日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

Physical Review B

A Guide to Monte Carlo Simulations in Statistical Physics: Some necessary background

The generalization of the Local Density Approximation (LDA) method for the systems with strong Coulomb correlations is presented which gives a correct description of the Mott insulators. The LDA+U method is based on the model hamiltonian approach and allows to take into account the non-sphericity of the Coulomb and exchange interactions. parameters. Orbital-dependent LDA+U potential gives correct orbital polarization and corresponding Jahn-Teller distortion. To calculate the spectra of the strongly correlated systems the impurity Anderson model should be solved with a many-electron trial wave function. All parameters of the many-electron hamiltonian are taken from LDA+U calculations. The method was applied to NiO and has shown good agreement with experimental photoemission spectra and with the oxygen Kα X-ray emission spectrum.

http://absimage.aps.org/image/MAR06/MWS_MAR06-2005-007233.pdf

First-principles calculations of electronic structure and spectra of strongly correlated systems: the LDA+U method

Advanced Functional Materials

Size effect on magnetic properties of a nano-graphene bilayer structure: A Monte Carlo study

The magnetic properties of an Ising antiferromagnetic model on a nanographene lattice which have spins that can take the values S=±3/2, ±1/2, are studied by Monte Carlo simulations. We only consider the nearest-neighbor interactions between the sites i and j. The zero field cooled and field cooled magnetizations, magnetic susceptibilities and hysteresis cycle are obtained for a nanographene structure with the effect of exchange interaction between sites i and j. The blocking temperature is also obtained for specific values of the external magnetic field.

Nanographene Magnetic Properties: A Monte Carlo Study

The effect of the defects on magnetic properties of a bilayer Ising ferromagnetic antiferromagnetic model is studied by Monte Carlo simulations, for a nano-graphene lattice with spins that can take the values σ=3/2 and S=5/2. We consider two ferromagnetic and antiferromagnetic bilayers with N=42 spins, with a random number of defects. We only consider the nearest-neighbor interactions between the site i and j on each layer. The effects of the defects on magnetization are investigated for fixed temperature, crystal field, and magnetic field values. The thermal dependency of each layer magnetization is calculated for fixed defect rate values K
 3 and K
 5, the crystal field, and external magnetic field. The magnetization hysteresis loops for several rate defects are also investigated as a function of the external magnetic field.

Magnetism of Nano-Graphene with Defects: A Monte Carlo Study

In this manuscript, we investigate the physical properties such as the magnetic and the electronic properties of the Co-based equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge). These investigations have been performed by employing the Quantum Espresso code in the framework of density functional theory (DFT). The generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) is used for all these calculations. The band structures, and density of states calculations, show that all these materials CoYCrZ (Z = Si and Ge) exhibit a half-metallic (HM) behavior only for the structure type II. Moreover, this structure type II is found to be the most stable configuration for all these alloys. On the other hand, it has been found that the Slater–Pauling is well described for the compound CoYCrGe, only for the configuration type II. In particular, the equiatomic quaternary Heusler alloys CoYCrSi and CoYCrGe are found to be half-metallic for the structure type II. This is due to the fact that they have 100% spin polarization SP. Also, the existence of complete SP in the studied alloys is the reason for which these materials are useful for spintronic device applications.

Investigation of the physical properties of the equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge): a DFT study

The magnetic behaviors of a mixed spins (2-1) hexagonal Ising nanowire with core–shell structure are investigated by using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperatures of core–shell are studied for different values of crystal field and exchange interactions. The thermal and magnetic hysteresis cycles are given for different values of the crystal field.

L. Bahmad

Papers

Size effect on magnetic properties of a nano-graphene bilayer structure: A Monte Carlo study

Nanographene Magnetic Properties: A Monte Carlo Study

Magnetism of Nano-Graphene with Defects: A Monte Carlo Study

Investigation of the physical properties of the equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge): a DFT study

Hysteresis and compensation behaviors of mixed spin-2 and spin-1 hexagonal Ising nanowire core-shell structure