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1.
Recently, we have demonstrated the successful synthesis of Fe
x
Co1−x
/Co
y
Fe3−y
O4 nanocomposites with various alkaline solutions by using surfactants-assisted-hydrothermal (SAH) process. In this article,
the synthesis of Fe
x
Co1−x
/CoyFe3−y
O4 nanocomposites with their sizes varying between 20 nm and 2 μm was reported. X-ray powder diffraction (XRD) analyses showed
that the surfactants, pH, precipitator, and temperature of the system play important roles in the nucleation and growth processes.
The magnetic properties tested by vibrating sample magnetometer (VSM) at room temperature exhibit ferromagnetic behavior of
the nanocomposites. These Fe
x
Co1−x
/Co
y
Fe3−y
O4 nanocomposites may have a potential application as magnetic carriers for drug targeting because of their excellent soft-magnetic
properties. 相似文献
2.
I. A. Garifullin D. A. Tikhonov N. N. Garif’yanov M. Z. Fattakhov K. Theis-Bröhl K. Westerholt H. Zabel 《Applied magnetic resonance》2002,22(3):439-452
Epitaxial V/Pd1−x Fe x (001) bilayers with a V thickness of the order of 40 nm and with a Pd1−x Fe x thickness in the range from 0.8 nm to 4.4 nm were prepared by molecular beam epitaxy techniques. The Curie temperature of the Pd1−x Fe x layers varies between 90 and 250 K. For a bilayer with a Pd1−x Fe x thickness of 1.2 nm the ferromagnetic resonance measurements revealed a decrease of the effective magnetization 4πM eff of the ferromagnetic layer below the superconducting transition temperature of V. As a possible explanation for this decrease we suggest a spatial modulation of the ferromagnetic order in the Pd1−x Fe x layer due to modifications of the indirect exchange interaction of magnetic ions via conduction electrons in the superconducting state. A comparison with a recent theoretical investigation supports this possibility. 相似文献
3.
Based on first-principle FLAPW-GGA calculations, we have investigated the electronic structure of the newly discovered oxygen-free
38-K superconductor Ba1−x
K
x
Fe2As2 in comparison with a parent phase—the tetragonal ternary iron arsenide BaFe2As2. The density of states, magnetic properties, near-Fermi band compositions, together with the Sommerfeld coefficients γ and
the molar Pauli paramagnetic susceptibility χ have been evaluated. The results obtained allow us to classify these systems as quasi-two-dimensional ionic metals, where the conduction is strongly anisotropic, occurring only in the (Fe-As) layers. According to our calculations, in the
case of the hole doping of BaFe2As2, the density of states at the Fermi level grows, which may be a factor promoting the occurrence of superconductivity for
Ba1−x
K
x
Fe2As2. On the other hand, Ba1−x
K
x
Fe2As2 lies at the border of the magnetic instability and the pairing interactions might involve the magnetic or orbital fluctuations.
The text was submitted by the authors in English. 相似文献
4.
K
β-to-K
α X-ray intensity ratios of Fe and Ni in pure metals and in Fe
x
Ni1−x
alloys (x=0.20, 0.50, 0.58) exhibiting similar crystalline structure have been measured following excitation by 59.54 keV γ-rays from a 241Am point source, to understand as to why the properties of permalloy Fe0.2Ni0.8 is distinct from other alloy compositions. It is observed that the valence electronic structure of Fe0.2Ni0.8 alloy is totally different from other alloys which may be attributed to its special magnetic properties. 相似文献
5.
Xiangqian Shen Mingquan Liu Fuzhan Song Yongwei Zhu 《Applied Physics A: Materials Science & Processing》2011,104(1):109-116
Sr1−x
La
x
Zn
x
Fe12−x
O19/poly(vinylpyrrolidone) (PVP) (0.0≤x≤0.5) precursor nanofibers were prepared by the sol–gel assisted electrospinning method from starting reagents of metal salts
and PVP. Subsequently, the Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers with diameters of around 100 nm were obtained by calcination of the precursor at 800 to 1000°C for 2 h. The precursor
and resultant Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer and
vibrating sample magnetometer. The grain sizes of Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers are in a nanoscale from 40 to 48 nm corresponding to the calcination temperature from 800 to 1000°C. With La–Zn
substitution content increase from 0 to 0.5, the grain size and lattice constants for the Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers obtained at 900°C show a steady reduction trend. With variations of the ferrite particle size arising from the
La–Zn substitution, the nanofiber morphology changes from the necklace-like structure linking by single elongated plate-like
particles to the structure building of multi-particles on the nanofiber cross-section. The specific saturation magnetization
of Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers initially increases with the La–Zn content, reaching a maximum value 72 A m2 kg−1 at x=0.2, and then decreases with a further La–Zn content increase up to x=0.5, while the coercivity exhibits a continuous reduction from 413 (x=0) to 219 kA m−1 (x=0.5). The mechanism for the La–Zn substitution and the nanofiber magnetic property are analyzed. 相似文献
6.
M. Almasi?Kashi A. Ramazani S. Doudafkan A. S. Esmaeily 《Applied Physics A: Materials Science & Processing》2011,102(3):761-764
FeNi nanowires were fabricated by ac and pulse electrodeposition into the alumina template matrix. The effects of continuous
ac electrodeposition as well as pulse features on the structure and magnetic properties of the nanowire arrays were studied.
The microstructures and magnetic properties of the Fe
x
Ni1−x
nanowires are seen to be independent of the deposition frequency and off-time between the pulses. The ac electrodeposited
Ni nanowires were not formed at more than 400 Hz deposition frequency, while the Fe
x
Ni1−x
nanowires, containing a small amount of Fe, formed in the all frequencies. For x less than 50% the coercivity slowly increases but over 50% Fe added to the FeNi alloy increases the coercivity with a higher
rate and maximum coercivity was seen for the Fe0.97Ni0.03. The Fe and Fe
x
Ni1−x
nanowires containing less than 30 at.% Ni was seen to have a bcc structures with (110) preferential direction while Fe
x
Ni1−x
nanowires with more than 30 at.% Ni showed (110) bcc (Fe) and/or (111) bcc (FeNi) plus (111) fcc (Ni). A preferential (111)
fcc structure was obtained for the Ni nanowires. 相似文献
7.
H. Xiang C.-X. Ji J. Joshua Yang Y. Austin Chang 《Applied Physics A: Materials Science & Processing》2010,98(4):707-710
The effect of the composition of ferromagnetic bcc Co100−x
Fe
x
electrodes on tunneling magnetoresistance (TMR) of Co100−x
Fe
x
/AlO
x
/Co100−x
Fe
x
/IrMn magnetic tunnel junctions was studied. The epitaxial growth of the bottom Co100−x
Fe
x
electrode leads to a high-quality electrode and interface, which significantly enhances the TMR ratio and the desired effect
for study. Other factors that could also affect TMR, such as interface roughness, tunneling barrier properties, and exchange-bias
properties, were kept the same within the uncertainty of the experiment in order to minimize their effects. The observed TMR
dependence on composition is attributed to the variation of the s-like electron densities of state of the bcc Co100−x
Fe
x
electrodes with different compositions. 相似文献
8.
The crystal structure and magnetic properties of Bi1 − x
A
x
FeO3 − x/2 (A = Ca, Sr, Pb, Ba), Bi1 − x
A
x
(Fe1 − x
Ti
x
)O3, and Bi1 − x
A
x
(Fe1 − x/2Nb
x/2)O3 solid solutions have been studied. It is shown that the homogeneous polar weak ferromagnetic state occurs in the vicinity
of a morphotropic phase boundary in the systems where dopant ions lead to the reduction of the unit cell volume in the polar
phase. In the case of A = Ca, the non-polar phase also exhibits weak ferromagnetism and the spontaneous magnetizations in
the polar and nonpolar phases differ only slightly. 相似文献
9.
X. Q. Shen J. Xiang F. Z. Song M. Q. Liu 《Applied Physics A: Materials Science & Processing》2010,99(1):189-195
By the electrospinning and calcination techniques, we have prepared uniform nanofibers of Co1−x
Zn
x
Fe2O4 (0.0≤x≤0.5) ferrites with diameters of 110–130 nm. The Co1−x
Zn
x
Fe2O4 nanofibers are single-phase spinels and the lattice constant with Zn content deviates from the Vegard’s law for these Co1−x
Zn
x
Fe2O4 nanofibers. The Co1−x
Zn
x
Fe2O4 nanocrystal grains by which are built nanofibers increase with calcination temperature. Variations of coercivity and saturation
magnetization with calcination temperature can be explained in terms of the grain-size (D) effect. The coercivity (H
c) of Co0.5Zn0.5Fe2O4 nanofibers varies as D
0.65 and basically follows the predicted D
2/3 dependence based on the random anisotropy model in a D range below the single-domain size around 40 nm. The saturation magnetization of Co1−x
Zn
x
Fe2O4 nanofibers initially increases with increasing Zn content, reaches a maximum value at x=0.3 and then decreases with further increase of Zn content, while the coercivity exhibits a continuous reduction with the
increase of Zn content. 相似文献
10.
The relative differences δ
ns
(n=1, 2, 3) of the spindependent conversion coefficients were measured for α-Fe and α=Fe2O3. In contrast to theoretical predictions of δ1s≃−10−5 we found δ1s≃−1.0(4)x10−2 for both α-Fe and α-Fe2O3. As a possible source for this difference we consider a dynamic coupling with the atomic spin during the conversion process. 相似文献
11.
S. V. Grigoriev V. A. Dyadkin S. V. Maleyev D. Menzel J. Schoenes D. Lamago E. V. Moskvin H. Eckerlebe 《Physics of the Solid State》2010,52(5):907-913
Two systems of noncentrosymmetric cubic helical magnets Mn1 − y
Fe
y
Si (y = 0.06, 0.08, 0.10) and Fe1 − x
Co
x
Si (x = 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.50) have been compared. The concentration dependences of the critical temperature
and magnetic field have been obtained using small-angle polarized-neutron scattering and analyzed in the framework of the
Bak-Jensen model. It has been established that, among the two interactions that play the main role in these systems, i.e.,
the isotropic symmetric ferromagnetic exchange and the Dzyaloshinskii-Moriya isotropic antisymmetric interaction, the former
interaction determines the critical temperature in the Mn1 − y
Fe
y
Si system and the latter interaction determines this temperature in the Fe1 − x
Co
x
Si system. 相似文献
12.
Bi4V2O11 exists in three phases viz. α, β, and γ. High temperature γ-phase can be stabilized to room temperature owing to its higher
conductivity by the partial substitution of metallic cations for vanadium in Bi4V2O11. Phase transitions from α → β and β → γ are composition and temperature-dependent. Mn2+-doped compounds Bi4V2−x
Mn
x
O11−
δ
(0 ≤ x ≤ 0.4) have been synthesized by solid state reaction technique and investigated by X-ray diffraction and ionic conductivity
measurement. High ionic conducting γ-phase is stabilized for x ≥ 0.2. The ionic conductivity of the series of Bi4V2−x
Mn
x
O11−
δ
samples has been measured by using ac impedance spectroscopy technique. The conductivity data do show departure from its
simple Arrhenius behavior for all of the compositions. The highest conductivity observed for x = 0.2 sample can be attributed to lower activation energy. 相似文献
13.
E. I. Lakhno E. I. Burmakin I. V. Korzun G. Sh. Shekhtman 《Physics of the Solid State》2012,54(3):504-507
The rubidium monoferrite RbFeO2-based solid solutions with the composition Rb2 − 2x
Fe2 − x
P
x
O4 have been synthesized, and their crystal structure and the temperature and concentration dependences of the total and electron
conductivities have been studied. The introduction of P5+ ions has been found to sharply decrease the electron conductivity that prevails in pure rubidium monoferrite and, at the
same time, to increase the ionic conductivity. The latter becomes dominant as the phosphorus concentration increases. The
maximum rubidium-cation conductivity of the materials under study is ∼3 × 10−2 S/cm at 300°C and ∼3 × 10−1 S/cm at 700°C. The results have been compared with the previously obtained data for similar solid solutions based on rubidium
monogallate and monoaluminate. 相似文献
14.
The results of investigations of the structure, electrical, and magnetic properties in the system of antiferromagnetic semiconductors
FexMn1−x
S (0<x⩽0.5) are described. It is established that metal-insulator transitions with respect to concentration and temperature are
connected with changes in the magnetic properties of the system.
Fiz. Tverd. Tela (St. Petersburg) 40, 276–277 (February 1998) 相似文献
15.
G. A. Petrakovskii L. I. Ryabinkina N. I. Kiselev D. A. Velikanov A. F. Bovina G. M. Abramova 《JETP Letters》1999,69(12):949-953
The magnetic, electric, magnetoresistive, and structural properties are investigated in the sulfide solid solutions FexMn1−2x
S, which are based on the antiferromagnetic semiconductor α-MnS (the fcc NaCl lattice). Colossal negative magnetoresistance
(δH∼−83% at 160 K for x ∼ 0.29), comparable to that observed in La-Ca-Mn-O polycrystals and films (δH∼−90% at 100 K and 40 kOe), is observed in compounds with intermediate concentrations 0.26<x<0.4, corresponding to the region
of incipient ferromagnetism.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 12, 895–899 (25 June 1999) 相似文献
16.
A study of the structure change with temperature in amorphous Fe100−xPx (13 x 24) alloys was carried out by measuring magnetization and thermal expansion and also by structural analysis using X-ray diffraction and differential thermal analysis (DTA). The structure of the amorphous alloys relaxes (the decrease of excess free volume) at temperatures 100–150 K below the crystallization temperatures. The alloys with x 15 transform into (α-Fe + amorphous) at about 600 K. The alloys with x15 transform into (α-Fe+amorphous+Fe3P) at about 600 K. With further heating, the alloys transform into (α-Fe+Fe3P) both of which are stable phases from the equilibrium phase diagram. 相似文献
17.
Neutron diffraction and magnetic methods are used to investigate ferrites from the system ZnxFe1−x
[Ni1−x
Fe1+x
]O4. In these investigations, no diffraction effects were observed that would indicate ordered positions for the perpendicular
projections of spins at 4.2 K over the entire ferrimagnetic range of concentrations x. However, the high-field magnetic susceptibility and intense small-angle scattering of neutrons observed at helium temperatures
in samples with x>0.45 are evidence of local angular structures with effective sizes of 1–10 nm. The temperatures at which these local angular
structures are disrupted are determined.
Fiz. Tverd. Tela (St. Petersburg) 40, 1503–1504 (August 1998) 相似文献
18.
X-ray, electrical conductivity, magnetic hysteresis and IR studies for the system Co2−x
Ge1−x
Fe2x
O4 were carried out. All the compounds, 0⩽x⩽1, showed cubic symmetry. X-ray intensity calculations, magnetic hysteresis measurements and IR studies indicated the presence
of Ge4+ at tetrahedral, Co2+ at octahedral and Fe3+ at both the sites. The activation energy and threshold frequency decreased with increasing value ofx. The compounds withx⩽0.5 arep-type and those withx⩾0.75 aren-type semiconductors. Magnetic hysteresis indicated that all the compounds are ferrimagnetic except forx=0 which is antiferromagnetic. The shapes of χ/χ
i
vsT plots, highH
c values andJ
R/Js ratios showed that all the compounds exceptx=0 exhibit single-domain behaviour. Curie temperature,T
c increased with increasing Fe3+ ions. The probable ionic configuration for the system is suggested as Ge
1−x
4+
Fe
x
3+
[co
2−x
2+
Fe
x
3+
]O
4
2−
. 相似文献
19.
The concentration dependences of the electronic properties (residual electrical resistivity, diffusion thermoelectric power,
normal Hall effect, and low-temperature specific heat) and the magnetic characteristics (magnetization and paramagnetic susceptibility)
of quasibinary (PdxPt1−x
)3Fe, Pt3MnxFe1−x
, (PdxAu1−x
)3Fe, and ScxTi1−x
Fe2 alloys are investigated. A relationship is established between the anomalous behavior of the kinetic properties and the variation
of the local magnetic moments. The absence of corresponding anomalies in the concentration dependence of the specific heat
indicates that the density of states at the Fermi level does not change significantly and, therefore, that the conventional
Mott two-band model cannot be used to describe the anomalies in the properties of the alloys in question. A single interpretation
of the sum-total of the experimental results is given on the basis of the theory of local fluctuations of the electron spin
density in metal magnets.
Fiz. Tverd. Tela (St. Petersburg) 39, 1257–1262 (July 1997) 相似文献
20.
N. B. Ivanova N. V. Kazak V. V. Markov S. G. Ovchinnikov V. V. Rudenko M. M. Abd-Elmeguid 《Physics of the Solid State》2004,46(8):1462-1468
A many-electron model of the energy band structure of VBO3 and of Fe1−x
VxBO3 solid solutions is proposed with strong electron correlations taken into account. Experimental optical absorption spectra
and data on the resistivity are discussed in the framework of the suggested model. Variation in the magnetic and electronic
properties of VBO3 and Fe1−x
VxBO3 under high pressure is predicted. For VBO3, a Mott-Hubbard (insulator-metal) transition is expected in the high-pressure phase. In Fe1−x
VxBO3 solid solutions, a nontrivial variation in the properties is predicted, leading to the appearance of a different magnetic
state.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 8, 2004, pp. 1422–1427.
Original Russian Text Copyright ? 2004 by Ivanova, Kazak, Markov, Ovchinnikov, Rudenko, Abd-Elmeguid. 相似文献