Ab initio calculations of half-metallic ferromagnetism in Cr-doped MgSe and MgTe semiconductors N.A. Noor a , S.M. Alay-e-Abbas b,c , M.U. Sohaib d , S.M. Ghulam Abbas e , A. Shaukat b,n a Department of Physics, University of the Punjab, Quaid-e-Azam Campus, 54590 Lahore, Pakistan b Department of Physics, University of Sargodha, Sargodha 40100, Pakistan c Department of Physics, GC University Faisalabad, Allama Iqbal Road, Faisalabad 38000, Pakistan d Lahore Development Authority, 54590 Lahore, Pakistan e Department of Chemistry, University of Agriculture, Faisalabad 38040, Pakistan article info Article history: Received 1 May 2014 Received in revised form 8 August 2014 Available online 19 August 2014 Keywords: Ab initio calculations Ferromagnetic materials Electronic properties Doped semiconductors abstract The full-potential linear-augmented-plane-waves plus local-orbitals (FP-LAPWþlo) method has been employed for investigation of half-metallic ferromagnetism in Cr-doped ordered zinc-blende MgSe and MgTe semiconductors. Calculations of exchange and correlation (XC) effects have been carried out using generalized gradient approximation (GGA) and orbital independent modified Becke–Johnson potential coupled with local (spin) density approximation (mBJLDA). The thermodynamic stability of the compounds and their preferred magnetic orders have been analyzed in terms of the heat of formation and minimum total energy difference in ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering, respectively. Calculated electronic properties reveal that the Cr-doping induces ferromagnetism in MgSe and MgTe which gives rise to a half-metallic (HM) gap at Fermi level (E F ). Further, the electronic band structure is discussed in terms of s (p)–d exchange constants that are consistent with typical magneto- optical experiment and the behavior of charge spin densities is presented for understanding the bonding nature. Our results demonstrate that the higher effective potential for the spin-down case is responsible for p–d exchange splitting. Total magnetic moment (mainly due to Cr-d states) of these compounds is 4m B . Importantly, the electronic properties and HM gap obtained using mBJLDA show remarkable improvement as compared to the results obtained using standard GGA functional. & 2014 Published by Elsevier B.V. 1. Introduction Light-emitting diodes (LED) and laser diodes operating in blue or ultraviolet (UV) spectral regions are important achievements in the field of optoelectronics. High ionicity of wide-gap II–VI compounds is of vital importance for electrochemical and optical coupling [1]. Apart from this, a growing effort has been directed toward the simultaneous manipulation of charge as well as spin degrees of freedom of electrons in semiconducting compounds for spintronic functionality. In this regard, the introduction of mag- netic ions into a nonmagnetic semiconductor host material is an excellent solution for effective spin injection. Successful doping of considerable amount of Mn atoms into InAs and GaAs has proven to be a historic breakthrough for the establishment of spintronic devices [2,3]. To date, significant research efforts have been made toward studying the role of ferromagnetism in semiconducting compounds like Europium (Eu) chalcogenides and Cr-based spinels as well as anti-ferromagnetism in II–VI compounds [4,5]. Mn-doped II–VI compounds are highly appreciated in the opto- electronic field owing to the strong room temperature ferromag- netic interactions among localized spins with low carrier concen- tration. In addition, the induction of ferromagnetic behavior due to free holes in II–VI has also been reported [6,7]. The magnetic impurity-doped semiconductors are termed half- metallic (HM) ferromagnetic (FM) if the electronic states at the Fermi level are 100% spin-polarized [8,9]. One of the pioneering first principles works done by Groot et al. [10] formulates the concept of half-metallicity in terms of spin-polarization for NiMnSb semi-Heusler alloy. Consequently, tremendous number of theoretical investigations resulted in the predictions of many HM materials due to which an appreciable number of HM materials have been experimentally realized [11,12]. Considerable research attention has been devoted to probing the half metallicity and ferromagnetic ordering for their influence on various physical properties [13,14]. However, it is indis- pensable for the practical application of spintronic devices to investi- gate materials for HM ferromagnetic behavior having compatibility with important III–V and II–VI compounds. An upsurge of experi- mental and theoretical investigations has been directed toward Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials http://dx.doi.org/10.1016/j.jmmm.2014.08.038 0304-8853/& 2014 Published by Elsevier B.V. n Corresponding author. Tel.: þ92 48 9230618; fax: þ92 48 9230671. E-mail address: schaukat@gmail.com (A. Shaukat). Journal of Magnetism and Magnetic Materials 374 (2015) 164–172