共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Balogh D. Kaptás L. F. Kiss T. Kemény I. Vincze K. Temst C. Van Haesendonck 《Hyperfine Interactions》2005,165(1-4):49-53
An (0.2 nm 57Fe / 2.6 nm Ag)75 granular multilayer sample and heterostructures with additional continuous Fe layers in different sequences were studied
in magnetic field applied at different temperatures. The broadening of the superparamagnetic lines was found to be very similar
for the three samples in applied fields both parallel and perpendicular to the sample plane. While the layer sequence has
no significant effect on the superparamagnetic properties, the continuous magnetic layers follow a different approach to saturation
in perpendicular magnetic fields. 相似文献
2.
Bangmin Zhang Guowei Wang Feng Zhang Yuhua Xiao Shihui Ge 《Applied Physics A: Materials Science & Processing》2009,97(3):657-661
A series of (FeCoNiNbB)
x
–(SiO2)1−x
nano-granular thin films were fabricated by magnetron sputtering with different oblique incidence angles θ. High-resolution transmission electron micrographs show that the films consist of amorphous CoFeM (M = Ni, Nb, B) alloy particles
with diameter about 2 nm surrounded by amorphous SiO2 matrix. Excellent soft magnetic properties have been achieved with a variable in-plane uniaxial magnetic anisotropy field
H
k0, which increases monotonically with θ and x, and decreases with the composition of B in FeCoM. For one typical sample of x=0.63 with θ=30°, H
ch and H
ce are 4.2 Oe and 5.4 Oe, respectively, ρ reaches 12.5 mΩ cm and 4π
M
s and H
k0 are 5.70 kG s and 92 Oe, respectively, which lead to a high ferromagnetic resonance frequency f
r of 2.2 GHz. Based on the analysis of experimental results, two sources for the origin of the magnetic anisotropy, namely
anisotropic magnetic coupling and orientation order of atomic pairs, are suggested. 相似文献
3.
F. J. A. den Broeder D. Kuiper H. C. Donkersloot W. Hoving 《Applied Physics A: Materials Science & Processing》1989,49(5):507-512
Superlattices of [001]fcc Co/Pd with varying Co thicknesses from one to eight atomic layers per modulation period were epitaxially grown on NaCl by vapour deposition in UHV. Transmission electron diffraction indicates lattice coherence between the Co and the Pd layers for Co thicknesses up to six atomic layers. If deposited at a substrate temperatureT
s=50°C, only the superlattices containing Ci-monolayers show perpendicular magnetization. By raisingT
s to 200°C, the perpendicular anisotropy for Co monolayers is increased, and is also observed for Co bilayers. We suggest that this is due tolayer smoothening, which increases Néel's interface anisotropy. For more than 6 atomic layers of Co a loss of coherence is observed atT
s=50°C, accompanied by a structure transformation to hcp Co with a (0001)Co(111)Pd orientation.Non-epitaxial polycrystalline [111]-multilayers have a different anisotropy versus thickness behaviour. For such multilayers the range of Co thicknesses giving perpendicular magnetization is extended from 8 Å up to 12 Å atT
s=200°C. The different behaviour of the single crystal [001] films is caused by a strong volume contribution to the anisotropy, which favours in-plane magnetization, opposing the perpendicular interface anisotropy. This easy-plane term is attributed to magneto-elastic anisotropy due to stretching of the Co layers, via a positive magnetostriction. 相似文献
4.
Synthesis, crystal structure, and dielectric properties of [C6H4(NH3)2]2ClBiCl6.H2O are reported. The compound crystallizes in the monoclinic system with space group P21/n. The unit cell dimensions are a = 9.836(5), b = 19.582(5), c = 13.082(5) ?, β = 104.731(5)° with Z = 4. The atomic arrangement can be described by an alternation of organic and inorganic layers. The anionic layer is built
up of octahedral of [BiCl6]3- arranged in sandwich between the organic layers. The crystal packing is governed by means of the ionic N–H···Cl hydrogen
bonds, forming a three-dimensional network. The dielectric properties have been investigated at temperature range from 297
to 410 K at various frequencies (10 Hz–100 kHz). Dielectric studies were performed to confirm results obtained with thermal
analysis. The evolution of dielectric constant as a function of temperature and frequency of single crystal has been investigated
in order to determine some related parameters. 相似文献
5.
M. N. Khlopkin 《JETP Letters》1999,69(1):26-30
The specific heat of a V3Si single crystal (T
c=17 K, H
c2=20 T) in magnetic fields up to 8 T isinvestigated experimentally for three orientations of the field relative to the crystallographic
directions — H∥〈001〉, H∥〈110〉, and H∥〈111〉. Both the upper critical magnetic field and the specific heat of the mixed state are observed to depend on the orientation
of the magnetic field relative to the crystallographic directions (anisotropy): The critical field reaches its maximum value
and the specific heat its minimum value in a field along the 〈001〉 direction. The anisotropy scale in both phenomena increases
as the magnetic field and reaches 3% in a 6 T field. The interrelationship of the upper critical field anisotropy and the
specific-heat anisotropy in type-II superconductors is studied. It is shown that the anisotropy of the specific heat in the
mixed state in weak fields can serve as a criterion for nontrivial pairing.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 26–29 (10 January 1999) 相似文献
6.
Yan-Fang Zhao Yong-Liang Zhao Feng Bai Xiao-yan Wei Yong-sheng Zhou Mei-na Shan Huan-huan Li Rui-jun Ma Xiao-tao Fu Yan Du 《Journal of fluorescence》2010,20(3):763-770
The complex of Tb(TPTZ)Cl3·3H2O was synthesized by adding the ethyl alcohol solution of TbCl3 (1 mmol) to the solution of 2,4,6-tris-(2-pyridyl)-s-triazine(TPTZ,1 mmol) with constant stirring. The solution which had
been filtered was kept at the room temperature for 4 weeks, and then a kind of transparent crystal was formed. Besides, nine
kinds of solid complexes in the different molar proportion of terbium to gadolinium had been synthesized by adopting the similar
method mentioned above. It was inferred from the elemental analysis and rare earth complexometry that the composition of these
complexes is (TbxGdy)(TPTZ)Cl3·3H2O (x : y = 0.9 : 0.1, 0.8 : 0.2, 0.7 : 0.3, 0.6 : 0.4, 0.5 : 0.5, 0.4 : 0.6, 0.3 : 0.7, 0.2 : 0.8, 0.1 : 0.9). The absorption
spectra and photoluminescence of the complexes were determined in dimethylsulfoxide (DMF), which showed that the excitation
of the complexes is mostly ligand based. The triplet state energy level of TPTZ was measured, indicating that the lowest excitation
state energy level of Tb(III) and the triplet state energy level of TPTZ match well each other. The fluorescent data indicated
that the fluorescent emission intensity of Tb3+ ions would be enhanced in the complexes after terbium was doped with Gd3+ ion. When x : y was 0.5 : 0.5, the fluorescent emission intensity was the largest. The result obtained by testing the X-ray
diffraction of the monocrystal revealed that the molecular formula of the mono-crystal complex is [Tb(TPTZ)(H2O)6]Cl3·3H2O. The number of metal ion coordinates is nine, and the tridentate TPTZ and six water molecules are bonded with terbium respectively.
Besides, it also revealed that the monocrystal belongs to the monoclinic system, and space group Cc with the following unit
cell parameters is a = 1.4785 (3) nm, b = 1.0547 (2) nm, c = 1.7385 (4) nm, β = 94.42 (3)°, V = 2.7028 (9) nm3 and Z = 4. 相似文献
7.
M. Bryushinin V. Golubev Y. Kumzerov D. Kurdyukov I. Sokolov 《Applied physics. B, Lasers and optics》2009,95(3):489-495
We report an experimental investigation of the non-steady-state photoelectromotive force in nanostructured GaN within porous
glass and polypyrrole within chrysotile asbestos. The samples are illuminated by an oscillating interference pattern created
by two coherent light beams and the alternating current is detected as a response of the material. Dependences of the signal
amplitude versus temporal and spatial frequencies, light intensity, and temperature are studied for two wavelengths λ=442 and 532 nm. The conductivity of the GaN composite is measured: σ=(1.1–1.6)×10−10 Ω−1 cm−1 (λ=442 nm, I
0=0.045–0.19 W/cm2, T=293 K) and σ=(3.5–4.6)×10−10 Ω−1 cm−1 (λ=532 nm, I
0=2.3 W/cm2, T=249–388 K). The diffusion length of photocarriers in polypyrrole nanowires is also estimated: L
D=0.18 μm. 相似文献
8.
FePS3 is a layered antiferromagnet (T
N=123 K) with a marked Ising anisotropy in magnetic properties. The anisotropy arises from the combined effect of the trigonal
distortion from octahedral symmetry and spin-orbit coupling on the orbitally degenerate5
T
2g
ground state of the Fe2+ ion. The anisotropic paramagnetic susceptibilities are interpreted in terms of the zero field Hamiltonian, ℋ=Σi [δ(L
iz
2
−2)+|λ|L
i
.S
i
]−Σ
ij
J
ij
S
i
.S
j
. The crystal field trigonal distortion parameter Δ, the spin-orbit coupling λ and the isotropic Heisenberg exchange,J
ij, were evaluated from an analysis of the high temperature paramagnetic susceptibility data using the Correlated Effective
Field (CEF) theory for many-body magnetism developed by Lines. Good agreement with experiment were obtained for Δ/k=215.5 K; λ/k=166.5 K;J
nn
k=27.7 K; andJ
nnn
k=−2.3 K. Using these values of the crystal field and exchange parameters the CEF predicts aT
N=122 K for FePS3, which is remarkably close to the observed value of theT
N. The accuracy of the CEF approximation was also ascertained by comparing the calculated susceptibilities in the CEF with
the experimental susceptibility for the isotropic Heisenberg layered antiferromagnet MnPS3, for which the high temperature series expansion susceptibility is available. 相似文献
9.
The magnetic hyperfine field of Se in nickel was measured by means of the time-differential perturbed angular correlation
(DPAC) technique, using the 755–250 keV γ-ray cascade fed in the decay of77Br. A value ofB
hf(NiSe)=+15.11(35) T was obtained at room temperature. The half-life of the 250 keV state and the anisotropy of the 755–250 keV
cascade were found to beT
1/2=9.68(6) ns andA
22=−0.454(9), respectively. 相似文献
10.
J. C. Debnath R. Zeng J. H. Kim P. Shamba S. X. Dou 《Applied Physics A: Materials Science & Processing》2012,106(1):245-250
Magnetic properties and magnetocaloric effects (MCEs) have been investigated in hydrogenated LaFe11.7 Si1.3H
x
(x=0,1.37, and 2.07) compounds. It is found that the Curie temperature, T
C, can be tuned from 192 to 338 K by adjusting the hydrogen content from 0 to 2.07. It is attractive that both thermal and
magnetic hysteresis are remarkably reduced because of the weakness of the itinerant-electron metamagnetic transition after
hydrogenation. The maximal hysteresis loss at T
C decreases from 33.4 to 8.8 J/kg as x increases from 0 to 2.07. For the samples with x=0,1.37, and 2.07, the maximal values of the isothermal magnetic entropy change, ΔS
M, are 20.9, 15.1, and 15.83 J/kg K for the increasing field and 20.76 J/kg K, 14.53 J/kg K and 15.61 J/kg K for the decreasing
field at T
C, with efficient refrigeration capacities of 439, 330, and 304 J/kg for a field change of 0–5 T, respectively. Large reversible
MCE and small hysteresis with considerable refrigeration capacity indicate the potential of LaFe11.7Si1.3H
x
hydride as a candidate magnetic refrigerant around room temperature. 相似文献
11.
Results are presented of an investigation of the magnetic properties of dilute frustrated ferrimagnetic spinels Li0.5Fe2.5−x
GaxO4 (x=0.8–1.2), which characterize the main parameters of the ferrimagnetic state and provide evidence of local violation of collinear
spin ordering and frustrations. In particular, measurements were made of the concentration dependences of the magnetic moment
n
0(x) and the Curie point T
c
(x), the magnetization isotherms σ
T
(H) at T=4.2 K and H⩽10 kOe, and also the low-and high-field magnetization polytherms σ
H
(T). It was established that for x⩾0.8 in fields exceeding the technical saturation field H
s
∼2 kOe, the temperature dependences of the high-field magnetization σ
H
(T) between 4.2 and 230 K cannot be described by the Bloch T
3/2 law whereas this law is satisfied for undiluted Li spinel (x=0). Over the entire temperature range (4.2–230 K) the experimental curves σ
H
(T) may be approximated by σ
H
(T)=σ
0(1−AT
3/2 − BT
5/2) for x=0.8–1.0 and σ
H
(T)=σ
0[1−CT
3/2exp(μ(H−H
0)/k
B
T)] for x=1.1, 1.2, where μH
0∼15 K is the internal field produced by competition between exchange interactions and frustrations.
Fiz. Tverd. Tela (St. Petersburg) 40, 1075–1079 (June 1998) 相似文献
12.
Good-quality hexagonal NbSe2 single crystals were prepared. In 2H-NbSe2, superconducting and charge density wave (CDW) transitions were found at T
s = 7.4 K and T
c = 35 K respectively as reported previously. We have noticed that these two transitions are changed to T
c = 42 K and T
s = 6.5 K, in 4H-NbSe2. Thermopower has shown clear anomaly at CDW transitions. The anisotropic upper critical field was calculated as ~3 and 6.3
for 2H- and 4H-single crystals around t = 0.81, where t = T/T
s, from resistivity and explained in terms of coherence length. From the relation, Hc2 (T)=Hc2 (0)[1-t2]H_{\rm c2} (T)=H_{\rm c2} (0)[1-t^2], Hc2l (0)H_{\rm c2}^l (0) was calculated as ~8.15 T and 16.98 T at t = 0.84 in 2H-NbSe2 and 4H-NbSe2 respectively. However, Hc2t (0) = 2.68H_{\rm c2}^t (0) = 2.68T for both single crystals. 相似文献
13.
T. Minamisono T. Ohtsubo Y. Nakayama T. Araki K. Mashitani K. Matsuda E. Takahashi M. Tanigaki Y. Someda M. Tanaka A. Kitagawa M. Fukuda K. Matsuta Y. Nojiri 《Hyperfine Interactions》1992,73(3-4):347-356
Hyperfine interactions of β-emitting17F implanted in single crystals of NaF and CaF2 were studied. The nuclear magnetic moment of theT
π=5/2+ state was determined with an improved precision to be |μ(17F;π=5/2+,T
1/2=64.5s|=4.72130±0.00025. nm. Isoscalar magnetic moments of the doubly closed shell ±1 nucleon nuclei around mass number 16
were derived and the effective nucleon mass in the nucleus was discussed. 相似文献
14.
A. Yildiz S. B. Lisesivdin M. Kasap S. Ozcelik E. Ozbay N. Balkan 《Applied Physics A: Materials Science & Processing》2010,98(3):557-563
The electrical conduction mechanisms in various highly resistive GaN layers of Al
x
Ga1−x
N/AlN/GaN/AlN heterostructures are investigated in a temperature range between T=40 K and 185 K. Temperature-dependent conductivities of the bulk GaN layers are extracted from Hall measurements with implementing
simple parallel conduction extraction method (SPCEM). It is observed that the resistivity (ρ) increases with decreasing carrier density in the insulating side of the metal–insulator transition for highly resistive
GaN layers. Then the conduction mechanism of highly resistive GaN layers changes from an activated conduction to variable
range hopping conduction (VRH). In the studied temperature range, ln (ρ) is proportional to T
−1/4 for the insulating sample and proportional to T
−1/2 for the more highly insulating sample, indicating that the transport mechanism is due to VRH. 相似文献
15.
D. Sarkisyan T. Becker A. Papoyan P. Thoumany H. Walther 《Applied physics. B, Lasers and optics》2003,76(6):625-631
An extremely thin cell (ETC) with the thickness of a Rb atomic vapor layer in the range of 100–300 nm was fabricated. It is
demonstrated that a simple laser-diode technique with a single resonant light beam is sufficient to observe separately all
of the atomic hyperfine transitions of the D
2 line of Rb (780 nm) and also allows us to measure the relative transition probabilities of the hyperfine transitions. The
onset of collisional self-broadening of the hyperfine transitions as the number density of atoms increases was studied. The
detrimental role of the atoms with slow longitudinal velocity in the sub-Doppler response of the Rb ETC is demonstrated by
studies in which the cell is tilted from normal incidence of the laser beam. It is also shown that using an ETC allows us
to resolve in a moderate external magnetic field the Zeeman splitting of the hyperfine transitions of the 87Rb D
1 transition F
g=1F
e=1,2.
Received: 19 February 2003 / Revised version: 4 April 2003 / Published online: 2 June 2003
RID="*"
ID="*"Corresponding author. Fax: +374/32-31172, E-mail: david@ipr.sci.am 相似文献
16.
To improve the cycle performance of spinel LiMn2O4 as the cathode of 4-V-class lithium secondary batteries, spinel phases LiM
x
Mn2 − x
O4 (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe0.05M
y
Mn1.95 − y
O4 (M=Li, Al, Ni, Co; y = 0.05, 0.1) were successfully prepared using the sol–gel method. The spinel materials were characterized by powder X-ray
diffraction (XRD), elemental analysis, and scanning electron microscopy. All the samples exhibited a pure cubic spinel structure
without any impurities in the XRD patterns. Electrochemical studies were carried out using the Li|LiM
x
Mn2 − x
O4 (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe0.05M
y
Mn1.95 − y
O4 (M=Li, Al, Ni, Co; y = 0.05, 0.1) cells. These cathodes were more tolerant to repeated lithium extraction and insertion than a standard LiMn2O4 spinel electrode in spite of a small reduction in the initial capacity. The improvement in cycling performance is attributed
to the stabilization in the spinel structure by the doped metal cations. 相似文献
17.
A. G. Moiseev 《Russian Physics Journal》2011,54(2):226-238
A method of calculating the effective deformation-potential constant E
1 for holes and longitudinal acoustic phonons in isotropic polycrystalline silicon is suggested. The deformation-potential
constant E
1 is estimated through the deformation potentials a, b, and d of the silicon single crystal. The procedure of averaging of the squared modulus of the hole and acoustic phonon interaction
Hamiltonian written in the plane wave basis over the polycrystal ensemble provides the basis for calculation of the constant
E
1 . It is demonstrated that for T = 200–600 K, hole concentration p = (5.0–10.0)∙1019 cm–3, and crystallite size d = 300–3000 ?, the deformationpotential constant E
1 is independent of the hole concentration p, temperature T, and crystallite size d. 相似文献
18.
In this work, a new simple and sensitive flow injection method is developed for the determination of homocysteine with spectrofluorimetric
detection technique. This method is based on the oxidation of homocysteine with Tl (III) in acidic media, producing fluorescence
reagent, TlCl32- (λex = 237 nm, λem = 419 nm). The effects of chemical parameters (including pH of the solutions, the buffer, Tl (III) and potassium chloride
concentrations), instrumental parameters (such as flow rate of the solutions, reaction coil length, and sample loop volume)
and temperature on the fluorescence intensity as an analytical signal are studied and optimized. In the optimum conditions
of the above variables, homocysteine can be determined in the range 4.0 × 10-7–40.0 × 10-6 M with the LDR from 4.0 × 10-7 to 25.0 × 10-6 M. The detection limit (with S/N = 3) is 6.0 × 10-8 M of homocysteine and precision for the injection of 5.0, 10.0 and 15.0 μM of homocysteine are 0.8%, 1.5% and 2.5% (n = 10) respectively. The rate of analysis is 90 samples per hour. The influence of potential interfering substances, including
amino acids and carbohydrates is also studied. The proposed method has been successfully used for the determination of homocysteine
in the real sample (blood serum and tap water) matrix. 相似文献
19.
A. A. Sorokin G. K. Ryasny B. A. Komissarova L. N. Fomicheva A. V. Tsvyashchenko S. M. Nikitin 《Hyperfine Interactions》2006,171(1-3):269-275
The perturbed angular correlation (PAC) measurements with the 111In-111Cd nuclear probe embedded into the lattice of the cubic (C15) Laves compound ZrZn2 showed that 111Cd nuclei experienced an axially symmetric electric quadrupole interaction with a frequency ν
Q
= 132.4 MHz at room temperature. The samples were synthesized and doped with the probe at a pressure 8 GPa. The temperature
dependence of ν
Q
was shown to be linear: ν
Q
(T) = 147(1 − 0.033 T) MHz. Since the value of ν
Q
is very close to that known for 111Cd in the lattice of Zn, we have checked if it could be assigned to residual Zn metal in the sample. For the Zn sample melted
and doped with 111In at 8 GPa we have obtained ν
Q
= 117.3 MHz at 300 K and 127 MHz at 80 K – both values considerably lower than that for 111In doped Zn samples prepared at an ambient pressure. These data, and the fact that ν
Q
(T) in Zn is known to follow the T
3/2 law, allow to attribute the ν
Q
value quoted above to 111Cd nuclei at the substitutional sites with tetrahedral symmetry in the Zn sublattice of ZrZn2. 相似文献
20.
We have studied the growth characteristics, structure, and parameters of the epitaxial heterostructures (001)NdBa2Cu3O7−δ
/(100)SrTiO3/(001)NdBa2Cu3O7−δ
grown by laser ablation on a (100)LaAlO3 substrate with a thin (∼2 nm) YBa2Cu3O7−δ
intermediate layer. The use of an YBa2Cu3O7−δ
intermediate layer promotes layered growth of the (200 nm) NdBa2Cu3O7−δ
layer, whose free-surface roughness is 4–5 nm. The resistance of the NdBa2Cu3O7−δ
layers began to fall off abruptly at T=92 K, and at T≈87 K it vanished completely. The critical current density in the NdBa2Cu3O7−δ
layers at T=76 K exceeded 106 cm2 A/cm2. The dielectric constant of the (400 nm) SrTiO3 layer sandwiched between the NdBa2Cu3O7−δ
epitaxial layers grew by roughly threefold as the temperature was lowered in the interval 300–4.2 K. When a bias voltage
of ±2.5V was applied to the NdBa2Cu3O7−δ
electrodes, the relative dielectric constant of the (400 nm) SrTiO3 intermediate layer fell from 1150 to 400 (T=32 K, f=100 kHz). The conductivity of the SrTiO3 intermediate layer in the direction perpendicular to the substrate plane increased with temperature and the electric field
strength.
Fiz. Tverd. Tela (St. Petersburg) 41, 395–403 (March 1999) 相似文献