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

Abstract

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.

Theoretical modeling of the electronic structure and Fermi surfaces of Gd4Sb3 and GdSb2 compounds

“…Among these synthesized compounds, the rareearth diantimonides, i.e., RSb2, were reported in a LaSb2-structural type and high-pressure orthorhombic type of structure [16]. In [11], we found that Gd4Sb3 is a half-metallic ferromagnet (HMF) with the gap of 0.67 eV only in the minority spin projection, while the majority spin projection is characterized by intensive metallic density of states. In the band structure of GdSb2, a Dirac-conelike feature near the Г, S points was theoretically predicted [11].…”

“…The intermetallic Gd4Sb3 and GdSb2 materials are crystallized in the and Th3P4-and SmSb2-types, respectively, i.e., space groups I-43d, # 220, and Cmce, # 64, for parameters see [11]. The theoretical modeling was carried in Quantum ESPRESSO set of computer programs [17,18].…”

“…In these PPs, the Gd 4f states are not taken as the valence electronic states. It was demonstrated in [11,20] that a ferromagnetic ordering of the Gd 4f moments provides magnetic moment of about 7 μB/Gd in the Gdbased intermetallic materials.…”

“…Recently, a number of RSb based on rare-earths R and antimony Sb have been found to contain topological features in the band structure: LaSb [6], NdSb [7], etc. The GdSb monoantimonide with the equiatomic composition was investigated both experimentally and theoretically [8,9,10,11]. Experimental angle-resolved photoemission spectroscopy discovered pockets at Г and X in spectra of RSb for R = Y, Ce, Gd, Dy, Ho, Tm, Lu [12].…”

“…In [11], we found that Gd4Sb3 is a half-metallic ferromagnet (HMF) with the gap of 0.67 eV only in the minority spin projection, while the majority spin projection is characterized by intensive metallic density of states. In the band structure of GdSb2, a Dirac-conelike feature near the Г, S points was theoretically predicted [11].…”