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[en] Highlights: • The increase in the internal parameters of the quantum ring, yields a decreasing of exciton binding energy and interband emission energy. The exciton binding energy increases as the radial thickness and height H of the quantum ring decrease. • The exciton binding energy increases with the pressure and decreases as the temperature increases. • The interband emission energy for exciton grows with pressure and is a decreasing function of the temperature. - Abstract: Using a variational approach, we have calculated the binding energies and interband emission energy of an exciton confined in quantum rings (QRs) structures under effects of the temperature and pressure, in the effective mass approximation. We have taken into consideration the difference in the effective masses of the charge carriers in two materials, well and barrier. The results that we have obtained show clearly that and are influenced by the structure geometries of QR (height , radial thickness and potential barrier), the temperature and pressure. Indeed, with a smaller geometric parameter, and become higher due to the improvement in confinement of the charge carriers. We have also observed that for a given value of the temperature, the pressure leads to an increasing of the and , and the latter quantities are decreasing with temperature. In addition, these variations of the and under the external perturbations are more remarkable in small for fixed , and for larger for a given value of the , because for the choice of a finite height of the barrier in the direction and an infinite confinement in direction.
[en] The self-consistent ab initio calculations, based on density functional theory approach (DFT) and using full potential linearised augmented plane wave (FLAPW) method, have been used to investigate both electronic and magnetic properties of the BaMnO3 perovskite. Spin-polarised calculations, including the spin-orbit interaction, are used to determine the energy of the ferromagnetic (FM) and antiferromagnetic (AFM) states of BaMnO3 perovskite. Obtained data from ab initio calculations are used as input for the Monte Carlo simulations to compute other magnetic parameters. Magnetisation, specific heat and magnetic entropy change have been given using the Monte Carlo simulations. The adiabatic temperature change, transition temperature and relative cooling power have been established.
[en] The self-consistent ab initio calculations based on the density functional theory approach using the full potential linear augmented plane wave method are performed to investigate both the electronic and magnetic properties of the NiFe compound. Polarized spin within the framework of the ferromagnetic state between magnetic ions is considered. Also, magnetic moments considered to lie along (001) axes are computed. The Monte Carlo simulation is used to study the magnetic properties of NiFe. The transition temperature T C, hysteresis loop, coercive field and remanent magnetization of the NiFe compound are obtained using the Monte Carlo simulation. (paper)
[en] Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full potential Linear Augmented Plane Wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the Mn2NiAl. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for Monte Carlo simulations to compute other magnetic parameters. Also, the magnetic properties of Mn2NiAl are studied using the Monte Carlo simulations. The variation of magnetization and magnetic susceptibility with the reduced temperature of Mn2NiAl are investigated. The transition temperature of this system is deduced for different values exchange interaction and crystal field. The thermal total magnetization has been obtained, and the magnetic hysteresis cycle is established. The total magnetic moment is superior to those obtained by the other method and is mainly determined by the antiparallel aligned MnI, MnII and Ni spin moments. The superparamagnetic phase is found at the neighborhood of transition temperature. - Highlights: • Ab initio calculations are used to study magnetic and electronic properties of Mn2NiX. • The transition temperature of Mn2NiX is established. • The magnetic hysteresis cycle of Mn2NiX (X = Al, Ga, In, Sn) is deduced. • The magnetic coercive field of Mn2NiX (X = Al, Ga, In, Sn) is given.