Nano-sized Ferrites Research Articles

Dielectric, magnetic, ferroelectric, and Mossbauer properties of bismuth substituted nanosized cobalt ferrites through glycine nitrate synthesis method

CoFe2-xBixO4 nanoferrites with x = 0, 0.05, 0.1, 0.5, and 1.0 have been synthesized by the glycine nitrate process. The present study investigates the effect of Bi3+ substitution on the microstructural, dielectric, ferroelectric, magnetic, and Mossbauer properties of CoFe2O4 nanoparticles. The X-ray diffraction technique was used to confirm the phase purity and estimate the crystallite size which revealed the formation of a secondary phase when Bi3+ concentration exceeds x = 0.5. Transmission electron microscopy indicated the formation of grains by aggregation of small crystallites with a reduction in grain size to 20 nm with an increase in Bi3+ content and also divulged the lattice parameter value to be 8.378 Å, confirming the crystalline nature of the synthesised sample. Dielectric properties performed in the frequency range of 100 Hz to 1 MHz determined that the dielectric behavior is attributed to the Maxwell-Wagner polarization and the activation energy of the specimens is calculated from the dielectric measurements. The hysteresis curve indicated the ferrimagnetic nature of the samples. The samples also exhibited a well saturated P-E loop with gradual lowering in remenant polarization, coercive field, and saturation polarization with an increase in bismuth concentration. Mössbauer spectroscopy analysis confirmed the changes in magnetic moment of ions, their coupling with neighbouring ions, and cation exchange interactions. Owing to the high physical, thermal, and chemical stabilities, these magnetic ceramics, CoFe2-xBixO4, possesses tremendous potential in major understanding of magnetism and in magnetic recording applications for high density information storage.

Role of Nd-Ni on structural, spectral and dielectric properties of strontium-barium based nano-sized X-type ferrites

The influence of neodymium and nickel substitution on structural and dielectric parameters was investigated in strontium-barium X-type hexagonal ferrites having composition SrBaCu2−xNixNdyFe28−yO46 (x = 0, 0.2, 0.4, 0.6, 0.8, 1 and y = 0, 0.02, 0.04, 0.06, 0.08, 0.1). Sol-gel method was employed for synthesizing these hexagonal ferrites. The XRD plots of all studied materials which were annealed at 1250°C show single phase characteristics. Lattice parameter ‘c’ increased as a consequence of larger radius of rare earth ion (Nd3+) as compared to (Fe3+), while lattice parameter ‘a’ showed very small variation. The cell volume was obtained in the range 2508.32–2523.75 (Å3). The inclusion of Nd-Ni also affected X-ray density, bulk density and porosity. The FTIR spectroscopy indicated the particular absorption peaks of hexagonal ferrites and it was performed in the range of 500–700cm−1. On account of Nd-Ni doping, the dielectric constant, dielectric loss and AC-conductivity showed decreasing trend. The occupancy of Nd3+ ions at octahedral site impedes the valence alternation of Fe3+; therefore there was decrease in dielectric permittivity. Ac conductivity has been decreased from 9.14 to 6.49 (Ωcm)−1 at frequency of 2.7GHz. The Cole-Cole plots of synthesized materials noticeably revealed grain boundary contribution. The appearance of single semi-circle in impedance Cole-Cole graphs confirms the exceptional role of grain boundaries in the conduction process. The considerably lower dielectric parameters of investigated nano X-type ferrites propose their feasibility for high-frequency applications (phase shifters, dielectric resonators, stealth technology etc).

Systematic study of Ce3+ on the structural and magnetic properties of Cu nanosized ferrites for potential applications

Ce3+ substituted Cu-spinel nanoferrites CuCexFe2−xO4 (x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were synthesized via sol–gel self-combustion hybrid route. Single phase spinel ferrite of Cu nanoferrites were examined using X-ray diffraction (XRD) analysis whereas the multiphase structure was observed as Ce contents increased from x = 0.06. Field emission scanning electron microscopy (FESEM), Thermogravimetric and differential thermal analysis (TGA and DTA) and Fourier transform infrared spectroscopy (FTIR) were used to find out the morphology phase and metal stretching vibrations of Ce3+ substituted nanocrystalline ferrites. The crystallite size was increased and found in the range of 25–91 nm. The agglomerations in Cu ferrite samples increase as the Ce3+ concentration increases. The magnetic properties such as remanence, saturation magnetization, coercivity, Bohr magneton and magnetocrystalline anisotropy constant (K) were determined using M−H loops recorded from a vibrating sample magnetometer (VSM). Saturation magnetization, remanence and coercivity are increased as the Ce3+ contents increase in Cu nanocrystalline samples. Moreover, law of approach to saturation (LoA) was used to calculate the maximum value of saturation for Ce-doped Cu nanoferrites. The soft magnetic behaviour of the Cu nanoferrite is observed as compared to the samples substituted with the increased Ce contents in Cu nanocrystalline ferrite. Bohr magneton and magnetocrystalline anisotropy are found to increase with the substitution of rare earth Ce3+ contents in Cu spinel nanocrystalline ferrite. Ce-doped Cu nanocrystalline ferrites with excellent properties may be suitable for potential applications in sensing, security, switching, core, multilayer chip inductor, biomedical and microwave absorption applications.

The Effect of Contact Non-equilibrium Plasma on Structural and Magnetic Properties of Mn\u0425Fe3\xa0\u2212\xa0X\u041e4 Spinels

Nano-sized manganese ferrites MnхFe3 − хО4 (х = 0–1.3) were prepared using contact non-equilibrium plasma (CNP) in two different pH (11.5 and 12.5). The influence of synthesis conditions (e.g., cation ratio and initial pH) on phase composition, crystallite size, and magnetic properties were investigated employing X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and magnetic measurement techniques. The formation of monodispersed faceted ferrite particles at х = 0–0.8 was shown. The FTIR spectra revealed reflection in region 1200–1700 cm−1 caused by the presence of water adsorbed on the surface of Fe3 − xMnxO4 micro-granules or embedded into their crystal lattice. The most sensitivity of reflection spectra to the composition changes takes place within a 400–1200 cm−1 range, typical to the stretching vibrations of Fe(Mn)–O (up to 700 cm−1 ), Fe(Mn)–OH, and Fe(Mn)–OH2 bonds (over 700 cm−1). The XRD results showed that the nanocrystalline MnхFe3 − хО4 (0 < x < 1.0) had cubic spinel crystal structure with average crystallite size 48–49 A. The decrease of crystalline size with the x increase was also observed.

Effect of the Fe/Ba Ratio and Sintering Temperature on Microstructure and Magnetic Properties of Barium Ferrites Prepared by Hydrothermal Method

Magnetoplumbite-type (M-type) hexagonal barium ferrite particles were synthesized by a hydrothermal method. The structure and magnetic properties of barium ferrites were investigated systematically, which indicated that the ratio of Fe/Ba (RF/B) and sintering temperature have an important effect on structure and performance. Phase composition, micro-morphology, and magnetic properties of the particles were investigated by X-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). When the ratio of Fe/Ba (RF/B) is even low or high, inferior images of XRD could be attained with certain impurities. When RF/B = 8, the single phase could be obtained without impurities. Micro-morphology of the particles exhibits the uniform plane hexagonal structures of nano-sized M-type ferrites when sintered at 800 °C. Saturation magnetization (M s) reaches the maximum value at RF/B = 7 (M s = 45.07 emu/g). The value of coercivity (H c) increases with the growth of RF/B, and H c is up to 6207 Oe when RF/B = 7. The effect of RF/B and temperature on magnetization (M s) and coercivity (H c) was studied in this paper.

Structural, spectral, electrical, dielectric and magnetic properties of Yb doped SrNiCo-X hexagonal nano-structured ferrites

Abstract Ytterbium (Yb) doped X-type hexagonal nano-sized ferrites (Sr2NiCoFe28O46) were fabricated by micro-emulsion method. The development of hexagonal structure of ferrite materials was confirmed by XRD analysis. The size of crystallites as determined by Scherrer's formula was found in the range 29–41 nm. The lattice strain of these ferrites was increased from 3.62 × 10−2 to 3.73 × 10−2 with the increased Yb-contents. The tetrahedral absorption bands shifted slightly towards higher frequency whereas octahedral bands shifted towards lower frequency side. The incorporation of Yb enhanced dc electrical resistivity significantly from 2.05 × 108 to 3.35 × 109 Ω-cm. The AC conductivity was increased with frequency whereas it decreased with the inclusion of Yb3+ ions. This distinctive behavior of these hexagonal ferrites may be suitable for microwave devices and electromagnetic attenuation applications. The doping of Yb3+ optimized coercivity whereas remanence and saturation magnetization were decreased. These ferrite materials can be used in longitudinal recording media due to more thermally stable and higher coercivity (577–671 Oe).

Sago starch: chelating agent in Sol-gel synthesis of cobalt ferrite nanoparticles

Starch from the stem of sago palm (Metroxylon sagu) was demonstrated as a chelating agent in the sol-gel synthesis of cobalt ferrite (CoFe2O4) nanoparticles. Variations in the weight ratio of metal nitrates to sago starch from 1:8 to 1:12 led to the particle size of 30–500 nm. However, further increase in sago starch to 1:16 resulted in ferrimagnetic hysteresis loops with a reduced coercive field and magnetization due to the second phase of hematite (α-Fe2O3). The synthesis conditions and products were comparable to those of the polyvinyl alcohol (PVA) sol-gel synthesis. Thus, sago starch can be implemented in the green synthesis of nanosized ferrites whose magnetic properties are tuned by varying of sol-gel compositions for each application.

A study of friction wear behaviour of nano-ferite modified epoxy resins

Ferrites are generally used to obtain soft magnets for domestic or industrial applications but their use in this direction had generated an increasing interest in modifying the polymer properties by dispersing in their volume certain amounts of these ceramic compounds. The current study focused friction wear behaviour induced by the presence of nano-sized strontium ferrite and barium ferrite in an epoxy matrix. The wear behaviour of nanoferite modified epoxy resins tests were conducted on a pin-on-disc geometry. Three types of epoxy resins had been used with 5% weight ratio of each type of ferrite and 10% weight ratio when both ferrites were used.

Coordination polymer-derived nano-sized zinc ferrite with excellent performance in nitro-explosive detection.

Herein, a mixed metal coordination polymer, {(H2pip)[Zn1/3Fe2/3(pydc-2,5)2(H2O)]·2H2O} 1 {where H2pip = piperazinediium and pydc-2,5 = pyridine-2,5-dicarboxylate}, was successfully synthesized using a hydrothermal technique. To confirm the structure and phase purity of 1, single crystals of an isomorphous pure Fe compound, {(H2pip)[Fe(pydc-2,5)2(H2O)]·2H2O} 1a, were synthesized based on similar synthetic conditions. Single crystal X-ray data of 1a confirmed the one-dimensional anionic metal-organic coordination polymer hydrogen bonded with protonated piprazine (piperazinediium) and lattice water molecules. The phase purity of 1 and 1a were confirmed via powder X-ray diffraction. Compound 1 was systematically characterized using IR, TGA, SEM, and EDX elemental mapping analysis. Compound 1 was used as a single source precursor for the preparation of nano-sized ZnFe2O4via thermal decomposition. The as-obtained ZnFe2O4 was fully characterized using PXRD, SEM, TEM, and EDX elemental mapping analysis. It was found that ZnFe2O4 was formed in its pure form with particle size in the nano-dimension. The aqueous dispersion of nano-sized ZnFe2O4 exhibits a strong emission at 402 nm upon excitation at 310 nm. This emissive property was employed for luminescence-based detection of nitroaromatic explosives in an aqueous medium through luminescence quenching for the first time. Importantly, selective detections have been observed for phenolic nitroaromatics based on differential luminescence quenching behaviour along with a detection limit of 57 ppb for 2,4,6-trinitrophenol (TNP) in water.

Structural, spectral, dielectric and magnetic properties of Ni0.5MgxZn0.5-xFe2O4 nanosized ferrites for microwave absorption and high frequency applications

Ni0.5MgxZn0.5−xFe2O4 (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) (NiMgZn) nano-sized ferrites were synthesized via sol-gel route. The average cation radius, bond lengths (A and B sites), shared (dAE, dBE) and unshared edges (dBEU) of the NiMgZn nanoferrites were determined from the XRD data. FTIR studies confirmed the spinel structure of NiMgZn nanoferrites. The force constant at tetrahedral and octahedral sites were calculated. The surface morphology was investigated from the micrographs. The dielectric parameters such as dielectric constant, dielectric loss factor, loss tangent and Q values with different concentration of Mg in NiZn nanoferrite were evaluated. It was found that the NiMgZn sample at x=0.5 showed high Q values with low dielectric losses at higher frequencies. The squareness ratio and coercivity values confirmed the super paramagnetic behaviour of the NiMgZn nano-sized ferrites. However, the saturation and remanence increased with the increasing Mg contents whereas coercivity values follow the Stoner-Wolforth model for NiMgZn at x=0, 0.2, 0.3 and 0.4. The NiMgZn nano-sized ferrites samples at x=0.1 and 0.5 show the variations in coercivity values which may be due to the strong LS coupling and super-exchange interactions of the metal cations at tetrahedral and octahedral sites. The dielectric and magnetic studies of NiMgZn nano-sized ferritesexplored their application in various technological and industrial fields such as magnetic storage, microwave absorption and high frequency applications.

Properties of Nanosized Ferrite Powders and Sintered Materials Prepared by the Co-Precipitation Technology, Combined with the Spray-Drying Method

Cobalt and nickel ferrites powders are synthesized by the co-precipitation technology, combined with the spray-drying method. The crystallite size, specific surface area (SSA), magnetic properties of synthesized products are investigated. All the synthesized ferrites are nanocrystalline single phase materials with crystallite size of 5-6 nm, the SSA of 80-85 m2/g and the calculated particle size of 13-15 nm. After spray-drying granules of the size up to 10 μm are obtained. After thermal treatment at 550 and 950 °C SSA decreases to 40-50 m2/g and 20-22 m2/g, respectively. The saturation magnetization at these temperatures increase from 17 to 40 emu/g for NiFe2O4 and from 51 to 77 emu/g for CoFe2O4. By the pressure-less sintering method the dense material forms at 1100 °C for CoFe2O4 and 1200-1300 °C for NiFe2O4.

Investigation of the Mechanical Properties of GdBa2Cu3O7−δ Added with Nanosized Ferrites ZnFe2O4 and CoFe2O4 Using Ultrasonic Measurement

Recently, there is much interest in studying the effect of nanosized ferrites addition on high- T c superconductors. However, little information is available on the mechanical properties. We have investigated the effect of (CoFe2O4) x and (ZnFe2O4) x nanosized ferrites with 0.01 ≤ x ≤ 0.40 on the mechanical properties of the high- T c superconducting compound GdBa2Cu3O7−δ (Gd-123) prepared by the conventional solid-state reaction technique. Elastic parameters including shear modulus (G), bulk modulus (B), and Young’s modulus (E) of all samples were inspected using ultrasonic measurements and compared with Vickers microhardness results. Furthermore, the porosity of the samples was investigated and correlated to Young’s modulus, which was corrected to zero porosity using different models. The corrected values were correlated with Vickers microhardness. Moreover, the Debye temperature (θ D) and the electron-phonon coupling factor (λ) were also determined as a function of x. We observed that the different nanoparticles addition has influenced the Gd-123 compound differently. For (ZnFe2O4) x added samples, the mechanical properties and Debye temperature improved up to x = 0.06, then deteriorated with further addition. However, (CoFe2O4) x addition improved the mechanical properties for all samples with x up to 0.40. We found that the proportionality constant between the corrected values of E and H v and G and H v are strongly dependent on the porosity corrections and the kind of superconducting material. This indicates that the widely used formula E = 81.96 H v may not be valid for all types of superconducting materials.

Modified structural and magnetic properties of nanocrystalline MnFe2O4 by pH in capping agent free co-precipitation method

Nano-sized manganese ferrite (MnFe2O4) particles were prepared using co-precipitation method in two different pH (9 and 11). The structural, morphological, optical and magnetic properties of as-synthesized nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis absorption and vibrating sample magnetometer (VSM). The FTIR spectra revealed two strong peaks at about 600 and 400cm−1 that can be attributed to the vibration mode of octahedral and tetrahedral sites of spinel structure of MnFe2O4, respectively. The XRD results showed that the nanocrystalline MnFe2O4 has pure cubic spinel crystal structure with average crystallite size of 11nm. The cation distribution of these nanoparticles was estimated by X-ray analysis data. The blue shift was observed in the band gap when compared with bulk sample which is due to the quantum size effect. The absence of hysteresis for MnFe2O4 nanoparticles indicated the superparamagnetic behaviour, as expected for single domain nanoparticles. The obtained value for saturation magnetization being less than its value of bulk ones and larger pH is due to surface effects. The calculated magnetic particle size was smaller than crystallite size estimated from the XRD results; which indicate the presence of dead layer on particle surface.

Synthesis and Structural Investigation of Nano-Sized Cadmium Ferrite

This report presents the synthesis of cadmium ferrite (CdFe2O4) by Oxalate co-precipitation and its subsequent characterization by using X-ray diffraction (XRD) and Fourier transform Infrared spectroscopy (FTIR) techniques. XRD results confirm the single cubic spinel phase formation with lattice parameter 8.7561Ao. An infrared spectroscopy study shows the presence of main two absorption bands indicating the presence of tetrahedral and octahedral group complexes, respectively, within the spinel lattice. We also report strain, hopping length (LA and LB) and dislocation density of ferrite sample.

Structural, spectral, dielectric and magnetic properties of Tb–Dy doped Li-Ni nano-ferrites synthesized via micro-emulsion route

Terbium (Tb) and dysprosium (Dy) doped lithium-nickel nano-sized ferrites (Li0.2Ni0.8Tb0.5xDy0.5xFe2−xO4 where x=0.00−0.08) were prepared by micro-emulsion technique. The X-ray diffraction (XRD) patterns confirmed the single phase cubic spinel structure. The lattice constant was increased due to larger ionic radii of Tb3+ and Dy3+ cations. The crystallite size was found in the range 30–42nm. The FTIR (Fourier transform infrared spectroscopy) spectra revealed two significant absorption bands (~400–600cm−1) which indicate the formation of cubic spinel structure. The peaking behavior of dielectric parameters was observed beyond 1.5GHz. The dielectric constant and dielectric loss were found to decrease by the increase of Tb–Dy contents and frequency. The doping of Tb and Dy in Li–Ni ferrites led to increase the coercive field (120–156Oe). The smaller magnetic and dielectric parameters suggested the possible utility of these nano-materials in switching and microwave devices applications.

Structural, magnetic and dielectric properties of terbium doped NiCoX strontium hexagonal nano-ferrites synthesized via micro-emulsion route

Terbium (Tb) doped X-type hexagonal nano-ferrites Sr2NiCoTbxFe28−xO46 (x=0.00, 0.05, 0.1, 0.15, 0.2) were synthesized via micro-emulsion route. Single phase X-type hexagonal structure was confirmed by X-ray diffraction (XRD) analysis. The crystallite size of the samples was found in the range of 15–25nm. The bulk density and X-ray density were enhanced while porosity was reduced with the increased Tb3+ contents. The development of hexagonal phase was investigated by thermogravimetric analysis. The fourier-transform infrared (FTIR) spectra revealed the formation of spectral bands (metal-oxygen stretching vibration) which confirmed the hexagonal ferrites. The dielectric constant has high value at low frequency and decreased with increased frequency. The dielectric loss is appreciably decreased by the Tb3+ incorporation and resonance phenomenon occurred beyond 1.7×109Hz. The saturation magnetization (76–54emu/g) and remanance (27–21emu/g) decreased while coercivity increased (610–747Oe) by Tb3+-incorporation in Sr2NiCoTbxFe28−xO46 ferrite. The values of squareness ratio (0.35–0.39) indicated that Tb-doped samples are single domain while un-doped material is multi domains. These synthesized nano-sized hexagonal ferrites have potential applications in high frequency and recording media devices.

Structural elucidation and magnetic behavior evaluation of rare earth (La, Nd, Gd, Tb, Dy) doped BaCoNi-X hexagonal nano-sized ferrites

Rare-earth (RE=La3+, Nd3+, Gd3+, Tb3+, Dy3+) doped Ba2NiCoRExFe28−xO46 (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400cm−1. Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3bVI). The higher values of coercivity (664–926Oe) of these nanomaterials suggest their use in longitudinal recording media.

Fast photoresponse of zinc ferrite nanotube arrays fabricated by electrodeposition

Although nano-sized zinc ferrite materials exhibit excellent visible light activity, their photoresponse characteristics as photodetectors have rarely been investigated. In this paper, zinc ferrite nanotube arrays were fabricated using electrodeposition with the aid of zinc oxide nanowire arrays as a template. These nanotube arrays showed tens of milliseconds-response photocurrents under the irradiation of a 532 nm solid-state laser, and the magnitudes of the photocurrents were linearly increased with increasing laser power. These features of ZnFe2O4 nanotube arrays revealed their potential applications in high-frequency or high-speed photodevices.

Isatin-based three-component synthesis of new spirooxindoles using magnetic nano-sized copper ferrite

CuFe2O4 nanoparticles were synthesized and employed as highly efficient catalysts in the three-component synthesis of biologically important spirooxindoles.

Covalency, hybridization and valence state effects in nano- and micro-sized ZnFe2O4

In the present work, Fe valence state, covalency effects, and metal–oxygen hybridization are discussed for ZnFe2O4 using X-ray absorption spectroscopy. A few sets of nano-sized and micro-sized zinc ferrite were synthesized using the nitrate method. Nanoparticles of ZnFe2O4 were synthesized by heating precursor at 300, 400, 500, 800, 1000, and 1200 °C for 1 h. To synthesize micro-sized ZnFe2O4, the obtained nanoparticles were annealed at 1200 °C for 12 h (bulk treatment). X-ray diffraction shows the presence of cubic spinel phase in nano-sized as well as micro-sized ZnFe2O4. Scanning electron microscopy measurements show that particle size ranges are 40–80 nm and 1–2 μm for nano-sized and micro-sized ZnFe2O4, respectively. Fe L-edge spectra of these materials envisage the presence of spectral features corresponding to t2g and eg symmetry states created due to Fe(2p3/2)-Fe(3d) and Fe(2p1/2)-Fe(3d) in octahedral crystal field. This reflects the presence of Fe3+ states in nano-sized and micro-sized ZnFe2O4. eg states dominate in micro-sized ZnFe2O4. O K-edge spectra for these materials can be distinguished by pre-edge and post-edge regions. Pre-edge and post-edge regions are associated with O(2p)–Fe(3d) and O(2p)–Fe(4s,4p) hybridized states. The extent of hybridization estimated from the intensity ratio of O(2p)–Fe(3d) and O(2p)–Fe(4s,4p) hybridized states is higher in nano-sized ZnFe2O4.