Experimental electronic phase diagram in a diamond-lattice antiferromagnetic system

We report the Ni-doping effect on the magnetic and electronic properties of thiospinel Co1-xNix[Co0.3Ir1.7]S4 (0 x 1). The parent compound Co[Co0.3Ir1.7]S4 exhibits antiferromagnetic order below TN similar to 292 K within the A-site diamond sublattice, along with a narrow charge-transfer gap. Upon Ni doping, an insulator-to-metal crossover occurs at x similar to 0.35, and the antiferromagnetism is gradually suppressed, with TN decreasing to 23 K at x = 0.7. In the metallic state, a spin-glass-like transition emerges at low temperatures. The antiferromagnetic transition is completely suppressed at xc similar to 0.95, around which a non-Fermi-liquid behavior emerges, evident from the T alpha temperature dependence with alpha approximate to 1.2-1.3 in resistivity and divergent behavior of C/T in specific heat at low temperatures. Meanwhile, the electronic specific-heat coefficient gamma increases substantially, signifying an enhancement of the quasiparticle effective mass. The magnetic phase diagram has been established, in which an antiferromagnetic quantum critical point is avoided at xc. Conversely, the observed glasslike tail above the critical concentration aligns more closely with theoretical predictions for an extended region of the quantum Griffiths phase in the presence of strong disorder.