Semimetallic, Half-Metallic, Semiconducting, and Metallic States in Gd-Sb Compounds

The electronic and band structures of the Gd- and Sb-based intermetallic materials have been explored using the theoretical ab initio approach, accounting for strong electron correlations of the Gd-4f electrons. Some of these compounds are being actively investigated because of topological features in these quantum materials. Five compounds were investigated theoretically in this work to demonstrate the variety of electronic properties in the Gd-Sb-based family: GdSb, GdNiSb, Gd₄Sb₃, GdSbS₂O, and GdSb₂. The GdSb compound is a semimetal with the topological nonsymmetric electron pocket along the high-symmetry points Γ-X-W, and hole pockets along the L-Γ-X path. Our calculations show that the addition of nickel to the system results in the energy gap, and we obtained a semiconductor with indirect gap of 0.38 eV for the GdNiSb intermetallic compound. However, a quite different electronic structure has been found in the chemical composition Gd₄Sb₃; this compound is a half-metal with the energy gap of 0.67 eV only in the minority spin projection. The molecular GdSbS₂O compound with S and O in it is found to be a semiconductor with a small indirect gap. The GdSb₂ intermetallic compound is found to have a metallic state in the electronic structure; remarkably, the band structure of GdSb₂ has a Dirac-cone-like feature near the Fermi energy between high-symmetry points Г and S, and these two Dirac cones are split by spin-orbit coupling. Thus, studying the electronic and band structure of several reported and new Gd-Sb compounds revealed a variety of the semimetallic, half-metallic, semiconducting, or metallic states, as well topological features in some of them. The latter can lead to outstanding transport and magnetic properties, such as a large magnetoresistance, which makes Gd-Sb-based materials very promising for applications.