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11.
The uniform NeFe2O4 powders with different particle size and morphologies (octahedral, cubic and spherical) have been prepared from different precursors via hydrothermal process. The nanocrystallines derived from precursor B in the weak alkali solution (pH≥10) are superparamagnetic. 相似文献
12.
C. Cannas A. Falqui A. Musinu D. Peddis G. Piccaluga 《Journal of nanoparticle research》2006,8(2):255-267
Nanocrystalline CoFe2O4 powders were prepared by decomposition of metal ion citrate precursors. Four samples were synthesized from precursor solutions having different pH values in the range <1–7.0. The powders were characterized by X-ray Diffraction, Thermogravimetry, Differential Thermal Analysis, N2 physisorption and Transmission Electron Microscopy. Magnetic properties were explored by a SQUID magnetometer. Three out of the four samples, coming from solutions of pH 2, 4 and 7, were produced by an autocombustion reaction and are very similar as regards average size of the nanoparticles (about 20 nm), their morphology and the magnetic properties, while the fourth sample was produced by a slower thermal decomposition and is composed of smaller nanoparticles (about 10 nm). 相似文献
13.
G. C. Papaefthymiou A. J. Viescas R. Horn E. Carney G. Zhao N. D. Chasteen J. Lee S. M. Gorun 《Hyperfine Interactions》2005,165(1-4):333-338
We present comparative Mössbauer investigations of nanosized FeOOH and FeOOD biomineral phases nucleated within the 7-nm diameter cavity of horse-spleen apoferritin in order to assess deuterium isotopic effects on nanoscale, bioinorganic lattice structures with extended hydrogen bond networks. Differences in magnetic anisotropy energy, packing density and degree of crystallinity in the resulting iron oxo-hydroxide nanophases obtained via D2O (heavy water) vs. H2O (light water) solution chemistry are noted. These observations point to the possibility of stabilizing new thermodynamic states in the solid-state by utilizing isotope effects, with important implications for new synthetic pathways to novel nano materials. 相似文献
14.
It is shown that hysteresis and susceptibility studies at various temperatures could provide an idea whether a magnetic sample
contains multidomain, single-domain or superparamagnetic particles. Our results on titanomagnetites with those of others on
cobalt substituted magnesium ferrites suggest that domain wall formation is inhibited in some of them whereby only single-domain
or superparamagnetic particles occur irrespective of the physical grain size of such materials. At high concentration of titanium
in titanomagnetites, the magnetic behaviour is similar to a spin glass, which we interpret as a transition of optimum single-domains
going over to superparamagnetic state. 相似文献
15.
16.
Hydrogen Treatment for Superparamagnetic VO2 Nanowires with Large Room‐Temperature Magnetoresistance 下载免费PDF全文
Zejun Li Yuqiao Guo Prof. Zhenpeng Hu Jihu Su Jiyin Zhao Junchi Wu Jiajing Wu Yingcheng Zhao Prof. Changzheng Wu Prof. Yi Xie 《Angewandte Chemie (International ed. in English)》2016,55(28):8018-8022
One‐dimensional (1D) transition metal oxide (TMO) nanostructures are actively pursued in spintronic devices owing to their nontrivial d electron magnetism and confined electron transport pathways. However, for TMOs, the realization of 1D structures with long‐range magnetic order to achieve a sensitive magnetoelectric response near room temperature has been a longstanding challenge. Herein, we exploit a chemical hydric effect to regulate the spin structure of 1D V–V atomic chains in monoclinic VO2 nanowires. Hydrogen treatment introduced V3+ (3d2) ions into the 1D zigzag V–V chains, triggering the formation of ferromagnetically coupled V3+–V4+ dimers to produce 1D superparamagnetic chains and achieve large room‐temperature negative magnetoresistance (?23.9 %, 300 K, 0.5 T). This approach offers new opportunities to regulate the spin structure of 1D nanostructures to control the intrinsic magnetoelectric properties of spintronic materials. 相似文献
17.
Violeta D. Kassabova-Zhetcheva Lilyana P. Pavlova Bisserka I. Samuneva Zara P. Cherkezova-Zheleva Ivan G. Mitov Mikhail T. Mikhov 《Central European Journal of Chemistry》2007,5(1):107-117
Structural and magnetic properties of Mg
x
Zn1−x
Fe2O4 powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg
x
Zn1−x
Fe2O4 (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns
of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes
from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely
small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to
explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts
remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones.
相似文献
18.
M.A. Itskovsky 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):283-296
Theory of magnetoquantum oscillations with spin-split structure in strongly anisotropic (two-dimensional (2D)) metal is developed
in the formalism of level approach. Parametric method for exact calculation of oscillations wave forms and amplitudes, developed
earlier for spin degenerate levels is generalized on a 2D electron system with spin-split levels. General results are proved:
1) proportionality relation between magnetization and chemical potential oscillations accounting for spin-split energy levels
and magnetic field unperturbed levels (states of reservoir), 2) basic equation for chemical potential oscillations invariant
to various models of 2D and 1D energy bands (intersecting or overlapping) and localized states. Equilibrium transfer of carriers
between overlapping 2D and 1D bands, characterizing the band structure of organic quasi 2D metals, is considered. Transfer
parameter, calculated in this model to be of the order of unity, confirms the fact that the wave form of oscillations in organic metals should be quasisymmetric up to ultralow temperature. Presented theory accounts for spin-split magnetization oscillations at magnetic field directions tilted relative to the anisotropic
axis of a metal. Theoretical results are compared with available experimental data on organic quasi-2D metal α-(BEDT-TTF)2KHg(SNC)4 explaining the appearance of clear split structure under the kink magnetic field and absence above by the corresponding change
in the electron g-factor rather than cyclotron mass.
Received 20 December 2000 and Received in final form 13 July 2001 相似文献
19.
S. Pleutin A. Ovchinnikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):521-531
The static polarizability of cylindrical systems is shown to have a strong dependence on a uniform magnetic field applied
parallel to the tube axis. This dependence is demonstrated by performing exact numerical diagonalizations of simple cylinders
(rolled square lattices), armchair and zig-zag carbon nanotubes (rolled honeycomb lattices) for different electron-fillings.
At low temperature, the polarizability as function of the magnetic field has a discontinuous character where plateau-like
region are separated by sudden jumps or peaks. A one to one correspondence is pointed out between each discontinuity of the
polarizability and the magnetic-field induced cross-over between the ground state and the first excited state. Our results
suggest the possibility to use measurements of the static polarizability under magnetic field to get important informations
about excited states of cylindrical systems such as carbon nanotubes.
Received 29 March 2001 and Received in final form 8 August 2001 相似文献
20.