共查询到20条相似文献,搜索用时 15 毫秒
1.
Nanostructured ferroxide particles with initial formula Ni0.5Zn0.5Fe2O4 are investigated. The aim was to explore the monodomain and the superparamagnetic states of the ferrospinel and the impact of the surface magnetic disorder on the magnetization processes. Mössbauer spectroscopy (MöS) demonstrated that the ion distribution follows the general formula (Zn0.5Fe0.5)A[Ni0.5Fe1.5]BO4, where A is the tetrahedral and B, the octahedral sublattice. MöS in an external magnetic field (5 T) at 4.2 K shows non-collinearity of the sublattices’ magnetic moments and deviations in the hyperfine magnetic field that could be related to a canting effect. Magnetic measurements were applied to characterize the temperature behavior of the magnetic properties and the a.c. complex magnetic susceptibility. 相似文献
2.
Ismayadi Ismail Mansor Hashim Khamirul Amin Matori Rosidah Alias Jumiah Hassan 《Journal of magnetism and magnetic materials》2012
Possible soaking-time effects on the magnetic and microstructural properties of polycrystalline samples of Ni0.5Zn0.5Fe2O4 have been studied. Nanosize powder produced by mechanical alloying was sintered at 800 °C with various soaking times. All samples showed the signature peak of Ni0.5Zn0.5Fe2O4 even with one hour of soaking time. The size distributions show a slow growth of microstructural evolution related to density, porosity and also to the magnetic hysteresis loops. Within these distributions it is observed that the formation of multi-domains is not possible and probably there are the regions of superparamagnetic and single-domain grains. From the permeability studies, it is believed that the rise of the magnetic moment on the B sites give rise to the total saturation magnetization with increase of soaking time. The hysteresis loop of one-hour soaking time showed paramagnetic behavior dominating while longer soaking times showed ferromagnetic behavior starting to dominate. The coercivity was observed to increase with soaking time, signaling the increase of the anisotropy fields which was attributed to the shape anisotropy and also to the magnetocrystalline anisotropy. By correlating the morphology, phase analysis, permeability and hysteresis loops results, it is believed that there was an increase in number of crystalline-growth regions which together formed a total mass of mixed superparamagnetic and ferromagnetic grains with the latter starting to dominate the samples. 相似文献
3.
Herein, a discussion of the effect of deposition temperature on the magnetic behavior of Ni0.5Zn0.5Fe2O4 thin films. The thin films were grown by r.f. sputtering technique on (1 0 0) MgO single-crystal substrates at deposition temperatures ranging between 400 and 800 °C. The grain boundary microstructure was analyzed via atomic force microscopy (AFM). AFM images show that grain size (φ∼70-112 nm) increases with increasing deposition temperature, according to a diffusion growth model. From magneto-optical Kerr effect (MOKE) measurements at room temperature, coercive fields, Hc, between 37and 131 Oe were measured. The coercive field, Hc, as a function of grain size, reaches a maximum value of 131 Oe for φ ∼93 nm, while the relative saturation magnetization exhibits a minimum value at this grain size. The behaviors observed were interpreted as the existence of a critical size for the transition from single- to multi-domain regime. The saturation magnetization (21 emu/g<Ms<60 emu/g) was employed to quantify the critical magnetic intergranular correlation length (Lc≈166 nm), where a single-grain to coupled-grain behavior transition occurs. Experimental hysteresis loops were fitted by the Jiles-Atherton model (JAM). The value of the k-parameter of the JAM fitted by means of this model (k/μo∼50 A m2) was correlated to the domain size from the behavior of k, we observed a maximum in the density of defects for the sample with φ∼93 nm. 相似文献
4.
Yanling Zhang Qinghong Zhang Yaogang Li Hongzhi Wang 《Journal of magnetism and magnetic materials》2010,322(14):2006-2009
A magnetic multi-walled carbon nanotubes-based (MWCNTs-based) composite, MWCNTs/Ni0.5Zn0.5Fe2O4, was synthesized via a facile solvothermal approach. The composites were characterized by X-ray diffraction analysis, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and vibrating sample magnetometry. The results confirmed that MWCNTs and Ni0.5Zn0.5Fe2O4 coexisted in the composites. The TEM and HRTEM results showed a thick layer of Ni0.5Zn0.5Fe2O4 was intimately connected to the surface of MWCNTs. The saturation magnetization value of the composites was 45.8 emu/g. Furthermore, the probable synthesis mechanism of the magnetic composites was also investigated based on the experimental results. 相似文献
5.
NiZn ferrite/polyvinylpyrrolidone composite fibres were prepared by sol–gel assisted electrospinning.Ni0.5Zn0.5Fe2O4 nanofibres with a pure cubic spinel structure were obtained subsequently by calcination of the composite fibres at high temperatures.This paper investigates the thermal decomposition process,structures and morphologies of the electrospun composite fibres and the calcined Ni0.5Zn0.5Fe2O4 nanofibres at different temperatures by thermogravimetric and differential thermal analysis,x-ray diffraction,Fourier transform infrared spectroscopy and field emission scanning electron microscopy.The magnetic behaviour of the resultant nanofibres was studied by a vibrating sample magnetometer.It is found that the grain sizes of the nanofibres increase significantly and the nanofibre morphology gradually transforms from a porous structure to a necklace-like nanostructure with the increase of calcination temperature.The Ni0.5Zn0.5Fe2O4 nanofibres obtained at 1000 C for 2 h are characterized by a necklace-like morphology and diameters of 100–200 nm.The saturation magnetization of the random Ni0.5Zn0.5Fe2O4 nanofibres increases from 46.5 to 90.2 emu/g when the calcination temperature increases from 450 to 1000 C.The coercivity reaches a maximum value of 11.0 kA/m at a calcination temperature of 600 C.Due to the shape anisotropy,the aligned Ni0.5Zn0.5Fe2O4 nanofibres exhibit an obvious magnetic anisotropy and the ease magnetizing direction is parallel to the nanofibre axis. 相似文献
6.
Samaila Bawa Waje Mansor Hashim Wan Daud Wan Yusoff 《Journal of magnetism and magnetic materials》2010,322(6):686-691
Co0.5Zn0.5Fe2O4 nanoparticles were prepared using mechanical alloying (MA) and sintering. The crystallite size, coercivity, retentivity and saturation magnetization were also measured. The frequency dependence of dielectric and the magnetic parameters, namely, real permittivity ε′, loss tanget tan δ, real permeability μ′ and loss factor μ″ were measured at room temperature for samples sintered from 600 to 1000 °C, in the frequency range 10 MHz to 1.0 GHz. The results show that the crystallite size of the resulting products ranges between 16 and 67 nm for as-milled sample and the sample sintered at 1000 °C, respectively. The sample sintered at 1000 °C, measured at room temperature exhibited a saturation magnetization of 37 emu g−1. The values of permittivity remain constant within the measured frequency, but vary with sintering temperature. The permeability values, on the other hand however vary with both the sintering temperature and the frequency, thus, the absolute value of the permeability decreased after the natural resonance frequency. 相似文献
7.
Nanocomposite of hard (BaFe12O19)/soft ferrite (Ni0.8Zn0.2Fe2O4) have been prepared by the sol–gel process. The nanocomposite ferrite are formed when the calcining temperature is above 800 °C. It is found that the magnetic properties strongly depend on the presintering treatment and calcining temperature. The “bee waist” type hysteresis loops for samples disappear when the presintering temperature is 400 °C and the calcination temperature reaches 1100 °C owing to the exchange-coupling interaction. The remanence of BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite with the mass ratio of 5:1 is higher than a single phase ferrite. The specific saturation magnetization, remanence magnetization and coercivity are 63 emu/g, 36 emu/g and 2750 G, respectively. The exchange-coupling interaction in the BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite is discussed. 相似文献
8.
B.K. Bammannavar 《Journal of magnetism and magnetic materials》2009,321(5):382-387
Magneto electric composites with composition (x) Ni0.5Zn0.5Fe2O4+(1-x) Ba0.8Pb0.2Zr0.8Ti0.2O3 (BPZT—barium lead zirconate titanate) in which x varies as 0.0, 0.15, 0.30, 0.45 and 1.0 mol% were prepared by standard double sintering ceramic method. The presence of constituent phases such as ferrite and ferroelectric was confirmed by X-ray diffraction. The structural analyses were carried out by using X-ray diffraction pattern. Scanning electron micrographs (SEM) were taken to understand the microstructure of the samples. The calculated values of the porosity of the samples lie between 4.5% and 16.2%. The hysteresis measurements were made to determine saturation magnetization (Ms), magnetic moment (μB) and coercivity (Hc). From the AC susceptibility measurements the contribution of both the single domain (SD) particles of the ferrite phase and mixed domain (SD+MD) particles of the composites in ME output were explained. The static magneto electric voltage coefficients (dE/dH)H were measured as a function of intensity of magnetic field and the maximum ME coefficient were observed for the composites with 30% of ferrite+70% of ferroelectric phase. 相似文献
9.
G. Alvarez H. Montiel M.P. Gutierrez 《Journal of magnetism and magnetic materials》2010,322(3):348-590
Magnetosensitive microwave absorption measurements of polycrystalline ferrite Ni0.35Zn0.65Fe2O4 was carried out at 9.4 GHz (X-band) as a function of temperature. Temperature dependence of the total linewidth (ΔHpp) deduced from the resonance spectra showed the passage through the Curie point (Tc~430 K). Additionally, the plot ΔHpp vs. T also indicated the existence of another magnetic phase transition at ~240 K, which can be associated with a Yafet-Kittel-type canting of the magnetic moments. Low-field microwave absorption (LFMA) and the magnetically modulated microwave absorption spectroscopy (MAMMAS) were used to give a further knowledge on this material. For low temperature, these techniques give evidence of a Yafet-Kittel-type canting of the magnetic moments. 相似文献
10.
D.G. ChenX.G. Tang J.B. WuW. Zhang Q.X. LiuY.P. Jiang 《Journal of magnetism and magnetic materials》2011,323(12):1717-1721
Ni0.5Zn0.5Fe2O4 (NZFO) spinel-type nanoparticles were directly fabricated by the chemical co-precipitation process using metal nitrate and acetate as precursors since nitrogen and carbon would be taken away in the forms of oxynitride and oxycarbide, respectively, after the precursors were annealed and then investigated in detail by employing X-ray diffraction (XRD), magnetic measurement and Raman spectroscopy. XRD analysis indicates that the as-prepared nanocrystals are all of a pure cubic spinel structure with their sizes ranging from 20.8 to 53.3 nm, as well as peaks of some samples shifting to lower angles due to lattice expansion. Calculations from the derived XRD data indicate that the activation energy is 30.83 kJ/mol. The magnetic measurements show that these samples are superparamagnetic. The saturation magnetization increases with annealing temperature, which may be explained by super-exchange interactions of Fe ions occurring at A- and B-sites. The variation of coercivity with particle size is interpreted on the basis of domain structure and crystal anisotropy. Furthermore, these nanoparticles exhibit a redshift phenomenon at lower temperatures seen in the Raman spectra, which could be related to ionic substitution. 相似文献
11.
Dense composites were prepared through incorporating the dispersed Ni0.8Zn0.2Fe2O4 ferromagnetic particles into Sr0.5Ba0.5Nb2O6 ferroelectric matrix. Extrinsic dielectric relaxation and associated high permittivities of the materials are reported in the composites. We used an ideal equivalent circuit to explain electrical responses in impedance formalism. A Debye-like relaxation in the permittivity formalism was also found. Interestingly, real permittivity (ε′) of the sample containing 30% Ni0.8Zn0.2Fe2O4 shows obvious independence of the temperature at 100 kHz. Dielectric relaxation and high-ε′ properties of the composites are explained in terms of the Maxwell-Wagner (MW) polarization model. 相似文献
12.
The effect of B2O3 addition to the microstructure and magnetic properties of Ni0.4Zn0.6Fe2O4 ferrite
Berat Yuksel Sebahattin Kirtay T. Osman Ozkan Engin Acikalin Hilkat Erkalfa 《Journal of magnetism and magnetic materials》2008
The effects of 0.01 and 0.1 mol B2O3 addition to the microstructure and magnetic properties of a Ni–Zn ferrite composition expressed by a molecular formula of Ni0.4Zn0.6Fe2O4 were investigated. The toroid-shaped samples prepared by pressing the milled raw materials used in the preparation of the composition were sintered in the range of 1000–1300 °C. The addition of 0.01 mol B2O3 increased the grain growth and densification giving rise to reduced intergranular and intragranular porosity due to liquid-phase sintering. The sintered toroid sample at 1300 °C gave the optimum magnetic properties of Br=170 mT, Hc=0.025 kA/m and a high initial permeability value of μi=4000. The increment of the B2O3 content to 0.1 mol resulted in a pronounced grain growth and also gave rise to large porosity due to the evaporation of B2O3 at higher sintering temperatures. Hence, it resulted in an air-gap effect in the hysteresis curves of these samples. 相似文献
13.
Ismayadi Ismail Mansor Hashim Khamirul Amin Matori Rosidah AliasJumiah Hassan 《Journal of magnetism and magnetic materials》2011,323(11):1470-1476
Ni0.5Zn0.5Fe2O4 has been synthesized using mechanical alloying method with two variables (milling time and ball-to-powder weight ratio (BPR)) were varied in order to study its effect on the magnetic properties of the material. The effects of these two variables were studied using XRD, SEM, TEM and later by impedance analyzer with the frequency range from 1 MHz to 1.8 GHz. The results obtained however show that there are no significant trends to relate the milling time and BPR with the permeability and losses of the material studied. After being sintered at 1150 °C, all the effects of alloying process seem to diminish. 相似文献
14.
Kinnari Parekh László Almásy Hyo Sook Lee R. V. Upadhyay 《Applied Physics A: Materials Science & Processing》2012,106(1):223-228
Zero field cooled dc-magnetization measurements of monodispersed Mn0.5Zn0.5Fe2O4 nanoparticles dispersed in kerosene exhibit two transitions at low temperatures. These transitions correspond to (i) the
superparamagnetic to blocked superparamagnetic and (ii) the blocked superparamagnetic to surface spin-glass like/quantum superparamagnetic
state upon lowering the temperature. The existence of a disorder surface is confirmed by recording small-angle neutron scattering
data below and above the Curie temperature. Magnetic relaxation analysis shows a plateau at low temperature (below 5 K) with
a slight minimum at 3 K, which is a characteristic of the surface spin-glass-like state. This is analyzed considering the
energy distribution n(E)∼1/E. The existence of surface disorder dominates at low temperature and mimics the transition from superparamagnetic to quantum
superparamagnetic states. 相似文献
15.
Nanocrystalline Ni0.5Cu0.5Fe2O4 was synthesized by sol-gel method with varying calcination temperature over the range of 500-1000. The powders obtained were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, thermal analysis (TG-DTG-DTA) of the precursor was carried out. The study reveals the simultaneous decomposition and ferritization process at rather low temperature (280-350). For the crystalline structure investigated, single cubic spinel is gained when the precursor was decomposed at 800-1000, whereas separated crystal CuO formed when calcination temperature is below 800. The increase of calcination temperature favors the appearance of FeB3+, CuA2+ and O on the spinel surface. The hydroxylation activity is relative to the amount of CuB2+ species on the spinel surface. The lattice oxygen species on the spinel surface are favorable for the deep oxidation of phenol. 相似文献
16.
通过在碱液中共沉淀Mn2+、Ni2+和Fe2+后制备了棒状的前躯体,前躯体于不同温度煅烧后制得了MnxNi0:5-xZn0:5Fe2O4棒状体. 利用X射线衍射仪和透射电镜对棒状体的物相、形貌及粒径进行了表征,并利用振动样品磁强计对磁性能进行研究. 结果表明长径比大于15的棒状,随着x值的增加,MnxNi0:5-xZn0:5Fe2O4样品的直径增加,长度下降,长径比变小,当x=0.5时其直径在50 nm左右而长径比减小到7~8. 随着x值的增加,样品的矫顽力先增加后减少,x值达到0.4时样品的矫顽力再次增加,当煅烧温度为600 oC,x=0.5时样品的矫顽力最大为134.3 Oe. 饱和磁化强度随着x值的增加先增加后减少,当煅烧温度为800 oC和x=0.2时达到最大为68.5 Oe. 相似文献
17.
Isabelle Chassaing Jean-Pierre Bonino Philippe Tailhades Abel Rousset Paul Mollard 《Journal of magnetism and magnetic materials》1993,120(1-3):274-277
The magneto-optical properties of Co-Mn spinel ferrite thin films vary according to the manganese content, the degree of oxidation of mangenese ions, and microstructure. Thermal treatments allow the magneto-optical performance to be increased while maintaining small crystallite size. 相似文献
18.
Microstructure and magnetic characteristics of nanocrystalline Ni0.5Zn0.5 ferrite synthesized by a spraying-coprecipitation method 下载免费PDF全文
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
19.
Srinivasan G. 《物理学报》2006,55(5):2548-2552
讨论了Ni0.8Zn0.2Fe2O4 (NZFO)与锆钛酸铅(PZT)的双层膜结构样品的磁电(ME)效应.NZFO粉料由溶胶-凝胶法制成,再经900℃热压,并高温烧结.在该双层膜中测量到了很强的磁电相互作用.发现横向的磁电效应比纵向效应大一个数量级,并且随NZFO烧结温度的提高而增加.当烧结温度从950℃上升到1380℃时,横向ME电压系数(αE)的最大值变化范围为25.6 mV Am-2≤αE≤199.6 mV Am-2.理论分析显示NZFO-PZT双层膜样品中ME效应源于NZFO与PZT之间相对良好的磁电耦合.
关键词:
镍铁氧体
PZT
热压法
ME效应 相似文献
20.
In the present study, spin-glass-like ordering has been observed in the spinel ZnFe2O4 ferrite. Field cooled (FC) and zero-field cooled (ZFC) DC magnetizations display divergence at low temperature, which indicates a frozen state with the freezing temperature of Tf=21 K. Frequency dependence of AC susceptibility measurement was performed on the sample. It shows a peak at around Tf, with the peak position shifting as a function of driving frequency, indicating a spin-glass-like transition of the sample. The sample shows a typical spin-glass behavior with a manifestation of non-equilibrium dynamics of the spin glass, such as aging, rejuvenation and memory effects. These experimental findings indicate that Zn-ferrite exhibits a spin-glass-like phase at low temperature and it is not canted antiferromagnetic. 相似文献