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1.
Assuming a simple model for the compound SmS we have performed calculations which indicate a definite tendency toward the observed semiconductor-metal phase transition under pressure. Our results lend support to the hypothesis that the transition is associated with a change in 4f occupancy of the Sm ion. 相似文献
2.
N. N. Stepanov N. V. Sharenkova V. V. Kaminskii M. M. Kazanin 《Physics of the Solid State》2012,54(8):1681-1683
The behavior of internal microstresses, the size of the X-ray coherent scattering region, and the residual amount of the metal phase during the cyclic loading of SmS single crystals at hydrostatic pressure above the critical pressure of the semiconductor-metal phase transition has been investigated. It has been shown that the samples are destroyed as the microstresses reach the values corresponding to the ultimate stress of SmS single crystals. As the number of loading cycles increases, the coherent scattering region gradually decreases, which is accompanied by a decrease in the amount of the metal phase in the samples. 相似文献
3.
Preparation and analysis of thin films containing samarium sulfide (SmS) is presented along with a review of relevant SmS properties. Films were deposited onto unheated substrates by the reactive evaporation of samarium in a backpressure of hydrogen sulfide. This technique yields films that contain significant quantities of impurities; however high-quality SmS crystals are also formed. A phase transition in the SmS crystals was observed both by spectrophotometry and x-ray diffraction. The film optical properties can be modeled with an effective medium calculation. The predicted spectra successfully reproduce the observed qualitative features over a wide range of wavelengths. 相似文献
4.
The structure of a metallic-phase film produced by mechanical polishing of polycrystalline SmS 总被引:1,自引:0,他引:1
N. V. Sharenkova V. V. Kaminskii A. V. Golubkov L. N. Vasil’ev G. A. Kamenskaya 《Physics of the Solid State》2005,47(4):622-626
X-ray diffraction is used to study the structure of a metallic-phase film that forms during controlled polishing of homogeneous polycrystalline semiconducting Sm1+xS samples. Structural changes that appear in the semiconducting phase under these conditions were studied. The x dependence of the thickness of the metallic layer forming on the sample surface is analyzed to explain the effect of excess samarium ions on the transformation parameters. The cause of the stabilization of the metallic modification of SmS after polishing is terminated is explained using estimates based on the measured sizes of coherent domains in samples of different compositions. The appearance and stabilization of the metallic phase are related to a decrease in and subsequent conservation of the coherent-domain size, respectively. 相似文献
5.
The mechanism of the emf appearing in a semiconductor under heating in the absence of external temperature gradients, an effect revealed by the present authors, is considered. The experiments were performed on samarium sulfide (SmS) single crystals. It is shown that the emf is generated by an abrupt change in the samarium ion valence, which results from the ion screening by the electrons activated into the conduction band. We succeeded in obtaining emf pulses 1.3 s long with an amplitude of up to 2.5 V at T ~ 460 K, as well as CW emf generation within the 375-to 405-K temperature interval with a maximum value of ~50 mV. 相似文献
6.
Within the framework of the Landau theory of phase transitions and the density functional method, it is shown that the structural
transformation from a body-centered cubic phase to a rhombohedral phase revealed in vanadium at 69 GPa is a first-order deformation
phase transition close to a second-order phase transition. 相似文献
7.
Yu. B. Kudasov 《Technical Physics》1998,43(12):1440-1444
An analysis is made of the diffusion of a static (slowly varying) magnetic field in a conductor in which a first-order phase
transition to the insulating state takes place under the action of the Joule heating. An investigation is made of the case
of subsonic propagation of the phase boundary. A (V1−X
CrX)2O3 solid solution is analyzed as a model substance. The application of this effect in pulsed high-current circuit breakers is
discussed.
Zh. Tekh. Fiz. 68, 43–48 (December 1998) 相似文献
8.
Model calculations explaining the mechanism of the semiconductor-metal phase transition in SmS are carried out. The model, slightly modified, draws upon methods employed earlier to account for the concentration mechanism of piezoelectric resistance and thermovoltaic effect in SmS. The stable results are obtained from calculations for the phase transition pressure under hydrostatic compression (P c ~ 700 MPa at T = 300 K). On this basis, it is concluded that the 4f levels of samarium ions and their excited states determine the value of P c . The proposed model is universal in character and can be applied to calculations of other effects in SmS, which are associated with Mott transitions and are accompanied by collective carrier delocalization. 相似文献
9.
V.A. Voloshin 《Solid State Communications》1982,42(5):347-351
A hypothesis is put forward that at pressure 30 kbar f-orbitals begin to participate in generation of a chemical bond between a rare-earth ion and oxygen. This phenomenon is presumed to be responsible for spectral changes observed in praseodymium ethylsulfate at its compression. 相似文献
10.
The dynamics of 90-degree interphase domain walls during a first-order Morin-type spin-reorientation phase transition is studied
theoretically. It is shown that an oscillatory motion of the walls with an amplitude that depends linearly on the field amplitude,
as well as a drift motion of the wall at a velocity proportional to the square of the field amplitude, are driven by an external
oscillating magnetic field. Drift of the entire domain structure as a whole is predicted to be possible.
Fiz. Tverd. Tela (St. Petersburg) 41, 274–282 (February 1999) 相似文献
11.
12.
S. V. Tarasenko 《Optics and Spectroscopy》2003,94(6):934-939
Conditions are determined at which the combined effect of the lattice and the spatial dispersion gives rise to the formation of a surface polariton with the participation of a soft mode in the vicinity of a dipole ferroelastic phase transition. 相似文献
13.
The high temperature x-ray method is used to study A1-B2 phase transitions in Cu-Pd alloys near a composition of 40 at.% Pd. An anomalous increase in mean square atomic displacements and a non-monotonic change in the lattice parameter with temperature are observed at the onset of the phase transitions. It is shown that upon heating of the quenched solid solution above 300°C the solid solution decomposes with formation of a two-phase mixture A1 + B2. Activation energies of the processes accompanying the structural phase transitions are calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 67–72, June, 1988. 相似文献
14.
The influence of the heat treatment of Fe0.1TiTe2 samples on the appearance of thermally induced “levitation” is investigated. It is postulated that this phenomenon is most
probably caused by undamped fluctuations of the electric charge on the surface of particles of the material.
Fiz. Tverd. Tela (St. Petersburg) 41, 680–683 (April 1999) 相似文献
15.
16.
Nikolaos Tetradis 《Zeitschrift fur Physik C Particles and Fields》1993,57(2):331-337
The perturbative effective potential for the Standard Model develops a barrier, at temperatures around the electroweak scale, which separates the minimum at zero field and a deeper non-zero minimum. This could create out of equilibrium conditions by inducing the localization of the Higgs field in a metastable state around zero. In this picture vacuum decay would occur through bubble nucleation. I show that there is an upper bound on the Higgs mass for the above scenario to be realized. The barrier must be high enough to prevent thermal fluctuations of the Higgs expectation value from establishing thermal equilibrium between the two minima. The upper bound is estimated to be lower than the experimental lower limit. This also imposes constraints on extensions of the Standard Model constructed in order to generate a strongly first order phase transition. 相似文献
17.
18.
Lindenberg AM Kang I Johnson SL Missalla T Heimann PA Chang Z Larsson J Bucksbaum PH Kapteyn HC Padmore HA Lee RW Wark JS Falcone RW 《Physical review letters》2000,84(1):111-114
Time-resolved x-ray diffraction with picosecond temporal resolution is used to observe scattering from impulsively generated coherent acoustic phonons in laser-excited InSb crystals. The observed frequencies and damping rates are in agreement with a model based on dynamical diffraction theory coupled to analytic solutions for the laser-induced strain profile. The results are consistent with a 12 ps thermal electron-acoustic phonon coupling time together with an instantaneous component from the deformation-potential interaction. Above a critical laser fluence, we show that the first step in the transition to a disordered state is the excitation of large amplitude, coherent atomic motion. 相似文献
19.
Abstract Existing experimental data for the antiferroelastic phase transition in strontium titanate are reviewed and analysed using a Landau free energy of the form ΔG = 1/2Aθs (cothθs/ Tc-colb.θ/T)Q2 + 1/4BQ 4 + 1/6CQ 6, with A = 0·6472 J K?1mol?1, B = 29·12 Jmol?1, C = 39·27 Jmol, T c= 105·6 K, θ S = 60·8 K. The temperature dependence of the critical exponent is found to be due to the delicate balance between the Q 4 and Q 6 terms in the free energy expansion, and the saturation of the order parameter at low temperatures. The spontaneous strains observed in this phase transition are not consistent with simple rotation of the TiO6 octahedra around [001], An alternative model is proposed, where these octahedra expand in order to preserve the volume of the twelve-fold co-ordinated Sr site and the spacing between SrO3 pseudo-closepacked layers. 相似文献
20.
We present the phase transition of high Curie temperature InMnP system grown by liquid phase epitaxy. InMnP system has a distribution of uniform islands on the surface layer which has a width of 40 nm and height of 30 nm. Two kinds of phase transition in the magnetization were observed. The origin of these structures and their influence for the magnetization are discussed from the view of two-dimensional Ising model. 相似文献