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effective-field theory on High Spin Systems with Biaxial Crystal field

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Communications in Theoretical Physics 2006年第6X期46卷 1105-1108页

作者： JIANG Wei GUO An-Bang LI Xin WANG Xi-Kun BAI Bao-Dong College of Sciences Shenyang University of Technology Shenyang 110023 China School of Electrical Engineering Shenyang University of Technology Shenyang 110023 China

Based on the effective-field theory with self-spin correlations and the differential operator technique, physical properties of the spin-2 system with biaxial crystal field on the .simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization, internal energy, specific heat, and susceptibility have been discussed in detail The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found.

关键词： effective-field theory magnetic properties biaxial crystal field quantum effects

Kinetic Ising model in a time-dependent oscillating external magnetic field:effective-field theory

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Chinese Physics B 2010年第5期19卷 187-194页

作者： Bayram Deviren Osman Canko Mustafa Keskin Institute of Science Erciyes University38039 KayseriTurkey Department of Physics Nevsehir University50300 NevsehirTurkey Department of Physics Erciyes University38039 KayseriTurkey

Recently, Shiet al. [2008 Phys. Left. A 372 5922] have studied the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field and presented the dynamic phase diagrams by using an effective-field theory （EFT） and a mean-field theory （MFT）. The MFT results are in conflict with those of the earlier work of Tome and de Oliveira, [1990 Phys. Rev. A 41 4251]. We calculate the dynamic phase diagrams and find that our results are similar to those of the earlier work of Tome and de Oliveira; hence the dynamic phase diagrams calculated by Shiet al. are incomplete within both theories, except the low values of frequencies for the MFT calculation. We also investigate the influence of external field frequency （w） and static external field amplitude （h0） for both MFT and EFT calculations. We find that the behaviour of the system strongly depends on the values of w and h0.

关键词： kinetic Ising model effective-field theory mean-field theory

Phase diagrams in mixed spin-3/2 and spin-2 Ising system with two alternative layers within the effective-field theory

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Chinese Physics B 2011年第6期20卷 112-124页

作者： Bayram Deviren Yasin Polat Mustafa Keskin Department of Physics Nevsehir University Institute of Science Erciyes University Department of Physics Erciyes University

The phase diagrams in the mixed spin-3/2 and spin-2 Ising system with two alternative layers on a honeycomb lattice are investigated and discussed by the use of the effective-field theory with correlations. The interaction of the nearest-neighbour spins of each layer is taken to be positive （ferromagnetic interaction） and the interaction of the adjacent spins of the nearest-neighbour layers is considered to be either positive or negative （ferromagnetic or antiferromagnetic interaction）. The temperature dependence of the layer magnetizations of the system is examined to characterize the nature （continuous or discontinuous） of the phase transitions and obtain the phase transition temperatures. The system exhibits both second- and first-order phase transitions besides triple point （TP）, critical end point （E）, multicritical point （A）, isolated critical point （C） and reentrant behaviour depending on the interaction parameters. We have also studied the temperature dependence of the total magnetization to find the compensation points, as well as to determine the type of behaviour, and N-type behaviour in Neel classification nomenclature existing in the system. The phase diagrams are constructed in eight different planes and it is found that the system also presents the compensation phenomena depending on the sign of the bilinear exchange interactions.

关键词： mixed spin-3/2 and spin-2 Ising system effective-field theory compensation phenomena phase diagrams

An effective-field theory study of hexagonal Ising nanowire: Thermal and magnetic properties

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Chinese Physics B 2014年第4期23卷 465-471页

作者： Yusuf Kocakaplan Ersin Kantar Institute of Science Erciyes University Department of Physics Erciyes University

By means of the effective-field theory （EFT） with correlations, the thermodynamic and magnetic quantities （such as magnetization, susceptibility, internal energy, specific heat, free energy, hysteresis curves, and compensation behaviors） of the spin-l/2 hexagonal Ising nanowire （HIN） system with core/shell structure have been presented. The hysteresis curves are obtained for different values of the system parameters, in both ferromagnetic and antiferromagnetic cases. It has been shown that the system only undergoes a second-order phase transition. Moreover, from the thermal variations of the total magnetization, the five compensation types can be found under certain conditions, namely the Q-, R-, S-, P-, and N-types.

关键词： hexagonal Ising nanowire effective-field theory hysteresis curve compensation behavior

Phase diagrams of spin-3/2 Ising model in the presence of random crystal field within the effective field theory based on two approximations

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Chinese Physics B 2013年第10期22卷 186-191页

作者： Ali Yigit Erhan Albayrak Department of Physics anklrl Karatekin University Department of Physics Erciyes University

The bimodal random crystal field （A） effects are investigated on the phase diagrams of spin-3/2 Ising model by using the effective-field theory with correlations based on two approximations： the general van der Waerden identity and the approximated van der Waerden identity. In our approach, the crystal field is either turned on or turned off randomly for a given probability p or q = 1 -p, respectively. Then the phase diagrams are constructed on the （A,kT/J） and （p,kT/J） planes for given p and A, respectively, when the coordination number is z = 3. Furthermore, the effect of randomization of the crystal field is illustrated on the （△,kT/J） plane for p = 0.5 when z - 3,4, and 6. All these are carried out for both approximations and then the results are compared to point out the differences. In addition to the lines of second-order phase transitions, the model also exhibits first-order phase transitions and the lines of which terminate at the isolated critical points for high p values.

关键词： spin-3/2 random crystal field effective-field theory isolated critical point

Phase diagrams of the spin-2 Ising model in the presence of a quenched diluted crystal field distribution

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Chinese Physics B 2012年第11期21卷 114-120页

作者： Ali Yigit Erhan Albayrak ankiri Karatekin University Department of Physics Erciyes University Department of Physics

We have investigated the random crystal field effects on the phase diagrams of the spin-2 Blume-Capel model for a honeycomb lattice using the effective-field theory with correlations. To do so, the thermal variations of magnetization are studied via calculating the phase diagrams of the model. We have found that the model displays both second-order and first-order phase transitions in addition to the tricritical and isolated points. Reentrant behavior is also observed for some appropriate values of certain system parameters. Besides the usual ground-state phases of the spin-2 model including ±2, ~1, and 0, we have also observed the phases ±3/2 and ±1/2, which are unusual for the spin-2 case.

关键词： spin-2 model random crystal field effective-field theory isolated critical points andtriciritical points

Effects of the trimodal random field on the magnetic properties of a spin-1 Ising nanotube

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Chinese Physics B 2013年第11期22卷 445-452页

作者： H. Magoussi A. Zaim M. Kerouad Laboratoire Physique des Mate'riaux et Mode'lisation des Syste`mes (LP2MS) Unite' Associe'e au CNRST-URAC:08 University Moulay Ismail Faculty of Sciences B.P. 11201 Zitoune

In this work, the hysteresis behavior of a nanotube, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms with ferro-or anti-ferromagnetic interracial coupling is studied in the presence of a random magnetic field. Based on a probability distribution method, the effective-field theory has been used to investigate the effects of the random magnetic field, the interfacial coupling constant, and the temperature on the hysteresis loops of the nanotube. Some characteristic behaviors have been found, such as the existence of double or triple hysteresis loops for appropriate values of the system parameters. The remanent magnetization and the coercive field, as functions of the temperature, are examined.

关键词： effective-field theory nanotube critical phenomena

Magnetic hysteresis, compensation behaviors, and phase diagrams of bilayer honeycomb lattices

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Chinese Physics B 2015年第10期24卷 453-459页

作者： Ersin Kantar Department of Physics Erciyes University

Magnetic behaviors of the Ising system with bilayer honeycomb lattice（BHL） structure are studied by using the effective-field theory（EFT） with correlations. The effects of the interaction parameters on the magnetic properties of the system such as the hysteresis and compensation behaviors as well as phase diagrams are investigated. Moreover, when the hysteresis behaviors of the system are examined, single and double hysteresis loops are observed for various values of the interaction parameters. We obtain the L-, Q-, P-, and S-type compensation behaviors in the system. We also observe that the phase diagrams only exhibit the second-order phase transition. Hence, the system does not show the tricritical point（TCP）.

关键词： bilayer honeycomb lattices effective-field theory magnetic hysteresis compensation behavior phase diagram

The impact of segment dilution on the magnetic and hysteretic properties of ferrimagnetic (1/2-1) segmented Ising nanowire

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Communications in Theoretical Physics 2024年第7期76卷 145-155页

作者： Ersin Kantar Sorgun Vocational School Yozgat Bozok UniversityYozgat 66700Turkey

This study explores the presence of diverse phase diagrams and hysteresis characteristics,as well as their dependencies on segment dilution,in an Ising-type core/shell segmented *** magnetic and hysteretic behavior of the nanostructure was carefully investigated by employing the effective-field theory and its respective diluted *** phase diagrams reveal characteristic phenomena that are influenced by the dilution ***,this study examined the variations in phase transitions and tricritical points by altering the dilution and physical parameters of the *** investigation also encompasses an examination of the hysteresis characteristics,including the hysteresis loop,coercivity,and remanence,in relation to the segment dilution dependence of the segmented *** was discovered that as the temperature rises,the hysteresis loop areas ***,intriguingly,at specific dilution and crystal area values,the hysteresis loop areas exhibit an augmentation.

关键词： segmented nanowire effective-field theory diluted effect phase diagrams hysteresis characteristics