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Abstract: Density functional FP-LAPW+lo calculations have been performed to study the structural, electronic and magnetic properties of Mg1−x Mn x Te for compositional parameter x =0.25, 0.50, 0.75 and 1. Our calculations reveal the occurrence of ferromagnetism in these compounds in which the transition-metal atom is ordered in a periodical way thereby interacting directly with the host atoms. Results extracted from electronic band structure and density of states (DOS) of these alloys show the existence of direct energy band gap for both majority- and minority-spin cases, while the total energy calculations confirm the stability of ferromagnetic state as compared to anti-ferromagnetic state. The total magnetic moment for Mg1−x Mn x Te for each composition is found to be approximately 5μB, which indicates that the addition of Mn content does not affect the hole carrier concentration of the perfect MgTe compound. Moreover, the s–d exchange constant (N 0 α) and p–d exchange constant (N 0 β) are also calculated which are in accordance with a typical magneto-optical experiment. The estimated spin-exchange splitting energies originated by Mn 3d states energies, i.e. Δ X (s–d) and Δ X (p–d), show that the effective potential for minority-spin is more attractive than that of the majority-spin. Also, the p–d hybridization is found to cause the reduction of local magnetic moment of Mn and produce small local magnetic moments on the nonmagnetic Mg and Te sites. [Copyright &y& Elsevier]

Abstract: Structural, electronic and optical properties of ternary alloy system Cd x Zn1−x S have been studied using first-principles approach based on density functional theory. Electronic structure, density of states and energy band gap values for Cd x Zn1−x S are estimated in the range 0≤ x ≤1 using both the standard local density approximation (LDA) as well as the generalized gradient approximations (GGA) of Wu–Cohen (WC) for the exchange-correlation potential. It is observed that the direct band gap of Cd x Zn1−x S decreases nonlinearly with the compositional parameter x, as observed experimentally. It is also found that Cd s and d, S p and Zn d states play a major role in determining the electronic properties of this alloy system. Furthermore, results for complex dielectric constant ɛ(ω), refractive index n(ω), normal-incidence reflectivity R(ω), absorption coefficient α(ω) and optical conductivity σ(ω) are also described in a wide range of the incident photon energy and compared with the existing experimental data. [ABSTRACT FROM AUTHOR]

To probe the applications in spintronics and sustainable energy devices of ZnMn 2 X 4 (X=S, Se, Te) spinels, their structural, elastic, electronic and thermoelectric properties have been studied in the present work. Structural properties reveal stability of ferromagnetic (FM) phase in these spinels which is further confirmed by computing the heat of formation for these compounds. The mechanical properties of the ZnMn 2 X 4 spinels have been investigated by computing their elastic constants, which show that all these spinels exhibit a brittle character. Moreover, electronic band structure and density of states reveal a half-metallic FM structure in all these spinels. Analysis of the band structure of these materials reveals a semiconducting nature in the spin down channel. Exchange constants (N 0 α and N 0 β) have been computed to directly probe the state splitting and our results large splitting of Mn 3d-states by N 0 β owing to its larger negative value as compared to N 0 α. The strong p-d hybridization is found to make exchange field dominant to crystal field which consequently induces ferromagnetism. In addition, the p-d hybridization reduces the magnetic moment of Mn ions by inducing traces of magnetic moments at non-magnetic sites. The observation of thermoelectric behavior within temperature range 200K–800K reveals positive Seeback coefficient indicating holes as majority charge carriers. Although the power factor is found to increase on going from ZnMn 2 S 4 to ZnMn 2 Te 4 , our results clearly show improvement of power factor with increasing temperature. Image 1 • Density functional theory calculations are performed for ZnMn 2 X 4 (X = S, Se, Te). • Structural analysis depict FM stability of ZnMn 2 X 4 (X = S, Se, Te). • The band structures analysis show their half-metallic nature of ZnMn 2 X 4 (X = S, Se, Te). • The computed magnetic parameters indicate potential spintronic devices applications. • The temperature effect on thermoelectric properties indicate that the material can be used even at elevated temperatures. [ABSTRACT FROM AUTHOR]

In this study, we have employed first-principle calculations to investigate the structural, mechanical, electronic, magnetic and the optical properties of Co-doped ZnS and ZnSe compounds. The ferromagnetic structural stability is determined from the calculated total energy difference between ferromagnetic and antiferromagnetic phases. The calculated mechanical properties show that these materials are mechanically stable, ductile and anisotropic. The modified Becke-Johnson local density approximation functional is used for accurate prediction of the electronic properties of Co-doped ZnS and ZnSe. The electronic band structures and density of states plots reveal ferromagnetic semiconducting behavior in these compounds, which is explained in terms of exchange and crystal field splitting energies, exchange constants and magnetic moments. The optical properties have been studied systematically by computing parameters like real and imaginary part of the dielectric constant, refractive index, extinction and absorption coefficients, optical conductivity, reflectivity and energy loss function. The tuning of band gap from ultraviolet to visible region with minimum optical loss, due to the Co doping, makes these materials suitable candidates for optoelectronic device fabrications. [ABSTRACT FROM AUTHOR]