We succeed in synthesizing equimolar-multi metal solid solutions of (Fe, Co, Ni, Cu)S2 and (Fe, Co, Ni, Cu, Ru)S2 by sintering at 900 °C under 2-4 GPa. These were stabilized by the high-entropy effect. Nevertheless, (Fe, Co, Ni, Cu, M)S2 (M = Zn, Mn, or Cd) was not obtained as single phase under the same synthetic conditions, mostly owing to the relatively large ionic radius of M2+. Single-crystal X-ray diffraction analysis shows that (Fe, Co, Ni, Cu)S2 crystallizes into a pyrite type with the space group Pa3 (#205) [a = 5.777(3) Å], randomly distributed at one site. The results of electrical resistivity and magnetic dc-susceptibility measurements indicate that both (Fe, Co, Ni, Cu)S2 and (Fe, Co, Ni, Cu, Ru)S2 are metals with ferrimagnetic ordering below Tc = 130 K. The band structure and the projected density of states (Fe, Co, Ni, Cu)S2, were obtained by density functional theory calculations in a high-entropy representative supercell, supporting the experimental results.
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