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Ortak Dersler Bölümü

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Browsing Ortak Dersler Bölümü by browse.metadata.publisher "Ieee-inst Electrical Electronics Engineers inc"

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    Citation - WoS: 8
    Citation - Scopus: 9
    Damping Constant (Linewidth) and the Relaxation Time of the Brillouin La Mode for the Ferroelectric-Paraelectric Transition in Pbzr1-Xtixo3
    (Ieee-inst Electrical Electronics Engineers inc, 2016) Kiraci, Ali; Yurtseven, Hamit
    The damping constant (linewidth) of the longitudinal acoustic (LA) mode is calculated as a function of temperature using the observed Brillouin frequencies of this mode from the literature for the ferroelectric-paraelectric transition (T-C = 657 K) in PbZr1-xTixO3 (x = 0.45). For this calculation of the damping constant, the pseudospin-phonon coupled model and the energy fluctuation model are used by fitting to the observed data for the Brillouin frequencies of the LA mode in the ferroelectric (T < T-C) and paraelectric (T > T-C) phases of this compound (x = 0.45). Values of the activation energy are deduced for both ferroelectric and paraelectric phases. The relaxation time is also obtained by means of fitting to the observed data from the literature for the inverse relaxation time at various temperatures in the paraelectric phase of PbZr1-xTixO3. The temperature dependences of the damping constant and of the relaxation time with the values of the activation energy that we have calculated indicate that the pseudospin-phonon coupled model and the energy fluctuation model are capable of describing the ferroelectric-paraelectric transition (T-C = 657 K) in PbZr1-xTixO3 (x = 0.45) adequately.
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    Article
    Citation - WoS: 3
    The Important Role of N(2) Ion in the Phase-Transition Mechanism of [N(ch3)4]2znbr4
    (Ieee-inst Electrical Electronics Engineers inc, 2020) Kiraci, Ali
    The chemical shift of the N(2)(CH3)(4) ion, which has been found to exhibit the similar anomalous behavior of the monoclinic angle $\Delta \beta $ , was related to the order parameter to evaluate the temperature dependence of the linewidth (damping constant) for N-14 nuclear magnetic resonance spectrum of this crystal in terms of the dynamic Ising models, namely the pseudospin-phonon-coupled (PS) and the energy fluctuation (EF) models. The results from both PS and EF models were successful to explain the abnormal behavior of the linewidth in the vicinity of the phase-transition temperature of ${T}_{C}= {287.6}$ K, when compared with the observed linewidth of the transverse acoustic soft mode in this crystal. As an extension of this work, the N-14 relaxation time and the values of the activation free energy were calculated as a function of temperature. The results indicate that the ferroelastic-paraelastic phase transition in this compound is of the order-disorder type.
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    Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Phenomenological Study of Manganese Antimonite Close To the Neel Temperature
    (Ieee-inst Electrical Electronics Engineers inc, 2021) Kiraci, Ali
    The anomalous behavior of the frequency f and specific heat C-p data for the new layered trigonal (P (3) over bar 1m) form of manganese antimonite (MnSb2O6) was analyzed by means of the power-law relations with the critical exponent alpha in the vicinity of the Neel temperature of T-N= 8.0 K. While the extracted values of a from both f and C-p below T-N (the same value of 0.06) match exactly the value 1/16 (= 0.06) predicted from the three-dimensional (3-D) Ising model, the extracted value of 0.65 from the C-p data above T-N is much higher than the predicted value of 1/8 (= 0.13) from the 3-D Ising model. As an extension of this work, the temperature dependence of the muon-spin relaxation rate (damping constant) lambda of MnSb2O6 was calculated from the pseudospin-phonon-coupled (PS) model and the energy fluctuation (EF) model below T-N. Our results are in good agreement with the data. In addition, the activation energy was calculated from the predicted values of. from both PS and EF models for MnSb2O6. Our results indicate an order-disorder-type transition at T-N = 8.0 K for MnSb2O6.