The effect of equivalent pressure and localized magnetism in Cu1−x−yAgxIr2S4system

The resistivity and magnetism for the Cu1−x−yAgxIr2S4 (x = 0, y = 0, 0.05, 0.1, 0.15; y = 0, x = 0, 0.05, 0.1, 0.15) system were investigated. A Peierls-like phase transition occurs at TMI~226 K for CuIr2S4. The transition is suppressed in the Cu1−xAgxIr2S4 system, which is attributed to that the substitution of Ag, with its larger radius, for Cu releases the pressure of Ir–Ir. The transition temperature TMI increases slightly with vacancies increasing in the Cu1−yIr2S4, which corresponds to the increase of pressure. Our explanation about the pressure release and increase can also be applied to clarifying the pressure effect which is still an open question. The magnetization rises at low temperatures below TMI. We suggest that it is attributed to remnant localized electrons, which do not participate in the Peierls-like phase transition, accompanied by spin-dimerization in this system. By fitting the experimental curves, we find that about 0.7% of the Ir4+ ions do not participate in the Peierls-like transition. The contributions of Pauli paramagnetism, Landau diamagnetism, Larmor diamagnetism and Curie magnetism can be distinguished.