共查询到20条相似文献,搜索用时 15 毫秒
1.
I. S. Tereshina G. A. Beskorovainaya N. Yu. Pankratov V. V. Zubenko I. V. Telegina V. N. Verbetsky A. A. Salamova 《Physics of the Solid State》2003,45(1):104-108
The structure and magnetic properties of RFe11TiN compounds (R=Gd or Lu) containing nitrogen are investigated. Magnetic measurements are performed on a magnetometer in magnetic fields up to 100 kOe in the temperature range from 4.2 to 750 K with the use of RFe11TiN single crystals, RFe11TiN powders placed in a ceramic cell, and samples oriented in an external magnetic field. It is found that the nitridation leads to an increase in the Curie temperature and the saturation magnetization. The samples studied are uniaxial over the entire temperature range of magnetic ordering. The magnetic anisotropy decreases upon nitridation. It is demonstrated that, within the local anisotropy model, the decrease in the magnetic anisotropy constant K1 can be explained by the redistribution of the electron density in the vicinity of the crystallographic positions occupied by iron atoms. 相似文献
2.
3.
The paper reports on an ellipsometric study of the optical properties of RNi5 (R = Y, La, Ce) paramagnetic intermetallic compounds. The dispersion measurements of the refractive index n and of the absorption coefficient k were conducted within a spectral interval 0.083–5.64 eV at room temperature. The behavior of optical interband conductivity with energy is analyzed. The results obtained are discussed in the frame of available information on the electronic band structure of these compounds. The plasma and relaxation frequencies of conduction electrons have been determined. 相似文献
4.
N. V. Mushnikov E. G. Gerasimov V. S. Gaviko P. B. Terent’ev K. A. Yazovskikh A. N. Pirogov 《Physics of the Solid State》2018,60(6):1082-1089
The magnetic structures that form in La1–xRxMn2Si2 (R = Sm, Tb) layered compounds with various concentrations x have been determined by magnetic neutron diffraction and magnetic measurements, and the magnetic phase diagrams have been built. It is shown that the formation of the magnetic structures is dependent not only on exchange interactions, but also on the type of the magnetic anisotropy of a rare-earth atom. It is found that, in La1–xTbxMn2Si2 compounds with 0.2 < x < 0.5, the competition of the Tb–Mn and Mn–Mn interlayer exchange interactions and the existence of a strong uniaxial magnetic anisotropy in the Mn and Tb sublattices leads to the frustrated magnetic state and prevents the formation of the long-range magnetic order in the Tb sublattice. 相似文献
5.
PRAMOD KUMAR YADAWA 《Pramana》2011,76(4):613-619
The ultrasonic properties of the hexagonal closed packed structured Ni3Mo, Ni3Nb and Ni3Ta compounds were studied at room temperature for their characterization. For the investigations of ultrasonic properties,
the second-order elastic constants using Lennard–Jones potential were computed. The velocities V
1 and V
2 have minima and maxima respectively at 45° with the unique axis of the crystal, while V
3 increases with respect to angle with the unique axis of the crystal. The inconsistent behaviour of angle-dependent velocities
is associated with the action of second-order elastic constants. Debye average sound velocities of these compounds increase
with the angle and has maximum at 55° with the unique axis at room temperature. Hence, when a sound wave travels at 55° with
the unique axis of these materials, the average sound velocity is found to be maximum. The results achieved are discussed
and compared with the available experimental and theoretical results. 相似文献
6.
From a macroscopic theory of the quantum vacuum in terms of conserved relativistic charges (generically denoted by q
(a) with label a), we have obtained, in the low-energy limit, a particular type of f(R) model relevant to cosmology. The macroscopic quantum-vacuum theory allows us to distinguish between different phenomenological
f(R) models on physical grounds.
The text was submitted by the authors in English. 相似文献
7.
Ricardo G. Landim Rafael J. F. Marcondes Fabrízio F. Bernardi Elcio Abdalla 《Brazilian Journal of Physics》2018,48(4):364-369
We explore the cosmological implications of the interactions among the dark particles in the dark SU(2) R model. It turns out that the relevant interaction is between dark energy and dark matter, through a decay process. With respect to the standard ΛCDM model, it changes only the background equations. We note that the observational aspects of the model are dominated by degeneracies between the parameters that describe the process. Thus, only the usual Λ CDM parameters such as the Hubble expansion rate and the dark energy density parameter (interpreted as the combination of the densities of the dark energy doublet) could be constrained by observations at this moment. 相似文献
8.
M. I. Ignatov V. V. Glushkov S. V. Demishev N. Yu. Shitsevalova A. V. Levchenko E. I. Khayrullin N. E. Sluchanko 《Journal of Experimental and Theoretical Physics》2007,105(1):55-57
Detailed measurements of the Seebeck coefficient S(T) in a broad range of temperatures (T = 2–300 K) have been performed for the first time for RB12 dodecaborides (R = Ho, Er, Tm, Lu) in paramagnetic (diamagnetic for LuB12) and antiferromagnetic states. At intermediate temperatures (10–300 K), the thermopower is determined by the interaction of carriers with phonon modes, which are related to the oscillations of rare-earth atoms in the framework of atomic clusters B12. A comparative analysis of the parameters determining photon drag the thermopower related to the phonon drag and the results of galvanomagnetic measurements shows evidence for a significant effect of spin fluctuations on the behavior of charge transport characteristics in RB12 compounds with strong electron correlations. 相似文献
9.
The spin and lattice dynamics of the R2CuO4 quasi-2D antiferromagnetic crystals (R=Pr, Nd, Sm, Eu, Gd) were studied in the millimeter-range electromagnetic wave band. Strong variations of the absorption coefficient were observed to occur at temperatures T≈T0. Absorption lines of electrical nature due to lattice dynamics were also revealed near the T0 temperatures. The observed anomalies are assumed to originate from phase transitions at T≈T0, which entail changes in the structural and magnetic properties. 相似文献
10.
We study the f (R)-Maxwell black hole imposed by constant curvature and its all thermodynamic quantities, which may lead to the Reissner-Nordström-AdS black hole by redefining Newtonian constant and charge. Further, we obtain the f (R)-Yang-Mills black hole imposed by constant curvature, which is related to the Einstein-Yang-Mills black hole in AdS space. Since there is no analytic black hole solution in the presence of Yang-Mills field, we obtain asymptotic solutions. Then, we confirm the presence of these solutions in a numerical way. 相似文献
11.
<Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">R</Emphasis>) global monopole revisited
Thiago R. P. Caramês Júlio C. Fabris E. R. Bezerra de Mello H. Belich 《The European Physical Journal C - Particles and Fields》2017,77(7):496
In this paper the f(R) global monopole is reexamined. We provide an exact solution for the modified field equations in the presence of a global monopole for regions outside its core, generalizing previous results. Additionally, we discuss some particular cases obtained from this solution. We consider a setup consisting of a possible Schwarzschild black hole that absorbs the topological defect, giving rise to a static black hole endowed with a monopole’s charge. Besides, we demonstrate how the asymptotic behavior of the Higgs field far from the monopole’s core is shaped by a class of spacetime metrics which includes the ones analyzed here. In order to assess the gravitational properties of this system, we analyze the geodesic motion of both massive and massless test particles moving in the vicinity of such configuration. For the material particles we set the requirements they have to obey in order to experience stable orbits. On the other hand, for the photons we investigate how their trajectories are affected by the gravitational field of this black hole. 相似文献
12.
The hierarchical structure of fermion masses of the Standard Model is explained in split fermion models by localizing the
fermions at different points in an extra dimension. We consider split fermion models with two bulk scalars compactified on an orbifold. In the static case we find analytical expression for the localizer. We also address the issue of stability of the localizer.
We also find exact solutions for the fermion zero modes. We explore the parameter space of the model. We find ample opportunity
for construction of phenomenologically viable theories exist. 相似文献
13.
J. Gasser B. Kubis N. Paver M. Verbeni 《The European Physical Journal C - Particles and Fields》2005,40(2):205-227
Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for
decays. Special emphasis is given to the stability of the inner bremsstrahlung-dominated relative branching ratio versus the K
e3 form factors, and on the separation of the structure-dependent amplitude in differential distributions over the phase space. For the structure-dependent terms, an assessment of the order p
6 corrections is given, in particular, a full next-to-leading order calculation of the axial component is performed. The experimental analysis of the photon energy spectrum is discussed, and other potentially useful distributions are introduced.Received: 9 December 2004, Published online: 21 February 2005PACS:
13.20.Eb, 11.30.Rd, 12.39.Fe 相似文献
14.
We investigate whether the new horizon first law proposed recently still work in f(R) theory. We identify the entropy and the energy of black hole as quantities proportional to the corresponding value of integration, supported by the fact that the new horizon first law holds true as a consequence of equations of motion in f(R) theories. The formulas for the entropy and energy of black hole found here are in agreement with the results obtained in literatures. For applications, some nontrivial black hole solutions in f(R) theories have been considered, the entropies and the energies of black holes in these models are firstly computed, which may be useful for future researches. 相似文献
15.
In a recent paper (Sharif and Shamir in Class. Quantum Grav. 26:235020, 2009), we have studied the vacuum solutions of Bianchi
types I and V spacetimes in the framework of metric f (R) gravity. Here we extend this work to perfect fluid solutions. For this purpose, we take stiff matter to find energy density
and pressure of the universe. In particular, we find two exact solutions in each case which correspond to two models of the
universe. The first solution gives a singular model while the second solution provides a non-singular model. The physical
behavior of these models has been discussed using some physical quantities. Also, the function of the Ricci scalar is evaluated. 相似文献
16.
In this paper, we reconstruct cosmological models in the framework of f(R,T) gravity, where R is the Ricci scalar and T is the trace of the stress-energy tensor. We show that the dust fluid reproduces ΛCDM, phantom–non-phantom era and phantom cosmology. Further, we reconstruct different cosmological models, including the Chaplygin
gas, and scalar field with some specific forms of f(R,T). Our numerical simulation for the Hubble parameter shows good agreement with the BAO observational data for low redshifts,
z<2. 相似文献
17.
During the last decade, as the experimental and computing means and techniques have rapidly evolved, the experimental investigation of the f7/2-shell nuclei has gained renewed interest. TheN = Z nuclei studied with the GASP array range from 44Ti to 52Fe. The results extended the knowledge of their structure up to high spins and excitation energies, above band terminations, where the competition with the charged-particles emission was initially thought to obscure the possibility of gamma-ray spectroscopy investigation. The paper highlights some of the most outstanding properties of these nuclei such as the nuclear rotation and backbending effects, band termination states, yrast traps, non-natural parity bands, competition between T = 0 and T = 1 pn pairing modes.Received: 30 October 2002, Published online: 16 March 2004PACS:
21.10.-k Properties of nuclei; nuclear energy levels - 21.60.Cs Shell model - 23.20.Lv
transitions and level energies - 27.40. + z
C.A. Ur: On leave from NIPNE Bucharest, Romania 相似文献
18.
V. Cirigliano H. Neufeld H. Pichl 《The European Physical Journal C - Particles and Fields》2004,35(1):53-65
We present a detailed numerical study of the Ke3 decays to
in chiral perturbation theory with virtual photons and leptons. We describe the extraction of the CKM matrix element |Vus| from the experimental Ke3 decay parameters. We propose a consistency check of the K + e3 and K0e3 data that is largely insensitive to the dominating theoretical uncertainties, in particular the contributions of
. Our analysis is highly relevant in view of the recent high statistics measurement of the K + e3 branching ratio by E865 at Brookhaven which does not indicate any significant deviation from CKM unitarity but rather a discrepancy with the present K0e3 data.Received: 22 January 2004, Published online: 30 April 2004Work supported in part by IHP-RTN, Contract No. HPRN-CT2002-00311 (EURIDICE) and by Acciones Integradas, Project No. 19/2003 (Austria), HU2002-0044 (MCYT, Spain) 相似文献
19.
The well-known energy problem is discussed in f (R) theory of gravity. We use the generalized Landau–Lifshitz energy–momentum complex in the framework of metric f (R) gravity to evaluate the energy density of plane symmetric solutions for some general f (R) models. In particular, this quantity is found for some popular choices of f (R) models. The constant scalar curvature condition and the stability condition for these models are also discussed. Further,
we investigate the energy distribution of cosmic string spacetime. 相似文献
20.
The conditions and the mechanisms of crystallization by liquid-phase epitaxy of undoped and Ce3+-doped RAlO3 (R = Lu, Lu-Y, Y, Tb) single-crystalline films on YAlO3 single-crystalline substrates at a considerable mismatch between the lattice constants of the single-crystalline films and
the substrate are analyzed. The maximum values of this mismatch at which the stable growth of the single-crystalline films
is observed are determined. It is demonstrated that transition layers are present between the substrates and the grown single-crystalline
films in which the difference between the lattice parameters of the single-crystalline film and the substrate is diminished.
The optical and luminescence characteristics of the undoped and Ce3+-doped RAlO3 (R = Y, Y-Lu, Lu, Tb) single-crystalline films, as well as the scintillation characteristics of the (Lu-Y)AlO3: Ce single-crystalline films under excitation by alpha-particles of the 239Pu source (5.15 MeV), are investigated. 相似文献