in cation distribution as a result of replacement of Mn-ion by Zn-ion thereby modifying the superexchange interaction between the A and B sublattices. The synthesized ferrofluids behaved as Newtonian fluids in the absence of the magnetic field, which naturally reflected the lack of large aggregates. However, under the magnetic field, viscosity increased because of formation of chain-like clusters of nanoparticles showing non-Newtonian behavior of the fluid. The viscosity increases with increase in zinc concentration, reaches maximum at x = 0.4 and decreases for further increase in zinc concentration. The variation in viscosity can be correlated to the modifications in saturation magnetization as a result of substitution of Zn.

Spin-wave propagation through a magnonic crystal in a thermal gradient

The properties of a magnonic crystal are expected to be strongly influenced by the presence of a thermal gradient. We investigated the propagation of backward volume and surface magnetostatic spin-waves in a 1D magnonic crystal (MC) exposed to a continuous spatial temperature gradient. It is shown that the thermal gradient applied along the propagation direction leads to a frequency shift and a modification of the transmission characteristics of the spin-waves. The frequency shift is caused by a variation in saturation magnetization due to the change in absolute temperature. The altered transmission manifests itself in a broadening of MC band gaps and the corresponding narrowing of the MC passbands and is understood to be a result of a spatial transformation of the spin-waves wavelengths in a thermal gradient. Furthermore, the transmission characteristics of spin-waves in a thermal gradient have been verified by numerical calculations based on the approach of the transmission matrix. The results of the calculations demonstrate a good agreement with the experimentally measured data.

Tuning of ferrimagnetic nature and hyperfine interaction of Ni2+ doped cobalt ferrite nanoparticles for power transformer applications

Ferrites may contain single domain particles which gets converted into super-paramagnetic state near critical size. To explore the existence of these characteristic feature of ferrites, we have performed magnetization(M-H loop) and Mössbauer spectroscopic studies of Ni2+ substitution effect in Co1-xNixFe2O4 (where x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles were fabricated by solution combustion route using mixture of carbamide and glucose as fuels for the first time. As prepared samples exhibit spinel cubic structure with lattice parameters which decreases linearly with increase in Ni2+ concentration. The M-H loops reveals that saturation magnetization(Ms), coercive field(Hc) remanence magnetization(Mr) and magnetron number(ηB) decreases significantly with increasing Ni2+ substitution. The variation of saturation magnetization has been explained on the basis of Neel's molecular field theory. The coercive field(Hc) is found strongly dependent on the concentration of Ni2+ and decrease of coercivity suggests that the particles have single domain and exhibits superparamagnetic behavior. The Mössbauer spectroscopy shows two ferrimagnetically relaxed Zeeman sextets distribution at room temperature. The dependence of Mössbauer parameters such as isomer shift, quadru pole splitting, line width and hyperfine magnetic field on Ni2+ concentration have been discussed. Hence our results suggest that synthesized materials are potential candidate for power transformer application.

Improved unipolar resistive switching characteristics of Au-doped nickel ferrite magnetic thin films for nonvolatile memory applications

Au-doped nickel ferrite (NiFe2O4-Au, NFO-Au) magnetic thin films were prepared on Pt/Ti/SiO2/Si substrates by a chemical solution deposition method to explore the effect of Au doping on unipolar resistive switching (RS) behavior. Experimental results reveal that 1% Au doped NFO film demonstrated considerably optimum switching parameters such as lower electroforming voltage, narrow distribution of SET/RESET voltages, good cycle-to-cycle endurance (103 cycles) and long data retention (105 s at 125 °C) as compared to NFO and Au-(0.5% and 2%) doped NFO films. The improved performance is attributed to suppressing of randomness of oxygen vacancies based filament by Au doping. Current transport conduction mechanisms are found to be Ohmic in low resistance state and Schottky emission in high resistance state. Physical model concerns for the rupture and formation of Au atoms assisted conductive filament inside the Au-doped NFO films based on the thermal effect of oxygen vacancies. Magnetic properties correlated with RS were measured and analyzed. The variation of saturation magnetization with different resistance state may be attributed to Au-doping induced different oxygen vacancies concentrations and make the conversion of valence states of Fe3+ and Fe2+ ions in octahedral sites easier. Our results provide a pathway towards the applications in nonvolatile RS memory and magnetoelectronic coupling devices.

Improve the Process of Enhancing Oil Recovery (EOR) by Applying Nanomagnetic Cobalt Ferrite Nanoparticles

In this paper we reported nano-crystalline cobalt ferrite powders were synthesized using co-precipitation method at 600 °C, 700 °C and 800 °C. The structural, morphological and magnetic properties of the powders were investigated by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). Infrared spectral analysis data between 200 and 1000 cm-1 defined the intrinsic cation vibrations of the characteristic spinel structure system. The saturation magnetization (Ms) and coercivity (Hc) of the CoFe2O4 were found to be in the range of 94-33 emu/g, which is still in the range of hard ferrite. The observed variation in saturation magnetization, coercivity and remanence magnetization as a function of increasing the temperature and grain size of samples. From this point of view, nano-scale size of nanoparticles makes them efficient for using in borehole stability maintaining for enhancing oil and gas recovery efficiency improvement. The large value of magnetic pressure (-2.95699) are expected to be useful in oil recovery applications. It has also been found that the choice of nanoparticles for application in oil recovery depends on nature, magnetic and electric properties of the reservoir rock.

A comparative study of the structural, magnetic and electrochemical properties of Al3+ and Cu2+ substituted NiZn ferrite/reduced graphene oxide nanocomposites

NiZn ferrite/reduced graphene oxide (Ni0.8Zn0.2Fe2O4/rGO) nanocomposite and Al3+ and Cu2+ substituted NiZn ferrite/reduced graphene oxide (Ni0.8Zn0.2Al0.1Fe1.9O4/rGO and Ni0.6Cu0.2Zn0.2Fe2O4/rGO) nanocomposites were directly synthesized by one-step hydrothermal route. XRD and FTIR confirmed the formation of Ni0.8Zn0.2Fe2O4/rGO, Ni0.8Zn0.2Al0.1Fe1.9O4/rGO and Ni0.6Cu0.2Zn0.2Fe2O4/rGO nanocomposites. The average crystallite size was found to be 16.9–20.4 nm. The substitution of Al3+/Cu2+ for Fe3+/Ni2+ ions promotes a variation in unit cell due to the difference of ionic radius between Al3+/Cu2+ and Fe3+/Ni2+, which leads the lattice parameter to vary from 8.353Å to 8.394 Å. Magnetic measurements reveal the saturation magnetization to vary with the replacement of Al3+/Cu2+ for Fe3+/Ni2+ ions. The variations of saturation magnetization in Al and Cu substituted NiZn ferrite/reduced graphene oxide nanocomposites have been explained in the light of Neel's two-sublattice theory. A maximum specific capacitance of 136.91 F/g and energy density of 16.80 W h/kg were obtained in Ni0.8Zn0.2Al0.1Fe1.9O4/rGO nanocomposite at a current density of 1 A/g. The enhanced electrochemical performances could be related to the high electronic conduction of Ni0.8Zn0.2Al0.1Fe1.9O4/rGO nanocomposite.

Plasma-assisted synthesis and study of structural and magnetic properties of Fe/C core shell

Pure and carbon-encapsulated iron nanoparticles with an average diameter of 25 nm were synthesized by using the DC plasma arc discharge method. Fe core nanoparticles were encapsulated with carbon layer, which is acting as protection layer against both oxidation and chemical reaction. The morphology and the Fe/C core/shell structure of the nanoparticles were studied by using field emission scanning electron microscopy and transmission electron microscopy. The x-ray diffraction study showed that the α-Fe phase exists with γ-Fe as an impurity. The studied samples have been interrelated with the variation of saturation magnetization, remanent magnetization and coercive field with the amount of carbon coating. The pure α-Fe sample shows saturation magnetization = 172 emu/g, and coercive field = 150 Oe, on the other hand few layer carbon coated α-Fe sample shows saturation magnetization =169 emu/g with higher coercive field 398 Oe.

Synthesis and characterization of DyxCoFe2−xO4 nanoparticles

In the present work, we report the synthesis of Dy doped CoFe2O4 nanoparticles using chemical method. Doping of Dy ions upto 0.15 in the host lattice does not result into impurity phase as revealed from X-ray diffraction (XRD) and Raman spectroscopy measurments. Near edge X-ray absorption fine structure measurments show the modification of Fe(3d)-O(2p) states and onset of 3+ valence state of Dy ions. Rietveld Refinment of XRD patterns, Mössbauer spectroscopy and Fe K-edge extended X-ray absorption fine structure measurments show cation reditribution after doping with Dy ions. All the synthesized nanoparticles exhibit ferrimagnetic like behavior. Coercivity increases with Dy doping concentration. Variation of saturation magnetization with Dy concentration is explained on the basis of cation redistribution and size effect.

The Microdefects, Magnetic Properties and Electron Characters of Fe-Ga Alloys

The microdefects, magnetic magnetization curves and electric characters of Fe100-xGax (x=16, 17, 18, 19, 20) were investigated by the means of X-ray diffraction, VSM modular on PPMS, positron lifetime spectroscopy and electric paramagnetic resonance spectroscopy. The X – ray diffraction patterns show that the Fe100-xGax alloys is similar to that of α – Fe, but the peaks move to low angle slightly. The result indicates Ga entered the iron lattice and the larger radium lead to the changing of the patterns. Positron lifetime spectra show that the intensity of the defects of the Fe100-xGax alloys varies obviously with different Ga content. The magnetizing curves were measured to check the saturation magnetization at room temperature. The variations of saturation magnetization do not monotonic decrease as expect with the increasing of Ga. When x=18, the magnetization is maximum; the minimum is x=20 because of the lowest iron content. The electron paramagnetic resonance spectrum shows that the peaks become narrower when the x decreases from 20 to 16. These results indicate that the addition of Ga has effect on the 3d electrons of Fe.

Structural and Magnetic Properties of Cu2+ Substituted Co–Zn Ferrite Nanoparticles, Synthesized by Sol–Gel Combustion Method

In this work, the effect of Cu content on structural and magnetic properties of Cobalt–Zinc Ferrite nanoparticles synthesized by sol–gel combustion method have been investigated. All the samples exhibit cubic spinel structure and the lattice constant decreases linearly with increasing Cu-content. Average crystallite sizes calculated from Debye–Scherrer formula are in the range of 51–100 nm. The broadening of X-ray diffraction peaks decrease with increasing Cu content ‘x’ suggest that crystallite size increases with increasing ‘x’. Cation distribution estimated form X-ray line intensity calculations show that Cu ions simultaneously occupy tetrahedral (A) and octahedral (B) sites with different ratio and Zn and Co ions occupies A and B sites respectively. With increasing Cu content a fraction of Co ions migrate to A site when x >0.2. Grain sizes estimated from SEM are found to be increase with increasing Cu content. Particle size calculated using TEM for the undoped Co–Zn ferrites is about 55 nm. Saturation magnetization (Ms), Coercivity (Hc) and remanent magnetization (Mr) that varies significantly with Cu-Content. Saturation magnetization decreases from 90.7 emu/g (x = 0.0) to 51 emu/g (x = 0.4). The proposed cation distribution supports the variation in saturation magnetization and Coercivity with increasing Cu content.

Correlation between ferromagnetism and the concentration of interfacial defects in multiferroic Bi7Fe2.75Co0.25Ti3O21 studied by positron annihilation

This paper investigated the effect of the annealing temperature on the interfacial defects and the magnetization of a single-phase multiferroic Bi7Fe2.75Co0.25Ti3O21. With the increase of annealing temperature, the average thickness of the nonaplates increased from 80 to 180nm. But the magnetic property measurement shows that the saturation magnetization gradually decreases with the increase of the annealing temperature correspondingly. Positron annihilation measurements reveal that the interfacial defects disappear obviously when the annealing temperature increased, which is found to agree well with the variation of saturation magnetization. The results suggest that with the higher concentration of interfacial defects may bring about higher saturation magnetization for the Aurivillius phase material, opening a window to improve the magnetic performance through controlling the concentration of interfacial defects.

Effect of magnetic pulse treatment on the magnetic characteristics of yttrium–iron garnets

The effect weak (10–100 kA m–1) low-frequency (10–20 Hz) pulsed magnetic fields have on the surface structure and magnetic characteristics of yttrium–iron garnet Y3Fe5O12 is studied by means of electron and Mossbauer spectroscopy. A mechanism is proposed for the variation of saturation magnetization in Y3Fe5O12 after magnetic pulse treatment. The mechanism is associated with the change in the spin state of iron ions localized in the tetrahedral sublattice.

Cation distribution and magnetic properties of Zn2+ substituted MnFe2O4 nanoparticles

Mn–Zn ferrite nanoparticles of the composition Mn1−xZnxFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) have been synthesized by a low temperature chemical co-precipitation method. The X-ray diffraction pattern confirms the synthesis of single crystalline phase of Mn–Zn ferrite nanoparticles. Crystallite size is of the order of 4–8 nm for all these samples. The lattice parameter decreases from 8.5075 to 8.4281 A with increase in zinc concentration. Formation of the spinel Mn–Zn ferrite was also supported by Fourier Transform Infrared Spectroscopy. Transmission electron microscopy was used to confirm the nanocrystalline nature of the samples. The magnetic measurements show superparamagnetic nature of the samples with zero remanence and coercivity. The saturation magnetization increases with increase in zinc concentration, reaches maximum at x = 0.4 and decreases for further increase in zinc concentration. The variation in saturation magnetization can be correlated to the modifications in cation distribution as a result of replacement of Mn-ion by Zn-ion thereby modifying the superexchange interaction between the A and B sublattices. Electron paramagnetic resonance (EPR) studies revealed that superexchange interaction between magnetic ions with oxygen ion and magnetic dipole interactions among nanoparticles are the two main factors, which determine EPR resonance parameters. The Curie temperature for MnFe2O4 nanoparticles is 394 °C and decreases to 95 °C for x = 0.6. Thus the relative composition of Mn and Zn can tune the Curie temperature of Mn–Zn ferrite nanoparticles which is very important for preparing the temperature sensitive ferrofluid that has the applications in the thermal management of the electronic systems.

Effects of sintering atmosphere and temperature on structural and magnetic properties of Ni-Cu-Zn ferrite nano-particles: Magnetic enhancement by a reducing atmosphere

In this work, effects of sintering atmosphere and temperature on structural and magnetic properties of Ni0.3Cu0.2Zn0.5Fe2O4 nanoparticles prepared by citrate precursor method have been studied. The structural characterization of the samples by X-ray powder diffraction and FT-IR spectroscopy is evidence for formation of a cubic structure with no presence of impurity phase. Calculated values of crystallite size and unit cell parameter show an increase with sintering temperature under different atmospheres. Variation of saturation magnetization with sintering temperature and atmosphere can be attributed to change of three factors: magnetic core size, inversion parameter and the change of Fe3+-ion concentration due to the presence of Fe4+ and Fe2+ ions. The saturation magnetization gradually grows with sintering temperature due to increase of magnetic core size and a maximum 63emu/g was achieved at 600°C under carbon monoxide-ambient atmosphere.

Novelty characterization and enhancement of magnetic properties of Co and Cu nanoferrites

Cobalt and copper nano ferrites synthesized by citrate technique were characterized by X-ray diffraction technique, field emission scanning electron microscopy, transmission electron micrographs, energy dispersive X-ray spectroscopy and atomic force microscope. The average crystallite sizes of Cu and Co were 24.7 and 37.7 nm respectively. The magnetic properties were studied by carrying out the hysteresis of MFe2O4 (M-Cu2+, Co2+) at room temperature and at 77 K. The data showed that CuFe2O4 has the lower saturation magnetization. While CoFe2O4 has the larger coercive field due to the high anisotropy of Co2+ ions. The variation in saturation magnetization and coercivity for the investigated samples were explained on the bases of exchange interactions. The magnetic properties of the investigated samples changed at low temperature (77 K) which were observed in shape of the magnetic hysteresis M(H) loops as well as the coercivity and the squareness values. Co samples will be hopeful for technological applications at or below room temperature.

Magnetic Properties of Polyvinyl Alcohol and Doxorubicine Loaded Iron Oxide Nanoparticles for Anticancer Drug Delivery Applications.

The current study emphasizes the synthesis of iron oxide nanoparticles (IONPs) and impact of hydrophilic polymer polyvinyl alcohol (PVA) coating concentration as well as anticancer drug doxorubicin (DOX) loading on saturation magnetization for target drug delivery applications. Iron oxide nanoparticles particles were synthesized by a reformed version of the co-precipitation method. The coating of polyvinyl alcohol along with doxorubicin loading was carried out by the physical immobilization method. X-ray diffraction confirmed the magnetite (Fe3O4) structure of particles that remained unchanged before and after polyvinyl alcohol coating and drug loading. Microstructure and morphological analysis was carried out by transmission electron microscopy revealing the formation of nanoparticles with an average size of 10 nm with slight variation after coating and drug loading. Transmission electron microscopy, energy dispersive, and Fourier transform infrared spectra further confirmed the conjugation of polymer and doxorubicin with iron oxide nanoparticles. The room temperature superparamagnetic behavior of polymer-coated and drug-loaded magnetite nanoparticles were studied by vibrating sample magnetometer. The variation in saturation magnetization after coating evaluated that a sufficient amount of polyvinyl alcohol would be 3 wt. % regarding the externally controlled movement of IONPs in blood under the influence of applied magnetic field for in-vivo target drug delivery.

Correlation of structural distortion with magnetic properties of Pr-YIG system

The structural and magnetic measurements are carried out to interpret the effect of substitution of Pr3+ into Y3Fe5O15 system. The evolution of the microstructure and magnetic properties of Y3-xPrxFe5O12 (x = 0.0–0.8) series were characterized by the X-ray diffraction technique (XRD), Far-Fourier Transform Infrared Spectroscopy (Far-FTIR), Vibrating Sample Magnetometer (VSM) and Mössbauer spectroscopy. The Rietveld refinement of the X-ray data indicated that single-phase garnet structure was achieved for all the obtained samples. The observed absorption bands in Far-FTIR spectra shows the substitution structural effects. The effect of Pr3+ on magnetic properties have been analyzed based on associating a specific superexchange interaction to configurations of iron ions with fixed number of Pr3+ at their vicinity. A random cation distribution model is used to discussed the results in detail. The Mössbauer analyses are consistent with the explanation of the magnetization behavior and interestingly revealed that how different configurations with different superexchange interactions contribute in saturation magnetization variation.

Hyperfine interaction and tuning of magnetic anisotropy of Cu doped CoFe2O4 ferrite nanoparticles

Ferrimagnetic oxides may contain single or multi domain particles which get converted into superparamagnetic state near a critical size. To explore the existence of these particles, we have made Mössbauer and magnetic studies of Cu2+ substitution effect in CoFe2−xO4 Ferrites (0.0, 0.1, 0.2, 0.3, 0.4, and 0.5). All the samples have a cubic spinel structure with lattice parameters increasing linearly with increase in Cu content. The hysteresis loops yield a saturation magnetization, coercive field, and remanent magnetization that vary significantly with Cu content. The magnetic hysteresis curves shows a reduction in saturation magnetization and an increase in coercitivity with Cu2+ ion substitution. The anisotropy constant, K1, is found strongly dependent on the composition of Cu2+ ions. The variation of saturation magnetization with increasing Cu2+ ion content has been explained in the light of Neel's molecular field theory. Mössbauer spectra at room temperature shows two ferrimagnetically relaxed Zeeman sextets. The dependence of Mössbauer parameters such as isomer shift, quadrupole splitting, line width and hyperfine magnetic field on Cu2+ ion concentration have been discussed.

Crystallization and high temperature functional properties in CoFeB films

Abstract CoFeB alloy films have been attracting much research interest for the applications in magnetoelectronic devices. In this study, crystallization and high temperature functional properties in the sputtered CoFeB alloy films were investigated. The as-deposited alloy films were amorphous and a nanocrystalline structure was formed after annealing, confirmed by X-ray measurements. Large variation in saturation magnetization with temperature was observed in thermomagnetic measurements, reflecting the interplay between crystallization and temperature dependent magnetization in the ferromagnetic alloy film. Pronounced changes in electrical resistivity and optical reflectance with temperature were observed in the alloy film, in accompany with the structural change. The activation barrier for crystallization was determined to be 1.32 eV from the electrical measurements, showing a good thermal stability of the alloy film.