The short-range order around boron, aluminum, and iron atoms in Fe75B25 and Fe70Al5B25 amorphous alloys has been studied by 11B and 27Al nuclear magnetic resonance at 4.2 K and 57Fe Mössbauer spectroscopy at 87 and 295 K. The average magnetic moment of iron atoms μ(Fe) in these alloys has been measured by a vibrating sample magnetometer. It has been revealed that the substitution of aluminum atoms for iron atoms does not disturb μ(Fe) in the Fe70Al5B25 alloy, gives rise to an additional contribution to the 11B NMR spectrum in the low-frequency range, and shifts maxima of the distribution of hyperfine fields at the 57Fe nuclei. In the Fe70Al5B25 amorphous alloy, the aluminum atoms substitute for iron atoms in the nearest coordination shells of boron and iron atoms. This alloy consists of nanoclusters in which boron and iron atoms have a short-range order of the tetragonal Fe3B phase type. 相似文献
The P2-type Na0.67Mn0.6Fe0.4O2 (NaMnFe), Na0.67Mn0.6Fe0.3Zn0.1O2 (NaMnFeZn), and Na0.67Mn0.6Fe0.2Zn0.1Ni0.1O2 (NaMnFeZnNi) are prepared using an acetate decomposition reaction and developed as promising cathode materials for high-capacity sodium-ion batteries. The XRD patterns show that Zn2+ and Ni2+ ions are successfully incorporated into the lattice of the Na-Mn-Fe-O system, and the P2-type structure remains unchanged after substitution. The charging/discharging tests exhibit that the Na0.67Mn0.6Fe0.4O2, Na0.67Mn0.6Fe0.3Zn0.1O2, and Na0.67Mn0.6Fe0.2Zn0.1Ni0.1O2 electrodes have the capacities of 200.4, 182.0, and 202.2 mAhg?1, respectively. The Na0.67Mn0.6Fe0.4O2 electrode has a higher initial capacity but faster capacity decay. When partially substituting Zn and Ni for Fe, the Na0.67Mn0.6Fe0.3Zn0.1O2 and Na0.67Mn0.6Fe0.2Zn0.1Ni0.1O2 electrodes exhibit lower reversible capacity but improved cycling stability (88.3 and 93.4% capacity retention over 100 cycles). The greatly improved electrochemical performance of the Na0.67Mn0.6Fe0.2Zn0.1Ni0.1O2 electrode apparently belongs to the contribution of the Zn2+ and Ni2+ substitution, which facilitates to alleviate the Jahn-Teller distortion of Mn and suppresses the polarization. 相似文献
To explain the magnetic properties of advanced ferromagnetic intermetallic compounds of the R2Fe17 (R is a rare-earth element) class, experimentalists often use the hypothesis of competition between ferromagnetic exchange and antiferromagnetic exchange between four types of the nearest iron atoms in nonequivalent lattice sites. For the rhombohedral Gd2Fe17 ferromagnet, we calculate the magnetic moments of iron and gadolinium ions, the parameters of exchange between Fe atoms, and Curie temperature TC at a zero pressure and during hydrostatic lattice compression. The magnetic moment of the unit cell of Gd2Fe17 is shown to decrease under pressure, and this decrease is almost completely associated with a decrease in the magnetic moments of Fe rather than Gd ions, the pressure dependence of the magnetic moments of which is weaker by an order of magnitude. In contrast to the hypothesis regarding the competition of exchange interactions between different kinds of Fe atoms, the parameters of exchange between the nearest iron atoms in different crystallographic sites are found to be positive ferromagnetic (at a zero pressure and during compression), and a ferromagnetic character of interaction is shown to remain unchanged under pressure even for Fe atoms in the so-called dumbbell sites with the nearest interatomic distances. The Curie temperature TC of Gd2Fe17 is shown to decrease with increasing pressure. The changes in the exchange parameters and the magnetic moments of Gd2Fe17 during compression are found to be mainly related to a change in the position of energy spectrum branches with respect to each other and the Fermi level ?F rather than to a change in the overlapping of wavefunctions, which play a minor role. 相似文献
To suppress the capacity fade of Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 material as cathode materials for lithium-ion battery, we introduce a LiF coating layer on the surface to improve the cycling performance of Li1.2Ni0.13Co0.13Mn0.54O2 material. The modified sample shows a capacity of 163.2 mAh g?1 with a capacity retention of 95% after 100 cycles at a current density of 250 mA g?1, while the pristine sample only delivers a capacity of 129.9 mAh g?1 with a capacity retention of 82%. Compared with the pristine material, the LiF-modified sample exhibits an obvious enhancement in the electrochemical performance, which will be very beneficial for this material to be commercialized on the new energy vehicles and other related areas. 相似文献
High discharge capacity and long life cycles of electrodes fabricated from various LiFePO4 powders have been used to select samples for detailed structural studies. In some samples, the presence of ferromagnetic Fe3P crystallites was revealed by the synchrotron X-ray diffraction analysis, with the integral intensity ratio of the peaks Fe3P (231) and LiFePO4 (112) equal to ~1/12. Small-angle polarized neutron scattering (SAPNS) detected the presence of magnetic nuclear contrasting regions with size of 17 ± 1 nm. The average diameter of LiFePO4 crystallites is 230 nm, and Fe3P crystallites were found as 17 × 54 nm2 plates. The high quality of these samples was provided by their manufacturer via synthesis of the Fe3P impurity phase. It can be stated that the set of studies, developed in the study, is helpful in a search for new effective impurity phases and in optimization of their parameters. 相似文献
The electronic structure and magnetic properties of Fe2SiC compound have been studiedusing the framework of an all-electron full-potential linearized augmented-plane wave(FP-LAPW) method within the local density (LSDA) and + U corrected(LSDA + U)approximations. An antiferromagnetic spin ordering of Fe atoms is shown to be the groundstate for this compound. From the electronic band structures and density of states (DOS),Fe2SiC has ametallic character and from the analysis of the site and momentum projected densities, itis deduced that the bonding is achieved through hybridization of Fe-3d with C-2p states andFe-3d withSi-3pstates. It is also pointed out that the Fe-C bonding is more covalent than Fe-Si. In theFM phase, the spin polarized calculations indicate that the total magnetic moment ofFe2SiC increasesfrom 0.41 to 4.33μB when the Hubbard U parameter for iron isconsidered. 相似文献
Array of dots have been designed by assembling a monolayer of polystyrene nanospheres (PN) on sputtered thin films having
Ni80Fe20 and Co composition with different thickness, ranging in the interval 20 ÷ 80 nm. Subsequently the films are nanopatterned
using the nanospheres as a mask during sputter etching with Ar+ ions. A Reactive Ion Etching (RIE) process before sputter etching is used to control the final diameter of the magnetic dots
that thus can be tailored as desired (typically ranging in the interval 250 ÷ 400 nm depending on the PN starting diameter).
In addition, electron beam lithography has been exploited to obtain arrays of dots in Ni80Fe20 thin films having approximately the same mean size and dot distance as in self-assembled samples. All films have been routinely
characterized by SEM and AFM microscopy to evaluate the microstructure. Magnetic domain patterns at magnetic remanence and
in the demagnetised state have been imaged by MFM microscopy technique. Room-temperature hysteresis properties have been measured
by an alternating gradient force magnetometer. In general, the magnetization process in all patterned films has been observed
to have features typical of a vortex whose nucleation field depends on sample thickness and mean dot dimension. A comparison
between magnetic arrays of Ni80Fe20 dots prepared by self-assembling of polystyrene nanospheres and electron beam lithography is presented to rule out the role
of microstructure (i.e., order, size, and mutual distance of the magnetic dots) on magnetic properties. 相似文献
A theoretical analysis of small-angle neutron scattering is performed for the Fe65Ni35 alloy at a temperature T=0.9TC=450 K. The results obtained indicate the existence of long-wavelength magnetic excitations that do not correspond to spin waves of the Holstein-Primakoff type. The possible nature of these excitations is discussed. 相似文献
The local magnetic and valence states of impurity iron ions in the rhombohedral La0.75Sr0.25Co0.9857Fe0.02O3 perovskite were studied using Mössbauer spectroscopy in the temperature range 87–293 K. The Mössbauer spectra are described by a single doublet at 215–293 K. The spectra contained a paramagnetic and a ferromagnetic component at 180–212 K and only a broad ferromagnetic sextet at T < 180 K. The results of the studies showed that, over the temperature range 87–295 K, the iron ions are in a single (tetrahedral) state with a valence of +3. In the temperature range 180–212 K, two magnetic states of Fe3+ ions were observed, one of which is in magnetically ordered microregions and the other, in paramagnetic microregions; these states are due to atomic heterogeneity. In the magnetically ordered microregions in the temperature range 87–212 K, the magnetic state of the iron ions is described well by a single state with an average spin S = 1.4 ± 0.2 and a magnetic moment μ(Fe) = 2.6 ± 0.4μB. 相似文献
We report a simple and novel method for surface biofunctionalization onto recently reported Ni80Fe20 permalloy nanoparticles (~71 nm) and the immobilization of a model protein, IgG from human serum. The strategy of protein
immobilization involved attachment of histidine-tagged streptavidin to the Ni80Fe20 nanoparticles via a non-covalent ligand binding followed by biotinylated human IgG binding on the nanoparticle surface using
the specific high affinity avidin–biotin interaction. The biofunctionalization of Ni80Fe20 permalloy nanoparticles was confirmed by Fourier Transform InfraRed (FTIR) spectroscopy and protein denaturing gel electrophoresis
(lithium dodecyl sulfate-polyacrylamide gel electrophoresis, LDS-PAGE). This protocol for surface functionalization of the
novel nanometer-sized Ni80Fe20 permalloy particles with biological molecules could open diverse applications in disease diagnostics and drug delivery. 相似文献
The results of a detailed structural and magnetic study clearly indicate that regardless of the thermal history of the samples,
Fe has a strong preference for the Ni sites in Ni-poor (nonstoichiometric) Ni75Al25 alloys. Fe substitution has a profound effect on the nature of magnetism in Ni25Al25
Article presented at the International Symposium on Advances in Superconductivity and Magnetism: Materials, Mechanisms and
Devices, ASMM2D-2001, 25–28 September 2001, Mangalore, India. 相似文献
The magnetic properties of the magnetite Fe3O4(110) surface have been studied by spin resolved Auger electron spectroscopy (SRAES). Experimental spin resolved Auger spectra
are presented. The results of calculation of Auger lines polarization carried out on the basis of electronic state density
are presented. Problems related to magnetic moments of bivalent (Fe2+) and trivalent (Fe3+) ions on the Fe3O4(110) surface are discussed. It is established that the deposition of a thin bismuth film on the surface results in significant
growth of polarization of iron Auger peaks, which is due to additional spin-orbit scattering of electrons by bismuth atoms. 相似文献
Li[Ni1/3Co(1-x)/3Mn1/3Fex/3] O2(x?=?0.0, 0.1, 0.3, 0.5, 0.7, and 0.9) cathode materials have been synthesized via hydroxide co-precipitation method followed by a solid state reaction. Thermogravimetry (TG) and differential thermal analysis (DTA) measurements were utilized to determine the calcination temperature of precursor sample. The crystal structure features were characterized by X-ray diffraction (XRD). The electrochemical properties of Li[Ni1/3Co(1-x)/3Mn1/3Fex/3]O2 were compared by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy(EIS), and galvanostatic charge/discharge test. Electrochemical test results indicate that Li[Ni1/3Co0.9/3Mn1/3Fe0.1/3] O2 decrease charge transfer resistance and enhance Li+ ion diffusion velocity and thus improve cycling and high-rate capability compared with Li[Ni1/3Co1/3Mn1/3]O2. The initial discharge specific capacity of Li[Ni1/3Co0.9/3Mn1/3Fe0.1/3] O2 was 178.5 mAh/g and capacity retention was 87.11 % after 30 cycles at 0.1C, with the battery showing good cycle performance. 相似文献
Single crystals of Pb2Fe2Ge2O9 have been grown. They were subjected to X-ray diffraction, magnetic, neutron diffraction, Mössbauer and spin resonance studies. It has been established that Pb2Fe2Ge2O9 is a weak ferromagnet with a Néel temperature TN = 46 K, and the exchange and spin-flop transition fields have been estimated. It has been demonstrated that the weak ferromagnetic moment is actually the result of the single-ion anisotropy axes for the magnetic moments of different magnetic sublattices being not collinear. 相似文献
The thermodynamic stability is a very important quantity for the electrode materials, because it is not only related to the electrochemical performances of the materials but also the safety issue of the cells. To evaluate the thermodynamic stability of LixNi0.5Mn1.5O4 (x = 0, 1), the formation enthalpies from elemental phases and oxides were obtained. The values for LiNi0.5Mn1.5O4 were calculated to be ?1341.10 and ?141.84 kJ mol?1, while those for Ni0.5Mn1.5O4 were ?949.11 and ?49.21 kJ mol?1. These values are much more negative than those of LiCoO2 and LiNiO2 compounds, indicating that the thermodynamic stability of LixNi0.5Mn1.5O4 is better than the two classic compounds. To clarify the microscopic origin, the density of states, magnetic moments, and bond orders were systematically investigated. The results showed that the excellent thermodynamic stability of LiNi0.5Mn1.5O4 is attributed to the absence of Jahn-Teller distortions, strong electrostatic interactions of Li–O ionic bond, and strong Ni–O/Mn–O ionic-covalent mixing bonds. After lithium extraction, the disappearance of the pure Li–O bonds leads to an increase of formation enthalpy, indicating a decreasing thermodynamic stability for Ni0.5Mn1.5O4 with respect to LiNi0.5Mn1.5O4. 相似文献
The crystal and magnetic structures of Fe1.087Te have been studied by neutron powder diffraction in the temperature range from 1.7 to 80 K at pressures of ≈0.4 and ≈1.2 GPa. No symmetry change of the tetragonal paramagnetic ambient pressure phase (space group P4/nmm) was observed for temperatures above 60 K and pressures up to ≈1.2 GPa. A novel pressure-induced phase of Fe1.087Te having orthorhombic symmetry (space group Pmmn) and incommensurate antiferromagneticbicollinear order was observed in the temperature range from 50 to 60 K at ≈1.2 GPa. The known monoclinic ambient pressure phase of Fe1.087Te (space group P21/n) with commensurate antiferromagnetic order was found to be stable up to at least ≈1.2 GPa at low temperature. 相似文献
The saturation magnetization, the perpendicular and rotational anisotropy constants, and the coercitivity of Ni75Fe16Cu5Mo4 thin magnetic films produced by rf sputtering are measured in the initial state and after annealing. A relation between the presence of perpendicular anisotropy and the “transcritical” state in the films is established. It is shown that, after additional thermal treatment, the magnetic softness of the films can be improved. 相似文献
Spinel ferrites can be used in magnetic targeting and microwave heating and can therefore be used for targeted and controllable drug delivery. We used the cetyltrimethylammonium bromide-assisted solvothermal method to synthesize a series of spinel ferrites (MxFe3-xO4, M=Mg, Mn, Fe, Co, Ni, Cu, Zn) with a mesoporous or hollow-mesoporous structure suitable for direct drug loading and the particle diameters ranging from 200 to 350 nm. We investigated the effects of M2+ cation on the morphology and properties of these products by analyzing their transmission electron microscopy images, mesoporous properties, magnetic properties, and microwave responses. We chose hollow-mesoporous MxFe3-xO4 (M=Fe, Co, Zn) nanoparticles, which had better overall properties, for the drug VP16 (etoposide) loading and microwave-controlled release. The CoxFe3-xO4 and Fe3O4 particles trapped 61.5 and 64.8%, respectively, of the VP16, which were higher than that (60.4%) of ZnxFe3-xO4. Controllable drug release by these simple magnetic nanocarriers can be achieved by microwave irradiation, and VP16-loaded CoxFe3-xO4 released the most VP16 molecules (more than 50% after 1 h and 69.1% after 6 h) under microwave irradiation. Our results confirm the favorable drug loading and microwave-controlled delivery by these ferrites, and lay a theoretical foundation to promote clinical application of the targeted controllable drug delivery system.
Graphical abstract In the present study, we prepared mesoporous or hollow-mesoporous spinel ferrites (MxFe3-xO4, M=Mg, Mn, Fe, Co, Ni, Cu, Zn) by CTAB-assisted solvothermal method and solved the problem of Cu and Ni impurities in CuxFe3-xO4 and NixFe3-xO4 products by means of magnetic separation and additional redox reactions, respectively. We investigated the effects of the M2+ cation on the morphology, mesoporous properties, magnetic properties, and microwave responses of these ferrites. Then, the drug loading and microwave-controlled drug release of hollow-mesoporous MxFe3-xO4 (M?=?Fe, Co, Zn) nanoparticles with better overall properties were also studied. CoxFe3-xO4 has the best overall performances for microwave-controlled drug release.
“Zero field”-Mössbauer and magnetization measurements have been performed on an amorphous Fe76Mo8Cu1B15 alloy in the temperature range of (10-340) K. The room-temperature Mössbauer spectrum exhibits magnetic dipole and electric quadrupole interactions. At approximately 306 K, the magnetic interactions vanish and the alloy shows fully paramagnetic behavior. On the other hand, the relative representation of paramagnetic component becomes weak with decreasing temperature and below 220 K the magnetic dipole interactions prevail. Below this temperature an anomaly in the low-temperature dependencies of ac susceptibility and of magnetization, measured during cooling the specimen from 340 K down to 20 K is observed. The anomaly on the magnetization curve vanishes in the field of 200 Oe. 相似文献
The effect of Fe2O3 in sodium zinc phosphate glass system containing CuO with the chemical composition 40P2O5:38ZnO:1CuO:(21 ? x)Na2O:xFe2O3 (where x = 1, 2, 3, 4, 5 and 6 mol%) has been studied. The glass formability of the prepared samples was examined by means of XRD which proved that there are no natural crystal contents. Archimedes method has been employed to measure the density of the prepared glass samples hence, the molar volume was calculated. The density and the molar volume were found to be increased by increasing Fe2O3 content. The optical spectroscopic analysis for the obtained glass samples has been carried out over the whole range (190–1000 nm) for studying the effect of bandpass absorption glass filter, its color peak center and UV cut-off. The center for bandpass filter is found to exhibit a red shift by increasing Fe2O3 content. Moreover, all glass samples showed a bandstop in UV-range which was increased by increasing Fe2O3 content. The results reveal the practicality of this glass composition in optical color glass bandpass filter for UV preventing applications such as UV-Laser protection. 相似文献