共查询到20条相似文献,搜索用时 15 毫秒
1.
The phase transition in the perovskite (Pv) SrRuO3 under pressure has been studied by using first-principles calculations based on density functional theory. The post-perovskite (Ppv) phase transition of SrRuO3 will take place under hydrostatic pressure of about 40 GPa. The stability of Ppv- SrRuO3 is justified by the enthalpy calculations, and this phase transition accompanies volume disconnection and magnetic moment collapses. The crystallographic data and the electronic structure of Ppv- SrRuO3 are also predicted. The crystal structure of Ppv- SrRuO3 is similar to that of Ppv- CaRuO3. A non-magnetic ground state is found in Ppv- SrRuO3. The strong hybridization of Ru and O is evident in the electronic structures of both phases. We expect that these results will help further understanding of SrRuO3 under high pressure. 相似文献
2.
Structural investigation using X-ray synchrotron
radiation has been performed on SrRuO3/SrTiO3/SrRuO3
epitaxial heterostructures, with each constituent layer a few unit cell
thick grown on (001) SrTiO3 substrate. Detailed information on the
evolution of the in-plane lattice structure has been obtained, in these
heterostructures, by grazing incidence diffraction measurements. The samples
have been grown by low-pressure pulsed laser deposition. Under our
deposition conditions, SrRuO3 layers grow with an elongated cell
perpendicular to the substrate surface. The in-plane pseudocubic lattice
parameters do not match the in-plane square SrTiO3 structure even in
the case of very thin SrRuO3 layers. Such a distortion was found to
decrease with increasing the thickness of the SrTiO3 barrier layer. 相似文献
3.
4.
5.
P. Orgiani C. Aruta G. Balestrino S. Lavanga P.G. Medaglia A. Tebano 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):23-28
Transport properties of SrRuO3 thin films were studied as a function of the epitaxial strain. SrRuO3 films were grown on (100) SrTiO3 substrates by the Pulsed Laser Deposition technique equipped with Reflection High Energy Electrons Diffraction (RHEED). Samples
thickness has been varied from a few unit cells to above 1000 ? while monitoring RHEED intensity oscillations. In thicker
films epitaxial strain was found to be progressively relaxed. SrRuO3 relaxed films (thickness 1000 ?) show metallic behavior for the whole temperature range with a ferromagnetic ordering at about 150 K. For thinner
films, ferromagnetic ordering occurs at progressively lower temperatures, until in films thinner than 400 ? it disappears.
Films thinner than 80 ? show a semiconducting behavior at low temperatures. Our results provide direct evidence of the crucial
role of the strain effect for conducting and magnetic properties of SrRuO3.
Received 16 July 2001 and Received in final form 22 October 2001 相似文献
6.
《Current Applied Physics》2020,20(12):1379-1385
SrRuO3 is an orthogonally distorted perovskite (Pbnm) structure whose ferromagnetism is often viewed as an itinerant ferromagnet. Although SrRuO3 has been studied for more than half a century, its structure, magnetism and transport properties are still poorly understood. In this paper, the structure and magnetic evolution of SrRuO3 are discussed in depth through the substitution of Ca2+ for Sr2+ at A sites. The results show that as the Ca substitution increases, the lattice constant decreases, the orthogonal distortion becomes larger, and the saturation magnetization MS, Curie temperature TC and Weiss temperature θp decrease accordingly. Eventually, the ferromagnetic SrRuO3 changes to paramagnetic CaRuO3. The critical exponent β of samples with different substitution contents was obtained by fitting the experimental results, and the value for SrRuO3 (β = 0.55) was similar to that obtained by mean field theory. However, the value increases with the substitution x of Ca, which can't be explained by any scaling theory. The results show that the increase in the value of β is related to the magnetic disorder caused by different magnetic interactions. Analysis using the Rhodes-Wohlfarth criterion indicates that Sr1-xCaxRuO3 has both itinerant-electron and localized-electron magnetism, which is consistent with the theoretical predictions. 相似文献
7.
Low-lying equilibrium geometric structures of Phosphorus-doped aluminum cluster Al
n
P (n = 2–12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density
functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within
the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to
Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated
for the ground-state structures within the GGA. It is observed that symmetric structures with the P atom occupying a peripheral
position are lowest-energy geometries of Al
n
P (n = 2, 4–11), while the P impurities of Al3P and Al12P prefer to occupy internal sites in the aluminum clusters. Generalized gradient approximation extends bond lengths as compared
to the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the HOMO–LUMO
gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within both GGA and LSDA. The
stability analysis based on the energies clearly shows the clusters with an even number of valence electrons are more stable
than clusters with odd number of valence electrons. 相似文献
8.
S. Fallahi H. Hadipour M. Akhavan 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(4):531-534
We have performed a first-principle calculation of the structural, electronic and high pressure properties of RuSr2GdCu2O8, a ferromagnetic superconductor, by employing a full-potential linearized augmented plane-wave method within the density-functional
theory. The effect of pressure was achieved by varying the volume of the unit cell with constant a:b:c ratio. The experimentally observed anti-phase rotation of RuO6 octahedra has been attributed to the residual forces on ORu which results in shear strain in the RuO2 layer. Partial charge analysis shows that applying pressure up to 6 GPa leads to hole creation in the CuO2 sheets which causes increase in the superconducting transition temperature. We have estimated the Curie temperature T
M
of this compound in the mean-field approximation using Heisenberg model with first-nearest neighbor exchange interactions
determined from DFT calculations for parallel and anti-parallel spin configurations of Ru moment in RuO2 planes. The effect of pressure causes the magnetic moment of Ru atoms to decrease due to the increase of hybridization between
the adjacent Ru atoms. The calculated exchange splitting in Cu d
x
2
-
y
2 states increases slightly with pressure but it is still very small that it does not affect superconductivity, and the hole
doping mechanism is dominant. 相似文献
9.
Yu. V. Knyazev A. V. Lukoyanov Yu. I. Kuz’min S. Gupta K. G. Suresh 《Physics of the Solid State》2016,58(12):2373-2378
The results of the investigation of the electronic structure and optical properties of the TbMn0.33Ge2 compound have been presented. The spin-polarized calculations of the band spectrum have been performed within the framework of the local spin density approximation (LSDA) with a correction for strong correlations in the 4f shell of the rare-earth ion (the LSDA + U method). The optical constants have been measured using the ellipsometric method and a number of spectral and electronic characteristics of the compound under investigation have been determined over a wide range of wavelengths. The interband part of the experimental dependence of the optical conductivity has been interpreted using the results of the calculation of the electron density of states. 相似文献
10.
We present results of LDA calculations (band structure, densities of states, Fermi surfaces) for possible iron based superconductor
BaFe2Se3 (Ba123) in normal (paramagnetic) phase. Results are briefly compared with similar data on prototype BaFe2As2 and (K,Cs)Fe2Se2 superconductors. Without doping this system is anti-ferromagnetic with T
Nexp ∼ 250 K and rather complicated magnetic structure. Neutron diffraction experiments indicated the possibility of two possible
spin structures (antiferromagnetically ordered “plaquettes” or “zigzags”), indistinguishable by neutron scattering. Using
LSDA calculated exchange parameters we estimate Neel temperatures for both spin structures within the molecular field approximation
and show τ1 (plaquettes) spin configuration to be more favorable than τ2 (zigzags). 相似文献
11.
Yu Feng Can Wang ShiLu Tian Yong Zhou Chen Ge HaiZhong Guo Meng He KuiJuan Jin GuoZhen Yang 《中国科学:物理学 力学 天文学(英文版)》2017,60(6):067711
BiFeO3 (BFO) thin films with BaTiO3 (BTO) or SrTiO3 (STO) as buffer layer were epitaxially grown on SrRuO3-covered SrTiO3 substrates. X-ray diffraction measurements show that the BTO buffer causes tensile strain in the BFO films, whereas the STO buffer causes compressive strain. Different ferroelectric domain structures caused by these two strain statuses are revealed by piezoelectric force microscopy. Electrical and magnetical measurements show that the tensile-strained BFO/BTO samples have reduced leakage current and large ferroelectric polarization and magnetization, compared with compressively strained BFO/STO. These results demonstrate that the electrical and magnetical properties of BFO thin films can be artificially modified by using a buffer layer. 相似文献
12.
Using the first-principles calculations based on density functional theory, the important role of electrode materials in determining the interfacial, ferroelectric stability and magnetoelectric properties in BaTiO3-based multiferroic tunnel junctions (MFTJs) have been investigated comparatively. It is found that the SrO–TiO2 interface of MFTJs with oxide electrode SrRuO3 is the most favorable interfacial structure. The average ferroelectric polarizations of MFTJs with electrode Co, FeCo and SrRuO3 are 25, 36 and 0 μC/cm2, respectively. The using of alloy electrode FeCo is more contributed to ferroelectric stability and the enhancement of magnetoelectric coupling of BaTiO3-based MFTJs. We expect our findings can provide an essential evaluation for the selection of electrode materials in spintronic storage devices. 相似文献
13.
We investigate the effects of Ru-doping in polycrystalline TbMn1−x
Ru
x
O3 (x≤0.10) on the multiferroicity. It is observed that the Ru substitution gradually melts away the dielectric anomaly at the
ferroelectric transition point and the ferroelectricity by suppressing the polarization, accompanied with a surprising low-temperature
dielectric plateau. While it is reasonable to observe the significant suppression of ferroelectricity, owing to the fact that
the Ru-doping disrupts the Mn spiral spin ordering and reduces the Mn–Mn spin angle, quantum fluctuations associated with
the Ru substitution, responsible for the low-temperature dielectric plateau, seems to be significant. 相似文献
14.
Orthorhombic GdMnO3 is studied using density functional theory considering the pseudo-potential plane-wave method within local-spin-density approximation, LSDA. The electronic band structure and density of states, for several hydrostatic pressures, are studied. The Mott transition was observed at 60 GPa. Calculated lattice parameters are close to the experimental measurements, and some indirect band gaps (S→Γ) were obtained within the LSDA level of calculation, between the occupied O-2p and unoccupied Gd-4f states. The variation of the gap reduces with increasing pressure, being well fitted to a quadratic function. 相似文献
15.
The results of the detailed scanning electron microscopy study of PrBa2Cu3O7-δ single crystals after the long-lasting high-temperature post-growth treatment are reported. The presence of the unstable
decomposition products on the crystal surface indicates that the onset of superconductivity must be related to the structural
transformations in the bulk (approximately 20% of the total volume of the examined crystals). The time-dependent character
of the superconductivity in the Pr-123 crystals could be attributed to the migration of defects in the Pr−Ba sublattice from
the bulk toward the surface. 相似文献
16.
P. S.R. Murthy K. R. Priolkar P. A. Bhobe A. Das P. R. Sarode A. K. Nigam 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):275-282
Effect of Co, Ru and Cu substitution at B and B’ sites on the magnetic and transport properties of LaSrCoRuO6
have been investigated. All the doped compositions crystallize in the monoclinic structure in the space group
P21/n indicating a double perovskite structure. While the magnetization and conductivity increase in Co and Ru
doped compounds, antiferromagnetism is seen to strengthen in the Cu doped samples. These results are explained on
the basis of a competition between linear Co-O-Ru-O-Co and perpendicular Co-O-O-Co antiferromagnetic interactions
and due to formation of Ru-O-Ru ferromagnetic networks. 相似文献
17.
Nadjet Metadjer Lilia Beldi Bachir Bouhafs Pierre Ruterana 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(10):240
The electronic structure and magnetic properties of Fe2SiC compound have been studiedusing the framework of an all-electron full-potential linearized augmented-plane wave(FP-LAPW) method within the local density (LSDA) and + U corrected(LSDA + U)approximations. An antiferromagnetic spin ordering of Fe atoms is shown to be the groundstate for this compound. From the electronic band structures and density of states (DOS),Fe2SiC has ametallic character and from the analysis of the site and momentum projected densities, itis deduced that the bonding is achieved through hybridization of Fe-3d with C-2p states andFe-3d withSi-3pstates. It is also pointed out that the Fe-C bonding is more covalent than Fe-Si. In theFM phase, the spin polarized calculations indicate that the total magnetic moment ofFe2SiC increasesfrom 0.41 to 4.33μ B when the Hubbard U parameter for iron isconsidered. 相似文献
18.
Yan Xiong Daoqian Zhu Shiheng Chen Hong Peng Yafeng Guan 《Journal of fluorescence》2010,20(1):269-274
A novel fiber-optic evanescent wave sensor (FOEWS) for O2 detection based on [Ru(bpy)3]2+-doped hybrid fluorinated ORMOSILs (organically modified silicates) has been developed. The sensing element was fabricated
by dip-coating the optical fiber with [Ru(bpy)3]2+-doped hybrid fluorinated ORMOSILs composed of n-propyltrimethoxysilane (n-propyl-TriMOS) and 3, 3, 3-trifluoropropyltrimethoxysilane (TFP–TriMOS). Fluorophores of [Ru(bpy)3]2+ were excited by the evanescent wave field produced on the fiber core surface and the emission fluorescence was quenched by
O2. Spectroscopic properties have been characterized by FTIR and UV–VIS absorption measurements. By using the presented hybrid
fluorinated ORMOSILs, which enhances the coating surface hydrophobicity, the quenching response is increased. The sensitivity
of the sensor is 7.5, which is quantified in terms of the ratio I
N2/I
O2 (I
N2 and I
O2 represent the fluorescence intensities in pure N2 and pure O2 environments, respectively). The limit of detection (L.O.D.) is 0.01% (3σ) and the response time is about 1 s. Meanwhile,
the proposed FOEWS has the advantages of easy fabrication, low cost, fast response and suitable sensitivity for oxygen monitoring
using a cheap blue LED as light source and coupling a miniature PMT detector directly to the optical fiber probe. 相似文献
19.
Ti42.5Zr7.5Cu40Ni5Sn5 bulk metallic glass with a critical diameter of 4 mm was fabricated by the conventional copper mould casting method. The
supercooled liquid region ΔT
x, reduced glass transition temperature T
rg, γ parameter, and δ parameter of the alloy were measured to be 63.9 K, 0.561, 0.393, and 1.400, respectively, implying that the alloy has an
excellent glass-forming ability. The bulk metallic glass exhibits high compressive fracture strength of 2162 MPa with distinct
plastic strain of 0.9%. The fracture surface consists mainly of vein-like patterns, typical of bulk glassy alloys.
Supported by the Program for New Century Excellent Talents in University of China and the National Natural Science Foundation
of China (NSFC)(Grant No. 50771040) 相似文献
20.
A. M. Pashaev B. G. Tagiev O. B. Tagiev Kh. B. Ganbarova 《Journal of Applied Spectroscopy》2011,78(2):266-271
We have ground bulk samples to obtain nanoparticles of (Ga2S3)1–x
(Eu2O3)
x
solid solutions, the sizes of which were determined using an atomic force microscope. The photoluminescence spectra of the
nanoparticles were studied in the temperature interval 77–300 K. We have established the mechanisms for emission and transfer
of energy from the matrix to the rare-earth ion, and we determined the Stokes shift (ΔS = 0.7 eV), the Huang–Rhys parameter
(S = 16), and the optical phonon energy (ħ−ω = 23 meV). 相似文献