共查询到20条相似文献,搜索用时 15 毫秒
1.
P.P. Hankare R.P. Patil S.D. Jadhav K.M. Jadhav 《Journal of magnetism and magnetic materials》2009,321(19):3270-3273
Nanocrystalline manganese-substituted lithium ferrites viz. Li0.5Fe2.5−xMnxO4 (2.5≤x≥0) were prepared by sol-gel autocombustion method. X-ray diffraction analysis confirmed that as the concentration of manganese increases the cubic phase changes to the tetragonal phase. The variation of saturation magnetization was studied as a function of manganese content. All the compositions indicate that they are ferrimagnetic in nature. The dielectric constant, dielectric loss tangent and ac conductivity of all samples were measured at room temperature as a function of frequency. These parameters decrease with increase in frequency for all of the samples. The substitution of manganese plays an important role in changing the structural and magnetic properties of these ferrites. The compositional variation of dielectric constant and d.c. resistivity shows an inverse trend of variation with each other. 相似文献
2.
Nanocrystalline La-substituted Zn–Cu–Cr ferrites Zn0.6Cu0.4Cr0.5LaxFe1.5−xO4 (x=0.00, 0.02, 0.04, 0.06) were prepared by a rheological phase reaction method. The obtained powders were characterized by X-ray diffractometer, transmission electron microscopy and vibrating sample magnetometer. Permeability of the samples was investigated using an impedance analyzer. The results indicated that ferrite samples had the single spinel phase at low La content. Lattice parameter increased with increasing La content, while particle size calculated from Scherrer's formula decreased with increasing La content in La-substituted ferrite samples. The magnetic properties of La-substituted ferrites were strongly affected by La content. The saturation magnetization decreased, while coercivity increased with increasing La content. The variation of real permeability with La content was investigated in the frequency range of 1 MHz–1 GHz. 相似文献
3.
M. Siva Ram PrasadB.B.V.S.V. Prasad B. RajeshK.H. Rao K.V. Ramesh 《Journal of magnetism and magnetic materials》2011,323(16):2115-2121
Polycrystalline Ni0.65−xCdxZn0.35Fe2O4 ferrites with x varying from 0.00 to 0.20 in steps of 0.04 have been prepared by conventional ceramic route. Calcination and sintering of samples were performed at 950 and 1250 °C for 4 and 2 h, respectively. The prepared samples were characterized by powder X-ray diffraction. The observed modifications in structure and increase in lattice constant are attributed to the difference in ionic radius of substituted Cd2+ ion and displaced Ni2+ ion. The room temperature specific saturation magnetization and Curie temperature are observed to decrease continuously with decrease in cadmium content and are attributed to the decline of A-B exchange interaction. The monotonic increase in initial permeability and decrease in magnetic loss are observed with cadmium concentration. An increase in dc electrical resistivity is observed up to x=0.12 of cadmium followed by a continuous decrease. The variation of electrical resistivity with temperature was measured in the temperature range of RT-140 °C and the corresponding activation energies for conduction obtained from the log ρ vs 1/T graphs. 相似文献
4.
Safia Anjum H.M. TahirK. Hussain M. Khaleeq-ur-RahmanM.S. Rafique S. Naseem 《Physica B: Condensed Matter》2011,406(13):2555-2558
Nickel Cadmium Aluminum Ferrites with the general formula Ni1−xCdxAl0.6Fe1.4O4 where x=0, 0.25, 0.50 and 0.75 were prepared through standard double sintering reaction method. The crystallography, surface morphology and magnetic properties were studied by X-ray diffractometer (XRD), Scanning Electron Microscope (SEM) and Vibrating Sample Magnetometer (VSM), respectively. The expected single phase spinel structure was confirmed by XRD analysis. Lattice parameter and X-ray density were increased monotonically by increasing Cd concentration due to the larger ionic radii of the cadmium ion. Surface topography of the samples consists of fine cubical shape microstructures. The average grain size increased with increase in cadmium concentration. The saturation magnetization was found to be increased with increase in cadmium content up to x=0.50 and then decreased with further increasing cadmium concentration for x=0.75. 相似文献
5.
S. Manjura Hoque M. Samir UllahF.A. Khan M.A. HakimD.K. Saha 《Physica B: Condensed Matter》2011,406(9):1799-1804
Li0.5−x/2CuxFe2.5−x/2O4 (where x=0.0-1.0) ferrites have been prepared by solid-state reaction. X-ray diffraction was used to study the structure of the above investigated ferrites at various sintering temperatures. Samples were sintered at 1000, 1100 and 1200 °C for 3 h in the atmosphere. For the sintering temperature of 1000 °C, Li0.5−x/2CuxFe2.5−x/2O4 undergoes cubic to tetragonal transformation for higher Cu content. However, for the sintering temperature of 1100 and 1200 °C, X-ray diffraction patterns are mainly characterized by fcc structure, though presence of tetragonal distortion was found by other temperature dependence of initial permeability curves. The lattice parameter, X-ray density and bulk density were calculated for different compositions. Curie temperature was measured from the temperature dependence of initial permeability curves. Curie temperatures of Li-Cu mixed ferrites were found to decrease with the increase in Cu2+ content due to the reduction of A-B interaction. As mentioned earlier, temperature dependence of initial permeability curves was characterized by tetragonal deformation for the samples containing higher at% of Cu. The complex initial permeability has been studied for different samples. The B-H loops were measured at constant frequency, f=1200 Hz, at room temperature (298 K). Coercivity and hysteresis loss were estimated for different Cu contents. 相似文献
6.
P.P. Hankare R.P. Patil U.B. Sankpal R. Sasikala I.S. Mulla 《Journal of magnetism and magnetic materials》2010,322(18):2629-9662
Nanocrystalline Li0.5Fe2.5−xCrxO4 (2.5≤x≥0) ferrites were prepared by a sol-gel autocombustion route. X-ray diffraction was employed to confirm the cubic spinel phase formation of the ferrites. The lattice parameter decreases with increase in Cr content. The saturation magnetization, coercivity and remanance were studied as a function of Cr content. The dielectric constant and dielectric loss were measured as a function of frequency in the frequency range 20 Hz-1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. In order to understand the conduction mechanism, complex impedance measurements were carried out. The substitution of chromium plays an important role in changing the dielectric and magnetic properties of lithium ferrites. 相似文献
7.
《Journal of magnetism and magnetic materials》2002,251(3):316-322
A series of Mn substituted MgCuZn ferrites (Mg0.2Cu0.2Zn0.6O) (Fe2−xMnxO3)0.97 with x=0.00,0.01,0.03,0.05,0.07 were prepared with nanosized precursor powders synthesized by a sol–gel auto-combustion method. All the ceramic samples can be sintered at low temperature (930°C) (below the melt point of Ag (961°C)). The effect of Mn content on microstructures and magnetic properties were investigated. Experiment shows that low temperature sintered MgCuZn ferrites doped with Mn possess higher initial permeability and better grain structure than that of low temperature sintered NiCuZn ferrites prepared by the same method. Therefor, Mn doped MgCuZn ferrites should be ideal materials for high inductance multilayer chip inductor. It is thought that the variation of initial permeability of MgCuZn ferrites with the Mn substitution was attributed to the decrease of magnetostriction constant. 相似文献
8.
Polycrystalline soft ferrite samples with general formula ZnNdxFe2−xO4 (where x=0, 0.01, 0.02 and 0.03) were synthesized by oxalate co-precipitation method. The samples were characterized by XRD and SEM techniques. The single phase cubic spinel structure of all the samples was confirmed by XRD. The lattice constant and grain size of the samples are found to decrease with increase in Nd3+ content. Room temperature DC resistivity of the Nd3+ substituted zinc ferrites is 102 times higher than that of zinc ferrite. The dielectric constant (ε′) and dielectric loss (tan δ) of all the samples were measured in the frequency range 20 Hz-1 MHz. The dielectric behaviour is attributed to the Maxwell-Wagner type interfacial polarization. The dielectric loss of the samples is found to decrease with increase in Nd3+ content. High resistivity and low dielectric loss makes these ferrites particularly suitable for high frequency applications. 相似文献
9.
P.P. Hankare U.B. SankpalA.V. Jadhav K.M. GaradkarB.K. Chougule 《Journal of magnetism and magnetic materials》2011,323(5):389-393
Ferrites with the general formula Cu1−xZnxFeMnO4 (where 0≤x≤1) were prepared through a citrate gel auto-combustion route. Structural characterizations carried out by X-ray diffraction reveal that the lattice constant increases with increase in zinc content. Transmission electron microscopic measurements confirm the nanoscale nature of the particles. Room temperature saturation magnetization was measured as a function of zinc concentration. The saturation magnetization increases up to x=0.25 and then decreases as zinc concentration increases. Dielectric permittivity, dielectric loss tangent, ac conductivity and complex dielectric impedance were studied in the frequency range 20 Hz-1 MHz. The results indicated a usual dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Dielectric loss showed similar behavior as dielectric permittivity. The ac conductivity increased linearly with frequency. Complex impedance spectroscopic studies confirmed that conduction in the samples is via grain boundaries. In general, substitution of zinc plays an important role in changing the structural, electrical and magnetic properties of these ferrites. 相似文献
10.
Ali Ghasemi Ebrahim GhasemiEbrahim Paimozd 《Journal of magnetism and magnetic materials》2011,323(11):1541-1545
Ni0.6−xCuxZn0.4Fe2O4 (x=0-0.5) ferrite nanoparticles were prepared, employing a reverse micelle process. X-ray diffraction and transmission electron microscopy evaluations demonstrated that single phase spinel ferrites with narrow size distribution were obtained. Vibrating sample magnetometer was employed to probe the magnetic properties of the samples. It was found that with an increase in copper content, the saturation magnetization decreases. Magnetic dynamics of the samples was studied by measuring a.c. magnetic susceptibility versus temperature at different frequencies. The phenomenological Néel-Brown and Vogel-Fulcher models were employed to distinguish between the interacting or non-interacting systems. The system exhibits that there is strong interaction among fine particles. 相似文献
11.
M.H.R. KhanA.K.M. Akther Hossain 《Journal of magnetism and magnetic materials》2012,324(4):550-558
A series of polycrystalline ferrites having nominal chemical composition Co0.50−xMnxZn0.5Fe2O4 (0<x<0.4) have been synthesized by the solid-state reaction technique. The XRD analysis confirms single phase cubic spinel structure for all compositions. Lattice constant increases from 0.84195 to 0.84429 nm with the increasing Mn content and obeys Vegard's law. The average grain size increases by increasing both Mn content and sintering temperatures. Room temperature saturation magnetization increases for x=0.1 and decreases for increasing Mn content. The coercivity decreases with increasing Mn content due to the decrease of anisotropy constant. A reentrant spin glass behavior of these samples is observed from the zero field cooled magnetization measurements. The real part of the initial permeability increases by increasing both Mn content and sintering temperatures. This is due to the homogeneous grain growth and densification of the ferrites. The highest initial permeability 137 is observed for x=0.4 sintered at 1573 K on the other hand, the highest relative quality factor (2522) is obtained for the sample Co0.2Mn0.3Zn0.5Fe2O4 sintered at 1523 K. The Mn substituted Co0.50−xMnxZn0.5Fe2O4 ferrites showed improved magnetic properties. 相似文献
12.
《Current Applied Physics》2010,10(4):975-984
Polycrystalline nickel–zinc–copper ferrites with chemical formula Ni0.6+xZn0.2Cu0.2VxFe2−2xO4,(0.0 ⩽ x ⩽ 0.25) were prepared by the ceramic route. The X-ray diffraction (XRD) analysis of the samples results confirms single-phase spinel structure. Scanning electron microscopy (SEM) of the prepared ferrites reveal that vanadium addition resulted in a rapid grain growth with large pores trapped inside the grains as the vanadium concentration increases. The ac conductivity σac has been studied as a function of frequency and temperature over the temperature range (300–600 K). The results obtained for these materials reveal a semiconductor – to semimetal transition as V5+ content increases. All studies composition exhibit a transition with change in the slope of conductivity. The obtained temperature Tc is found to be decrease with the increasing vanadium content. The hopping of electrons between Fe3+ and Fe2+ as well as the hole hopping between Ni3+ and Ni2+ are found to responsible for the conduction mechanism. The relation of the universal exponent s with temperature gives evidence for the presence of the correlation barrier hopping (CHB) mechanism in these compounds. The impedance technique has been used to study effect of grain and grain boundary on the electrical properties. The analysis data show only one semi-circle for all samples except for sample with x = 0.05. The results suggested that the conduction mechanism takes place predominantly through the grain in the studied samples. 相似文献
13.
L. G. Antoshina E. N. Evstaf’eva A. I. Kokorev A. A. Opalenko A. I. Firov 《Physics of the Solid State》2007,49(3):493-496
The x-ray structural properties of samples in the CuGaxAlxFe2?2x O4 (x = 0?0.7) and CuGaxAl2x Fe2?3x O4 (x = 0?0.5) systems are studied. It is found that magnetic ordering in dilute copper ferrites affects their structural properties. It is concluded that the frustration of magnetic coupling leads to suppression of the cooperative Jahn-Teller effect in dilute copper ferrites with a frustrated magnetic structure. 相似文献
14.
Nanometric nickel copper ferrites Ni1−xCuxFe2O4, 0≤x≤0.45 were prepared by the citrate precursor method. X-ray diffraction measurements confirm the formation of single phase cubic spinel structure. The lattice parameter (a) is increased with increasing Cu2+ ion substitution. The crystallite size was calculated from XRD data and compared with that obtained from TEM micrographs. A significant increase in the density is observed with increasing Cu content. The IR absorption spectra were used for the detection and confirmation of the chemical bonds in spinel ferrites. The dielectric constant ε′ and dielectric loss showed a decrease with increasing frequency for all samples. The decrease in the ac conductivity was ascribed to the increase in hopping length. 相似文献
15.
Y.M. Al Angari 《Journal of magnetism and magnetic materials》2011,323(14):1835-1839
Nano-sized NiFe2−xLaxO4 ferrites (x=0.00, 0.01, 0.02, 0.03, 0.04, 0.5, 0.07 and 0.09) were synthesized for the first time by using metal nitrate and egg-white extract in aqueous medium. The ferrites were characterized by DTA-TG, XRD, TEM, FT-IR and VSM techniques. The thermal decomposition behavior revealed that the precursors were completely decomposed at about 420 °C. TEM image shows agglomerated nanoparticles with crystallite sizes agrees well with that estimated by XRD measurement. XRD patterns show a secondary phase of LaFeO3 besides the cubic structure of the La-substituted ferrites. The lattice parameters, X-ray density and crystallite size were found to increase with the increasing La content. The VSM measurement exhibited a ferromagnetic property for all the samples at room temperature. With increasing La, Ms was found to decrease while Hc increased. The decrease in the saturation magnetization is attributed to the paramagnetic properties of lanthanum, which prefer to substitute iron present in the octahedral sites. The increase in the coercivity is due to either the stronger magnetocrystalline anisotropy induced by La substitution or the change in the crystallite size. 相似文献
16.
《Journal of magnetism and magnetic materials》2001,233(3):224-229
Mn-doped NiCuZn ferrites with compositions of (Ni0.2Cu0.2Zn0.6)O(Fe2−x,MnxO3)0.98 (x=0, 0.02, 0.04, 0.06) were prepared by a novel sol–gel auto-combustion process. The synthesized nano-sized ferrite powders can be sintered at 900°C, and the sintered ferrites are characterized by fine-grained microstructural feature and high permeability. Mn content in formulations largely affects the grain size and main electromagnetic properties of sintered NiCuZn ferrites. With increasing Mn content, the initial permeability is significantly increased, while the electrical resistivity and quality factor are decreased. The dielectric constant and dissipation factor are also affected by the incorporation of MnO2. The possible mechanism for the influence of MnO2 on the electromagnetic properties was discussed. 相似文献
17.
S.A. Saafan T.M. Meaz M.K. El Nimr M. Bakr 《Journal of magnetism and magnetic materials》2010,322(16):2369-2374
Promising future applications of ferrite nanoparticles in medicine, drug delivery, sensors and ferrofluids are expected to be in wet or humid environments. Therefore nanostructured powders of ferrites having the chemical compositions.NixZn (1−x)Fe2O4 with (x=0.0, 0.25, 0.5, 0.75, and 1) were pressed immediately after preparation - by the co-precipitation method - without any drying to simulate a humid environment. The nanoparticles were characterized by X-ray diffraction analysis (XRD) to be sure of the formation of the ferrite in nanoscale. The infrared (IR) spectroscopy of the samples ensures the existence of water as well as the characteristic absorption bands of ferrites. The ac and dc conductivity of the samples had been investigated immediately after preparation (the as-prepared samples). Then, the samples were dried at 200 °C for about 12 h and reinvestigated. The behavior of conductivity differs significantly in the two cases showing a noticeable effect due to humidity. Also, the magnetic induction of the as-prepared samples was investigated by using the vibrating sample magnetometer (VSM). The samples show superparamagnetic behavior. 相似文献
18.
B.D. Padalia V. Krishnan M.J. Patni N.K. Radhakrishnan S.N. Gupta 《Journal of Physics and Chemistry of Solids》1973,34(7):1173-1178
K-absorption edges of cations in the manganites of magnesium, nickel, copper, zinc and cadmium and ferrite samples of composition, Mg1?x Mnx Fe2O4 (x=0, 0·25, 0·50, 0·75, 1·0), have been recorded employing a 40 cm curved mica crystal spectrograph of transmission type. It is observed that the absorption edges for the specimen shift towards the shorter wavelength side of the metal edge position. Shifts of both the absorption edges and the main absorptoin peaks for ferrites and manganites have been compared with compounds in which the oxidation state of the cation is well known. It is found that the manganese ions in these ferrites and manganites exist in valence states two and three respectively while iron in the ferrite samples is present in oxidation state three. An attempt has been made to interpret the observed absorption edge features in the light of neutron and X-ray diffraction studies on the same ferrite and manganite samples. 相似文献
19.
Ashok B. Gadkari Tukaram J. Shinde 《Journal of magnetism and magnetic materials》2010,322(24):3823-972
Nanocrystalline ferrite powder having the general formula Mg1−xCdxFe2O4+5% Sm3+ (x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by chemical oxalate co-precipitation technique. The synthesized powder was characterized by X-ray, IR and SEM techniques. The XRD analysis confirms cubic spinel phase with orthoferrite secondary phase. The lattice constant increases with increase in Cd2+ content (x). It is smaller than that for pure Mg-Cd ferrites. The average crystallite size lies in the range 28.69-32.66 nm. Saturation magnetization and magnetic moment increase with cadmium content up to x=0.4 and decrease thereafter. This is attributed to the existence of localized canted spin. The decrease in saturation magnetization and magnetic moment beyond x=0.4 is due to the presence of triangular spin arrangement on B-site. Coercivity and remanent magnetization decrease while Y-K angles increase with Cd2+ content. The Sm3+ addition improves the magnetic properties. 相似文献
20.
The synthesis of a series of Mg–Cu–Zn ferrites with the substitution of Cu for Mg has been obtained by solid-state reaction method. Microstuctural and structural analyses were carried out using a scanning electron microscope and X-ray diffraction (XRD), respectively. The lattice parameter is found to increase with increasing copper content. A remarkable densification is observed with the addition of Cu ions in the ferrites. Microstructural analyses indicate that CuO influences the microstructure of the ferrites by the formation of liquid phase during sintering. The grain size significantly increases with increasing copper content. Exaggerated grain growth is observed for the samples of x=0.25–0.35. The initial magnetic permeability (μ′) increases sharply with increasing concentration of Cu ions. This increase in μ′ is explained with the grain growth mechanism and enhanced densification of the ferrites. The resonance frequency of all the samples shifts toward the lower frequency as the permeability increases with Cu content. Sintering temperature Ts also affects the densification, grain growth and initial magnetic permeability of the samples. 相似文献