Pressure dependence of the Raman modes of LiIO3

The pressure dependence of the Raman modes of LiIO₃ at room temperature was studied up to 78 kbar in a gasketed sapphire-anvil cell. Nonlinear frequency increases were observed in all modes involving translation of the light Li⁺ atom. This behavior is more marked in the lowest frequency A mode, which involves translations along the c-axis. Other modes slow smaller linear frequency increases, with increasing pressure. The TO-LO splittings of all but the highest frequency modes are seen to be independent of pressure. This indicates that charge transfer between ions is negligible. For modes derived from internal vibrations of IO₃^- ions an increase in this splitting with increasing pressure is observed, indicating some intra-ion redistribution of charge. Mode Grüneissen parameters are obtained for representative modes of all allowed symmetries in each of the three frequency ranges in which the Raman spectrum of the material can be divided.     

Raman scattering in FeF3

Peaks in the FeF₃ phonon Raman spectrum are assigned to the A_1g(312 cm^-1) and E_g(105, 187, 450 cm^-1) representations of the D⁶_3d group. Anomalous temperature dependence of the frequency, intensity and line width of the 187 cm^-1 line has been observed.     

Light scattering by polaritons associated with ordinary photons in LiIO3

The upper ordinary polariton dispersion branch associated with photons has been experimentally investigated in the region where the coupling with phonons is non-negligible. Good agreement is obtained with calculated dispersion curves. The appearance of minima of the scattering cross sections is discussed.     

Raman scattering in monodomain RbCoF3

Polarized Raman spectra are reported for scattering from a single oriented antiferromagnetic domain in RbCoF₃. Monodomain samples were achieved by the application of a small [100] uniaxial stress. Spectra were recorded at 2 K using non-absorbed, orange laser light. The D_4h symmetry assignments for the principal features are: 34(Γ⁺₅), 335 (Γ⁺₁ and Γ⁺₁), 420 (Γ⁺₁), 950 (Γ⁺₃) and 1050 cm^-1 (Γ⁺₁). These results are not consistent with the prediction of previous models for magnetic exciton scattering.     

Raman scattering in magnetic US3

A Raman scattering investigation of magnetic US₃ has been made from 7 to 300 K. Comparison of room temperature spectra with those of the non magnetic isostructural sulfide HfS₃ allowed the assignment of most of the lines to $\textcolor{red}{}\text{=}\text{0}$ optical phonons. Drastic changes take place in the 10?150 cm^?1 range when lowering the temperature down to 7 K : four equally spaced lines appear at 54, 72.5, 91 and 109.5 cm^?1. Three of them broaden significantly with increasing temperature and disappear near 50 K, at which previous measurements indicate a maximum in the magnetic susceptibility and suggest a magnetic phase transition. The stronger fourth line is still observed at 100 K and merges into a phonon line at higher temperature. These four lines are attributed to electronic transitions within the 5f² configuration of U⁴⁺. Their temperature dependences appear to involve a spin-dependent scattering mechanism and are consistent with antiferromagnetic ordering.     

Raman scattering from two-phonon resonance states in SrTiO3

Two-phonon Raman spectroscopy has been performed on SrTiO₃ from 13.3 to 295 K. In the low frequency region, softenings of two bands are observed. With decreasing temperature, they showed sharpening of structure and intensity transfer. It is concluded that one band comes from two-phonon resonance state of ferroelectric soft mode. Theoretical investigations are performed by using thermodynamic Green's function and by taking into account quartic anharmonicity of the lattice force.     

Resonance Raman scattering from amorphous As2S3

Resonance Raman scattering from amorphous As₂S₃, obtained by temperature tuning the band edge through the He-Ne 6328 Å laser line, is reported.     

Raman scattering from 1T-TaS2

Raman measurements on the 1T-polytype of TaS₂ are reported. In the commensurate charge density wave state, a large number of Raman-active peaks are observed below 400 cm^-1. Most of these peaks are attributed to k = 0 optic phonons resulting from superlattice formation.     

Raman scattering from phonons and magnons in antiferromagnetic Fe3BO6

Raman scattering by phonons and by magnon pairs has been observed in Fe₃BO₆. Of the predicted 60 Raman-active modes, 39 have been identified and classified according to their symmetries. The two-magnon band shows a strong decrease in intensity with increasing temperature, and almost vanishes close to T_N = 508 K. The origin of this effect is attributed to the existence of a nearly dispersionless magnon branch.     

The Raman scattering of Zn3As2

The Raman scattering of Zn₃As₂ crystal is presented within 50–420 cm⁻¹ energy range. The group theory method are used to determine symmetry of the allowed lattice modes, and further to discuss the results obtained.     

Raman scattering in 3RNbS2

Raman scattering spectra on a layer type compound 3RNbS₂ were measured at 300 and 77 K, and three peaks were observed at 382, 325 and 281 cm^?1 at 300 K. The vibration modes were analyzed in terms of Bromley's nearest neighbour model, and a good agreement with the experiment was obtained.     

Raman scattering in CeB6

Raman spectra of phonons in CeB₆ were measured. The observed three peaks were assigned to the A_1g, E_g and F_2g phonon modes. The frequencies of the modes suggest that the Ce ion is in the trivalent state.     

Raman scattering from magnons in CoCl2 and FeCl2

One-magnon Raman scattering has been observed in the metamagnets CoCl₂ and FeCl₂. The k = 0 magnon energies are 16 ± 1 cm^-1 at 21 K and 16.4 ± 0.4 cm^-1 at 12 K, respectively and these values are in good agreement with previous AFMR and neutron scattering results. A search for two-magnon scattering in both compounds was unsuccessful, largely because of masking from nearby first-order phonons and a weak temperature dependent broad band at 140 cm^-1 in CoCl₂, which is assigned to two-phonon scattering from acoustic phonons.     

Enhanced Raman scattering from nano-SnO2 grains

We present the Raman spectra of nano-SnO_{2} grains with sizes from 4nm to 80nm excited by 532nm and 1.06μm lines. The enhanced Raman scattering of the nanograins is observed for both exciting lines when the grain size is less than 8nm. The less the grain size is, the more intensely the Raman scattering is enhanced. According to our results, the enhancements of the Raman intensity are a few tenfolds and different for different exciting lines when the grain size is 4nm. It can be attributed to enhanced Raman scattering by electron－hole pair excitations in the nanograins that originate from sub-microscopic (10nm) size and other defect- and surface-related features. A critical size that divides respective predominance of bulk properties and the defect-, surface-, and size-related features can be determined to be about 8nm.     

Contours pattern in LiIO3 crystal using ruby laser

Contours pattern due to second harmonic generation has been recorded successfully in the nonlinear crystal of LiIO₃ using a partially focused ruby laser beam as the fundamental radiations. The result is verified theoretically.     

Raman scattering of NiS2

Raman scattering measurements of NiS₂ is done and five optical phonon peaks are found. These peaks are assigned to A_g, E_g and 3T_g phonons which are all of the Raman active optical phonons in pyrite-type crystal. The results are compared with those of FeS₂ and MnS₂.     

Raman scattering of LiGaO2

The Raman spectrum of LiGaO₂ is reported together with a preliminary identification of the optical modes and their temperature dependence between 6 and 700 K. The observed temperature dependence of the lines gave no indication for second order processes. However, at low temperatures additional lines have been observed indicating a phase transition at approximately 65 K.     

2LiIO3·HIO3的晶体结构与相变

本文用差热分析、热失重以及X射线衍射等方法,对LiIO₃·HIO₃二元系的相平衡进行了研究,观察了以α-LiIO₃为基的固溶体和以2LiIO₃·HIO₃为基的固溶体的热学性质和晶体结构。2LiIO₃·HIO₃属六方晶系,空间群为P6₃,是α-LiIO₃的同晶型结构。20℃的点阵常数为:α=5.555?,c=4. 关键词：     

Raman scattering in Ag-intercalated TiS2

Ag-intercalated TiS₂ has been investigated using electron diffraction and Raman scattering. The energies of the E_g-1 and A_1g modes in 1T-TiS₂ at 300 K were found to be 232 and 336 cm^-1, respectively. In Ag_0.3TiS₂, at an ambient temperature of 4.2 K, modes were observed at 207, 239, 277, 311, and 347 cm^-1. Three of these modes have been associated with the formation of a superlattice at low temperatures. The superlattice formation was observed by electron diffraction and is attributed to an ordering of the silver atoms at interlayer interstices.     

Raman scattering in quasi-one-dimensional ZrTe5

Raman scattering experiments on the compound ZrTe₅ isostructural with HfTe₅ have been performed at temperatures between 300–313 K. The Raman spectra of ZrTe₅ resemble those of HfTe₅ excepting two high frequency modes which should include the most characteristic diatomic mode. In spite of structural similarity with the transition-metal trichalcogenides, the Raman scattering activity cannot be directly compared. These unexpected results and the unusual temperature dependence of the Raman intensities suggest the possibility of a structural instability in HfTe₅ and/or ZrTe₅ in relation with the anomalies in the transport properties and in the X-ray forbidden reflections.