Browsing by Author "Yurtseven, H."

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Analysis and Calculation of the Magnetization, Magnetic Susceptibility and the Specific Heat Close To Phase Transitions in Heterometallics
(Elsevier, 2019) Dugan, E. Kilit; Yurtseven, H.
The temperature dependence of the magnetization for DMFeNi and DMFeCu is calculated by the molecular field theory and it is also analyzed as functions of temperature and the magnetic field by the power-law formulae close to the phase transitions in these compounds by using the observed data from the literature. From the analysis, values of the critical exponents beta (temperature-induced order parameter at H = 100 Oe) and delta (field-induced order parameter at T = 2 K) are deduced. Also, using the observed M-H data, magnetic susceptibility is calculated as a function of the magnetic field for DMFeNi and DMFeCu. Regarding the thermal properties of MOFs, the specific heat of DMFeFe, as an example, is calculated by an Ising model superimposed on an Einstein and/or Debye model using the observed C-P data from the literature. Our analyses and calculations indicate a nearly second order (or weakly first order) transition for the heterometallics studied here.
Analysis of Magnetization as a Function of Temperature for Comn1-X Fe X Ge
(Springer, 2017) Yuce, S.; Dogan, E. Kilit; Emre, B.; Bruno, N. M.; Karaman, I.; Yurtseven, H.
Our experimental measurements for the magnetization M as a function of temperature are analyzed for the multilayer structure of CoMn1-x Fe (x) Ge for x = 0.085 and x = 0.12 at constant magnetic fields of 3, 5, and 7 T. For this analysis, a power-law formula is used below the transition temperature T-C for these compositions and the values of the critical exponent beta for the magnetization M (order parameter) are determined. Our analysis indicates that a first order transition at lower concentrations (x = 0.085) changes toward a second order at higher concentrations (x = 0.12) at constant magnetic fields (3, 5, and 7 T) for the multilayer CoMn1-x Fe (x) Ge, as observed experimentally.
Analysis of the Dielectric Constant, Spontaneous Polarization and the Coersive Field Close To the Phase Transitions in Ferroelectric K2cocl4
(Taylor & Francis Ltd, 2016) Yurtseven, H.; Dogan, E. Kilit
Temperature dependence of the dielelctric constant epsilon(a) along a axis and the spontaneous polarization P-S is analyzed near the ferroelectric transition (T-C = 182 degrees C) in K2CoCl4. The power-law formula is used for the analysis of the observed data from the literature. Critical exponents we determine from our analysis indicate that K2CoCl4 exhibits a weak first order transition. Coercive field EC is also analyzed using the experimental data which decreases smoothly as the temperature increases toward the transition temperature T-C. It is concluded that the theoretical model(s) with the non-zero applied electric field, can explain the ferroelectric properties of K2CoCl4 close to the phase transitions.
Analysis of the Magnetization as a Function of the Magnetic Field at the Transition Temperature for La0.6nd0.4mn2si2
(Springer, 2015) Yurtseven, H.; Dogan, E. Kilit; Emre, B.; Acet, M.
We analyze in this study our experimental data for the magnetization (M) as a function of the magnetic field (H) at various constant temperatures for the multilayer structure of La Nd-0.6 Mn-0.4 Si-2 (2) close to the ferromagnetic-antiferromagnetic transitions. This analysis is performed at the transition temperatures (T (c)) for the M vs. H- H (c) (H (c) is the critical field) according to a power-law formula above and below H (c), and the values of the critical isotherm delta are deduced for La Nd-0.6 Mn-0.4 Si-2 (2). We also calculate the magnetic field (H- H (c)) dependence of the isothermal susceptibility chi (T) at constant temperatures above and below H (c), and we obtain the critical behaviour of chi (T) for this multilayer structure. Our delta values indicate that the ferromagnetic-antiferromagnetic transition in La Nd-0.6 Mn-0.4 Si-2 (2) changes its character from a first order (discontinuous) toward a second-order (continuous) one as the constant temperature changes.
Analysis of the Specific Heat of P-Azoxyanisole (Paa) Near the Phase Transitions
(Taylor & Francis Ltd, 2010) Kilit, E.; Yurtseven, H.
The analysis of the experimental data for the specific heat Cp at various temperatures is given here near the nematic-isotropic liquid (TNI = 133.9 degrees C) and the solid-nematic (TSN = 117.6 degrees C) transitions in p-azoxyanisole (PAA). The analysis of the specific heat Cp is performed according to a simple power-law formula and a renormalisation-group expression. The values of the critical exponent are extracted above and below the transition temperatures of TNI and TSN for this liquid crystalline material. Our exponent values are compared with the predictions of a three-dimensional Ising model and XY model for liquid crystals. Using the specific heat Cp, the temperature dependence of the enthalpy H and the entropy S is calculated in the nematic phase (T TSN) of p-azoxyanisole.
Analysis of the Susceptibility of Condensed Oxygen Under High Pressures and in Strong Magnetic Fields
(Elsevier Science Bv, 2017) Dogan, E. Kilit; Yurtseven, H.
The temperature dependence of the magnetic susceptibility is analyzed at some constant pressures by a power-law formula using the experimental data from the literature for the alpha - beta and beta - gamma transitions in oxygen. A weak discontinuous (nearly continuous) transition occurring from the a to the beta phase, becomes more discontinuous (weakly first order) for the beta - gamma transition as observed experimentally, which can be explained in terms of the critical exponents deduced from our analysis. The magnetic field dependence of the differential susceptibility is also analyzed in this study for the alpha - O-2 at 4.2 K by a power-law formula using the experimental data. lambda-type of observed behaviour of the differential susceptibility is discussed in terms of our analysis for the alpha - O-2. (C) 2016 Elsevier B.V. All rights reserved.
Calculation of the H-T Phase Diagram, Magnetization and Susceptibility in Layered Structures
(Elsevier Science Bv, 2015) Yurtseven, H.; Dogan, E. Kilit; Emre, B.; Acet, M.
The magnetic Field-temperature (H-T) phase diagram is calculated using the mean held theory by expanding the free energy in terms of the uniform and staggered magnetization for the ferromagnetic-antiferromagnetic transitions in the La0.6Nd0.4Mn2Si2 multilayer structures. Using our experimental measurements, analysis of the magnetization as a function of the magnetic held at constant temperatures from 45 K to 250 K is performed by a power-law formula close to the ferromagnetic-antiferromagnetic transitions. Also, by obtaining the magnetic field dependence of the isothermal susceptibility chi(T) from the M-H curves, chi(T) vs. H-H-c, is analyzed (H-c is the critical magnetic field) using a powerlaw formula for the antiferromagnetic-ferromagnetic (AF-FM) transitions in La0.6Nd0.4Mn2Si2. It is found that a discontinuous (first order) transition which occurs at the lowest (45 K) and the highest (250 K) temperatures, changes to a continuous one at a constant temperature at around 100 K as the magnetic Field carries the systems from the antiferromagnetic to the ferromagnetic phase. Values of the critical exponents associated with this transition are deduced and they are compared with the predictions of some theoretical models. (C) 2015 Elsevier B.V. All rights reserved.
Calculation of the Magnetization and the Heat Capacity for [Nh2 Nh3][M(hcoo)3] (M=fe, Mn) Near the Phase Transitions
(Taylor & Francis Ltd, 2022) Yurtseven, H.; Dogan, E. Kilit
Temperature dependence of the magnetization M(T) is calculated for [NH2 NH3][M(HCOO)(3)] (M=Fe, Mn), namely, HyFe (perovskite and chiral) below T m =12.5 K and, for HyMn (chiral) below and above T m =7.9 K (at 100 Oe) by the molecular field theory (MFT). Close to the magnetic transition temperature ( T m ), the temperature (at 100 Oe) and the field (at 2K) dependence of the magnetization M(T, H) is analyzed by the power-law formula using the literature data. Magnetic susceptibility is predicted as a function of the field (T = 2K). Also, the temperature dependence of the heat capacity is calculated by the compressible Ising model close to the structural phase transitions in perovskite ( T C =347 K) and chiral ( T C =336 K) HyFe and the chiral ( T C =296 K) HyMn. Our results indicate that HyM (M=Fe, Mn) exhibit weak first order or near second order transitions (magnetic transition and the structural phase transitions).
Calculation of the Phase Diagram of N-Alkanes (Cnh2n+2) by the Landau Mean Field Theory
(Elsevier, 2022) Yurtseven, H.; Dogan, E. Kilit
We study the temperature T and concentration n (number of carbon atoms) dependence on the transitions of the liquid, rotator (R-I, R-II, R-III, R-IV and R-V) and crystal phases in n-alkanes (CnH2n+2). The Landau phenomenological model is used by expanding the free energy in terms of the lattice distortion parameter (D) and the tilt angle (theta) of the rotator (and crystal) phases with their quadratic coupling (D-2 theta(2)). The phase line equations are obtained with some approximations by considering the first order transitions between the phases in n-alkanes. By assuming the temperature and concentration dependence of some parameters in the Landau mean field expansion, the T-n phase diagram is established by using the observed data from the literature. Our results are satisfactory to explain the first order transition between the phases, mainly for the rotator and crystal phases in n-alkanes (CnH2n+2). The T-n phase diagrams can also be obtained for some other compounds of similar structures by the Landau phenomenological model as given in this study. (C) 2022 Elsevier B.V. All rights reserved.
Calculation of the T-P Phase Diagrams for the Halogenomethane Compounds (ccl4-Nbrn, N=0, 1, 2, 4) Using the Mean Field Theory
(Pleiades Publishing inc, 2019) Yurtseven, H.; Isik, S. B.; Dogan, E. Kilit
The T-P phase diagrams of the halogenomethane compounds (CCl4-nBrn, n = 0, 1, 2, 4) are calculated using a mean field model. By expanding the free energy in terms of the order parameters for the transitions of the liquid (L), rhombohedral (R), face-centered cubic (FCC) and monoclinic (M) phases in those compounds, the phase line equations are derived and they are fitted to the experimental data from the literature. This method of calculating the T-P phase diagram is satisfactory to explain the T-P measurements for the halogenomethane compounds and it can also be applied to two-component systems.
Calculation of the T-X Phase Diagram for the First-Order Smectic-Hexatic Transitions in Binary Mixtures
(Aip Publishing, 2022) Kilit Dogan, E.; Yurtseven, H.
This work gives the T-X phase diagram calculated from the Landau mean field model for the smectic-hexatic transitions in binary mixtures, particularly, in THI-13+THI-17. It is calculated near the SmC-SmF (Hex F)-Hex B triple point by considering transitions of SmC-SmF, SmF-HexB, and SmC-Hex B as the first order. The phase line equations are fitted to the experimental T-X phase diagram from the literature for this binary mixture by assuming the temperature and concentration dependence of the coefficients in the Landau free energy expansion. Calculations are given in some detail to describe the smectic-hexatic transitions in the THI-13+THI-17, which can also be considered for other binary mixtures under the Landau mean field model studied here. Published under an exclusive license by AIP Publishing.
Critical Behavior of the Dielectric Susceptibility for the Ferroelectric Liquid A7
(Springer, 2011) Yurtseven, H.; Kilit, E.
The temperature dependence of the dielectric susceptibility is studied here for the smectic A-isotropic liquid transition of the ferroelectric A7. From the analysis of the experimental data for the dielectric constant, the critical behavior of the dielectric susceptibility is described close to the smectic A-isotropic liquid transition in this liquid crystal.
Ferromagnetic and Antiferromagnetic Properties in Layered Structures (La0.6nd0.4mn2si2)
(Elsevier, 2015) Dogan, E. Kilit; Emre, B.; Yurtseven, H.
Temperature dependences of the magnetization (ferromagnetic) and the staggered magnetization (anti-ferromagnetic) are analyzed for various ferromagnetic (FM) and antiferromagnetic (AF) phases of the layered structure of La0.6Nd0.4Mn2Si2 using the experimental data at a constant magnetic field of 50 Oe. For this analysis, a mean field model with the quadratic coupling between the magnetization (FM) and the staggered magnetization (AF) is considered and the expressions derived from the mean field model for the magnetization and the staggered magnetization, are fitted to the experimental data. Our results indicate that the quadrupole-quadrupole interactions for the ferromagnetic and antiferromagnetic spin configurations play a dominant role to describe the ferromagnetic and antiferromagnetic properties of the layered structure of La0.6Nd0.4Mn2Si2. (C) 2015 Elsevier B.V. All rights reserved.
A First-Order Transition of the Smectic A-Smectic C* in Ferroelectric Liquid Crystals
(Taylor & Francis Ltd, 2012) Kilit, E.; Yurtseven, H.
The static dielectric constant is calculated as a function of temperature using a mean field model close to the smectic A-smectic C* transition for the ferroelectric liquid crystal 4-(3-methyl-2-chlorobutanoyloxy)-4'-heptyloxybiphenyl (A7). This calculation of the dielectric constant is performed for the pure optically active compound (T-c = 73.4 degrees C) and the temperature range is determined for a first-order smectic A-smectic C* transition from the mean field model. Our predicted values describe adequately the observed behaviour of the dielectric constant close to the smectic A-smectic C* transition and also the temperature range in the smectic A phase of A7.
Magnetic Ordering in Two Ferromagnetic Sublattices of Two Mixed-Valence Iron(ii)-Iron(iii) Metal Formate Frameworks
(Pergamon-elsevier Science Ltd, 2019) Yurtseven, H.; Dogan, E. Kilit
Temperature dependence of magnetization (M) is calculated for two mixed-valence iron(II) - iron(III) metal formate frameworks (MOFs) with the two ferromagnetic sublattices below T-comp (compensation temperature) at 100 Oe by the molecular field theory. Temperature dependence of magnetization (M-T) is analyzed between T(comp )and T-ord = 39K (ordering temperature) by the power-law formula using the literature data for those compounds. Power-law analysis is also carried out for the field dependence of magnetization (M-H) for 0 < H < 50 Oe interval (T = 2 K) by using the literature data for those MOFs. From both power-law analyses, the temperature-induced (beta) and field-induced (delta) critical exponents for magnetization are deduced for the compounds studied. Calculation and analysis of magnetization for two ferromagnetic sublattice system, indicate that two mixed-valence iron (II)-iron(III) MOFs undergo weakly first order or nearly second order magnetic phase transition.
Magnetic, Thermal and Ferroelectric Properties of Mofs (Mhym, M = Fe, Mn) Close To Phase Transitions
(Elsevier, 2021) Yurtseven, H.; Dogan, E. Kilit
Magnetic, thermal and ferroelectric properties of MOFs (metal organic frameworks), in particular, the compounds CH3NH2NH2M(HCOO)(3) (MHyM) with M = Fe and Mn, are studied close to phase transitions. For the magnetic properties, the molecular field theory at low temperatures and the power-law formula within the framework of an Ising pseudospin-phonon coupled model close to TC are performed by using the observed magnetization data for MHyFe and MHyMn from the literature. For the thermal properties, particularly, the heat capacity CP, Ising compressible model with the power-law formula is introduced to analyze the experimental data by considering the two anomalies in CP at the critical temperatures (TC1 and TC2) for MHyFe and MHyMn. Within these two anomalies, the ferroelectric properties of MHyMn are also studied by analyzing the observed data for the spontaneous polarization PS using the power-law formula. Our calculations show that the molecular field theory is satisfactory for the temperature dependence of the magnetization at low temperatures well below TC at constant fields, with the M(T) at 0.1 kOe close to TC in MHyFe. Values of the critical exponent beta for the magnetization from our analysis using the power-law formula close to T-C(=T-m), are acceptable for both compounds (MHyFe and MHyMn). Regarding the thermal properties, an Ising compressible model is adequate to describe the observed behaviour of the heat capacity C-P with the two anomalies (TC1 and TC2) for MHyFe and MHyMn. Also, for the ferroelectric properties of those compounds the temperature dependence of the spontaneous polarization P-S at TC1 and TC2 (MHyMn) is studied by the power-law formula from an Ising compressible model which describes the observed behaviour of P-S in this compound.
Magnetization Studied as a Function of Temperature and Magnetic Field for Ferromagnetic Transition in Dmnafe
(Springer, 2020) Kilit Dogan, E.; Yurtseven, H.
Magnetization has been calculated as a function of temperature in the ferromagnetic phase of (CH3)(2)NH2Na0.5Fe0.5(HCOO)(3)denoted by DMNaFe as one of the metal formate framework by using molecular field theory. CalculatedM(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.
Temperature and the Field Dependence of the Magnetization Close To Order-Disorder Phase Transitions in Dmmn and the Chromium-Doped Dmmn
(Pergamon-elsevier Science Ltd, 2018) Yurtseven, H.; Dogan, E. Kilit
We study the temperature and field dependence of the magnetization M(T,H) for the order-disorder transition in DMMn and the chromium-doped DMMn close to T-c. By analyzing the experimental data for M(T,H) from the literature according to the power-law formula, values of the critical exponent (beta) and the critical isotherm (delta) are deduced and also, the temperature dependence of magnetization M(T) is calculated from the molecular field theory for those compounds. Our calculated M(T) and the values of beta and delta from the analysis of M(T,H) indicate that DMMn and chromium-doped DMMn undergo nearly second order transition. (C) 2018 Elsevier Ltd. All rights reserved.
Temperature Dependence of the Dielectric Constant Calculated Using a Mean Field Model Close To the Smectic a - Isotropic Liquid Transition
(intech Europe, 2011) Yurtseven, H.; Kilit, E.
Thermodynamic Parameters of Cholesteric/Smectic a Transition in Cholesteric Myristate and Its Binary Mixture Cm/Pcpb
(Maik Nauka/interperiodica/springer, 2018) Yurtseven, H.; Dogan, E. Kilit
Thermodynamic properties of the cholesteryl myristate (CM) and its binary mixture CM/PCPB (p-pentylphenyl-2-chloro-4(p-pentylbenzoyl)-benzoate) are studied at the concentrations of x (PCPB) = 0.052 and 0.219 as a function of temperature near the cholosteric/smectic A transition. By analyzing the observed molar volume from the literature, the temperature dependences of the thermal expansion, isothermal compressibility and the difference in the specific heat are calculated and, the Pippard relations are established for those compounds close to the cholesteric/smectic A transition. Predictions of the thermodynamic quantities and the Pippard relations can be examined by the experimental measurements of the CM and its binary mixture of CM/PCPB close to the cholesteric/smectic A transition.