共查询到20条相似文献,搜索用时 31 毫秒
1.
A. G. Gavriliuk I. A. Trojan I. S. Lyubutin S. G. Ovchinnikov V. A. Sarkissian 《Journal of Experimental and Theoretical Physics》2005,100(4):688-696
The high-pressure magnetic states of iron borate 57FeBO3 single-crystal and powder samples have been investigated in diamond anvil cells by nuclear forward scattering (NFS) of synchrotron radiation at different temperatures. In the low-pressure (0 < P < 46 GPa) antiferromagnetic phase, an increase of the Neél temperature from 350 to 595 K induced by pressure was found. At pressures 46–49 GPa, a transition from the antiferromagnetic to a new magnetic state with a weak magnetic moment (magnetic collapse) was discovered. It is attributed to the electronic transition in Fe3+ ions from the high-spin 3d5 (S = 5/2, 6A1g) to the low-spin (S = 1/2, 2T2g) state (spin crossover) due to the insulator-semiconductor-type transition with extensive suppression of strong d-d electron correlations. At low temperatures, NFS spectra of the high-pressure phase indicate magnetic correlations in the low-spin system with a magnetic ordering temperature of about 50 K. A tentative magnetic P-T phase diagram of FeBO3 is proposed. An important feature of this diagram is the presence of two triple points where magnetic and paramagnetic phases of the high-spin and low-spin states coexist. 相似文献
2.
V. I. Petinov 《Technical Physics》2017,62(6):882-889
Influence of temperature and magnetic field H on magnetism of spherical Gd nanoparticles of different sizes (89, 63, 47, 28, and 18 nm) was studied in the temperature range 250 K < T < 325 K. The particles were obtained by metal vapor condensation in the flow of helium. The particles with d = 18 nm did not show a magnetic transition; their structure is a combination of two cubic phases (FCC1 and FCC2). Large particles remained in the HCP phase and had an admixture of the FCC1 phase, the amount of which decreased as the particle sizes increased; magnetic transition took place at T c = 293 K. The admixture of O2 did not alter the structure but decreased the magnetization σ and magnetic permeability μ. An orientation transition in polycrystalline gadolinium initiated by the magnetic field H was proved in an experiment. The orientation transition in Gd particles smaller than 63 nm, the magnetic structure of which is close to the single-domain structure, occurred near T c without the influence of H. 相似文献
3.
N. I. Kourov Yu. A. Perevozchikova H. W. Weber V. V. Marchenkov 《Physics of the Solid State》2016,58(7):1355-1360
The transport properties of half-metallic ferromagnetic Heusler alloys Co2MeAl (Me = Ti, V, Cr, Mn, Fe are transition 3d metals) have been measured in the temperature range of 4–900 K. The specific features of the behavior of the resistivity have been considered in the framework of the two-current model of conductivity that takes into account the existence of the energy gap in the electronic spectra of the alloys near the Fermi level of one of electron subbands that differs in the spin direction. 相似文献
4.
P. Castorina D. E. Miller H. Satz 《The European Physical Journal C - Particles and Fields》2011,71(6):1673
We consider deconfined matter in SU(N) gauge theory as an ideal gas of transversely polarized quasi-particle modes having a temperature-dependent mass m(T). Just above the transition temperature, the mass is assumed to be determined by the critical behavior of the energy density
and the screening length in the medium. At high temperature, it becomes proportional to T as the only remaining scale. The resulting (trace anomaly based) interaction measure Δ=(ϵ−3P)/T
4 and energy density are found to agree well with finite temperature SU(3) lattice calculations. 相似文献
5.
Pramod Bhatt E. Carlegrim A. Kanciurzewska M. P. de Jong M. Fahlman 《Applied Physics A: Materials Science & Processing》2009,95(1):131-138
Thin film iron-tetracyanoethylene Fe(TCNE)
x
, x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed
physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron
spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE)
x
is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results.
The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge
transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE)
x
system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T
C
) seen for Fe(TCNE)
x
-type magnets. 相似文献
6.
I. V. Ovchinnikov T. A. Ivanova A. N. Turanov R. R. Garipov 《Physics of the Solid State》2009,51(10):2058-2063
Significant differences in the manifestation of spin-crossover properties of the mesogen compounds [FeL
2]X with oxysalicylidene-N′-ethyl-N-ethylenediamine ligands L and anions X = PF6− and SCH− have been found by means of electron paramagnetic resonance. The electron paramagnetic resonance data and the quantum-chemical
calculation within the density functional theory enables us to establish that the observed specific features are associated
with the incorporation of the SCH− ion into the first coordination sphere of the Fe(III) ion. The role of the transition of the material to the liquid-state
phase in the formation of a low-dimensional (two-dimensional) structure with stronger intermolecular interactions has been
revealed. 相似文献
7.
L. K. Aminov A. A. Ershova V. N. Efimov S. L. Korableva I. N. Kurkin B. Z. Malkin A. A. Rodionov 《Physics of the Solid State》2010,52(10):2070-2075
The EPR spectra of Ce3+ impurity ions in LiYF4, LiLuF4, and LiTmF4 double-fluoride single crystals have been investigated at a frequency of ∼9.3 GHz in the temperature range 5–25 K. The effective
g factors of the ground Kramers doublet of the cerium ions in three crystals are close to each other (g
‖ = 2.737, g
⊥ = 1.475 for LiYF4:Ce3+). A superhyperfine structure of the EPR spectrum of Ce3+ ions in the LiTmF4 Van Vleck paramagnet has been observed in the external magnetic field B oriented along the crystallographic axis c (B ‖ c). The superhyperfine structure of the EPR soectra of the Ce3+ ions in the LiYF4 and LiLuF4 diamagnetic matrices is resolved for B ⊥ c. Possible factors responsible for this pronounced difference in the properties of the systems studied have been discussed. 相似文献
8.
F. Finkel D. Gómez-Ullate A. González-López M.A. Rodríguez R. Zhdanov 《Communications in Mathematical Physics》2003,233(2):191-209
The B
N
hyperbolic Sutherland spin model is expressed in terms of a suitable set of commuting Dunkl operators. This fact is exploited
to derive a complete family of commuting integrals of motion of the model, thus establishing its integrability. The Dunkl
operators are shown to possess a common flag of invariant finite-dimensional linear spaces of smooth scalar functions. This
implies that the Hamiltonian of the model preserves a corresponding flag of smooth spin functions. The discrete spectrum of
the restriction of the Hamiltonian to this spin flag is explicitly computed by triangularization. The integrability of the
hyperbolic Sutherland spin chain of B
N
type associated with the dynamical model is proved using Polychronakos's ``freezing trick'.
Received: 14 February 2002 / Accepted: 19 June 2002 Published online: 10 December 2002
RID="*"
ID="*" Corresponding author. E-mail: artemio@fis.ucm.es
RID="**"
ID="**" On leave of absence from Institute of Mathematics, 3 Tereschenkivska St., 01601 Kyiv-4 Ukraine
Communicated by L. Takhtajan 相似文献
9.
The conductivity of poly(N-vinylimidazole) (PVIM) and its fluoroborate salt (PVIM–HBF4) are reported here. N-vinylimidazole is polymerized by free radical method and PVIM–HBF4 is prepared by acidification of PVIM with HBF4. The polyelectrolyte so formed has been characterized by infrared, hydrogen-1 nuclear magnetic resonance, thermogravimetric
analyzer, and differential scanning calorimetry. Frequency and temperature dependence of AC conductivity has been studied
to learn about the electrical conduction behavior in the materials. The electrical conductivity of the new material is found
to be in the range of 10−5 to 10−6 S cm−1.There is about 102- to 103-fold increase in conductivity of the polyelectrolyte. The material is shown to be a predominantly ionic conductor with t
ion ≈ 0.88. Apparent activation energies are found to be 0.397 and 0.250 eV for the polymer and the polyelectrolyte, respectively. 相似文献
10.
Y. Xiao Y. Su C. M. N. Kumar C. Ritter R. Mittal S. Price J. Perßon Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(2):113-121
The physical and structural properties of Fe1.11Te and
Fe1.11Te0.5Se0.5 have been investigated by means of
X-ray and neutron diffraction as well as physical property
measurements. For the Fe1.11Te compound, the structure
distortion from a tetragonal to monoclinic phase takes place at 64 K
accompanied with the onset of antiferromagnetic order upon cooling.
The magnetic structure of the monoclinic phase was confirmed to be
of antiferromagnetic configuration with a propagation vector
k = (1/2, 0, 1/2) based on Rietveld refinement of neutron
powder diffraction data. The structural/magnetic transitions are
also clearly visible in magnetic, electronic and thermodynamic
measurements. For superconducting Fe1.11Te0.5Se0.5
compound, the superconducting transition with T
c
= 13.4 K
is observed in the resistivity and ac susceptibility measurements.
The upper critical field H
c2 is obtained by measuring
the resistivity under different magnetic fields. The Kim’s critical
state model is adopted to analyze the temperature dependence of the
ac susceptibility and the intergranular critical current density is
calculated as a function of both field amplitude and temperature.
Neutron diffraction results show that
Fe1.11Te0.5Se0.5 crystalizes in tetragonal structure
at 300 K as in the parent compound Fe1.11Te and no structural
distortion is detected upon cooling to 2 K. However an anisotropic
thermal expansion anomaly is observed around 100 K. 相似文献
11.
V. V. Sikolenko I. O. Troyanchuk D. V. Karpinsky A. Rogalev F. Wilhelm R. Rosenberg D. Prabhakaran E. A. Efimova V. V. Efimov S. I. Tiutiunnikov I. A. Bobrikov 《Physics of the Solid State》2018,60(2):288-291
Spin transitions of cobalt ions in LaCoO3 single crystals have been studied by the method of X-ray magnetic circular dichroism (XMCD) at the K- and L2,3-edges of Co3+ ions. The orbital momentum of cobalt ions obtained for the K-edge at the 3d level in the region of the spin transition in the temperature range from 25 to 120 K increases by a factor of approximately 1.6, whereas the slope of the magnetization curve value in the same temperature range and magnetic field increases by a factor of more than 10. XMCD experiments at the cobalt L2,3-edges demonstrate gradual growth of the ratio of the orbital momentum to the spin one L/S from 0.48 to 0.53 in the temperature range from 60 K to 120 K. 相似文献
12.
M. Hamani Daouda Manuel E. Rodrigues M. J. S. Houndjo 《The European Physical Journal C - Particles and Fields》2012,72(2):1893
We develop the reconstruction of the f(T) gravity model according to the holographic dark energy. T is the torsion scalar and its initial value from the teleparallel gravity is imposed for fitting the initial value of the
function f(T). The evolutionary nature of the holographic dark energy is essentially based on two important parameters, Ω
V
and ω
V
, respectively, the dimensionless dark energy and the parameter of the equation of state, related to the holographic dark
energy. The result shows a polynomial function for f(T), and we also observe that, when Ω
V
→1 at the future time, ω
V
may cross −1 for some values of the input parameter b. Another interesting aspect of the obtained model is that it provides a unification scenario of dark matter with dark energy. 相似文献
13.
T. B. Charikova N. G. Shelushinina G. I. Kharus O. E. Sochinskaya A. A. Ivanov 《Physics of the Solid State》2009,51(11):2229-2234
The temperature dependences of the resistivity of single-crystal films of the Nd2 − x
Ce
x
CuO4 + δ
n-type superconductors with x = 0.14 (underdoped region) and x = 0.15 (optimal doping region) and different degrees of disorder δ have been investigated in various magnetic fields (B ‖ c, J ‖ ab) in the temperature range 0.4–300 K. It has been demonstrated that there are differences in the behavior of the dependences
of the slope of the upper critical field $
(dB_{c2} /dT)_{T \to T_c }
$
(dB_{c2} /dT)_{T \to T_c }
on the disorder parameter for the underdoped samples (x = 0.14) and the samples with the optimal doping (x = 0.15). The study of the dependence of the slope of the upper critical field on the degree of disorder has made it possible
to discriminate experimentally between the superconductors with the d pairing and anisotropic s pairing. It has been revealed that the relative stability of the n-type superconductor with the optimal doping with respect to disordering is possibly due to the strong anisotropy of impurity
scattering with symmetry of the d type. 相似文献
14.
15.
I. L. Drichko I. Yu. Smirnov A. V. Suslov O. A. Mironov D. R. Leadley 《Journal of Experimental and Theoretical Physics》2010,111(3):495-502
Magnetoresistivity ρ
xx
and ρ
xy
and the acoustoelectronic effects are measured in p-Si/SiGe/Si with an impurity concentration p = 1.99 × 1011 cm−2 in the temperature range 0.3–2.0 K and an tilted magnetic field up to 18 T. The dependence of the effective g factor on the angle of magnetic field tilt θ to the normal to the plane of a two-dimensional p-Si/SiGe/Si channel is determined. A first-order ferromagnet-paramagnet phase transition is observed in the magnetic fields
corresponding to a filling factor ν = 2 at θ ≈ 59°–60°. 相似文献
16.
A. Ehresmann W. Kielich S. Klumpp P. V. Demekhin I. D. Petrov V. L. Sukhorukov B. M. Lagutin R. Müller-Albrecht H. Schmoranzer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(2):161-169
Photon-induced fluorescence spectroscopy was applied to measure absolute
fluorescence emission cross sections from the main 5s- and first satellite
levels of XeII upon photoionization from XeI in a broad exciting-photon energy
range (23–28 eV) with 20 meV bandwidth of the exciting radiation and in a
narrow energy range (23.25–23.50 eV) with a bandwidth of 1.8 meV. The
average fluorescence resolution amounted to 0.07 nm.
Fluorescence emission cross sections were computed with taking into account
many-electron correlations and doubly excited states. Computed cross sections,
especially in integrated form, agree well with the results of experiment. Many
features observed in the high resolution experiment are identified to
originate from nf-Rydberg series. 相似文献
17.
Mostefa Djermouni Ali Zaoui Salima Kacimi Nawel Benayad Abdelkader Boukortt 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(2):28
Ferromagnetism and ferroelectricity in Eu monochalcogenides have been investigated by ab initio density functional theory in the DFT+U approach. Exchange interaction parameters and Curie temperatures under pressure are studied and discussed using Heisenberg Hamiltonian with first and second-nearest-neighbor interactions. The calculations showed that the hydrostatic pressure perfectly improves the Curie temperature (EuO: T C = 175 K; EuS: T C = 33.8 K) and in the other hand it cannot induce the spontaneous polarization (P s ). The effect of uniaxial and biaxial pressure is also studied. Although the uniaxial strains slightly increases the Curie temperature, it ensures the ferrolectricity in these systems by producing a spontaneous polarization of the order of P s (EuO) = 57.50 μC/cm2 and P s (EuS) = 42.86 μC/cm2 with pressures of 5% and 4%, respectively. The search for new model systems is a necessity to better understand the physics related to multiferroïc materials and to consider possible applications. 相似文献
18.
N. I. Kourov V. V. Marchenkov Yu. A. Perevozchikova A. V. Korolev H. W. Weber 《Physics of the Solid State》2016,58(12):2434-2437
The temperature dependences of the magnetization of ferromagnetic Heusler alloys Co2 YAl, where Y = Ti, V, Cr, Mn, Fe, and Ni have been studied at H = 50 kOe in the range 2 K < T < 1100 K. It is shown that the high-field (H ≥ 20 kOe) magnetization is described within the Stoner model. 相似文献
19.
Vladimir A. Kulbachinskii Boris M. Bulychev Vladimir G. Kytin Alexey V. Krechetov Valeriy P. Tarasov Elizaveta A. Konstantinova Yuriy A. Velikodnyi Yuriy B. Muravlev Andrey V. Zoteev 《Central European Journal of Physics》2010,8(1):101-112
Sodium fullerides Na
n
C60 (n = 2, 3) have been synthesized by a liquid phase reaction and investigated with X-ray diffraction (XRD), nuclear magnetic
resonance (NMR), electron paramagnetic resonance, and differential thermal analysis. XRD data indicate that the crystal structure
of Na2C60 at 300 K is face centered cubic (FCC). A phase transition from primitive cubic to FCC crystal structure has been observed
in this work in Na2C60 fulleride at 290 K. The transition is accompanied by the step-like change of paramagnetic susceptibility. The crystal structure
of Na3C60 is more complicated than, and different from, what has been reported in the literature. A nearly seven-fold increase of paramagnetic
susceptibility with increasing temperature has been observed in the Na3C60 fulleride at 240–260 K. In the same temperature range, a new line at about 255 ppm appears in the 23Na NMR spectrum, indicating a significant increase of electron density near the Na nucleus. The observed effect can be explained
by a metal-insulator transition caused by a structural transition. 相似文献
20.
Ivan I. Stoikov Elena A. Yushkova Igor S. Antipin Alexander I. Konovalov 《Journal of nanoparticle research》2011,13(12):6603-6611
The effect of solvent nature and temperature on the formation of 3D-dimensional SAM (self-assembled monolayers on nanoparticles)
based on synthetically available stereoisomers of p-tert-butyl thiacalix[4]arenes tetrasubstituted at the lower rim by pyrrolidide and octylamide groups (cone, partial cone, and 1,3-alternate) with lithium and silver nanoparticles were determined by dynamic light-scattering and transmission electron microscopy.
It was found that the variation of the temperature of the system and the nature of the solvent leads to the formation discrete
or extended particles (CH2Cl2) (98–110 nm), nanostructures (CH3CN) (120–295 nm) or three-dimensional SAM (DMF) (1–13 nm; 46–622 nm). 相似文献