Browsing by Author "Dogan, E. Kilit"

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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 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.
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.
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.
Structural, Electronic, Dynamic, Optic and Elastic Properties of Mgscga Via Density Functional Theory
(Pergamon-elsevier Science Ltd, 2021) Dogan, E. Kilit; Gulebaglan, S. Erden
The structural, electronic and phonon properties of the MgScGa compound were investigated by density functional theory using the generalized gradient approximation. Some basic structural properties of this compound, such as the lattice constants, bulk modulus and pressure derivative of the bulk module have been studied. Electronic properties were investigated by calculating and analyzing the electronic band structure and total density of states graphs for the MgScGa compound. Electronic band structure calculations showed that MgScGa compound has a semiconductor structure. Phonon spectra were calculated using a linear response method within the framework of the total predicted state density, density functional perturbation theory for the MgScGa compound. A factor group analysis has been performed in order to get the decomposition of whole representation of Gamma of MgScGa compound into irreducible representation. For investigation of optic properties; real and imaginary components of complex dielectric function, reflectivity (R), refractive index (n), extinction coefficients (k), energy-loss functions for volume (L-V) and surface (L-S), the effective number of valence electrons per unit cell (N-eff) were calculated. Elastic properties are revealed by calculating the elastic stiffness constants, Bulk, Shear and Young modulus, Poisson Ratio, Flexibility Coefficient and Zener anisotropy constant.
Structural, Thermodynamic and Phonon Properties of Sbsi and Sbsbr Single Crystals
(Korean Physical Soc, 2013) Dogan, E. Kilit; Aycibin, M.; Gulebaglan, S. Erden; Secuk, M. N.; Erdinc, B.; Akkus, H.
The structural, dynamical and thermodynamic properties of antimony sulfoiodide (SbSI) and antimony sulfobromide (SbSBr) are investigated by using an ab-initio pseudopotential method applying density functional theory (DFT) within the local density approximation (LDA). The dynamical properties, such as the phonon dispersion and the phonon density of states, are calculated. Making a factor group analysis we classify the phonon modes. Moreover, the thermodynamic properties, such as the entropy and the constant-volume specific heat, as functions of temperature and the phonon contribution to the free energy and the internal energy are calculated.
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.
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.