Antiferromagnetic quantum phase transition near x=1.00 in NiS2-xSex system

Abstract

There may be an antiferromagnetic quantum phase transition near x=1.0０ in NiS2-xSex system. The polycrystalline samples of NiS2-xSex (x=0.96, 0.98, 1.00, 1.05, 1.10 and 1.20) were prepared by the solid state reaction method, and the measurements of their structure, magnetization and resistivity were carried out. It is found that the temperature dependence of susceptibility is typical characteristic of a strongly correlated electron system. Similar to high Tc superconductors, the relationship between resistivity and temperature displays a linear behavior in a wide temperature range from 50 to 300 K. For NiS2-xSex(x=0.98 and 1.00) samples, its ρ(T) is proportional to T3/2 at lower temperatures (3—30 K), which shows a non-Fermi-liquid behavior. But for NiS2-xSex (x=1.10 and 1.20) samples, its ρ(T) is proooportional to T2 at lower temperatures (3—30 K), which shown the Fermi-liquid behavior. The antiferromagnetic quantum spin fluctuation related to quantum phase transition is discussed in detail.