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Exploring ferromagnetic half-metallic nature of Cs2NpBr6 via spin polarized density functional theory

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Chinese Physics B 2020年第6期29卷 364-368页

作者： Malak Azmat Ali g murtaza A Laref Department of Physics Government Post Graduate Jahanzeb College Saidu SharifSwat 19130Khyber PakhtunkhwaPakistan Materials Modeling Laboratory Department of PhysicsIslamia College Peshawar 25120Khyber PakhtunkhwaPakistan Department of Physics and Astronomy College of SciencesKing Saud UniversityRiyadh11451 Kingdom of Saudi Arabia

By employing the spin resolved density functional theory, half-metallic character is investigated in Cs2NpBr6 having a K2PtCl6-type structure. The results precisely predict the half-metallic behavior of Cs2NpBr6. In spin-down state it presents an indirect band gap, while in spin-up channel it turns metallic. The structure optimization confirms the half-metallic nature in ferromagnetic configuration. The calculated magnetic moment is 3 μB toward which the main contributor is the Np ***, all the computed results are compared with the available experimental and theoretical values. According to the present analysis, we recommend Cs2NpBr6 for spintronic applications.

关键词： half-metallic ferromagnetic magnetic moment spintronics

Energy transport for ion acoustic waves in a spin polarized quantum plasma

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Communications in Theoretical Physics 2020年第1期72卷 124-129页

作者： M Ayub Z Iqbal H A Shah g murtaza Salam Chair Department of PhysicsG.C.UniversityKatchery RoadLahore 54000Pakistan Department of Physics G.C.UniversityKatchery RoadLahore 54000Pakistan Department of Physics Mirpur University of Science and TechnologyMirpur-10250(AJK)Pakistan

The separate spin evolution quantum hydrodynamics(SSE-QHD)model is used to investigate the energy behavior for ion acoustic waves in degenerate quantum *** results show that the energy flow speed decreases with spin polarization *** is also shown that it decreases with the increasing rate up to a certain range of wave number and then it goes to zero *** is observed that Bohm potential suppresses the energy flow *** is also noticed that the energy flow speed deviates from the group velocity even in the absence of Bohm potential ***,the contribution of of Bohm poential effect in spin polarized plasma reduces the extent of deviation.

关键词： spin polarization quantum plasma ion acoustic wave energy flow speed

Alfvén waves in temperature anisotropic Cairns distributed plasma

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Communications in Theoretical Physics 2020年第3期72卷 83-87页

作者： S Ayaz Imran A Khan Z Iqbal g murtaza Salam Chair Department of PhysicsGC University Lahore Katchery Road54000 LahorePakistan

The dispersion relations and Landau damping of Alfven waves in kinetic and inertial limits are studied in temperature anisotropic Cairns distributed *** the case of kinetic Alfven waves(KAWs),it is found that the real frequency is enhanced when either the electron perpendicular temperature or the non-thermal parameter A *** inertial Alfven waves(IAWs),the real frequency is slightly affected by the electron temperature anisotropy and *** the real frequency,the damping rate of KAWs is reduced when the electron perpendicular temperature or A *** the case of IAWs,the temperature anisotropy and A either enhance or reduce the damping rate depending upon the perpendicular *** results may be helpful to understand the dynamics of KAWs and IAWs in space plasmas where the non-Maxwellian distribution of particles are routinely observed.

关键词： Cairns distribution kinetic Alfven waves inertial Alfven waves

Kinetic Instability of Anisotropic Drift Wave Accompanied by Field Aligned Currents in Solar Coronal Loop

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Communications in Theoretical Physics 2018年第10期70卷 470-476页

作者： Hafsa Naim Ch.Uzma g.murtaza Salam Chair Department of Physics GC University

Solar coronal loops are frequently accompanied by the field-aligned currents, which drive instabilities if the drift velocity u0 > v A the Alfv′en velocity. For our choice of parameters, the critical threshold value of u0/v A is ～ 3.0 for growth and the corresponding current filling factor ～ 10-3-10-4. Below this value we are no longer in the kinetic *** coronal loops also have short-scale density gradients within each loop. The electron resonance in the presence of density gradient causes the drift mode to grow. We study the effect of these two free energy sources, the electron drift and the density gradient, in the presence of temperature anisotropy T⊥_α > T∥_α. These effects simultaneously exist in the coronae. Using gyrokinetic theory, we investigate the influence of these effects, examine how they interplay with each other and study the consequent growth of the magnetosonic wave. We observe that kinetic instability driven by density gradient can be suppressed by field-aligned currents. The temperature anisotropy with chosen signatures causes further stabilizing effect. The results may prove useful to study the heating mechanism of solar coronal loops, acceleration of particles and confinement of particles in the thermonuclear reactors.

关键词： solar corona coronal loops temperature anisotropy density inhomogeneity field-aligned currents gyrokinetic

Linear Analysis of Obliquely Propagating Longitudinal Waves in Partially Spin Polarized Degenerate Magnetized Plasma

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Communications in Theoretical Physics 2017年第12期67卷 791-797页

作者： Z.Iqbal g.murtaza A.Hussain Salam Chair Department of Physics G.C. University Lahore Department of Physics Mirpur University of Science and Technology

Linear analysis of low frequency obliquely propagating electrostatic waves in a partially spin polarized degenerate magnetized plasma is presented. Using Fourier analysis, a general linear dispersion relation is derived for low frequency electrostatic lower hybrid(LH) wave, ion acoustic(IA) wave and ion cyclotron(IC) wave in the presence of electron spin polarization. It is found that the electron spin polarization gives birth to a new spin-dependent wave(spin electron acoustic wave) in the spectrum of these waves. Further, the electron spin polarization also causes drastic shifts in the frequency spectrum of these waves. These effects would have a strong bearing on wave phenomena in degenerate astrophysical plasmas.

关键词： spin polarization longitudinal waves degenerate plasma

Ordinary Mode Instability in a Cairns Distributed Electron Plasma

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Communications in Theoretical Physics 2018年第6期69卷 699-703页

作者： K.Azra Z.Iqbal g.murtaza Salam Chair Department of PhysicsG.C.UniversityLahore 54000Pakistan

Employing the linearized Vlasov-Maxwell equations, a generalized dispersion relation for the ordinary mode is derived by employing the Cairns distribution function. The instability of the mode and its threshold condition is investigated. It is found that the temperature anisotropy χ= TⅡ I⊥〉 1 required to excite the instability varies with density values whereas the growth rate is dependent on various parameters like non-thermMity A, equilibrium number density no and temperature anisotropy. It is found that with the increase in the values of any of the parameters A, no and X, the growth rate is enhanced and the k-domain is enlarged. The results are applicable for space plasma environments like solar wind.

关键词： ordinary mode Cairns distribution temperature anisotropy instability

Electronic Band Structure and Optical Response of Spinel SnX_(2)O_(4)(X=Mg,Zn)through Modified Becke-Johnson Potential

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Chinese Physics Letters 2013年第4期30卷 177-180页

作者： A.Manzar g.murtaza R.Khenata S.Muhammad Hayatullah Department of Physics Hazara University MansehraKPKPakistan Materials Modeling Lab Department of PhysicsIslamia College UniversityPeshawarPakistan LPQ3M Laboratory Institute of Science and TechnologyUniversity of MascaraAlgeria Department of Physics and Astronomy King Saud UniversityP.O.Box 2455Riyadh 11451Saudi Arabia

The modified Becke–Johnson exchange potential approximation is applied to predict the band structure,optical parameters and electron density of SnMg_(2)O_(4)and SnZn_(2)O_(4).The local density approximation,generalized gradient approximation(ggA),EV-ggA significantly underestimate the direct band gap values compared to modified Becke–Johnson *** band gap dependent optical parameters such as dielectric constant,index of refraction,reflectivity,and optical conductivity are calculated and analyzed.A prominent feature of cation replacement is observed and analyzed for these studied *** replacement of the cation Mg by Zn leads to a significant reduction in the value of band gap and consequently affects its dependant optical *** variation is of crucial importance for device fabrication in different regions of the spectrum.

关键词： approximation (4) Modified

The effect of replacing pnictogen elements on the physical properties of SrMg_2X_2(X=N,P,As,Sb,Bi) Zintl compounds

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Chinese Physics B 2018年第4期27卷 369-375页

作者： g murtaza Abdul Ahad Khan M Yaseen A Laref Naeem Ullah Inayat ur Rahman Materials Modelling Labortary Department of PhysicsIslamia College University Department of Physics University of the Peshawar Department of Physics University of AgricultureFaisalabad Department of Physics and Astronomy College of ScienceKing Saud University Department of Physics City University of Hong Kong

The effect of replacing the anion from N to Bi down the group in the periodic table is investigated on SrMg2X2（X = N,P,As,Sb,Bi）.A full potential linearized augmented plane wave plus local orbitals method is used along with different exchange–correlation potentials to obtain the lattice constants,phonons,electronic,and optical properties of the Sr Mg2X2（X = N,P,As,Sb,Bi） Zintl compounds.A good agreement is achieved and our calculations are validated by previous experimental and theoretical *** compounds have shown stable dynamical behavior with gamma centered longitudinal response having no imaginary *** band structures reveal the semiconducting nature of the *** Pnictogen（X）-p state contributed mainly in the valence band and the Sr-d state forms the conduction of the *** charge transfer and low overlapping of the atomic densities indicates the preferable ionic bonding character of these *** the optical properties,real and imaginary parts of dielectric function,complex refractive index,birefringence,reflectivity,and optical conductivity are *** compounds can be utilized in the optical and optoelectronic devices.

关键词： Zintl compounds band structure optical response

Electronic Band Profile and Optical Response of Spinel MgIn_(2)O_(4)through Modified Becke-Johnson Potential

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Chinese Physics Letters 2013年第6期30卷 190-193页

We employ the first-principles technique based on the modified Becke–Johnson(BJ)exchange potential for the prediction of the electronic band structure,optical properties,and electron density of the cubic MgIn_(2)O_(4)spinel *** is found that the calculated band gap value with the modified BJ approximation is significantly improved over the results based on the generalized gradient approximation and the local density approximation in comparison to the experimental *** band gap dependent optical parameters such as the dielectric constant,refractive index,reflectivity,optical conductivity,and electron density are *** optical response suggests that MgIn_(2)O_(4)is an applicant material in optoelectronic devices in various parts of the energy spectrum like MgAl_(2)O_(4)and Mgga_(2)O_(4).

关键词： approximation Modified reflectivity