Ferromagnetic quantum phase transition in Co(S1-xSex)2 system

In Co(S1-xSex)2 system, a transition from ferromagnetic to paramagnetic state occurs near x = 0.11. In order to research the physical properties of the samples near this transition, polycrystalline samples of Co(S1-xSex)2 (0.0≤x≤0.16) were prepared. And their structure and resistivity were measured. It is found that the ferromagnetic transition temperature TC is suppressed by Se doping in the relation TC(1-x)1/2. And the ferromagnetic phase transition goes from the second to the first order. The temperature dependence of resistivity, ρ(T), shows a Fermi-liquid behavior, ρ(T)=ρ0+AT2, in Co(S1-xSex)2 (xρ(T) occurs in the samples near a critical concentration x=0.11. It is suggested that the phase transition near x=0.11 is a quantum phase transition, and the quantum critical spin fluctuation at zero temperature results in non-Fermi liquid behavior.