First-principles study of the new compounds CrGa₂Sb₂ and CrGaSb synthesized under high pressure

We present the density-functional calculations of the compounds CrGa₂Sb₂ and CrGaSb synthesized recently under high pressure. Calculation reproduces well all details of the crystal structure of these compounds, their spin ordering, and a larger metallicity of CrGaSb comparing to CrGa₂Sb₂. Particular attention is given to the room temperature ferromagnetic compound CrGa₂Sb₂, where the huge resistivity hinting at the possible semiconducting properties was measured. To understand the mechanism of its anisotropic conductivity, we analyze the band structure, calculated kinetic and optical characteristics of this compound. It is found that the density of states of CrGa₂Sb₂ has a pseudogap near the Fermi level, where the Cr atoms do not dominate, but contribute even less than the atoms of Ga and Sb. This explains a very high calculated resistivity of CrGa₂Sb₂, which can be characterized as a ferromagnetic compound with a low metallic conductivity. This type of conductivity remains unchanged, when a possible Cr-deficiency of CrGa₂Sb₂ is taken into account or the MBJ-LDA exchange-correlation potential is used instead of the GGA-LDA one in calculation. The potential of this compound for the development of spintronic materials is discussed.