Calculation of the Spontaneous Polarization and the Dielectric Constant for the Ferroelectric N(CH3)4HSO4 Using the Mean Field Model

2017 ◽  
Vol 36 (9) ◽  
pp. 863-869
Author(s):  
H. Yurtseven ◽  
M. Celik ◽  
H. Karacali
Keyword(s):  
Experimental Data ◽  
Dielectric Constant ◽  
Spontaneous Polarization ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
Temperature Dependences ◽  
Inverse Susceptibility ◽  
The Mean ◽  
Fitting Parameters

AbstractThe temperature dependences of the spontaneous polarization and the dielectric constant (susceptibility) are calculated using the mean field model for the ferroelectric N(CH3)4HSO4. Expressions derived from the mean field model for the spontaneous polarization and the inverse susceptibility are fitted to the experimental data from the literature. The fitting parameters in the expansion of the free energy in terms of the spontaneous polarization are determined within the temperature intervals in the ferroelectric and paraelectric phases of N(CH3)4HSO4. Our results show that the temperature dependences of the spontaneous polarization and the dielectric constant as predicted from our mean field model, describe adequately the observed behavior of N(CH3)4HSO4 in the ferroelectric and paraelectric phases.

Calculation of the thermodynamic quantities of perovskite metal organics DMAKCr and perovskite HyFe close to the weakly first-order relaxor-like structural transformation using the mean field theory

2019 ◽  
Vol 33 (11) ◽  
pp. 1950103 ◽  
Author(s):  
H. Yurtseven ◽  
Ö. Tarı
Keyword(s):  
Field Theory ◽  
Field Model ◽  
Mean Field Theory ◽  
Mean Field ◽  
Excess Heat Capacity ◽  
Mean Field Model ◽  
First Order ◽  
Entropy Formula ◽  
Inverse Susceptibility ◽  
The Mean

Weakly first-order or nearly second-order phase transitions occurring in metal–organic frameworks (MOFs), particularly in DMAKCr and perovskite HyFe, are studied under the mean field model by using the observed data from the literature. In this work, mainly thermal and magnetic properties among various physical properties which have been reported in the literature for those MOFs are studied by the mean field theory. By expanding the free energy in terms of the magnetization (order parameter), the excess heat capacity ([Formula: see text]C[Formula: see text]) and entropy ([Formula: see text]S), latent heat (L), magnetization (M) and the inverse susceptibility ([Formula: see text]) are calculated as a function of temperature close to the weakly first-order phase transition within the Landau phenomenological model which is fitted to the experimental data from the literature for C[Formula: see text] (DMAKCr and perovskite HyFe) and for magnetization M (HyFe). Our predictions of the excess heat capacity ([Formula: see text]C[Formula: see text]) and entropy ([Formula: see text]S) agree below T[Formula: see text] with the observed data within the temperature intervals studied for DMAKCr and perovskite HyFe. From our predictions, we find that magnetization decreases continuously whereas the inverse susceptibility decreases linearly with increasing temperature toward the transition temperature in those MOFs as expected for a weakly first-order transition from the mean field model.

scholarly journals Analysis of the Dielectric Constant as a Function of Temperature at Constant Electric Fields for the Smectic A-Smectic G Transition in A6

2012 ◽  
Vol 2012 ◽  
pp. 1-5
Author(s):  
H. Yurtseven ◽  
E. Kilit
Keyword(s):  
Dielectric Constant ◽  
Electric Fields ◽  
Field Model ◽  
Mean Field ◽  
Dielectric Susceptibility ◽  
Ferroelectric Liquid Crystal ◽  
Mean Field Model ◽  
Smectic A ◽  
Observed Behaviour ◽  
The Mean

The temperature dependence of the dielectric constant is studied under some fixed electric fields for the smectic G- (tilted-) smectic A (orthogonal) transition of the ferroelectric liquid crystal of compound A6. For this study, a mean field model with the quadrupole-quadrupole interactions is introduced. By fitting the inverse dielectric susceptibility from the mean field model to the experimental data from the literature, the observed behaviour of the dielectric constant is described satisfactorily for the smectic AG transition in A6. The transition temperature induced by an external electric field is also discussed for this ferroelectric compound.

Calculation of the tilt angle and susceptibility for the α–β transition in quartz using a mean field model

2017 ◽  
Vol 31 (09) ◽  
pp. 1750092 ◽  
Author(s):  
H. Yurtseven ◽  
U. Ipekoğlu ◽  
S. Ateş
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Tilt Angle ◽  
Phenomenological Model ◽  
Order Parameter ◽  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
The Mean

Tilt angle (order parameter) and the susceptibility are calculated as a function of temperature for the [Formula: see text]–[Formula: see text] transition in quartz using a Landau phenomenological model. The tilt angle as obtained from the model is fitted to the experimental data from the literature and the temperature dependence of the tilt angle susceptibility is predicted close to the [Formula: see text]–[Formula: see text] transition in quartz. Our results show that the mean field model explains the observed behavior of the [Formula: see text]–[Formula: see text] phase transition in quartz adequately and it can be applied to some related materials.

Critical X-Ray Scattering in Mixed Piezoelectric Material PbZr0.6Ti0.4O3

2015 ◽  
Vol 245 ◽  
pp. 211-216 ◽  
Author(s):  
Daria Andronikova ◽  
Yurii Bronwald ◽  
Roman Burkovsky ◽  
Dmitry Chernyshev ◽  
Alexey Filimonov ◽  
...  
Keyword(s):  
Field Model ◽  
Mean Field ◽  
Mean Field Model ◽  
X Ray ◽  
X Ray Scattering ◽  
Peak Intensity ◽  
Temperature Dependences ◽  
The Mean ◽  
Model Temperature ◽  
Ray Scattering

The results of the experimental study of the critical X-ray scattering (CS) in PbZr0.6Ti0.4O3 (PZT40) single-crystal are presented. Temperature evolution of the CS lineshape and intensity was analyzed. It is demonstrated that CS can be described in terms of the mean-field model. Temperature dependences of the peak intensity of the CS, proportional to the static susceptibility, and the correlation length of the «ferroelectric fluctuations» follow the Curie-Weiss law with the Curie temperature Tc=638 K. Obtained results confirm the second-order character of the phase transition in the PZT40.

Single-Crystal Magnetic Properties of [Co(NH3)5(OH2)] [Cr(CN)6] Between 2 and 300 K

1992 ◽  
Vol 45 (11) ◽  
pp. 1899 ◽  
Author(s):  
PA Reynolds ◽  
CD Delfs ◽  
BN Figgis ◽  
B Moubaraki ◽  
KS Murray
Keyword(s):  
Ising Model ◽  
Field Model ◽  
Mean Field ◽  
Zero Field ◽  
Spin Orbit Coupling ◽  
Zero Field Splitting ◽  
Magnetic Exchange Interaction ◽  
Mean Field Model ◽  
Magnetic Exchange ◽  
The Mean

The magnetic susceptibilities along and perpendicular to the c axis (hexagonal setting) between 2.0 and 300 K at a magnetic field of 1.00 T, and the magnetizations at field strengths up to 5.00 T, are presented for single crystals of [Co(NH3)5(OH2)] [Cr(CN)6]. The results are interpreted in terms of zero-field splitting (2D) of the ground 4A2g term by spin-orbit coupling and of magnetic exchange interaction between the chromium atoms. The magnetic exchange is modelled as one of Ising or mean-field in type. The exchange is found to be quite small: J = -0.18(6) cm-1 if the Ising model is employed, and -0.03(1) cm-1 for the mean-field model. The model adopted for the exchange has a strong influence on the value of the parameter D obtained. When the Ising model is used D is deduced to be -0.28(9) cm-l; when the mean-field model is used D is -0.14(4) cm-l. The g-values deduced are in agreement with those from e.s.r. measurements at higher temperatures and do not depend on the exchange model. In any case, D is found to be sufficiently large that it must be considered in a polarized neutron diffraction experiment on the compound.

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