Temperature dependence of the linewidth of the first-order Raman spectrum for GeO2 powder

The first-order Raman spectrum of A_1g mode in GeO₂ powder was measured at a temperature range of 130–973 K and the linewidths at these temperatures were obtained. The temperature dependence of the linewidths was analysed by the phonon dispersion curves based on the rigid ion model, and the results show that it was caused perhaps by the cubic anharmonic term in crystal potential energy.     

Temperature dependence of the linewidth of the first-order Raman spectra for MnF2 crystal

The first-order Raman spectra ofE _gandA _1g modes in MnF₂ crystal were measured at temperatures from 4.2 to 563 K, and the values of the linewidths obtained. The temperature dependence of the linewidths was analyzed by the phonon dispersion curves based on the rigid ion model, and the result showed that it was caused approximately by the cubic anharmonic term in crystal potential energy.     

Temperature dependence of phonon linewidth in β-AgI

The temperature dependence of the linewidth and frequency of a TO one-phonon mode of β-AgI is measured using far infrared and Raman spectroscopy. Near the β-α transition an anomalous damping is observed. A very simple model is proposed to explain this damping by interactions between phonons and ionic carriers.     

Temperature dependence of SSW linewidth in metallic thin films

Measurements of the standing spin wave linewidth H _n at 17·6 GHz from 6 °K to 400 °K are presented for two permalloy films whose structure is either polycrystalline or epitaxial. It is shown that in both films, H _n is proportional ton ² (n is the mode number). Although H _n is little modified by temperature (20% variation maximum over the entire temperature range), we experimentally state that the slopep of H _n (n ²) is a linear function of the saturation magnetizationM which agrees with a planar inhomogeneity model.The authors wish to thank H. Pascard and F. Hoffmann who have prepared and selected the films as also E. Villain and A. Gatineau for invaluable technical assistance.     

Temperature dependence of the antiferromagnetic resonance linewidth in MnF2

The temperature dependent contribution to the antiferromagnetic resonance linewidth in MnF₂ has been measured at K-band frequencies (～ 23 GHz) between 5° and 40°K. It can be closely approximated by a T⁴ power law except at the highest temperatures.     

Temperature dependence of the pseudocontact shift in lanthanide shift reagents

The method of calculating the pseudocontact shift of lanthanide shift reagents as a power series of T⁻ⁿ, the reciprocal of temperature, developed by Bleaney has been extended to the T⁻³ term. Using crystal field parameters reported in the literature, it is found that the T⁻³ term is no more than 10% of the T⁻² term in magnitude at room temperature for all ions to which the theory is applicable. The calculations show that even though the pseudocontact shift cannot be fitted exactly to a T⁻² temperature dependence, the simple equation for the T⁻² term is adequate for estimating the actual shift at room temperature to an accuracy of 10 to 20%.     

Modified phonon confinement model for size dependent Raman shift and linewidth of silicon nanocrystals

A modified phonon confinement model considering the size distribution, an improved phonon dispersion curve and a confinement function is developed for the calculation of size dependent Raman spectra of the silicon (Si) nanocrystals. The model is capable of simultaneous calculations of the Raman shift, intensity and linewidth. The calculated size dependent redshift and linewidth of Raman spectra are in good agreement with the available experimental data in literature and better than previously reported theoretical results. The rapid rise in the redshift and linewidth for relatively smaller Si nanocrystals are well reproduced. The asymmetric behavior of Raman spectra is also obtained from the present model.     

Temperature dependence of the ESR linewidth in KFeS2

The ESR linewidth in KFeS₂ has been measured in the range 80–340 K. The linewidth is found to decrease steadily as the temperature is increased, without any discontinuity or singularity at the transition temperature T_N=245 K. In the paramagnetic state, the region of enhanced linewidth extends further above T_N than for two-and three-dimensional compounds such as K₂MnF₄ and MnF₂.     

Temperature dependence of EPR linewidth in one-dimensional magnets: A quasi-classical approach

An analytical expression for the EPR linewidth of an exchange-coupled 1/2-spin chain originating from uniform Dzyaloshinskii-Moriya interaction is derived using a quasi-classical approach. The expression successfully reproduces the results obtained by numerical quantum mechanical calculations based on Green’s function method at T > 2J/k _B.     

Temperature dependence of the positive-muon knight shift in MnSi

The temperature dependence of the μ⁺ Knight shift in weakly-helimagnetic MnSi has been measured in the temperature range between 28 and 300 K. The observed shift is found to be directly proportional to the host susceptibility in the paramagnetic state with a hyperfine coupling constant of —4.8 kOe/_μB.     

Temperature dependence of the isomer shift in white tin

The OPW method is used to study the temperature-dependent isomer shift of β-Sn above the room temperature from the contributions including both the crystal pseudopotential with the Debye-Waller factor and the self-energy effect. It is shown that, although the self-energy contribution to the absolute value of the isomer shift in β-Sn is negligibly small, its rate of change with respect to temperature is at least of the same order, but with different sign, as that of the Debye-Waller factor term. We conclude that the increase in the isomer shift of β-Sn with temperature observed experimentally can be well accounted for by the effect of self-energy interactions.     

Temperature dependence of phase shift in ferrite phase shifters

Reciprocal ferrite phase shifters exhibit a pronounced dependence of phase shift upon temperature. In a sample of magnesium-copper-chromium ferrite it is shown that the temperature dependence of the phase shift is basically determined by the temperature dependence of the microwave magnetic permeability.In conclusion the authors wish to thank G. I. Yudin for making the measurements of phase shift and its dependence on the field for various temperatures.     

Raman scattering from CuBr and CuI

Detailed temperature-dependent Raman spectra of CuI and CuBr are reported for the first time. Spectra have been recorded between room temperature and 6K. Peaks arising from scattering by the zone-center optic phonon modes have been identified and their frequencies compared with those determined by neutron scattering and infrared measurements. The LO phonon energy in CuBr is found to reflect the negative thermal expansion at low temperatures while the TO phonon frequency does not follow this behavior. Second-order features of the CuI spectrum are identified using available phonon dispersion curves.     

Temperature dependence of the broad A1 (TO) phonon Raman linewidth in BaTiO3

The temperature dependence of the A₁ (TO) broad phonon linewidth is discussed. It is shown that it can adequately be accounted for by assuming a simple model where the Ti ions are sitting off the center of the unit cell and tunneling through a double well in the direction of the ferroelectric axis.     

Temperature dependence of Raman scattering in Co-doped AlN whiskers

Raman studies are reported for the A ₁ (TO), E ₂ (high) and E ₁ (LO) phonons of Co-doped AlN whiskers from 78 K to 778 K. The temperature dependence of the Raman shifts and line widths of these phonons can be well described by an empirical model which takes into account the contribution of the thermal expansion of the lattice and the symmetric decay of phonons into two and three identical phonons with lower energy. Our results show that the three-phonon process is the dominant decay channel in A ₁ (TO), E ₂ (high) and E ₁ (LO). The symmetric decay of A ₁ (TO) may be attributed to the production of two LA phonons near the M symmetry point of the Brillouin zone. For E ₂ (high), the symmetric decay may be near the M and L symmetry points. The E ₁ (LO) phonon, whose decay behavior has not been identified in AlN, may decay near the H and K symmetry points of the Brillouin zone. Compared with undoped AlN, the stronger temperature dependence of the A ₁ (TO) and E ₂ (high) phonons in Co-doped AlN whiskers was observed, which is probably due to the distortion of the lattice and the much larger tensile stress after doping Co into AlN.     

Temperature dependence of the Knight shift for cadmium in palladium

The Knight shift and its temperature dependence for a Cd impurity in palladium metal were measured by means of DPAD- and DPAC-methods utilizing the well known 5/2⁺, 247-keV state in¹¹¹Cd. The shift at 80 K was found to be KS (CdPd, 80 K)=?0.8(2)%. The observed variation of the KS in the temperature range from 80 K up to 1400 K is 0.5%. For calibration purposes an accurate remeasurement of the magnetic moment of the 5/2⁺ state in¹¹¹Cd was necessary and yieldedμ(¹¹¹Cd, 5/2⁺, 247 keV)=?0.7697(20) n.m.     

Temperature dependence of Raman scattering and anharmonic properties in LiNbO_3

The temperature dependence of the Raman spectrum in LiNbO \(_3\) is investigated from 100 to 700 K. The various sources of asymmetry of Raman bands and artefacts are discussed before analyzing the temperature dependence of A \(_1\) and E first-order phonon lines. The phonon frequency downshift and damping increase on heating are interpreted in terms of normal volume expansion and third- and fourth-order anharmonic potentials. Anharmonic contributions are highly anisotropic and mainly explain the temperature dependences of both frequency and damping of A \(_1\) optical vibrational modes along the ferroelectric axis. Results are consistent with Caciuc et al. (Phys Rev B 61:8806, 2000) predictions.     

Temperature dependence of anomalous and ordinary Raman scattering in β-AgI

We report careful measurements of the temperature dependence of Raman scattering in β-AgI, with particular emphasis on the region 12°K to 150°K. Our main result is that the anomalous features in the Raman spectra of β-AgI are definitely first order. Furthermore from the temperature dependence of the anomalous scattering intensity we infer the possibility of a first partial disordering in the Ag⁺ sublattice at about 50°K.     

Temperature dependence of the Mössbauer isomer shift

The isomer shift for nuclei in solids is calculated taking into account the core electron charge density, the overlap effects, the charge transfer effects, and the crystal field effects. The importance of the dynamical electron phonon interaction is pointed out. It is found that the phonon-induced dynamical configurational mixing and the dynamical charge transfer play an important role and contribute to a dynamical isomer shift which enhances the temperature-dependent second-order Doppler shift. It is found that the internal conversion and the electron capture give information which is related to the isomer shift. In mixedvalence compounds such as EuCu₂Si₂, the center shift of the M?ssbauer lines has been explained as if arising from the phonon-induced dynamical isomer shift.