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1.
Observation of Antiferromagnetic Spin-Flop Transition in λ-type BETS Salts Using AFM Microcantilever
H. Tanaka S. Hara M. Tokumoto H-B. Cui H. Kobayashi A. Kobayashi 《Journal of Low Temperature Physics》2006,142(3-4):609-612
Antiferromagnetic spin-flop transitions in a series of λ- (BETS)2FeBr
x
Cl4-x
are observed using piezoresistive AFM microcantilever. The measurements are carried out on a tiny single crystal using a
sample rotator and the easy axis changes with increasing the bromine content x. The Néel temperature and spin-flop transition
field also rise with increasing the bromine content x, suggesting an enhancement of π-d interactions by replacement of chlorine
with bromine atoms in this mixed-halide anion system. 相似文献
2.
Ch. Sameera Devi M. Vithal G. S. Kumar G. Prasad 《Journal of Materials Science: Materials in Electronics》2011,22(12):1855-1864
Lead free (Ba(1−3x)Nd(2x))(Ti(1−y)Zry)O3 (x = 0, 0.025, y = 0, 0.025, 0.05) ceramics were prepared successfully using sol–gel method. The effect of Nd, Zr content
on dielectric and polarisation properties of BaTiO3 were studied using dielectric and hysteresis measurements. SEM analysis proved that the particle size of compounds as prepared
were in the order of 30–60 nm. The ferroelectric phase transition from tetragonal to cubic phase was observed around 130 °C
for pure BaTiO3. With the addition of Nd (2.5 mol%) and increasing content of Zr (2.5 and 5 mol%), it was observed that transition temperature
(Tc) shifts to lower temperatures (70–50 °C), but didn’t show any relaxor behaviour. Dielectric measurements showed an increase
in the values at room temperature in all the doped samples. The synthesized ceramics exhibited typical P–E hysteresis loops
at room temperature accompanied by saturation polarisation (Ps) and remanent polarisation (Pr). Behaviour of polarisation phenomena in these compounds showed interesting results with increasing temperature. 相似文献
3.
V. V. Vashuk O. P. Ol’shevskaya V. F. Savchenko L. V. Kokhanovskii O. V. Strukova V. E. Lukashevich 《Inorganic Materials》2000,36(11):1173-1177
Sr,1 - xCexFe1 - yCoyO3-δ(x ≤ 0.15,0 <y < 1) solid solutions with the cubic perovskite structure were prepared by solid-state reactions. The lattice parameter of the
solid solutions was shown to depend not only on the metal composition but also on oxygen stoichiometry. With increasing Fe
or Ce content, the stability of the materials toward oxygen loss rises, which is accompanied by a reduction in the lattice
parameter and thermal expansion coefficient in air and helium between 300 and 1000‡C. The room-temperature electrical conductivity
of the solid solutions increases systematically with Co content (y = 0-1.0) and passes through a maximum atx = 0.10 with increasing Ce content. 相似文献
4.
W. Cheikh-Rouhou Koubaa M. Koubaa Abdelwaheb Cheikhrouhou 《Journal of Materials Science》2009,44(7):1780-1786
Structural, magnetic, and magnetocaloric properties of monovalent doped La0.7Ba0.2M0.1MnO3 (M = Na, Ag, K) powder samples, synthesized using the solid state reaction at high temperature, have been experimentally
investigated. The Rietveld refinement of the X-ray powder diffraction shows that all our synthesized samples are single phase
and crystallize in the distorted rhombohedral system with space group. Lattice parameters and the unit cell volume increases with increasing average A-site ionic radius 〈r
A〉. The Mn–O–Mn bond angle decreases with increasing 〈r
A〉, ranging from 168.32° (M = Na) to 165.91° (M = K). All our studied samples undergo a paramagnetic–ferromagnetic transition.
The Curie temperature T
C, shifts slightly to a lower temperature with increasing 〈r
A〉, which is consistent with large cationic disorder. Magnetic entropy change, , deduced from isothermal magnetization curves, reaches 3.04, 3.14, and 3.01 J/kg K for M = Na, Ag, and K, respectively, in
a magnetic applied field change of 5T. Large relative cooling power (RCP) value of 337.9 J/kg is obtained for La0.7Ba0.2K0.1MnO3 sample, at a field change of 5T. This relatively large value associated to a Curie temperature of 311.5 K makes the present
compound a promising candidate for the magnetic refrigerators around room temperature. 相似文献
5.
S. K. Dey C. G. Wang W. Cao S. Bhaskar J. Li G. Subramanyam 《Journal of Materials Science》2006,41(1):77-86
Frequency and phase agile microwave components such as tunable filters and phase shifters will require ferroelectric thin
films that exhibit a nonlinear dependence of dielectric permittivity (ɛ
r
) with dc electric bias, as well as a high material (Δɛ
r
/tan δ) and device (or K-factor in phase shift/dB) figure of merits (FOM). Therefore, voltage tunable (Pb0.3Sr0.7)TiO3 (PST) thin films (90–150 nm) on (0001) sapphire were deposited by metal-organic chemical vapor deposition at rates of 10–15 nm/min.
The as-deposited epitaxial PST films were characterized by Rutherford backscattering spectroscopy, X-ray methods, field emission
scanning electron microscope, high resolution transmission electron microscopy, Raman spectroscopy, and electrical methods
(7–17 GHz) using coplanar waveguide test structures. The epitaxial relationships were as follows: out-of-plane alignment of
[111] PST//[0001] sapphire, and orthogonal in-plane alignments of [
] PST//[
] sapphire and [
] PST//[
] sapphire. The material FOM and device FOM (or K-factor) at 12 GHz were determined to be 632 and ∼13 degrees/dB, respectively.
The results are discussed in light of the nanostructure and stress in epi-PST films. Finally, a rational basis for the selection
of PST composition, substrate, and process parameters is provided for the fabrication of optimized coplanar waveguide (CPW)
phase shifters with very high material and device FOMs. 相似文献
6.
Berdan Özkurt Ahmet Ekicibil M. Ali Aksan Bekir Özçelik M. Eyyüphan Yakinci Kerim Kiymaç 《Journal of Low Temperature Physics》2007,147(1-2):31-48
Measurements of the electrical resistance (R-T), thermoelectric power (S-T) and thermal conductivity (κ-T) have been carried out on the superconductor Bi1.7Pb0.3-x
Gd
x
Sr2Ca3Cu4O12+y
, (0.01 ≤ x ≤ 0.1). According to the XRD patterns the volume fraction of the Bi-2223 phase decreases in favor of Bi-2212.
All the samples show normal metallic behavior down to their relevant transition temperature, T
c
. T
c
-values decrease significantly with increasing Gd concentration in the system. The hole concentration per Cu has been calculated
by using the Presland method and found to decrease with increasing Gd content. The thermoelectric power values of the samples
are positive and increase in magnitude with increasing the substitution level. The results obtained have been analyzed in
terms of “Two band model with linear T-term” and “Xin’ s two band model”. A very good agreement between the first model and our thermoelectric power data was obtained, but the fit to the second
model was poor. The substitution has considerable effect on the thermal conductivity, κ. The magnitude of κ is suppressed
and a peak appears just below their T
c
, values but becomes weaker and broader when the Gd concentration is increased.
相似文献
7.
Saket Asthana 《Bulletin of Materials Science》2011,34(2):279-282
The magnetic and transport properties of the compounds Nd0·5Sr0·5Mn1-x_{{\rm 1}-{x}}Cox_{{x}}O3 (x = 0·1, 0·3 and 0·5), synthesized by citrate–gel route have been investigated. The spin transition in cobaltates at low temperatures
affects the magnetic as well as transport properties. The irreversibility behaviour between the zero-field cooled (ZFC) and
field cooled (FC) magnetization as a function of temperature becomes stronger with increasing Co content. This is understood
on the basis of glassy behaviour, which becomes more robust with increasing Co substitution. The non-saturating M–H behaviour
indicates strong magnetic inhomogeneities which may cause the magnetic phase separation at the nanoscopic length scale. The
double exchange interaction is stronger between Mn3 + –O2 − –Mn4 + as compared to Co3 + –O2 − –Co4 + pairs. Co-substitution suppresses the double exchange which will lead to cluster/spin glass like behaviour as well as semiconducting
features due to localization of charge carriers (mobile eg{e}_{\rm g} electrons). 相似文献
8.
A. H Wafik A. M Abd-El-Rahman A. M Massoud S. A Mazen 《Journal of Materials Science》1997,32(14):3749-3752
The spinel series CuxFe3-xO4 + δ, 0 ≤ δ ≤ 0.4 (where x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0) has been investigated by means of X-ray diffraction and Barkhausen jumps.
Analysis of X-ray intensity data showed that this system separates into two phases at x < 1. The percentage of phase separation decreases with increasing copper content. The system shows a single phase at x = 1. The mean potential difference, V
B, and the frequency, F
B, of Barkhausen jumps were measured as a function of the magnetizing current. Addition of copper enhances the irreversible
motion of domain walls. The sample with x = 1 shows the highest values of V
B and F
B. The potential energy of the walls increases with increasing copper content.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
9.
Kaichiro Chiba Takayuki Goto Masakatsu Mori Takao Suzuki Katsutoshi Seki Tetsuo Fukase 《Journal of Low Temperature Physics》1999,117(3-4):479-483
The external field dependence of the hyperfine field at La-site has been studied on La
2–x
Sr
x
CuO
4
(x=0.115) and La
2–x
Ba
x
CuO
4
(x=0.125), where the magnetic ordering in Cu-3d spins exists at low temperature. In La
1.885
Sr
0.115
CuO
4, a significant decrease in the resonance line width was observed above a field of H
c
7.5T, which is the direct evidence of the spin-flop in the canted-spin system with Dzyaloshinski-Moriya interaction. The spin-flop field H
c
of 7.5T is slightly lower than that in La
2
CuO
4
(H
c 10T), reflecting the decrease of the tilting angle of the CuO
6
octahedra by the substitution of Sr
2+
ion for La-site. 相似文献
10.
The layer type MoSe
x
Te2−x
(0 ≤x ≤ 2) have been grown in single crystalline form by chemical vapour transport technique using bromine as the transporting
agent. The electrical resistivity and Hall mobility perpendicular to thec-axis of the crystals were measured at room temperature. The variation of the Seeback coefficient with temperature was also
investigated. 相似文献
11.
Huan Deng Hongmei Deng Pingxiong Yang Junhao Chu 《Journal of Materials Science: Materials in Electronics》2012,23(6):1215-1218
Multiferroic BiCr
x
Fe1−x
O3 (BCFO) (0 ≤ x ≤ 0.12) thin films were fabricated on silicon substrates by sol–gel technique. The microstructure and properties of the films
are characterized using X-ray diffraction, spectroscopic ellipsometry, micro-Raman spectrometry and a Modular Control system.
The BCFO films are the rhombohedral structure with the Cr content up to 7%. Raman scattering spectra of the BCFO films demonstrate
the transformation of structure with the Cr content exceeding 10%. The band gap of the BCFO films is from 2.53 to 2.82 eV
with the Cr content being from 0 to 12%. The magnetization of the BCFO films is significantly enhanced with the increasing
of the Cr content. 相似文献
12.
The influence of bismuth (Bi) on the dielectric and ferroelectric properties of Sr0.5Ba0.5−xBixTiO3 (BST, 0 ≤ x ≤ 0.030 mol) thin films was studied. The results showed that the dielectric constant (εr) and dielectric loss (tan δ) decreased, and temperature, Tm, for maximum and εr (Curie temperature), moved to lower temperature with increasing Bi content. The Pr, Ps and Ec were 0.22 μC/cm2, 0.32 μC/cm2 and 60 kV/cm, respectively for Sr0.5Ba0.485Bi0.015TiO3 thin films measured at 100 Hz, 20 V. The microstructure of BST thinfilms was studied by XRD and TEM. Tetragonal perovskite
grains existed in BST thin films, but the grain size decreased with increasing doping ratio in BST. The characteristic absorption
band for octahedron [TiO2] (471.65 cm−1) was shifted to lower wave number. 相似文献
13.
Glass samples of the system (15Li2O–30ZnO–10BaO–(45 − x)B2O3–xCuO where x = 0, 5, 10 and 15 mol%) were prepared by using the melt quenching technique. A number of studies, viz. density, differential
thermal analysis, FT-IR spectra, a.c. conductivity and dielectric properties (constant εφ, loss tan δ, a.c. conductivity,
σac, over a wide range of frequency and temperature) of these glasses were carried out as a function of copper ion concentration.
The analysis of the results indicate that the density increases while molar volume decreases with increasing of copper content
indicates structural changes of the glass matrix. The glass transition temperature, T
g, and crystallization temperature, T
c, increase with the variation of concentration of CuO referred to the growth in the network connectivity in this concentration
range, while glass-forming ability parameter (T
c − T
g) decreases with increasing CuO content, indicates an increasing concentration of copper ions that take part in the network-modifying
positions. The FT-IR spectra evidenced that the main structural units are BO3, BO4, and ZnO4. The structural changes observed by varying the CuO content in these glasses and evidenced by FTIR investigation suggest
that the CuO plays a network modifier role in these glasses while ZnO plays the role of network formers. The dielectric constant
decreased with increase in temperature and CuO content. The variation of a.c. conductivity with the concentration of CuO passes
through a maximum at 5 mol%. In the high temperature region, the a.c. conduction seems to be connected with the mixed conduction
viz., electronic conduction and ionic conduction. 相似文献
14.
Interaction of bromine ions with water clusters that have absorbed the molecules of oxygen and ozone is studied using a molecular-dynamics
simulation of flexible molecules. The cases of location of Br− ions on the surface and in the bulk of the cluster are described. Water clusters with ozone molecules remain stable during
their interaction with the Br− ions, while oxygen molecules are found to evaporate from the cluster when Br− ions appear in its bulk. In the presence of Br− ions, the infrared spectra of systems with O3 molecules are observed to be intensified. The intensities of the IR spectra with O2 molecules may both increase and decrease depending on the arrangement of the Br− ions. The Raman spectra are sensitive to the appearance of Br− ions only for systems that contain oxygen molecules. As a result of interaction with the Br− ions, the power of IR radiation emitted by the clusters can not only increase, but also decrease. 相似文献
15.
The effect of fibre concentration, strain rate and weldline on tensile strength, tensile modulus and fracture toughness of
injection-moulded thermoplastic polyurethane (TPU) reinforced with different concentration levels of short glass fibres was
investigated. It was found that tensile strength, σc, of single-gated mouldings increased with increasing volume fraction of fibres, ϕf, according to a second order polynomial function of the form and increased linearly with natural logarithm of strain rate (). Tensile modulus and fracture toughness (at initiation) of single-gated mouldings increased linearly with increasing ϕf (rule-of-mixtures) and . A linear dependence was obtained between fibre efficiency parameter for composite modulus, ηE, and . The presence of weldline in double-gated mouldings reduced tensile strength, tensile modulus and fracture toughness of TPU
composites but had no significant effect upon properties of the TPU matrix. All the aforementioned properties increased with
increasing fibre concentration and showed a linear dependence with respect to . Weldline integrity factor for all three properties decreased with increasing fibre concentration showing no strain-rate
effect of any significance. Results indicated that tensile strength was more affected by the presence of weldline than tensile
modulus or fracture toughness. It was noted that composite properties in the presence of weldline were still much greater
than those for the unweld matrix. Weldline integrity values close to unity indicated that measured properties for the matrix
were not significantly affected by the weldline. 相似文献
16.
A. K BHATTACHARYA A HARTRIDGE K. K MALLICK C. K MAJUMDAR D DAS S. N CHINTALAPUDI 《Journal of Materials Science》1997,32(3):557-560
A series of gels with nominal composition Fe2−xCrxO3 (x=0–2) was prepared at room temperature by an inorganic sol–gel route and studied by X-ray diffraction and Mossbauer spectroscopy.
The gels dried at 105°C were found to be X-ray amorphous, but Mossbauer studies revealed the gels to be nano-crystalline solid-solution
particles of the composition above, with super-paramagnetic properties. Further heating to 600°C gave crystalline X-ray patterns
which allowed lattice parameter and crystallite size calculations to be made. It was found that lattice parameters and crystallite
sizes decreased with increasing chromia content, and that at the higher chromia/iron ratios, a partially collapsed Mossbauer
pattern results, indicating reductions in crystallite size and hyperfine field with increasing chromia content.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
17.
Nb3+-substituted garnet nanoparticles Y3−xNdxFe5O12 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were fabricated by a sol-gel method and their crystalline structures and magnetic properties
were investigated by using X-ray diffraction (XRD), thermal analysis (DTA/TG), and vibrating sample magnetometer (VSM). The
XRD patterns of Y3−xNdxFe5O12 have only peaks of the garnet structure and the sizes of particles range from 34 to 70 nm. From the results of VSM, it is
shown that when the Nd concentration x ( 1.0, the saturation magnetization of Y3−xNdxFe5O12 increases as the Nd concentration (x) is increased, and gets its maximum at x = 1.0, but when x ( 1.0, the saturation magnetization
decreases with increasing the Nd concentration (x), this may be due to the distortion of the microstructure of Y3−xNdxFe5O12, which leads to the decrease of the effective moment formed by Fe3+. Meanwhile, it is observed that with the enhancement of the surface spin effects, the saturation magnetization rises as the
particle size is increased. 相似文献
18.
K. Chandramouli G. Srinivas Reddy Koduri Ramam 《Journal of Materials Science: Materials in Electronics》2009,20(2):132-138
The effect of A-site substitution of Ce3+ in tungsten bronze structured PBN ceramics with the general formula, Pb(x − 3y/2)Ce
y
Ba(1 − x)Nb2O6 and the stoichiometric chemical formula, Pb(0.65 − 3y/2)Ce
y
Ba0.35Nb2O6, where y = 0, 2, 4, 6, 8 and 10 mol% ceramic compositions synthesized through solid state reaction method are reported. The X-ray
diffraction studies exhibited the presence of an orthorhombic phase, and its intensity increased with the increasing Ce3+ content up to y = 6 mol% or A3 composition. The lattice parameters, unit cell volume and density as a function of Ce3+ concentration are discussed. It is observed that increasing Ce3+ content in A-site influenced the dielectric properties. The optimum dielectric properties of room temperature dielectric
constant (εRT) and dielectric maximum
() are observed in y = 6 mol% or A3 composition while Curie temperature (T
c) and dielectric loss (tan δ) constantly decreased from undoped to y = 10 mol%, and thus A3 composition or 6 mol% Ce modified tungsten bronze structured-PBN could be suitable for capacitor applications. 相似文献
19.
Pellets of ceramic Na1−xKxNbO3 (x = 0, 0.2 and 0.5), were prepared by conventional solid-state reaction method. Prepared samples were characterized using
XRD and SEM. The frequency and temperature variation of dielectric constant, loss tangent and dielectric conductivity of prepared
samples were measured in the frequency range from 10 KHz-1 MHz, and in the temperature range from 50–250°C for x = 0.2 and
0.5, and between 50 and 480°C for x = 0 compositions. It was observed that the dielectric constant and loss tangent decrease,
and conductivity increases with increasing frequency. Near the transition temperature the material shows anomalous behaviour
for the observed properties, and the peaks of dielectric constant and loss tangent were observed shifting towards lower temperature
with increasing frequency. 相似文献
20.
We considerk(k)≥2 independent populations (treatments or systems) and an solutely continuous member of location-scale family of distributions,
index by the location parameter μ
i
(-∞ < μ
i
< ∞) and scale parameter θ
i
(θ
i
> 0), is used to model the observations from the ith population,i=1,...k. The problem of simultaneous selection of two subsets, one containing population associated with the smallest ϕ-value and
other containing population with the largest ϕ-value with probability at least a pre-specified value
is considered when the data are censored. We also construct 100P
*% simultaneous upper and two-sided confidence intervals for
where θ[1] ≤ ... ≤ θ[k] denotes the ordered values of ϕs. The proposed procedures, based on sample quasi ranges, are useful when the experimenter
has smaller samples or censored samples or there is suspicion of outliers in the samples. The results are applied to exponential
populations model and, for thes casi: (i) the constants have been computed to apply the proposed multiple comparisons; (ii)
two members of the proposed class have been compared with the existing procedure. A numerical example is also given. 相似文献