Temperature dependence of the damping constant and the order parameter close to the λ phase transitions in ammonium halides

Yurtseven, H.; Karaçalı, H.

doi:10.1016/j.saa.2005.10.054

Cited by 8 publications

(14 citation statements)

References 24 publications

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“…NH 4 Br is an ammonium salt which undergoes the -phase transition from the disordered phase II ͑␤ phase͒ to the antiferro-ordered phase III ͑␥ phase͒ at T = 234 K, as the temperature is lowered. In the disordered ␤ phase which has the CsCl structure with the 0 h 1 − P m 3m symmetry, the NH 4 + ions are distributed randomly between two equivalent energy states.…”

Section: Introductionmentioning

confidence: 99%

“…1 In the ␥ phase ͑phase III͒ which has a tetragonal structure with the D 4h symmetry, the NH 4 + ions are orientated antiparallel in the a-b plane and they are all parallel along the c-axis. As the temperature decreases further down to ϳT c = 78 K, the antiferro-ordered ␥ phase is transformed into the ferro-ordered phase IV ͑␦ phase͒ in NH 4 Br. In this phase which has also the CsCl structure with the T d 1 − P43m symmetry, the NH 4 + ions are all parallel to each other.…”

Section: Introductionmentioning

confidence: 99%

“…The two possible orientations of the ammonium ions can be specified as the Ising spin variable ͑up and down orientations of the Ising spin͒. Thus, NH 4 Br crystal can be studied as an Ising pseudospin-phonon coupled system due to Yamada et al 2 This Ising pseudospin-phonon coupled model considers the interaction between an NH 4 + ion ͑pseudospin͒ and the Br − ion ͑phonon͒. Matsushita 3 extended this model by including interactions among the pseudospins and phonons in NH 4 Br and interpreted the temperature dependence of phonons qualitatively.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, NH 4 Br crystal can be studied as an Ising pseudospin-phonon coupled system due to Yamada et al 2 This Ising pseudospin-phonon coupled model considers the interaction between an NH 4 + ion ͑pseudospin͒ and the Br − ion ͑phonon͒. Matsushita 3 extended this model by including interactions among the pseudospins and phonons in NH 4 Br and interpreted the temperature dependence of phonons qualitatively. Recently, we have studied the temperature de-pendence of the damping constant and the order parameter based on Mashushita's theory.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, we have studied the temperature de-pendence of the damping constant and the order parameter based on Mashushita's theory. 4 Apart from an Ising pseudospin-phonon coupled model, various models such as a simplified model with competing interactions between the NH 4 + ions, 5 an electrostatic model, 6 and a microscopic model 7 have been reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH₄Br at high pressures

Yurtseven¹,

Cekic²

2010

Physics Essays

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The Raman frequencies are calculated here at various temperatures for the 7 ͑56 cm −1 ͒ and 5 ͑134 cm −1 ͒ lattice modes in the disordered phase II of NH 4 Br. The lattice parameter data obtained at zero pressure are used to calculate the Raman frequencies of those modes studied for constant pressures of 0.1, 108, and 637.5 MPa in phase II of the NH 4 Br crystal. Through the mode Grüneisen parameter which is kept constant in the disordered phase II, the Raman frequencies calculated decrease linearly with increasing temperature at all fixed pressures for both lattice modes of NH 4 Br. Measurements of the Raman frequencies for the lattice modes of interest can be conducted to examine our calculations under the temperature and pressure variations given here for NH 4 Br.Résumé: Les fréquences Raman sont calculées ici à différentes températures pour les modes de réseau 7 ͑56 cm −1 ͒ et 5 ͑134 cm −1 ͒ dans la phase désordonneé II de NH 4 Br. Les paramétres de réseau obtenues à une pression nulle sont utilisés pour calculer les fréquences Raman de ces modes étudiés pour des pressions constantes de 0.1, 108 et 637.5 MPa dans la phase cristalline II de NH 4 Br. Grâce au paramétre de mode Grüneisen qui est maintenu constant dans la phase désordonnée II, les fréquences Raman calculées diminuent linéairement avec l'augmentation de la température à toutes les pressions fixées pour les deux modes de réseau de NH 4 Br. La mesure de la fréquence Raman pour le mode de réseau considéré peut être effectuée pour examiner nos calculs dans le cadre des variations de température et de pression données ici pour NH 4 Br.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH₄Br at high pressures

Yurtseven¹,

Cekic²

2010

Physics Essays

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Calculation of the Raman frequency and the damping constant of a coupled mode in the ferroelectric and paraelectric phases in KH₂PO₄

Karaçalı

Kiraci

Yurtseven

2010

Physica Status Solidi (b)

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The Raman frequency of the coupled mode v À associated with the order parameter is calculated as a function of pressure from the mean field theory in the ferroelecric phase of KDP. Using the frequencies of the coupled mode, the pressure dependence of the damping constant G À is calculated by the proton spin 1 Introduction As a ferroelectric (FE) material, KDP (KH 2 PO 4 ) was discovered [1] and its order-disorder phase transition (T C ¼ 122 K) due to the proton [2] was studied many years ago. This transition is of a second order from the paraelectric (PE) to the FE phase as the temperature decreases at the atmospheric pressure. At room temperature, this FE crystal is in the PE phase with the tetragonal structure and I42d (D

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Magnetization Studied as a Function of Temperature and Magnetic Field for Ferromagnetic Transition in DMNaFe

Doğan

Yurtseven

2020

Journal of Elec Materi

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Magnetization has been calculated as a function of temperature in the ferromagnetic phase of (CH 3 ) 2 NH 2 Na 0.5 Fe 0.5 (HCOO) 3 denoted by DMNaFe as one of the metal formate framework by using molecular field theory. Calculated M(T) is compared with the magnetization measured as a function of temperature (H = 10 Oe) in field-cooling and zero-field-cooling regimes from the literature, and a power-law analysis of the experimental data was performed for DMNaFe. Magnetization measured as a function of the magnetic field, as reported in the literature, has also been analyzed by the power-law formula. The magnetization indicates a weak first-order (or nearly second-order) ferromagnetic transition in DMNaFe.

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Temperature dependence of the damping constant and the order parameter close to the λ phase transitions in ammonium halides

Cited by 8 publications

References 24 publications

Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH₄Br at high pressures

Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH₄Br at high pressures

Calculation of the Raman frequency and the damping constant of a coupled mode in the ferroelectric and paraelectric phases in KH₂PO₄

Magnetization Studied as a Function of Temperature and Magnetic Field for Ferromagnetic Transition in DMNaFe

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Temperature dependence of the damping constant and the order parameter close to the λ phase transitions in ammonium halides

Cited by 8 publications

References 24 publications

Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH4Br at high pressures

Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH4Br at high pressures

Calculation of the Raman frequency and the damping constant of a coupled mode in the ferroelectric and paraelectric phases in KH2PO4

Magnetization Studied as a Function of Temperature and Magnetic Field for Ferromagnetic Transition in DMNaFe

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Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH₄Br at high pressures

Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH₄Br at high pressures

Calculation of the Raman frequency and the damping constant of a coupled mode in the ferroelectric and paraelectric phases in KH₂PO₄