Half-metallic magnetism of Co 2 CrX (X ¼ As, Sb) Heusler compounds: An ab initio study Ulvi Kanbur, G ¨ okhan G ¨ oko˘ glu à Department of Physics, Karab¨ uk University, 78050 Karab¨ uk, Turkey article info Article history: Received 8 October 2010 Received in revised form 22 December 2010 Keywords: Ab initio calculation Half-metal Electronic structure abstract In this study, we present the electronic, magnetic, and structural properties of two novel half-metallic full-Heusler compounds, Co 2 CrAs and Co 2 CrSb, in cubic L2 1 geometry. The calculations are based on the density functional theory within plane-wave pseudopotential method and spin-polarized generalized gradient approximation of the exchange-correlation functional. The electronic band structures and density of states of the systems indicate half-metallic behavior with vanishing electronic density of states of minority spins at Fermi level, which yields perfect spin polarization. The calculated magnetic moments of both systems in L2 1 structure are 5.00 m B , which are largely localized on the chromium site. The energy gaps in minority spin states are restricted by the 3d-states of cobalt atoms on two different sublattices. The formation enthalpies for both structures are negative indicating stability of these systems against decomposition into stable solid compounds. & 2011 Published by Elsevier B.V. 1. Introduction Half-metallic ferromagnets (HMFs) have attracted great atten- tion due to extraordinary physical properties and several techno- logical applications in various fields. NiMnSb half-Heusler compound is the firstly discovered half-metallic ferromagnet with C1 b structure and F 43m space group [1]. HMFs are characterized by the metallic band structure for one spin state, while the electronic band structure of other spin state presents an insulat- ing character yielding a perfect spin polarization at Fermi level. This situation also results in a spin-polarized electrical conduc- tivity, which is very sensitive to applied magnetic field. HMFs have central importance in spin-dependent electronic applica- tions: spintronics [2,3], giant magneto-resistance spin valve [4], and spin injection to semiconductors [5–7]. These types of materials have been extensively studied in view of the first principles calculations, and several compounds are predicted to be half-metallic [8–13]. The electronic structure and magnetic properties of half- and full-Heusler compounds with various combinations of constituent elements have been studied extensively in previous works [14,15]. A recent compre- hensive ab initio study reviews the electronic structure and spin- polarization properties of half-metallic Heusler alloys [16]. Among the several Co-based full-Heusler compounds (Co 2 YZ) in cubic L2 1 structure, Co 2 MnSi system seems to be the most promising material for spintronics applications due to the ideal physical properties like high Curie temperature (T c ¼ 985 K) [17] and wide band gap in minority spin channel [13]. Co-based Heusler compounds are investigated theoretically in view of the density functional calculations and most of them are pre- dicted to be half-metallic [11–14,17–19]. Moreover, Co 2 MnSi compound is used in production of thin films [20–22] and devices [23,24]. The half-metallic behavior of full-Heusler compounds presents more complicated characteristics than that of half-Heusler alloys due to the presence of the states located entirely at the Co sites [14,25] resulting an ideal local moment system [26,27]. The integer magnetic moment is an important characteristic property for half-metallic systems in stoichiometric composition. The total magnetic moments of the perfect HMFs obey Slater–Pauling [28,29] rule, in which the saturation magnetic moment scales with the number of valance electrons [30]. Besides Co–Mn based full-Heusler compounds, there is a lack of study in literature on Co–Cr based Heusler systems. In this work, the electronic structure and magnetic properties of two novel full-Heusler compounds, Co 2 CrAs and Co 2 CrSb, are investi- gated using plane-wave pseudopotential method and spin-polar- ized generalized gradient approximation (sGGA) of the density functional theory. To the best of our knowledge, there is no comprehensive study on electronic structure and half-meta- llicity of these systems in literature. The rest of the paper is organized as follows: The details of the calculations performed and Heusler geometry are described in Section 2. The features - of bulk L2 1 structures of the compounds under study are pre- sented in Section 3. Then, paper concludes with a summary in Section 4. 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2011 Published by Elsevier B.V. doi:10.1016/j.jmmm.2010.12.034 à Corresponding author. Tel.: + 90 370 433 8374; fax: + 90 370 433 8334. E-mail address: ggokoglu@gmail.com (G. G ¨ oko˘ glu). Please cite this article as: U. Kanbur, G ¨ o. G¨ oko˘ glu, J. Magn. Magn. Mater. (2011), doi:10.1016/j.jmmm.2010.12.034 Journal of Magnetism and Magnetic Materials ] (]]]]) ]]]–]]]