Intermetallic solid solution Fe _1-xCo _xGa ₃: Synthesis, structure, NQR study and electronic band structure calculations

Unlimited solid solution Fe _1-xCo _xGa ₃ was prepared from Ga flux. Its crystal structure was refined for Fe _0.5Co _0.5Ga ₃ (P4 ₂/mnm, a=6.2436(9), c=6.4654(13), Z=4) and showed no ordering of the metal atoms. A combination of the electronic band structure calculations within the density functional theory (DFT) approach and ^69,71Ga nuclear quadrupole resonance (NQR) spectroscopy clearly shows that the Fe-Fe and Co-Co dumbbells are preferred to the Fe-Co dumbbells in the crystals structure. The band structure features a band gap of about 0.4 eV, with the Fermi level crossing peaks of a substantial density of electronic states above the gap for x>0. The solid solution is metallic for x>0.025. The study of the nuclear spin-lattice relaxation shows that the rate of the relaxation, 1/T ₁, is very sensitive to the Co concentration and correlates well with the square of the density of states at the Fermi level, N ²(E _F).