The complete Raman spectra of a single crystal LiNiPO4 for wide temperature range are reported. Of the 36 Raman-active modes predicted by group theory, 33 have been detected. successfully analyzed in terms internal (PO4)3− and external modes. Multiphonon scattering is also discussed. Low-frequency lines, observed antiferromagnetic phase, assigned to magnon discussed briefly.

Point contacts have been discovered to present excellent and unprecedented characteristics when used as gas sensors. A novel concept has tested successfully opens the way useful applications. Copper point were investigated in media such NOx, HCl, H2S human breath. They reveal high sensitivity these gases: measured signal increases by 2-3 orders of magnitude upon exposure. Sensor parameters are fully restored action ceases. Stable reproducibility experimental results was observed after...

A giant softening by $30\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ of the 490 and $620\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ Jahn-Teller breathing optical phonon modes is observed in Raman spectroscopy below Curie temperature single crystalline $\mathrm{La}\mathrm{Mn}{\mathrm{O}}_{3+\ensuremath{\delta}}$ $(0.085\ensuremath{\leqslant}\ensuremath{\delta}\ensuremath{\leqslant}0.125)$. pseudogaplike suppression a continuum Fano antiresonance at...

The Raman scattering spectrum of single crystal TbFe3(BO3)4 was studied in the frequency range 3–500 cm−1 at temperatures from 2 to 300 K. It found that high- and low-temperature phases there exist additional phonon lines which were not known before. In high-temperature phase, these originate LO–TO splitting polar phonons. Appearance low temperature phase is due both a reduction symmetry under transition an increase primitive cell volume. established frequencies some magneto-ordered are...

This work describes the gas-sensitive properties of a one-dimensional organic conductor before and after exposure to carbon monoxide human breath. A sensitive material, an anion-radical salt tetracyanoquinodimethane, has been investigated by infrared spectroscopy electrical resistivity measurements. Drastic spectral changes are found gas showing that compound interacts strongly with breath, monoxide, ammonia. Under breath action resistance more than three orders magnitude while adsorption...

Optical absorption spectra of the layered semiconductor MnPS3 are measured in temperature range 12-160 K, which covers magnetic ordering temperature. It is shown that interband optical coefficient well described by a model for direct allowed transitions three-dimensional compounds, while increases lead to an effective reduction band gap. A theoretical proposed crystalline MnPS3. comparison experimental data with theory indicates chosen adequate.

Results of comprehensive, detailed studies the magnetic and resistive properties nanocompound p-La0.8Mn1.04O3.5 at temperatures 4.2–300 K in fields up to 9 T are reported. These temperature, field, frequency dependences magnetization susceptibility indicate that, below T* ≈ 265 nanocomposite is a phase-segregated state with ferromagnetic inclusions that form superparamagnet. A unique interrelation between resistance found. The effect aging on studied.

The Raman-active phonons in perovskite-like LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0) are studied by measuring the Raman spectra at temperatures of 295 5 K. changes with Co doping correlated decrease orthorhombic distortions. Surprisingly, more phonon lines observed than allowed for rhombohedral LaCoO3 structure.

The Raman-active phonons and magnetic excitations in the orbitally ordered, quasi one-dimensional Heisenberg antiferromagnet KCuF3 are studied as a function of temperature range between 3 290 K different scattering configurations. low-energy Eg B1g phonon modes show an anomalous softening (∼25% ∼13%, respectively) room characteristic TS = 50 K. In this range, freezing-in F− ion dynamic displacements is proposed to occur. addition, mode at about 260 cm−1 clearly splits below TS. width lines...

One-phonon and multiphonon excitations of the single-crystalline LaCoO3 were studied using Raman spectroscopy in temperature region 5–300K. First-order spectra show a larger number phonon modes than allowed for rhombohedral structure. Additional are interpreted terms activated due to lattice distortions, arising from Jahn–Teller (JT) activity intermediate-spin (IS) state Co3+ ions. In particular, 608-cm−1 stretching-type mode shows anomalous behavior peak energy scattering intensity as...

Nontrivial magnetic field dependence of the polarization Kramers doublet absorption lines (15 971–15 978 cm−1) was observed in range 4I9/2 → 2H11/2 optical transition Nd3+ ion an easy-plane antiferromagnet NdFe3(BO3)4 transversal Zeeman effect geometry. Values g factor and effective exchange with Fe3+ subsystem were determined for excited state from splitting. A semiempirical equation proposed description intensities polarized components corresponding to 15 cm−1. Besides scaling factors,...

Low-temperature relaxation of magnetization in Pr0.4Bi0.3Ca0.3MnO3 ceramics was measured after cooling a magnetic field and aging at temperatures from 5 K to 38 near the transition temperature magnetically ordered state. It found that process has thermoactivation character first stage is described terms Arrhenius equation. Its activation energy Q ≈ 1.1 meV comparable with antiferromagnetic interaction this compound. The temperature–time dependence rate second by power law. slows down as...

We describe the results of electronic Raman scattering experiments in two differently doped single crystals La2−xSrxNiO4 (x=0.225 and 1/3). In B1g symmetry a crossover from weakly interacting to pseudogap-like behavior is observed at charge-ordering temperature Tco. B2g redistribution continua with decreasing accompanied by loss spectral weight below Tco low-frequency region due opening pseudogap. The slope response vanishing frequencies investigated, too. Its symmetry, which predominantly...

We report a neutron and Raman scattering study of single-crystal La(2)CuO(4.05) prepared by high temperature electrochemical oxidation. Elastic measurements show the presence two phases, corresponding to edges first miscibility gap, all way up 300 K. An additional oxygen redistribution, driven electronic energies, is identified at 250 K in (RS) experiments simultaneous onset two-phonon two-magnon scattering, which are fingerprints insulating phase. directly an antiferromagnetic ordering...

Raman scattering of light in the KTb(WO4)2 single crystal is investigated frequency range 3–950 cm−1 at 5 K. The ground multiplet 7F6 Tb3+ ion split by field with symmetry C2, and all components are detected. It found that first excited electronic quasidoublet consists two singlet levels different separated from ∼75 cm−1. Behavior detected external magnetic fields H ⊥ C2 || C2. Spectroscopic splitting factors determined for crystal. Experimental data support view low temperatures case Ising...

The new concept of creation supersensitive gas sensors by means the application point contacts as sensitive element type has been proposed. validity proposed was confirmed experimental data: effect enhanced sensitivity to action toxic gases (NOx , HCl) revealed. Nonmonotonic conductivity changes samples under investigations were observed upon exposition various volunteers’ breath gas. These results open way for development noninvasive diagnostics methods human organism state use contacts.

The low-frequency ferromagnetic resonance (FMR) spectra of nanocomposite manganites p-La0.78Mn0.99O3.5 and p-La0.80Mn1.04O3.5 with the cubic perovskite structure hole conductivity were studied. samples prepared under pressure 7.5 GPa in oxygen atmosphere. It was found that temperature dependence FMR parameters vicinity Curie point is similar to magnetization. characteristic time decay metastable magnetic phase above T* (metal-semiconductor transition) its formation below determined.

Electronic correlation effects in La2−xSrxNiO4 (x=1/3 and 0.225) lead to spontaneous phase separation into microscopic spin/charge stripes with commensurate incommensurate order, respectively. Raman scattering experiments on such single-crystalline materials show a rich phenomenology of phonon magnon anomalies due the new, self-organized periodicities. These are observable as function temperature but can also be induced by cooling seemingly small magnetic fields leading reorganization stripe...

Abstract Elastic moduli of LiNiPO 4 linear magnetoelectric single crystal were determined using Brillouin light scattering measurements at room temperature. The obtained values the elastic are following: c 11 = 189.6 ± 0.2, 22 192.6 0.4, 33 229.6 44 58.9 0.5, 55 70.4 0.6, 66 75.7 12 71.4 0.9, 13 71.0 0.8, and 23 54.5 0.9 in units 10 dyn/cm 2 . Determination refractive indices a He–Ne laser wavelength 632.8 nm was also carried out by means Brewster angle, following obtained: n 1.713 0.003, b...

Phonon spectra of solid substitutional solutions with finite concentrations impurities were analyzed on the microscopic level. The local phonon densities impurity atoms calculated, in particular formation quasilocal vibrations and their evolution increasing concentration investigated. Modification spectral host lattice by manifestation Ioffe-Regel crossover (scattering fast propagating phonons quasi-localized vibrations) analyzed. It is shown that such scattering causes features as "boson...