Antiferromagnetic quantum phase transition near x =1.00 in NiS 2- x Se x system

There may be an antiferromagnetic quantum phase transition near x =1.0０ in NiS 2- x Se x system. The polycrystalline samples of NiS 2- x Se x ( 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 T c superconductors, the relationship between resistivity and temperature displays a linear behavior in a wide temperature range from 50 to 300 K. For NiS 2- x Se x ( x =0.98 and 1.00) samples, its ρ ( T ) is proportional to T 3/2 at lower temperatures (3—30 K), which shows a non-Fermi-liquid behavior. But for NiS 2- x Se x ( x =1.10 and 1.20) samples, its ρ ( T ) is proooportional to T 2 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.