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1.
SrFe12−x(Sn0.5Zn0.5)xO19 thin films with x=0−5 were synthesized by a sol-gel method on thermally oxidized silicon wafer (Si/SiO2). The site preference and magnetic properties of Zn-Sn substituted strontium ferrite thin films were studied using 57Fe Mössbauer spectroscopy and magnetic measurements. Mössbauer spectra displayed that the Zn-Sn ions preferentially occupy the 2b and 4f2 sites. The preference for these sites is responsible for the anomalous increase in the magnetization at high Zn-Sn substitutions. X-ray diffraction (XRD) patterns and field emission scanning electron microscope (FE-SEM) micrographs demonstrated that single phase c-axis hexagonal ferrite films with rather narrow grain size distribution were obtained. Vibrating sample magnetometer (VSM) was employed to probe magnetic properties of samples. The maximum saturation of magnetization and coercivity at perpendicular direction were 265 emu/g and 6.3 kOe, respectively. It was found that the complex susceptibility has linear variation with static magnetic field. 相似文献
2.
Ali Ghasemi Azadeh Ashrafizadeh Carla Fabiana Cerqueira Machado Xiaoxi Liu 《Journal of magnetism and magnetic materials》2010,322(20):3064-3071
In this study CuxMg0.5−xZn0.5Fe2O4 (x=0-0.5) nanoparticles and thin films were prepared by sol-gel processing. The morphologies of nanoparticles were observed by transmission electron microscope (TEM). The Mössbauer spectroscopy (MS) was employed to determine the site preference of the constitutive elements. Magnetic dynamics of the nanoparticles was studied by the measurement of AC magnetic susceptibility versus temperature at different frequencies. The phenomenological Néel-Brown and Vogel-Fulcher models were employed to distinguish between interacting or non-interacting system. Results exhibited that there is strong interaction between fine particles. X-ray diffraction (XRD) patterns of the thin films indicate the formation of single-phase cubic spinel structure. Atomic force microscope (AFM) was employed to evaluate the surface morphologies of the prepared thin films. Vibrating sample magnetometer (VSM) was employed to probe magnetic properties of samples. It was found that with an increase in the amount of copper, the saturation of magnetization and initial permeability increase. 相似文献
3.
Zn-doped nickel ferrite nanoparticles (Zn0.6Ni0.4Fe2O4) have been prepared via a surfactant, polyethylene glycol assisted hydrothermal route. X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), and vibrating scanning magnetometry (VSM) were used for the structural, morphological, and magnetic characterizations of the product, respectively. TEM analysis revealed that the nanoparticles have a narrow size distribution, with average particle size of 15±1 nm, which agrees well with the XRD based estimate of 14±2 nm. The absence of saturation and remanent magnetization, and coercivity in the high temperature region of the M-H curve and non-zero magnetic moments indicate superparamagnetism of the nanoparticles with a canted spin structure. The appearance of a peak on the temperature-dependent zero-field cooling magnetization curve at ∼190 K indicates the blocking temperature of the sample. 相似文献
4.
《Journal of magnetism and magnetic materials》2005,294(2):e37-e41
Due to the magnetic anisotropy introduced by the Co2+ ion in octahedral sites of cubic spinel ferrites, it is possible to tailor the magnetic properties by changing the cobalt content. Magnetic fluids with magnetite-cobalt ferrite nanoparticles given by the formula Co(x)Fe(3−x)O4 with x=0, 0.2 and 0.4 were prepared. Kerosene and oleic acid were used as liquid carrier and surfactant, respectively. Spherical magnetic nanoparticles were obtained by coprecipitation from metal salts and ammonium hydroxide; afterwards the magnetic fluids were obtained by a peptization process. Powder properties were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherma (BET), vibrating sample magnetometry (VSM) and fluids by transmission electron microscopy (TEM), thermogravimetric analyzer (TGA), VSM and the short-circuited transmission line technique. 相似文献
5.
Yong Cao Qingze Jiao Hongbo Liu Xinliang Tang Yun Zhao 《Physica E: Low-dimensional Systems and Nanostructures》2009,41(10):1824-1827
A magnetic composite of nitrogen-doped carbon nanotubes (CNx) decorated with nickel nanoparticles was synthesized by a chemical precipitation and deoxidization method. The decorated CNx were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD pattern showed that CNx, nickel nanoparticles and little nickel oxides coexisted in the composite, TEM observation indicated that nickel nanoparticles were highly dispersed on the outer walls of CNx, Magnetic measurements by VSM demonstrated that the saturated magnetization and remanence of CNx were improved, while the coercivity was lowered after decorating with nickel nanoparticles. 相似文献
6.
《Physica E: Low-dimensional Systems and Nanostructures》2010,42(10):1824-1827
A magnetic composite of nitrogen-doped carbon nanotubes (CNx) decorated with nickel nanoparticles was synthesized by a chemical precipitation and deoxidization method. The decorated CNx were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD pattern showed that CNx, nickel nanoparticles and little nickel oxides coexisted in the composite, TEM observation indicated that nickel nanoparticles were highly dispersed on the outer walls of CNx, Magnetic measurements by VSM demonstrated that the saturated magnetization and remanence of CNx were improved, while the coercivity was lowered after decorating with nickel nanoparticles. 相似文献
7.
Mn–Zn ferrite nanoparticles (Mn1−xZnxFe2O4) are synthesized by a hydrothermal precipitation approach using metal sulfate solution and aqueous ammonia. The analysis methods of XRPD, TEM, TGA, and VSM are used to characterize the magnetic nanoparticles. Through the characterization of the precipitated nanoparticles, the effects of the reacting component proportions and preparation techniques on the Curie temperature, the magnetization, and the size distribution of Mn–Zn ferrite nanoparticles are discussed. Furthermore, the Mn–Zn ferrite nanoparticles are used to prepare ferrofluid. Variation of the magnetic properties of the ferrite nanoparticles with the composition content x of Zn and the magnetic moment of the nanoparticles are discussed. 相似文献
8.
We report on the synthesis of Zn0.7Ni0.3Fe2O4 nanoparticles via microwave assisted combustion route by using urea as fuel. XRD and FT-IR analyses confirm the composition and structure as spinel ferrite. The crystallite size estimated from XRD (16.4 nm) and the magnetic core size (15.04 nm) estimated from VSM agree well, while a slightly smaller magnetic diameter reflects a very thin magnetically dead layer on the surface of the nanoparticles. Morphological investigation of the products was done by TEM which revealed the existence of irregular shapes such spherical, spherodial and polygon. Magnetization measurements performed on Zn0.7Ni0.3Fe2O4 nanoparticles showed that saturation was not attained at even in the high magnetic field. The sample shows superparamagnetic behavior at around the room temperature and ferromagnetic behavior below the blocking temperature which is measured as 284 K. 相似文献
9.
This work correlates the magnetic properties to the microstructure of the calcined nanocrystalline CdxCo1-xZr0.05Fe1.95O4 (0.0 ≤ x ≤ 0.3 in a step of 0.05) powders produced by Pechini sol–gel method. The dry gel was grinded and calcined at 700 °C in a static air atmosphere for 1 h. The thermal decomposition process of dried gel was studied by thermo gravimetric analysis (TGA) combined with differential analysis (DTA). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometer (VSM) were carried out to investigate the structural bonds identification, crystallographic properties, morphology and magnetic properties of the obtained powders. The XRD pattern of the samples showed that the synthesized materials were of a single cubic phase with the nanocrystalline Co–Zr–Cd ferrite which had an average crystallite size of 32–40 nm and particle size of 55 nm resulted from FE-SEM. The magnetic properties were measured from the hysteresis loops. The magnetic measurements had indicated that the coercivity and the magnetization decreased by increasing the Cd content. 相似文献
10.
Structural analysis of nickel doped cobalt ferrite nanoparticles prepared by coprecipitation route 总被引:1,自引:0,他引:1
K. Maaz S. Karim A. Mashiatullah J. Liu M.D. Hou Y.M. Sun J.L. Duan H.J. Yao D. Mo Y.F. Chen 《Physica B: Condensed Matter》2009,404(21):3947-3951
Magnetic nanoparticles of nickel substituted cobalt ferrite (NixCo1−xFe2O4:0≤x≤1) have been synthesized by co-precipitation route. Particles size as estimated by the full width half maximum (FWHM) of the strongest X-ray diffraction (XRD) peak and transmission electron microscopy (TEM) techniques was found in the range 18–28±4 nm. Energy dispersive X-ray (EDX) analysis confirms the presence of Co, Ni, Fe and oxygen as well as the desired phases in the prepared nanoparticles. The selective area electron diffraction (SAED) analysis confirms the crystalline nature of the prepared nanoparticles. Data collected from the magnetization hysteresis loops of the samples show that the prepared nanoparticles are highly magnetic at room temperature. Both coercivity and saturation magnetization of the samples were found to decrease linearly with increasing Ni-concentration in cobalt ferrite. Superparamagnetic blocking temperature as determined from the zero field cooled (ZFC) magnetization curve shows a decreasing trend with increasing Ni-concentration in cobalt ferrite nanoparticles. 相似文献
11.
Surasing Chaiyakun Artorn Pokaipisit Pichet Limsuwan Boonlaer Ngotawornchai 《Applied Physics A: Materials Science & Processing》2009,95(2):579-587
Titanium dioxide thin films were deposited on three different unheated substrates by unbalanced magnetron sputtering. The
effects of the sputtering current and deposition time on the crystallization of TiO2 thin films were studied. The TiO2 thin films were deposited at three sputtering current values of 0.50, 0.75, and 1.00 A with different deposition times of 25,
35, and 45 min, respectively. The surface morphology of the films was investigated by atomic force microscopy (AFM). The structure
was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The film thickness was determined
by field emission scanning electron microscopy (FE-SEM), and the optical property was evaluated with spectroscopic ellipsometry.
The results show that polycrystalline anatase films were obtained at a low sputtering current value. The crystallinity of
the anatase phase increases as the sputtering current increases. Furthermore, nanostructured anatase phase TiO2 thin films were obtained for all deposition conditions. The grain size of TiO2 thin films was in the range 10–30 nm. In addition, the grain size increases as the sputtering current and deposition time
increase. 相似文献
12.
We present an investigation of properties of CoxZn1−xFe2O4 (x=0.0-1.0) nanoparticles synthesized by a polyethylene glycol (PEG)-assisted hydrothermal route. X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and vibrating scanning magnetometry (VSM) were used to characterize the structural, morphological and magnetic properties. The particle size obtained from TEM and XRD are consistent with each other. It was observed that the lattice constant for each composition decreases with increasing Co substitution and follows Vegard's law. Magnetization measurements show that while the materials with high Zn substitution are superparamagnetic at room temperature, they are ferromagnetic at temperatures lower than the blocking temperature. The materials with less Zn substitution are ferromagnetic below room temperature. Magnetizations and the coercivities of the samples decrease with the Zn substitution. The resultant overall magnetic behavior of the superparamagnetic samples are found to be considerably different than that of conventional superparamagnetic systems due to the antiferromagnetic interactions both in intra- and inter-cluster spins, and size (effective moment) distribution of the particles. 相似文献
13.
Darko Makovec Alojz Kodre Iztok Arčon Miha Drofenik 《Journal of nanoparticle research》2011,13(4):1781-1790
ZnFe2O4 bulk material shows a normal-spinel structure and a closely defined composition at Zn2+/Fe3+ ≅ 0.5. However, the composition of zinc ferrite, prepared as nanoparticles, can be varied in a broad range without losing
the single-phase spinel structure. In this article, structural mechanisms enabling this non-stoichiometry were studied using
the X-ray absorption fine structure (EXAFS) in combination with X-ray diffractometry (XRD), transmission electron microscopy
(TEM), and magnetic measurements. Nanoparticles with a narrow size distribution were synthesized using co-precipitation in
water-in-oil microemulsions. First, the structure of the stoichiometric zinc-ferrite nanoparticles was studied in dependence
of their size and the annealing temperature. EXAFS analysis showed that the degree of inversion x (as defined in the compound formula (Zn1 − x
Fe
x
)[Fe2 − x
Zn
x
]O4, with round and square brackets representing the tetrahedral and octahedral sites, respectively) increased with decreasing
nanoparticles size. The structure of the stoichiometric nanoparticles and the nanoparticles of comparable size displaying
Zn/Fe ratio of 0.2 (Fe-rich) and 0.7 (Zn-rich) were then compared. Analysis showed that the non-stoichiometry is structurally
compensated predominantly in the core of the nanoparticle by the adjusted distribution of Zn and Fe ions over the two sublattices
of the spinel structure. 相似文献
14.
Li0.5Fe2.5−xMnxO4 (0≦x≦1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion, using lithium nitrate, ferric nitrate, manganese nitrate and carbohydrazide as the starting materials. The process takes only a few minutes to obtain as-received Mn-substituted lithium ferrite powders. The resultant powders annealed at 650 °C for 2 h and were investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermomagnetic analysis (TMA). The results revealed that the Mn content were strongly influenced the magnetic properties and Curie temperature of Mn-substituted lithium ferrite powder. As for sintered Li0.5Fe2.5−xMnxO4 specimens, substituting an appropriate amount of Mn for Fe in the Li0.5Fe2.5−xMnxO4 specimens markedly improved the complex permeability and loss tangent. 相似文献
15.
R. Raeisi Shahraki M. EbrahimiS.A. Seyyed Ebrahimi S.M. Masoudpanah 《Journal of magnetism and magnetic materials》2012
Single phase zinc ferrite (ZnFe2O4) nanoparticles have been prepared by the coprecipitation method without any subsequent calcination. The effects of precipitation temperature in the range 20–80 °C on the structural and the magnetic properties of zinc ferrite nanoparticles were investigated. The crystallite size, microstructure and magnetic properties of the prepared nanoparticles were studied using X-ray diffraction (XRD), Fourier transmission infrared spectrum, transmission electron microscope (TEM), energy dispersive X-ray spectrometer and vibrating sample magnetometer. The XRD results showed that the coprecipitated nanoparticles were single phase zinc ferrite with mixture of normal and inverse spinel structures. Furthermore, ZnFe2O4 nanoparticles have the crystallite size in the range 5–10 nm, as confirmed by TEM. The magnetic measurements exhibited that the zinc ferrite nanoparticles synthesized at 40 °C were superparamagnetic with the maximum magnetization of 7.3 emu/g at 10 kOe. 相似文献
16.
In this work, formation of gold nanoparticles in radio frequency (RF) reactive magnetron co-sputtered Au-SiO2 thin films post annealed at different temperatures in Ar + H2 atmosphere has been investigated. Optical, surface topography, chemical state and crystalline properties of the prepared films were analyzed by using UV-visible spectrophotometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD) techniques, respectively. Optical absorption spectrum of the Au-SiO2 thin films annealed at 800 °C showed one surface plasmon resonance (SPR) absorption peak located at 520 nm relating to gold nanoparticles. According to XPS analysis, it was found that the gold nanoparticles had a tendency to accumulate on surface of the heat-treated films in the metallic state. AFM images showed that the nanoparticles were uniformly distributed on the film surface with grain size of about 30 nm. Using XRD analysis average crystalline size of the Au particles was estimated to about 20 nm. 相似文献
17.
Spinel Co1−xMnxFe2O4 nanoparticles were prepared by the sol-gel combustion technique. X-ray diffraction (XRD), atomic force microscopy (AFM) and vibration sample magnetometer (VSM) studies have been carried out in order to understand the temperature dependence of their properties. It is observed that the high concentration of Mn2+ substituted into CoFe2O4 tends to reduce the particle size. Furthermore, the influence of Mn on the magnetic and thermal characteristics of Co1−xMnxFe2O4 nanoparticles has been investigated in detail. 相似文献
18.
J. López L.F. González-BahamónJ. Prado J.C. CaicedoG. Zambrano M.E. GómezJ. Esteve P. Prieto 《Journal of magnetism and magnetic materials》2012,324(4):394-402
Ferrofluids are colloidal systems composed of a single domain of magnetic nanoparticles with a mean diameter around 30 nm, dispersed in a liquid carrier. Magnetic Co(1−x)ZnxFe2O4 (x=0.25, 0.50, 0.75) ferrite nanoparticles were prepared via co-precipitation method from aqueous salt solutions in an alkaline medium. The composition and structure of the samples were characterized through Energy Dispersive X-ray Spectroscopy and X-ray diffraction, respectively. Transmission Electron Microscopy (TEM) studies permitted determining nanoparticle size; grain size of nanoparticle conglomerates was established via Atomic Force Microscopy. The magnetic behavior of ferrofluids was characterized by Vibrating Sample Magnetometer (VSM); and finally, a magnetic force microscope was used to visualize the magnetic domains of Co(1−x)ZnxFe2O4 nanoparticles. X-ray diffraction patterns of Co(1−x)ZnxFe2O4 show the presence of the most intense peak corresponding to the (311) crystallographic orientation of the spinel phase of CoFe2O4. Fourier Transform Infrared Spectroscopy confirmed the presence of the bonds associated to the spinel structures; particularly for ferrites. The mean size of the crystallite of nanoparticles determined from the full-width at half maximum of the strongest reflection of the (311) peak by using the Scherrer approximation diminished from (9.5±0.3) nm to (5.4±0.2) nm when the Zn concentration increases from 0.21 to 0.75. The size of the Co-Zn ferrite nanoparticles obtained by TEM is in good agreement with the crystallite size calculated from X-ray diffraction patterns, using Scherer's formula. The magnetic properties investigated with the aid of a VSM at room temperature presented super-paramagnetic behavior, determined by the shape of the hysteresis loop. In this study, we established that the coercive field of Co(1−x)ZnxFe2O4 magnetic nanoparticles, the crystal and nanoparticle sizes determined by X-ray Diffraction and TEM, respectively, decrease with the increase of the Zn at%. Finally, our magnetic nanoparticles are not very hard magnetic materials given that the hysteresis loop is small and for this reason Co(1−x)ZnxFe2O4 nanoparticles are considered as soft magnetic material. 相似文献
19.
Thin films of lithium ferrite (with general composition Li0.5Fe2.5O4) were fabricated at low temperatures (up to 650 °C) by citrate-route using spin-deposition technique. Deposited films consisted of nanometer-sized grains as evidenced by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. XRD patterns for annealed films showed broad peaks exhibiting a spinel phase. Size of nanocrystallites is estimated to be 3-7 nm using Scherrer's equation. Average grain size ∼8.5 nm is observed from TEM images of films annealed at 650 °C. Scanning electron micrographs show the formation of spherical aggregates of around 130 nm in diameter. The AFM analysis clearly evidenced the development of nanograins even at low (∼500 °C) annealing temperatures. Significant decrease in complex dielectric permittivity (∈′ − j∈″) with frequency is observed in the low frequency (100 Hz-1 MHz) as well as in X-band microwave frequency (8-12 GHz) region. ∈′ is found to be in the range of 15.7-33.9 in low frequency region, whereas in X-band microwave frequency region, it is found to lie between 3.9 and 4.9. Similarly, ∈″ is found to be 0.16-5.9 in the low frequency region, and 0.002-0.024 in the X-band microwave frequency region. Room temperature dc resistivity of these films is estimated to lie in the range of 106-108 Ω cm. These results strongly suggest that citrate-route processed nanocrystalline lithium ferrite thin films are promising candidates for monolithic microwave integrated circuits (MMICs). 相似文献
20.
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