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1.
A series of powders of M-typed barium hexaferrites doped with Co, Zn and Sn of general formula BaFe12-2xCox/2Znx/2SnxO19 (x=0-2.0) were prepared by the co-precipitation/molten salt method. The structures, particle morphology and magnetic properties of the products were characterized by X-ray powder diffraction, vibrating sample magnetometer and ESEM/EDX. The results show that the crystallinity of the samples decreases with increase in the doping amount x. When x is less than 0.6, it is possible to obtain perfectly crystallized hexagonal BaFe12-2xCox/2Znx/2SnxO19, where the diameters of the particles are around 500 nm. The saturation magnetization of pure barium ferrite BaFe12O19 produced with this method is 71.9 A m2 kg−1 at room temperature and the intrinsic coercivity (Hc) is 367.8 kA m−1. The doped barium hexaferrite powder obtained when x is between 0.3 and 0.4 exhibits high saturation magnetization and a temperature dependence of coercivity close to zero. 相似文献
2.
Barium ferrites substituted by Mn-Sn, Co-Sn, and Mn-Co-Sn with general formulae BaFe12−2xMnxSnxO19 (x=0.2-1.0), BaFe12−2xCoxSnxO19 (x=0.2-0.8), and BaFe12−2xCox/2Mnx/2SnxO19 (x=0.1-0.6), respectively, have been prepared by a previously reported co-precipitation method. The efficiency of the method was refined by lowering the reaction temperature and shortening the required reaction time, due to which crystallinity improved and the value of saturated magnetization increased as well. Low coercivity temperature coefficients, which are adjustable by doping, were achieved by Mn-Sn and Mn-Co-Sn doping. Synthesis efficiency and the effect of doping are discussed taking into account accumulated data concerning the synthesis and crystal structure of ferrites. 相似文献
3.
Irshad Ali M.U. Islam M. Ishaque Hasan M. Khan Muhammad Naeem Ashiq M.U. Rana 《Journal of magnetism and magnetic materials》2012
CoHoxFe2−xO4 ferrites (x=0.00–0.1) were prepared by the co-precipitation technique and the effect of holmium substitution on the magnetic properties was investigated. X-ray diffraction reveals that the substituted samples show a second phase of HoFeO3 along with the spinel phase. The magnetic properties such as the saturation magnetization (Ms), coercivity (Hc) and remanence (Mr) are obtained from the hysteresis loops. It is observed that the Ms decreases while Hc increases with Ho3+ substitution. The decrease of saturation magnetization is attributed to the weakening of exchange interactions. The coercivity increases with increase of the Ho3+ concentration, which is attributed to the presence of an ultra-thin layer at the grain boundaries that impedes the domain wall motion. Low field AC susceptibility was also measured over the temperature range 300–600 K at the frequency of 200 Hz. It decreases with the increase of temperature following the Curie–Weiss law up to the Curie temperature. Above the Curie temperature it shows paramagnetic behavior. The increase in coercivity suggests that the material can be used for applications in perpendicular recording media. 相似文献
4.
In this study, effect of lanthanum substitution on the phase composition, lattice parameters and magnetic properties of barium hexaferrite has been studied in samples synthesized in ammonium nitrate melt. Samples, prepared with different lanthanum amount and having various initial Fe/(Ba+La) ratios in between 12 and 2 {(Ba1−xLax)·n Fe2O3, where 0≤x≤1 and 1≤n≤6)}, are sintered at temperatures from 800 to 1200 °C. The lattice parameters, both a and c, decreases with increasing La amount which results in a decrease of the unit cell volume. The scanning electron microscope micrographs show that the pure and La-substituted sample with x=0.3, both calcinated at 1000 °C, have grain sizes smaller than 1 μm. The coercivities of the La-substituted samples increase with increasing La amount and reaches to a maximum value of 5.73 kOe, when x=0.3. Sintering at higher temperatures (above 1000 °C) decreases the coercivity, resembling a transition from single to multi-domain behavior of the particles, while saturation magnetization of the samples continues to increase due to the increasing grain size. Magnetization measurements of the samples prepared with different Fe/(Ba+La) molar ratios, n's, revealed that the specific saturation magnetization slightly increases with decreasing n, while coercivities fluctuates around 5.5 kOe. However, a sharp increase in the saturation magnetization has been observed in the sample having n=1 and washed in HCl. It was measured as 59.2 emu/g at 15 kOe, which is higher than that of the pure sample (57.5 emu/g). Thus, the magnetic parameters are optimized in the sample Ba0.7La0.3Fe12O19 so as to maximize both coercivity and specific saturation magnetization in the HCl-washed sample synthesized by starting with an unusually low Fe/(Ba+La) molar ratio of 2 (or n=1). 相似文献
5.
Yue Zhang Zhi Yang Yong Liu Rui Xiong Jing Shi GaoLin Yan 《Journal of magnetism and magnetic materials》2010,322(21):3470-3475
Cobalt ferrite nano-particles were prepared using the co-precipitation method followed by annealing treatment. The formation of nano-particles with different composition, microstructure and sizes were confirmed by X-ray diffraction, Raman, thermogravimetric-differential thermal analysis and transmission electron microscope. The magnetic hysteresis loops measured at room temperature revealed smaller effective magnetic anisotropy constant, coercivity and remanence ratio for the samples prepared by adding the NaOH solutions into the mixed solutions of Co2+ and Fe3+ ions due to the formation of Co3+ ions. A small saturation magnetization and an enhanced coercivity were observed for the nano-particles prepared by adding the mixed solutions of Co2+ and Fe3+ ions into the NaOH solutions, which was related to the formation of outer layers with poor crystallization on the surfaces of the cobalt ferrite nano-crystals. Furthermore, the existence of these outer layers induced the oxidation of Co2+ ions in cobalt ferrite nano-crystals at 200 and 300 °C, and led to a large change on the composition and magnetic properties. 相似文献
6.
The synthesis of hexagonal barium ferrite (BaFe12O19) was studied under hydrothermal conditions by a method in which a significant amount of ferrous chloride was introduced alongside ferric chloride among the starting materials. Though all of the Fe2+ ions in the starting material were converted to Fe3+ ions in the final product, Fe2+ was confirmed to participate differently from the Fe3+ used in the conventional method in the mechanism of forming barium ferrite. Indeed the efficiency of the synthesis and the quality of the product and the lack of impurities such as Fe2O3 and BaFe2O4 were improved when Fe2+ was included. However, the amount of ferrous ions that could be included to obtain the desired product was limited with an optimum ratio of 2:8 for FeCl2/FeCl3 when only 2 h of reaction time were needed. It was also found that the role of trivalent Fe3+ could be successfully replaced by Al3+. Up to 50% of the iron could be replaced by Al3+ in the reactants to produce Al-doped products. It was also found that the ratio of Fe2+/M3+ could be increased in the presence of Al3+ to produce high quality barium ferrite. 相似文献
7.
The structural and magnetic powders prepared by properties of barium ferrite the sol-gel method
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In this paper,M-type hexagonal barium ferrite powders are synthesized using the sol-gel method.A dried precursor heated in air is analyzed in the temperature range from 50 to 1200 C using thermo-gravimetric analysis and differential scanning calorimetry.The effects of the additives and the cacinating temperature on the magnetic properties are investigated,and the results show that single-phase barium ferrite powders can be formed.After heat-treating at 950 C for 4h with 3 wt% additive,the coercivity and saturation magnetization are found to be 440 Oe and 57.9 emu/g,respectively. 相似文献
8.
Spinal ferrites having the general formula Co1 − x
Zn
x
Fe2 − x
Al
x
O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were prepared using the wet chemical co-operation technique. The samples were annealed
at 800°C for 12 h and were studied by means of X-ray diffraction, magnetization and low field AC susceptibility measurements.
The X-ray analysis showed that all the samples had single-phase cubic spinel structure. The variation of lattice constant
with Zn and Al concentration deviates from Vegard’s law. The saturation magnetization σ
s and magneton number n
B measured at 300 K using high field hysteresis loop technique decreases with increasing x, suggesting decrease in ferrimagnetic behaviour. Curie temperature T
C deduced from AC susceptibility data decreases with x, suggesting a decrease in ferrimagnetic behaviour.
相似文献
9.
The structural and magnetic properties of barium ferrite powders prepared by the solben gel method
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In this paper, M-type hexagonal barium ferrite powders are synthesized using the sol-gel method. A dried precursor heated in air is analyzed in the temperature range from 50 to 1200 ℃ using thermo-gravimetric analysis and differential scanning calorimetry. The effects of the additives and the cacinating temperature on the magnetic properties are investigated, and the results show that single-phase barium ferrite powders can be formed. After heat-treating at 950 ℃ for 4h with 3 wt% additive, the coercivity and saturation magnetization are found to be 440 Oe and 57.9 emu/g, respectively. 相似文献
10.
Sunil Rohilla Sushil KumarP. Aghamkar S. SunderA. Agarwal 《Journal of magnetism and magnetic materials》2011,323(7):897-902
Magnetic nanocomposites consisting of cobalt ferrite nanoparticles embedded in silica matrix were prepared by the coprecipitation method using metallic chlorides as precursors for ferrite. Subsequently composites were annealed at 100, 200 and 300 °C for 2 h. The samples were structurally characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The magnetic properties were measured in the temperature range of 10-300 K using vibrating sample magnetometer (VSM). The effects of thermal treatment on structural and magnetic properties of nanocomposites were investigated. When the samples were annealed, CoFe2O4 nanocrystallites were observed in the SiO2 matrix, whose size increases with increase in annealing temperature. The coercivity and saturation magnetization of nanocomposite (annealed at 300 °C for 2 h) are much higher than that of bulk cobalt ferrite. The realization of adjustable particle sizes and controllable magnetic properties makes the applicability of the CoFe2O4 nanocomposite more versatile. 相似文献
11.
Nano-spinel ferrites synthesized via chemical co-precipitation method are small in size and have serious agglomeration phenomenon, which makes separation difficult in the subsequent process. Ni0.4Cu0.2Zn0.4Fe2O4 ferrites nanoparticles were synthesized via co-precipitation assisted with ultrasonic irradiation produced by ultrasonic cleaner with 20 kHz frequency using chlorinated salts and KOH as initial materials. The effects of ultrasonic power (0, 40 W, 60 W, 80 W) and reaction temperature on the microstructure and magnetic properties of ferrite nanoparticles were investigated. The structure analyses via XRD revealed the successful formation of pure (NiCuZn)Fe2O4 ferrites nanospinel without any impurity. The crystallites sizes were less than 40 nm and the lattice constant was near 8.39 Å. The TEM showed ferrite particle polygonal. M−H analyses performed the saturation magnetization and coercivity of ferrite nanoparticles obtained at the reaction temperature of 25℃ were higher than at 50℃ with same power. The samples exhibited the highest values of Ms 55.67 emu/g at 25℃ and 47.77 emu/g at 50℃ for 60 W and the lowest values of Hc 71.23 Oe at 25℃ for 40 W and 52.85 Oe at 50℃ for 60 W. The squareness ratio (SQR) were found to be lower than 0.5, which revealed the single magnetic domain nature (NiCuZn)Fe2O4 nanoparticles. All the outcomes show the ultrasonic irradiation has positive effects on improving the microstructure and increasing magnetic properties. 相似文献
12.
Effect of substitution of diamagnetic trivalent indium ions on the composition Mg0.2Mn0.5Ni0.3InxFe2−xO4 with x varying from 0.1 to 0.3 in steps of 0.1 using citrate precursor techniques has been investigated. Single-phase cubic spinel structure of these samples has been confirmed from X-ray diffraction analyses. Micro structural features were examined by TEM images. Lattice constant ‘a’ initially increases up to x = 0.1 and thereafter it decreases with further increase in x. This indicates that variation of ‘a’ with x do not obey Vegard's law. Nonlinear behavior of ‘a’ with x may be due to substitutional effect of larger In3+ ions (0.91Å) with smaller Fe3+ ions (0.67Å) in Mg-Mn-Ni ferrite. Ferrites have been investigated for their structural and magnetic properties such as variations in lattice constant, saturation magnetization, coercivity, retentivity, initial permeability, magnetic loss and relative loss factor (RLF). Fairly constant value of initial permeability over a wide frequency range (0.075–10 MHz) and low values of relative loss factor of order of 10−6–10−5 in same frequency range are main achievement of present investigations. RLF has been reduced by three orders of magnitude as compared to those samples prepared by conventional method. Low values of relative loss factor even at a high frequency indicate that prepared materials may have great potential for use in microwave devices. Possible mechanisms contributing to these properties have been discussed in this paper. 相似文献
13.
Ailin Xia Chuangui JinDexin Du Guohui Zhu 《Journal of magnetism and magnetic materials》2011,323(12):1682-1685
We prepared NiZnCu ferrite powders with nominal composition Ni0.4−xZn0.6CuxFe2O4 (x=0-0.2) via chemical coprecipitation method with NaOH and Na2CO3 as coprecipitators. The structural and magnetic properties of these compounds were studied and compared. It is found that all the specimens exhibit single-phase structure after annealing. The saturation magnetization of specimens with NaOH as coprecipitator is lower than that with Na2CO3 as coprecipitator. It is also found that the growth of grains is hindered for specimens using Na2CO3 as coprecipitator. 相似文献
14.
K. Jalaiah K. Vijaya Babu K. Rajasekhar Babu V. Venkat Kumar R.V. Krishnaiah 《Chinese Journal of Physics (Taipei)》2018,56(5):2039-2051
The zirconium and copper co-substituted Ni0.75Zn0.25ZrxCuxFe2-2xO4 (where x?=?0.05, 0.1, 0.15, 0.2) ferrites have been prepared by sol-gel auto-combustion method. The XRD patterns provide the evidence of single phase cubic spinel structure. The theoretical and experimental lattice parameters have resemblance with increase dopant concentration. The sintered density and porosity show the opposite trend with dopant concentration. The FT-IR spectrum of prepared samples reveal cubic spinel with () space group. The wave numbers of tetrahedral and octahedral sites show agnate trend. The dielectric constant and loss factors decreased with increasing dopant concentration. The saturation magnetization and net magnetic moment have the identical trend with increasing dopant concentration. The coercive field is decreased with increasing dopant concentration. The Y–K angles are increased with increasing dopant concentration. The Q-factor in prepared samples, exhibit narrower frequency bands with increasing frequency. 相似文献
15.
Cd0.8Zn0.2S bulk compound doped with different concentrations of copper have been prepared by chemical co-precipitation (CCP-I) and modified CCP method (CCP-II). The structural, optical and electrical properties of Cd0.8Zn0.2S:Cu compounds grown by these methods have been investigated by using XRD, SEM, EDAX, UV spectroscope and DC electrical conductivity techniques. X-ray diffraction studies on Cd0.8Zn0.2S compounds doped with various mole% of copper revealed that they possessed polycrystalline nature with hexagonal structure. SEM micrographs taken on samples grown by CCP-I showed that the crystallites have needle like shape and no such regular shape was observed on CCP-II grown samples and in both of them the crystallite size varied differently with the variation in the concentration of copper. The energy gap of a sample grown by CCP-II, evaluated from optical absorption studies, are more than that of the sample grown by CCP-I. This may be attributed to the variation observed in the crystallite sizes of the respective sample grown by two methods. Further, the electrical conductivity variations in CCP-I and II samples were explained based on Eg value, crystallite size and grain boundary conduction in the samples. The activation energies of both CCP-I and II samples were explained on the basis of the differences in their preparation methods. Finally, it was concluded that the CCP-II method is more suitable to grow Cd0.8Zn0.2S:Cu compounds with uniform average crystallite size and energy gap for low doping concentration of Cu (∼4 mole%). 相似文献
16.
Free-standing Ni0.23Cu0.11Zn0.66Fe2O4 thick films have been prepared using a modified tape-casting method from a viscous paint. The surface morphology, saturation magnetization (Ms), coercivity (Hc) and complex permeability of the thick films were studied. It is demonstrated that the thick films have relatively larger complex permeability and higher resonance frequency as compared to their bulk material counterparts. 相似文献
17.
The magnetic properties and magnetocaloric effect of an antiferromagnetic/ferromagnetic(AFM/FM)BiFeO_3/Co bilayer with mixed-spin(5/2,3/2) have been studied based on Monte Carlo simulation.The magnetization, susceptibility, and critical temperature are investigated under various exchange couplings and an external magnetic field. In particular, the influence of exchange couplings and an external magnetic field on the magnetic entropy change, adiabatic temperature change, and the relative cooling power(RCP) are studied. The simulation results indicated that the decrease of the exchange coupling and the increase of external magnetic fields can cause an increase of magnetic entropy change, adiabatic temperature change, and RCP. In addition, the hysteresis loops of the system are presented for different exchange couplings and temperatures. 相似文献
18.
19.
Microstructure and magnetic characteristics of nanocrystalline Ni0.5Zn0.5 ferrite synthesized by a spraying-coprecipitation method
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Nanocrystalline Ni0.5Zn0.5 ferrite with average grain sizes ranging from 10 to 100 nm is prepared by using a spraying-coprecipitation method. The results indicate that the nanocrystalline Ni0.5Zn0.5 ferrite is ferromagnetic without the superparamagnetic phenomenon observed at room temperature. Specific saturation magnetization of nanocrystalline Nio.sZno.5 ferrite increases from 40.2 to 75.6 emu/g as grain size increases from 11 to 94nm. Coercivity of nanocrystalline Ni0.5Zn0.5 ferrite increases monotonically when d 〈 62 nm.The relationship between the coercivity and the mean grain size is well fitted into a relation Hc - d^3. A theoretically evaluated value of the critical grain size is 141nm larger than the experimental value 62nm for nanocrystalline Ni0.5Zn0.5 ferrite. The magnetic behaviour of nanocrystalline Ni0.5Zn0.5 ferrite may be explained by using the random anisotropy theory. 相似文献
20.
采用简单的两步水热法合成了不同In2O3质量比的In2O3/ZnO异质结复合材料.通过X射线衍射仪(XRD)、紫外-可见分光光度计(UV-vis)和扫描电子显微镜(SEM)对复合材料的结构、形貌和性能进行了表征.同时还使用UV-vis分光光度计测试了异质结降解罗丹明B(RhB)的光催化活性.实验结果表明,与纯ZnO和In2O3相比,In2O3的引入将ZnO的吸收光谱扩展到可见光区域,从而提高了其光生电子和空穴的分离.此外,In2O3/ZnO异质结在可见光照射对RhB具有较高的光催化活性.5 wt%-In2O3/ZnO异质结对RhB的降解率为84.3%,且具有良好的光催化稳定性.In2O3/ZnO异质结复合材料在有机染料废水的降解中有更广阔的应用前景. 相似文献