共查询到20条相似文献,搜索用时 31 毫秒
1.
M. D. Durruthy-Rodríguez J. Costa-Marrero M. Hernández-Garcia F. Calderón-Pi?ar Célia Malfatti J. M. Yá?ez-Limón 《Applied Physics A: Materials Science & Processing》2011,103(2):467-476
In this work, visible photoluminescence was observed at room temperature in a sintered Pb(Zr1-xTix)1-y NbyO3\mathrm{Pb}(\mathrm{Zr}_{1-x}\mathrm{Ti}_{x})_{1-y} \mathrm{Nb}_{y}\mathrm{O}_{3} perovskite-type structure system, doped with Nb using the next excitation bands 325, 373 and 457 nm. The intensity and energy
of such emissions have been studied by changing the Nb concentration (0<y<0.01) and the Ti content (x), with x=0.20,0.40,0.53,0.60 and 0.80, on both sides of the morphotropic phase boundary (MPB) zone. The principal bands become visible
at energies of 1.73, 2.56 and 3.35 eV. The results reveal the role of the Nb5+ ion substitutions by Zr4+ or Ti4+ ions and the symmetry presented in the rhombohedral or tetragonal side of the MPB. Raman spectra which are similar for compositions:
20/80, 40/60 and 53/47 (tetragonal phases) show nine bands, centered around 137, 194, 269, 331, 434, 550, 612, 712 and 750
cm−1. The spectra for samples 60/40 and 80/20, rhombohedral phase, show significant differences, only six bands appear, centered
around 124, 209, 234, 330, 549 and 682 cm−1. In addition, optical absorption spectroscopy, structural and micro-structural measurements were carried out by using Uv-vis
spectroscopy, X-ray diffraction and scanning electron microscopy techniques, respectively. The experimental results of band
gap energy, e.g., in our samples are in accordance with the findings by J. Baedi et al. in the calculations of band structure,
energy gap and density of states for different phases of Pb(Zr1−x
Ti
x
)O3 using density functional theory (DFT). 相似文献
2.
V. S. Zakhvalinski? R. Laiho T. S. Orlova A. V. Khokhulin 《Physics of the Solid State》2008,50(1):63-70
The temperature dependences of the magnetic susceptibility χ(T) and the electrical resistivity ρ(T) of ceramic samples of La1 − x
Ca
x
MnO3 with x = 0.67 (LCMO) and La1 − x
Ca
x
Mn1 − y
Fe
y
O3 with x = 0.67 and y = 0.05 (LCMFO) are investigated in magnetic fields B = 50–105 G and the temperature range T = 4.2–400 K. Both samples undergo a transition from the paramagnetic state to a state with charge (orbital) ordering (CO)
at temperatures T
CO ≈ 272 K for LCMO and T
CO ≈ 222 K for LCMFO. The behavior of the paramagnetic phase in the temperature range 320–400 K for LCMO and 260–400 K for LCMFO
is described by the Curie-Weiss law with effective Bohr magneton numbers p
eff = 4.83 μB (LCMO) and 4.77 μB (LCMFO), respectively. The disagreement between the observed positive Weiss temperatures (θ ≈ 175 K (LCMO) and θ ≈ 134 K
(LCMFO)) and negative Weiss temperatures required for the antiferromagnetic ground state can be explained by the phase separation
and transition to the charge-ordered state. The magnetic irreversibility for T < T
CO is accounted for by the existence of a mixture of the ferromagnetic and antiferromagnetic phases, as well as the cluster
glass phase. At low temperatures, doping with iron enhances the frustration of the system, which manifests itself in a more
regular behavior of the decay rate of the remanent magnetization with time. The temperature dependence of the electrical resistivity
in the range of the charge-ordered phase conforms to the variable-range hopping model. The behavior of the electrical resistivity
is governed by the complex structure of the density of localized states near the Fermi level, which includes a soft Coulomb
gap Δ = 0.464 eV for LCMO and 0.446 eV for LCMFO. It is established that the ratio between the localization radii of charge
carriers a for LCMFO and a
und for LCMO is a/a
und = 0.88.
Original Russian Text ? V.S. Zakhvalinskiĭ, R. Laiho, T.S. Orlova, A.V. Khokhulin, 2008, published in Fizika Tverdogo Tela,
2008, Vol. 50, No. 1, pp. 61–68. 相似文献
3.
Ihor Studenyak Yuriy Neimet Csaba Cserháti Sándor K?kényesi Edvardas Kazakevi?ius Tomas ?alkus Algimantas Ke?ionis Antanas Orliukas 《Central European Journal of Physics》2012,10(1):206-209
Structural studies of (Ag3AsS3)
x
(As2S3)1−x
chalcogenide superionic glasses in the compositional range x = 0.3–0.9 were performed by scanning electron microscopy. Temperature and compositional dependences of transmission coefficient,
electrical conductivity, and activation energy were investigated 相似文献
4.
5.
A. A. Demidov I. A. Gudim E. V. Eremin 《Journal of Experimental and Theoretical Physics》2012,114(2):259-272
The magnetic properties of ferroborate single crystals with substituted compositions Nd1 − x
Dy
x
Fe3(BO3)4 (x = 0.15, 0.25) with competing exchange Nd-Fe and Dy-Fe interactions are investigated. For each composition, we observed a
spontaneous spin-reorientation transition from the easy-axis to the easy-plane state and step anomalies on the magnetization
curves for the spin-flop transition induced by a magnetic field B | c. The measured parameters and effects are interpreted using a unified theoretical approach based on the molecular field approximation
and on calculations performed in the crystal-field model for the rare-earth ion. The experimental temperature dependences
of the initial magnetic susceptibility from T = 2 K to T = 300 K, anomalies on the magnetization curves for B | c in fields up to 1.8 T, and their evolution with temperature, as well as temperature and field dependences of magnetization
in fields up to 9 T are described. In the interpretation of experimental data, the crystal-field parameters in trigonal symmetry
for the rare-earth subsystem are determined, as well as the parameters of Nd-Fe and Dy-Fe exchange interactions. 相似文献
6.
利用射频磁控溅射的方法在SrTiO3(001) 基片上制备了(La0.7Sr0.3MnO3)m(BiFeO3)n超晶格结构.对所制备的超晶格结构进行了50—150℃温度范围内的电流-电压测试分析.结果表明,随着BiFeO3薄膜的厚度减小,温度的升高,(La0.7Sr0.3MnO3)m(BiFeO3)n超晶格结构的电流变大.进一步根据介质导电模型对(La0.7Sr0.3MnO3)m(BiFeO3)n超晶格结构的导电特性做了分析.在温度较低或者电场较弱时,所制备的(La0.7Sr0.3MnO3)m(BiFeO3)n超晶格结构表现为欧姆导电,而在高温,高电场的情况下,其导电行为由空间电荷限制电流机理主导.
关键词:
超晶格薄膜
多铁
空间电荷限制电流 相似文献
7.
I. A. Starkov A. S. Kozhemyachenko S. F. Bychkov A. P. Nemudry N. Z. Lyakhov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1059-1061
The oxygen permeability of ceramic SrCo0.8 − y
Fe0.2Nb
y
O3 − z
(0 ≤ y ≤ 0.2) and La0.3Sr0.7Co0.6Fe0.2Nb0.2O3 − z
disc membranes as a function of temperature and oxygen partial pressure was studied. Kinetic analysis was performed based
on the experimental data on oxygen permeability as a function of oxygen partial pressure. 相似文献
8.
用固相反应法制备系列Nd0.67Sr0.33MnOy(y = 3.00—2.80)多晶样品.样品输运性质表现出自旋相关电致电阻特征.对氧含量等于化学计量样品,在测量温度范围内电阻不随负载电流变化,I-V曲线符合线性欧姆定律.对氧含量低于化学计量样品,当高于某一特征温度时,电阻变化符合线性欧姆定律;但低于这一特征温度时,电阻大小与负载电流有关,I-V曲线偏离线
关键词:
钙钛矿结构锰氧化物
电致电阻效应
自旋相关界面输运
氧缺陷 相似文献
9.
R. S. Iskhakov E. A. Denisova S. V. Komogortsev L. A. Chekanova Yu. E. Kalinin A. V. Sitnikov 《Physics of the Solid State》2010,52(11):2263-2266
This paper reports on the results of the investigation of the relation between the magnetic microstructure and ferromagnetic
resonance (FMR) in ferromagnetic metal-insulator composites by using granular alloys (Co41Fe39B20)
x
(SiO2)1 − x
and Co
x
(SiO2)1 − x
as an example. A comparative analysis of the properties of FMR spectra and parameters of random magnetic anisotropy leads
to correlations between these quantities. It has been found that the main mechanism that determines the FMR line width in
the films under investigation is the exchange narrowing mechanism. 相似文献
10.
In the EPR of (La1––x
Gd
y
Ce
x
)Al2 a bottleneck in the relaxation of the conduction electrons to the lattice is present at sufficiently high Gd-concentrations. The bottleneck can be broken by decreasing the Gd-concentration or by adding Cerium as a spin-flip-scatterer.g-factor and line broadening are measured for (La1–y
Gd
y
)Al2 and (La1––x
Gd
y
Ce
x
)Al2 as a function of temperature and Gd- and Ce-concentrations. The Cerium induced relaxationsrate
eL
(Ce) increases linearly with Ce-concentration up tox0.025. This corresponds to the fact, well known by measurements of the Kondo anomalies, that Cerium impurities show no significant interaction up to rather high concentrations. 相似文献
11.
S. A. Vyzulin A. V. Gorobinskii Yu. E. Kalinin E. V. Lebedeva A. V. Sitnikov N. E. Syr’ev I. T. Trofimenko Yu. I. Chekrygina I. G. Shipkova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1380-1382
Comparative investigations of static magnetic properties, magnetoresistance, and ferromagnetic resonance data of multilayer
nanostructures consisting of CoFeZr-Al2O3 composite magnetic layers and amorphous silicon semiconductor spacers were performed in a layer thickness range below 5 nm.
The influence of layer dimension parameters and chemical peculiarities of silicon on the inner structure and type of magnetic
interactions in nanostructures with 35 and 46 at % magnetic phase composite layers is discussed. 相似文献
12.
A. K. Zvezdin A. M. Kadomtseva Yu. F. Popov G. P. Vorob’ev A. P. Pyatakov V. Yu. Ivanov A. M. Kuz’menko A. A. Mukhin L. N. Bezmaternykh I. A. Gudim 《Journal of Experimental and Theoretical Physics》2009,109(1):68-73
Magnetic and magnetoelectric properties of ferroborate single crystals with complex composition (Tb1 − x
Er
x
Fe3(BO3)4, x = 0, 0.75) and with competing exchange Tb-Fe and Er-Fe interactions are investigated. Jumps in electric polarization, magnetostriction,
and magnetization are observed as a result of spin-flop transitions, as well as a considerable decrease in the critical field
upon an increase in the Er concentration, in a field H
c
parallel to the c axis. The observed behavior of phase-transition fields is analyzed and explained using a simple model taking into account
anisotropy in g factors and exchange splitting of funda-mental doublets of the easy-axis Tb3+ ion and easy-plane Er3+ ion. It is established that magnetoelectric and magnetostriction anomalies under spin-flop transitions are mainly controlled
by the Tb subsystem. The Tb subsystem makes a nonmonotonic contribution ΔP
a
(H
a
, T) to polarization along the a axis: the value of ΔP
a
reverses its sign and increases with temperature due to the contribution from the excited states of the Tb3+ ion.
Original Russian Text ? A.K. Zvezdin, A.M. Kadomtseva, Yu.F. Popov, G.P. Vorob’ev, A.P. Pyatakov, V.Yu. Ivanov, A.M. Kuz’menko,
A.A. Mukhin, L.N. Bezmaternykh, I.A. Gudim, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol.
136, No. 1, pp. 80–86. 相似文献
13.
A. V. Pashchenko V. P. Pashchenko A. G. Sil’cheva V. K. Prokopenko A. A. Shemyakov Yu. F. Revenko V. P. Komarov S. V. Gorban’ 《Physics of the Solid State》2011,53(2):309-315
The structure and properties of lanthanum strontium manganite perovskites La0.6Sr0.2Mn1.2 − y
Cr
y
O3 ± δ (y = 0–0.3) sintered at 1430°C have been studied by X-ray, resistive, and magnetic (χac and 55Mn NMR) methods. The parameter of the rhombohedrally distorted (R
$
\bar 3
$
\bar 3
c) perovskite structure decreases with increasing y. The real perovskite structure contains point (anion and cation vacancies) and cluster-type nanostructure defects. The analysis
of asymmetrically broadened 55Mn NMR spectra has confirmed the high-frequency electron-hole exchange Mn3+ ↔ Mn4+ and local inhomogeneity of their surrounding by other ions and point and cluster-type defects. An increase in the Cr content
leads to an increase in the resistivity and the magnetoresistive effect and a decrease in the metal-semiconductor and ferromagnetic-paramagnetic
phase transition temperatures (T
ms
and T
c
) due to the distortion of the exchange interactions Mn3+ ↔ Mn4+ by chromium ions, vacancies, and clusters. Introduction of Cr decreases the ferromagnetic component and increases the activation
energy. The magnetoresistive effect near T
ms
and T
c
is caused by scattering of charge carriers from intercrystallite nanostructure inhomogeneities of the lattice, and the low-temperature
effect is associated with the tunneling on mesostructural intercrystallite boundaries. 相似文献
14.
Guo-Yu Lan Yang-Wei Lin Zong-Hong Lin Huan-Tsung Chang 《Journal of nanoparticle research》2010,12(4):1377-1388
This article describes the synthesis of highly water-soluble Zn
x
Hg1−x
Se
y
S1−y
quantum dots (QDs) in aqueous solution through a simple photo-assisted reaction between ZnSe QDs and mercury(I) nitrate dihydrate
[Hg2(NO3)2·2H2O]. In order to deduce the optimal synthesis conditions, we varied several parameters, including the concentrations of mercaptosuccinic
acid (MSA) and Hg2(NO3)2·2H2O, the illumination time, and the reaction temperature. When irradiated at temperatures below 80 °C, the ZnSe QDs reacted
with the S2− ions formed rapidly from MSA and the Hg2+ ions formed from Hg2
2+ ions to form Zn
x
Hg1−x
Se
y
S1−y
QDs through a process of photo-etching and surface combination. Under different conditions, we prepared a series of Zn
x
Hg1−x
Se
y
S1−y
QDs that emit fluorescence at the maximum wavelengths ranging from 405 to 760 nm. Inductively coupled plasma-mass spectrometry
and transmission electron microscopy/energy dispersive spectrometry revealed that the content of Hg in the Zn
x
Hg1−x
Se
y
S1−y
QDs was greater when the synthesis was conducted at higher temperature. The Zn0.88Hg0.12Se0.44S0.56 QDs exhibit improved photostability than crude ZnSe QDs and possess long lifetimes (τ1 ~ 38 ns and τ2 ~ 158 ns). 相似文献
15.
A. A. Mukhin V. Yu. Ivanov A. M. Kuz’menko A. S. Prokhorov A. A. Pronin S. N. Barilo G. L. Bychkov S. V. Shiryaev 《JETP Letters》2010,91(3):147-154
The effect of the substitution of Co2+, Mn2+, and Zn2+ ions for Ni2+ ions on the magnetic, dielectric, and ferroelectric properties of vanadate single crystals (Ni1 − x
T
x
)3V2O8 has been analyzed. It has been found that the low-level (x ≤ 0.1) substitution of both magnetic and nonmagnetic ions stabilizes the ferroelectric state with a cycloidal magnetic structure.
The existence region of this state is expanded to low temperatures down to 3 K for Zn2+ and below 1.8 K for Co2+ and Mn2+ owing to the suppression of a low-temperature weak ferromagnetic phase. At the same time, the ferroelectric phase disappears
completely at large concentrations of Co and Mn. The effect of magnetic fields on the magnetic and ferroelectric states has
been analyzed. It has been shown that the magnetic field along the c axis suppresses the ferroelectric state, whereas the magnetization along the antiferromagnetism axis (a axis) induces the reentrant phase transition from a paraelectric weak ferromagnetic structure to a ferroelectric structure.
The corresponding H-T phase diagrams have been drawn. 相似文献
16.
A. V. Ivanov Yu. E. Kalinin V. N. Nechaev A. V. Sitnikov 《Physics of the Solid State》2009,51(12):2474-2479
The concentration dependences of the electrical resistivity and complex permeability of [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
multilayer structures and (Co45Fe45Zr10)
x
(Al2O3)100 − x
composites have been studied. It has been established that introduction of a semiconductor interlayer into the (Co45Fe45Zr10)
x
(Al2O3)100 − x
composites substantially decreases the electrical resistivity of [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
multilayer structures. The concentration dependences of the real and imaginary parts of the complex permeability of the [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
nanomultilayer structures substantially differ from those of the (Co45Fe45Zr10)
x
(Al2O3)100 − x
composites. The real part of the complex permeability of the [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
nanomultilayer structures follows the curve with a minimum near the percolation threshold of the composite, and the imaginary
part smoothly decreases as the ferromagnetic phase concentration increases. The results obtained are explained by the increase
in the bifurcation temperature due to the conduction electrons of the semiconductor interlayer, which favor magnetic ordering
of ferromagnetic grains. 相似文献
17.
I. V. Bodnar 《Journal of Applied Spectroscopy》2010,77(5):654-657
Single crystals of In2Se3 and CuIn5Se8 compounds and (In2Se3)1–x·(CuIn5Se8)x solid solutions have been grown from the melt using the Bridgman method and their composition and structure determined. It
is shown that the crystals have n-type conductivity. Their transmission spectra were studied in the self-absorption edge region
at 80 and 295 K. Based on the spectral measurements, the band gap width (Eg) was determined and the band gap concentration dependences were plotted. It is found that Eg varies with the x composition nonlinearly. Using the dielectric model of Van Vechten–Bergstresser and the Hill–Richardson
pseudo potential model, Eg(x) was calculated theoretically. 相似文献
18.
Kuldeep Chand Verma R. K. Kotnala N. S. Negi 《Applied Physics A: Materials Science & Processing》2009,96(4):1009-1015
The effect of nanosize grains to enhance dielectric tunability in chemically prepared (Pb1−x
Sr
x
)TiO3 (PST) (x=0.1 to 0.5) thin films has been observed. The grain size is evaluated from X-ray diffraction patterns and atomic force microscopy.
The average grain size lies in the range of 80–23 nm with varying Sr content. The nanosize grains in the PST films control
the dielectric behavior up to the higher frequency region and exhibit large tunability with low loss factor at room temperature.
The current–voltage characteristics show a large tunability as electron transport takes place within a highly resistive Fermi
gap. 相似文献
19.
20.
M. S. Lebedev 《Optics and Spectroscopy》2009,107(5):776-779
Capabilities of the method of laser null ellipsometry for the study of optical parameters of thin films of multicomponent
alloys are demonstrated. Films of alloys (HfO2)
x
(Al2O3)1 − x
on single-crystal silicon are obtained by the chemical vapor deposition with the use of the following volatile compounds:
hafnium dipivaloylmethanate (IV) and aluminum acetylacetonate (III). The selection of initial sets for their optical parameters
is justified. The selected model is shown to correspond to experimental data. In films deposited from the mixture of precursors,
the refractive index increases from a substrate to a film surface. Due to the separation of sources, films described by a
single-layer model were deposited. This fact is indicative of the homogeneous distribution of components over the film thickness. 相似文献