Temperature Dependence of the IR Frequencies and FWHM of the Ρ (NH2) Mode for DMFeCu, DMFeNi and DMFeZn Crystals

Date

2018-05-06

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Kurt, Mustafa
Yurtseven, Hasan Hamit
Kurt, Arzu

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https://hdl.handle.net/11511/75425

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Temperature dependence of the Raman bandwidths and intensities of a lattice mode near the tricritical and second order phase transitions in NH4Cl Karacali, H; Yurtseven, Hasan Hamit (2006-01-11) We calculate here the temperature dependence of the damping constant using the expressions derived from the Matsushita's theory and the temperature dependence of the order parameter from the molecular field theory for the tricritical (1.5 kbar) and second order (2.8 kbar) phase transitions in NH4Cl. Our calculations are performed for the nu(5) (174 cm(-1)) Raman mode of NH4Cl for the pressures studied. Predictions for the damping constant are in good agreement with our observed Raman bandwidths of this latt...
Temperature dependence of the Raman frequencies and bandwidths close to phase transitions in ammonium halides Yurtseven, Hasan Hamit (2001-09-01) In this study, we give the temperature dependence of our observed frequencies and bandwidths for the Raman optical modes in the ammonium halides close to the phase transitions of the first order (NH4 Br), tricritical (NH4Cl) and second order (NH4Cl). Using the predictions of an [sing pseudospin-phonon coupled model, which considers interactions between two spin and two phonons, our observed Raman data have been interpreted qualitatively. Our results show that an Ising model considered here can explain the o...
Temperature dependence of Raman-active mode frequencies and linewidths in TlGaSe2 layered crystals Yuksek, NS; Hasanlı, Nızamı (2005-03-01) Raman spectra of TlGaSe2 crystal at different temperatures are discussed. The temperature dependence of frequency shifts and linewidths of the Raman peaks in the frequency region of 10-320 cm(-1) have been measured in the range from 50 to 320 K. The analysis of the experimental data showed that the temperature dependencies of phonon frequencies and linewidths are well described by considering the contributions from thermal expansion and lattice anharmonicity. The anharmonic contribution (phonon-phonon coupl...
Temperature dependence of the polarization and the dielectric constant near the paraelectric-ferroelectric transitions in BaTiO3 Yurtseven, Hasan Hamit (Springer Science and Business Media LLC, 2013-09-01) Temperature dependences of the spontaneous polarization and the dielectric constant are calculated near the paraelectric-ferroelectric (cubic-tetragonal) transition in BaTiO3 using our mean field model. By expanding the free energy in terms of the spontaneous polarization (order parameter), expressions for the temperature dependence of the spontaneous polarization and the dielectric constant are derived. By considering the temperature dependence of the Raman frequencies for the lattice mode (310 cm(-1)) whi...
Temperature dependence of the damping constant and the relaxation time close to the tetragonal-cubic phase transition in SrZrO3 Yurtseven, Hasan Hamit (2017-01-15) The damping constant Gamma(sp) due to the pseudospin-phonon coupling is calculated as a function of temperature using the pseudospin-phonon coupled model and the energy fluctuation model close to the tetragonal-cubic transition (T-C = 1443 K) in SrZrO3. Using the observed Raman frequencies and the linewidth (FWHM) of the soft modes (E-g and A(1g)) from the literature, predictions of both models studied, are examined for the tetragonal-cubic transition in this crystalline system. Values of the activation ene...

Citation Formats

M. Kurt, H. H. Yurtseven, and A. Kurt, “Temperature Dependence of the IR Frequencies and FWHM of the Ρ (NH2) Mode for DMFeCu, DMFeNi and DMFeZn Crystals,” 2018, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/75425.