共查询到20条相似文献,搜索用时 31 毫秒
1.
I. M. Shmyt’ko E. A. Kudrenko V. V. Sinitsyn B. S. Red’kin E. G. Ponyatovsky 《JETP Letters》2005,82(7):409-412
The structural changes induced by a 9-GPa pressure in Eu2(MoO4)3 single crystals at room temperature have been studied using x-ray diffraction. It is established that a structural phase transition from the initial tetragonal phase to the new high-pressure tetragonal phase occurs rather than solid-phase amorphization that was observed previously in polycrystalline samples. The samples in the observed transition remain single-crystalline despite a significant difference (ΔV ~ 18%) between the specific volumes of the initial and final phases. It is shown that the transition from the initial state to the high-pressure phase occurs via the formation of broad transition zones featuring a continuous and smooth change of the crystal lattice parameters. 相似文献
2.
T. N. Fursova A. V. Bazhenov S. S. Khasanov A. P. Kiselev V. V. Sinitsyn S. Z. Shmurak 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(5):619-621
The influence of high-pressure hydrostatic compression and subsequent annealing on the structural properties of β’-phase single
crystals of europium molybd ate was studied by IR spectroscopy and X-ray diffraction. It was demonstrated that after compression,
the IR spectra exhibit drastic changes and do not depend on the initial crystallographic orientation of a single crystal.
The high-pressure compression of single crystals followed by their annealing was found to result in the formation of β’-Eu2(MoO4)3 single crystals with the same crystallographic orientation as that of the initial samples. 相似文献
3.
The effects accompanying the ferroelastic phase transition in Hg2Br2 polycrystalline samples are compared in an x-ray diffraction study with similar effects observed to occur in Hg2Br2 single crystals. In particular, an analysis is made of the “orthorhombic” splitting of the basal plane reflections and the behavior with temperature of the Bragg and diffuse reflections from the X points of the Brillouin zone, which characterize the behavior of the order parameter and its fluctuations, respectively. Polycrystalline samples exhibit strong smearing of the phase transition effects originating from the existence of damaged surface layers and elastic and plastic strain fields which induce order parameter fluctuations over a wide temperature range. 相似文献
4.
We present a study by Raman spectroscopy and X-ray diffraction/diffuse scattering of C60 single-crystals treated at high-pressure and high-temperature. This allowed us to obtain structural information on the C60 dimer state which can be considered as an intermediate state in the polymerization process. In the 1-6 GPa pressure range the crystals are primarily formed of dimers with additional minor fractions of monomers, 1D and 2D polymers, as shown by the analysis of the Raman spectra. The dimers are disordered within an average cubic lattice derived from that of the monomer. Single-crystal diffraction patterns reveal a characteristic diffuse scattering intensity distribution which has been simulated by calculating the diffuse scattering produced by dimer and trimer model structures. Satisfactory agreement is obtained for random positional and orientational disorder of the C60-C60 dimers although a small concentration of similarly disordered trimers is likely. In a first approximation the dimer/trimer disorder can be considered as random but various inter-dimer correlations are probably present, as discussed.Received: 3 October 2003, Published online: 19 February 2004PACS:
61.48. + c Fullerenes and fullerene-related materials - 61.43.Bn Structural modeling: serial-addition models, computer simulation - 78.30.Na Fullerenes and related materialsT. Wågberg: Present address: Groupe de Dynamique des Phases Condensées, Université Montpellier II, Place E. Bataillon, CC026, 34095 Montpellier, France 相似文献
5.
D. P. Pavlov I. I. Piyanzina V. M. Mukhortov A. M. Balbashov D. A. Tayurskii I. A. Garifullin R. F. Mamin 《JETP Letters》2017,106(7):460-464
The temperature dependence of the electrical resistance has been studied for heterostructures formed by antiferromagnetic LaMnO3 single crystals of different orientations with epitaxial films of ferroelectric Ba0.8Sr0.2TiO3 deposited onto them. The measured electrical resistance is compared to that exhibited by LaMnO3 single crystals without the films. It is found that, in the samples with the film, for which the axis of polarization in the ferroelectric is directed along the perpendicular to the surface of the single crystal, the electrical resistance decreases significantly with temperature, exhibiting metallic behavior below 160 K. The numerical simulations of the structural and electronic characteristics of the BaTiO3/LaMnO3 ferroelectric?antiferromagnet heterostructure has been performed. The transition to the state with two-dimensional electron gas at the interface is demonstrated. 相似文献
6.
V. I. Maksimov T. P. Surkova V. D. Parkhomenko E. N. Yushkova 《Physics of the Solid State》2016,58(4):650-659
The structural state of a bulk Zn0.95Fe0.05Se cubic crystal grown by the chemical transport method from the gas phase has been investigated using thermal neutron diffraction at room temperature. It has been found that the measured neutron diffraction patterns of the crystal, in addition to structural Bragg peaks, contain a clearly identified system of superstructure reflections with the wave vector k = (1/3 1/3 1/3)2π/a (where a is the parameter of the cubic unit cell), which is interpreted as a clear evidence of the incipient transition state preceding the concentration phase transformation fcc ? hcp. It has been shown that the resulting structural state includes an inhomogeneous microstrain field with the possible appearance of long-wavelength modulations based on the initial sphalerite structure. 相似文献
7.
A. A. Bykov I. A. Zobkalo A. A. Dubrovskii O. P. Smirnov S. E. Nikitin K. Yu. Terent’ev S. V. Gavrilov K. A. Shaikhutdinov 《Journal of Experimental and Theoretical Physics》2017,124(5):786-791
The temperature and field dependences of the magnetization, the electrical resistivity, and the magnetostriction of bilayer lanthanum manganite La1.4Sr1.6Mn2O7 single crystals and cobalt-doped La1.4Sr1.6(Mn0.9Cu0.1)2O7 are measured. The magnetostriction of the cobalt-doped compound increases as compared to the initial La1.4Sr1.6Mn2O7 compound, and the magnetization and the magnetoresistance of the former compound change substantially. Powder and single-crystal neutron diffraction patterns are used to detect ferromagnetic ordering in La1.4Sr1.6(Mn0.9Co0.1)2O7 at a temperature below T C ~ 45(2) K, and this ordering coexists with antiferromagnetic correlations, which develop at temperatures below T C ~ 80(5) K. 相似文献
8.
L. V. Udod G. A. Petrakovskiĭ A. M. Vorotynov O. A. Bayukov D. A. Velikanov A. V. Kartashev A. F. Bovina Yu. G. Shvedenkov M. Baran R. Szymczak 《Physics of the Solid State》2007,49(3):500-504
This paper reports on the first study of the temperature and field dependences of the magnetization, heat capacity, and electrical properties of synthesized polycrystalline samples of aerugite Co10Ge3O16, as well as on x-ray diffraction analysis of this compound. It is shown that the cobalt ions in this compound occupy three nonequivalent positions. The results of the experimental and theoretical studies suggest that aerugite is a ferrimagnet with two uncompensated magnetic moments of the cobalt atom per formula unit. 相似文献
9.
D. P. Kozlenko T. A. Chan S. E. Kichanov Z. Jirák L. S. Dubrovinsky B. N. Savenko 《JETP Letters》2011,92(9):590-594
The crystal structure and Raman spectra of Pr0.7Ca0.3MnO3 manganite at high pressures of up to 30 GPa and the magnetic structure at pressures of up to 1 GPa have been studied. A structural
phase transition from the orthorhombic phase of the Pnma symmetry to the high-pressure orthorhombic phase of the Imma symmetry has been observed at P ∼ 15 GPa and room temperature. Anomalies of the pressure dependences of the bending and stretching vibrational modes have
been observed in the region of the phase transition. A magnetic phase transition from the initial ferromagnetic ground state
(T
C = 120 K) to the A-type antiferromagnetic state (T
N = 140 K) takes place at a relatively low pressure of P = 1 GPa in the low-temperature region. The structural mechanisms of the change of the character of the magnetic ordering
have been discussed. 相似文献
10.
S. I. Vorob’ev E. I. Golovenchits V. P. Koptev E. N. Komarov S. A. Kotov V. A. Sanina G. V. Shcherbakov 《JETP Letters》2010,91(10):512-517
The magnetic properties of the EuMn2O5 multiferroic (samples consisting of single crystals and ceramic samples) have been investigated by the muon-spin-relaxation
(μSR) method in the temperature range of 10–300 K. Below the magnetic ordering temperature T
N = 40 K, the loss of the polarization of muons and the effect of the external magnetic field have been observed. Both phenomena
can be explained by an additional channel of the depolarization of muons owing to the appearance of muons in a medium with
a low electron density due to the charge separation process (the redistribution of the electron density in the phase transition
process). The “memory” phenomenon has been revealed in a sample in the external magnetic field; the memory relaxation time
depends on the size of the structure units of the samples (single crystals or ceramic grains). 相似文献
11.
G. I. Vinogradova L. V. Anzina V. G. Veselago M. V. Glushkov T. N. Menshchikova É. G. Zhukov 《Physics of the Solid State》2007,49(5):912-917
The results of an investigation into how the composition of annealing mixtures influences the Curie temperature of single crystals of the CdCr2Se4 ferromagnetic semiconductor are reported. The mechanism of doping of single crystals is analyzed, and the role played by each of the components of the annealing batch is established. It is concluded that the indirect exchange involving n-type carriers near impurity gallium ions leads to a sharp increase in the phase transition temperature (from 130 to 172 K) of the samples. The dependences of the magnetization of samples with different phase transition temperatures on the temperature and magnetic field are compared. 相似文献
12.
Keka R. Chakraborty S. M. Yusuf P. S. R. Krishna M. Ramanadham A. K. Tyagi 《Pramana》2004,63(2):251-255
We have synthesized polycrystalline La0.95Nd0.05CrO3 sample by doping the La-site of LaCrO3 with Nd and its magnetic properties have been studied using DC magnetization and neutron diffraction techniques. DC magnetization
study shows a paramagnetic to a weak ferromagnetic-like transition at ∼295 K followed by signatures of a spin reorientation
phenomenon at 233 and 166 K and, finally a transition to an antiferromagnetic-like phase at ∼21 K. Low-temperature neutron
diffraction measurements confirm a weak ferrimagnetic ordering of Cr3+ moments at all temperatures below 295 K. 相似文献
13.
Yu. F. Markov E. M. Roginskii D. Wallacher 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1198-1202
The rhombic splitting of basal plane reflections and the thermal behavior of fundamental and diffuse reflections from X-points of the Brillouin zone characterizing the behavior of an order parameter and its fluctuations, respectively, were studied
in polycrystalline Hg2Cl2 and Hg2Br2 samples. In the case of polycrystalline samples, a strong broadening of phase transition effects was observed, due to damaged
surface layers and elastic and plastic stress fields inducing order parameter fluctuations over a wide temperature range. 相似文献
14.
L. Nedelcu A. Ioachim M. I. Toacsan M. G. Banciu I. Pasuk M. Buda N. Scarisoreanu V. Ion M. Dinescu 《Applied Physics A: Materials Science & Processing》2008,93(3):675-679
Ba0.6Sr0.4TiO3 (BST) bulk ceramic synthesized by solid state reaction was used as target for thin films grown by pulsed laser deposition
(PLD) and radiofrequency beam assisted PLD (RF-PLD). The X-ray diffraction patterns indicate that the films exhibit a polycrystalline
cubic structure with a distorted unit cell. Scanning Electron Microscopy investigations showed a columnar microstructure with
size of spherical grains up to 150 nm. The capacitance–voltage (C–V) characteristics of the BST films were performed by applying
a DC voltage up to 5 V. A value of 280 for dielectric constant and 12.5% electrical tunability of the BST capacitor have been
measured at room temperature. 相似文献
15.
Manglesh Dixit Shovit Bhattacharya Rajneesh Mohan Kiran Singh P. S. R. Krishna Vilas Shelke N. K. Gaur R. K. Singh 《Pramana》2004,63(2):233-237
The HgO-added YBa2Cu3O7−δ (YBCO) superconductor has been studied for its structural and superconducting properties. Polycrystalline YBCO samples were
synthesized through solid-state reaction method by adding HgO in different concentrations without using oxygen annealing.
All the samples showed a sharp superconducting transition temperature around 90 K. The X-ray diffraction patterns of all the
samples revealed monophasic Y-123 nature. The structural studies were carried out by neutron scattering and Rietveld analysis.
The neutron scattering revealed that Hg is not incorporated in the Y-123 system and has shown optimum oxygen concentration.
The significant role played by the HgO is to provide oxygen ambient through its decomposition, thus changing the oxygen balance
in favour of high Cu-valence state. 相似文献
16.
Prasanta Dhak D. Dhak M. Das T. Subashchandrabose P. Pramanik 《Journal of nanoparticle research》2011,13(9):4153-4159
This study reports a facile, gram-scale synthesis of FeNbO4 nanorods via hydrothermal route, using iron nitrate [Fe(NO3)3] and niobium tartarate (Nb tartarate) in presence of potassium peroxosulfate. The formation of single phase, polycrystalline
orthorhombic structure of FeNbO4 was confirmed by the careful analysis of the X-ray diffraction (XRD) pattern. The average crystallite size, calculated using
a few XRD peaks, was found to be 12.8 nm. As indicated by transmission electron microscopy (TEM) and field emission scanning
electron microscopy, the average length and diameter of the rods were found to be only 25 × 7 nm and 47 × 14 nm, respectively.
The selected area electron diffraction and high-resolution transmission electron microscopy (HRTEM) data of the single rod
implied that FeNbO4 nanorods were polycrystalline in nature and grew up along the c-axis. HRTEM also revealed that the fringes are equidistant with a lattice separation of 0.91 Ǻ, which corresponded to the
(111) plane of the FeNbO4 crystal. Elemental composition of the nanorods was confirmed using electron dispersive X-ray spectroscopy analysis while
binding state of the surface was intervened through X-ray photoelectron spectroscopy. Mechanistic investigations suggested
that potassium peroxosulfate played a crucial role in the unidirectional growth of particles. The synthetic method is simple,
amenable to scale up and contributes a new tool box for the development of FeNbO4-based one-dimensional (1D) structures that appears to be more promising for a myriad of applications, compared to their 3D
counterparts. 相似文献
17.
V. Ya. Shur V. A. Shikhova D. V. Pelegov A. V. Ievlev L. I. Ivleva 《Physics of the Solid State》2011,53(11):2311-2315
The results of the study of nano- and microdomain structure evolution in single crystals of relaxor ferroelectric strontium
barium niobate Sr0.61Ba0.39Nb2O6 doped by cerium are presented. It was shown that the initial nanodomain structure represents a self-similar three-dimensional
maze. The fractal dimension and average period were revealed. It was demonstrated that application of series of alternating
electric field pulses makes it possible to produce a single-domain state in the surface layer. The features of the growth
and “merging,” as well as the shape of ensembles of isolated nanodomains formed during switching from the single-domain state,
were investigated. The formation of the nanodomain ensembles was considered as a result of the self-organized discrete switching
controlled by determined nucleation. 相似文献
18.
E. Govea-Alcaide I. García-Fornaris P. Muné R. F. Jardim 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):373-378
Measurements of the electrical resistivity as a function
of temperature, ρ(T), for different values of applied
magnetic field, Ba (0 ≤ Ba ≤ 50 mT), were performed in
polycrystalline samples of Bi1.65Pb0.35Sr2Ca2
Cu3O10+δ subjected to different uniaxial compacting
pressure (UCP). We have found appreciable differences in the grain
orientation between samples by using X-ray diffractometry. From
the X-ray diffraction patterns performed, in powder and pellet
samples, we have estimated the Lotgering factor along the (00l)
direction, F(00l). The results indicate that F(00l)
increases ~23% with increasing UCP suggesting that grains
of these samples are preferentially aligned along the c-axis,
which is parallel to the compacting direction. The resistive
transition of the samples have been interpreted in terms of the
thermally activated flux-creep model. In addition, the effective
intergranular pinning energy, U0, have been determined for
different applied magnetic field. The magnetic field dependence of
U0, for Ba > 8 mT, was found to follow a H- α
dependence with α = 0.5 for all samples. The analysis of the
experimental data strongly suggested that increasing UCP results
in appreciable changes in both the grain alignment and the grain
connectivity of the samples. We have successfully interpreted the
data by considering the existence of three different
superconducting levels within the samples: the superconducting
grains, the weak-links, and the superconducting clusters. 相似文献
19.
L. S. Kamzina I. P. Raevskii S. M. Emel’yanov S. I. Raevskaya E. V. Sahkar 《Physics of the Solid State》2004,46(5):908-914
The dielectric and optical (optical transmission, small-angle light scattering, birefringence) properties of PMNT-0.2 single crystals and their variation induced by a dc electric field have been studied. The birefringence was found to increase anomalously at the transition from the rhombohedral ferroelectric to the inhomogeneous relaxor phase (the spontaneous ferroelectric transition temperature Tsp). Below Tsp, the dielectric and optical properties were observed to exhibit anomalies originating from reorientation and growth of domains in size. Unlike ferroelectric relaxors of the type of PbB′1/3B′2/3O3 and PbB′1/2B′1/2O3, in PMNT-0.2 neither induction of the ferroelectric phase by an electric field nor thermally stimulated destruction of the ferroelectric state occurs through the percolation mechanism (i.e., they are not accompanied by anomalously narrow maxima in small-angle light scattering). This is attributed to the inhomogeneous structure of the relaxor phase, as a result of which the phase transition does not take place simultaneously in various regions of the crystal. 相似文献
20.
N. V. Volkov G. A. Petrakovskii V. N. Vasil’ev K. A. Sablina 《Physics of the Solid State》2002,44(7):1350-1354
Two phases, paramagnetic and ferromagnetic, were shown by the magnetic resonance method to coexist below the temperature T C in La0.7Pb0.3MnO3 single crystals exhibiting colossal magnetoresistance. The magnetic resonance spectra were studied in the frequency range 10–78 GHz. The specific features in the behavior of the spectral parameters were observed to be the strongest at the temperatures corresponding to the maximum magnetoresistance in the crystals. The concentration ratios of the paramagnetic and ferromagnetic phases in the samples were found to be sensitive to variations in temperature and external magnetic field. This behavior suggests realization of the electronic phase separation mechanism in the system under study. 相似文献