Systematic study of room-temperature ferromagnetism and the optical response of Zn_1−xTM_xS/Se (TM  =  Mn, Fe, Co, Ni) ferromagnets: first-principle approach

Abstract

The structural, magnetic and optical characteristics of Zn TM S/Se (TM = Mn, Fe, Co, Ni and x = 6.25%) have been investigated through the full-potential linearized augmented plane wave method within the framework of density functional theory. The optimized structures have been used to calculate the ferromagnetic and the antiferromagnetic ground-state energies. The stability of the ferromagnetic phase has been confirmed from the formation and the cohesive energies. The Heisenberg model is used to elucidate the Curie temperature (T) of these alloys. From the band structures and density of states plots, it has been observed that TM-doped ZnS/Se alloys appear to be semiconductors and exhibit ferromagnetism. In addition, the observed ferromagnetism has also been explained in terms of direct exchange energy Δ (d), exchange splitting energy Δ (pd), crystal-field energy (E ), exchange constants (N α and N β) and magnetic moments that shows potential spintronic applications. The optical behaviors of these alloys have been explained in terms of real and imaginary parts of the dielectric constant ε(ω), refractive index n(ω), extinction coefficient K(ω), reflectivity R(ω) and absorption coefficient σ(ω), in the energy range 0-25 eV. The calculated static limits of the band gaps and real part of the dielectric constants satisfy the Penn model. The critical limits of the imaginary part of the dielectric constants and absorption coefficients indicate that these alloys can be operated in the visible and the ultraviolet region of the electromagnetic spectrum; therefore, make them important for optoelectronic applications.

Half Metallic Ferromagnetism and Transport Properties of Zinc Chalcogenides ZnX2Se4 (X = Ti, V, Cr) for Spintronic Applications

“…Depending upon the number of unpaired electrons in the outermost shell, the magnetic moment of Ti is 2µ B , V is 3µ B and Cr is 4µ B . This increase in magnetic moment is due to increase in unpaired electrons in the outer shells whose integral values ensure the complete spin polarization (See Table 3 ) [ 37 , 38 , 39 , 40 ].…”

Boosting the Photocatalytic Ability of Bandgap Engineered (Na0.5Bi0.5)TiO3–BaTiO3 by N–Ni Codoping

“…The calculated result reveals the valence band maximum (VBM) is mainly composed of N 2p, O 2p, and Ni 3d while the conductive band minimum (CBM) mainly consists of the energy state of Ti 3d. For (N 3– , Ni 2+ )-codoped NBT-BT composition, there are five degenerate orbitals in Ni 3d states, which will split into two degenerate orbitals of e g and three degenerate orbitals of t 2g under the action of the crystal field . Because the state energies of Ni 3d t 2g , N 2p, and O 2p are close, the coupling between the energy states of N 3– 2p and Ni 2+ 3d is obtained.…”

“…For (N 3− , Ni 2+ )codoped NBT-BT composition, there are five degenerate orbitals in Ni 3d states, which will split into two degenerate orbitals of e g and three degenerate orbitals of t 2g under the action of the crystal field. 38 Because the state energies of Ni 3d t 2g , N 2p, and O 2p are close, the coupling between the energy states of N 3− 2p and Ni 2+ 3d is obtained. Besides, the structure of Ni (O 2 N 2 + V O ..…”

Understanding the role of 5d electrons in ferromagnetism and spin-based transport properties of K2W(Cl/Br)6for spintronics and thermoelectric applications

“…DE = E AFM − E FM . 33,34 The computed T c values are 613 K and 597 K for K 2 WCl 6 and K 2 WBr 6 , respectively. The high T c values make these compounds suitable for spintronic applications.…”