Entity

Time filter

Source Type

Tétouan, Morocco

Sahu S.,KIIT University | Rout G.C.,Condensed Matter Physics Group
Journal of Magnetism and Magnetic Materials | Year: 2016

We present here a tight-binding model study of generation of magnetism and pseudo-spin polarization in monolayer graphene arising due to substrate, impurity and Coulomb correlation effects. The model Hamiltonian contains the first-, second- and third-nearest-neighbor hopping integrals for π electrons of graphene besides substrate induced gap, impurity interactions and Coulomb correlation of electrons. The Hubbard type Coulomb interactions present in both the sub-lattices A and B are treated within the mean-field approximation. The electronic Green's functions are calculated by using Zubarev's technique and hence the electron occupancies of both sub-lattices are calculated for up and down spins separately. These four temperature dependent occupancies are calculated numerically and self-consistently. Then we have calculated the temperature dependent pseudo-spin polarization, ferromagnetic and anti-ferromagnetic magnetizations. We observe that there exists pseudo-spin polarization for lower Coulomb energy, u<2.2t1 and pseudo-spin polarization is enhanced with substrate induced gap and impurity effect. For larger Coulomb energy u>2.5t1, there exists pseudo-spin polarization (p); while ferromagnetic (m) and antiferromagnetic (p m) magnetizations exhibit oscillatory behavior. With increase of the substrate induced gap, the ferromagnetic and antiferromagnetic transition temperatures are enhanced with increase of the substrate induced gap; while polarization (p) is enhanced in magnitude only. © 2016 Elsevier B.V. Source


Fahd C.,Condensed Matter Physics Group | Anas H.,National School of Technology | Otman A.,Electronics and Microwaves Group | Mounia C.,Condensed Matter Physics Group | Mounir E.Y.,Condensed Matter Physics Group
International Journal of Microwave and Optical Technology | Year: 2015

In this paper, Chirped Fiber Bragg Grating (FBG) has been introduced as a dispersion compensator in dense Wavelength Division Multiplexing (WDM) for optical long-haul network. The new model has been compared with a previous work proposed by other authors having DCF as dispersion compensator. Both configurations have been modeled and simulated using the same initial setting so as to prove the efficiency of our model. For this purpose, different parameters of the Chirped FBG which include chirp parameter, apodization function and grating length, have been investigated in order to get the most suitable settings of the proposed model. The WDM transmission system is simulated using the advanced tools of Optisystem 7.0. The simulation results have been examined and validated by analyzing the eye diagram for short and long channel lengths, the Q-factor, the BER analysis and nonlinear effects at WDM network. © 2015 IAMOT. Source

Discover hidden collaborations