Effect of Co substitution on the magnetic properties in Fe_1−xCo_xGa₃

We investigated the effect of Co substitution in Fe_1−xCo_xGa₃ by means of electric resistivity and magnetic measurements. Nearly ferromagnetic behaviors were observed in Fe_1−xCo_xGa₃ system by the chemical substitution of Co for Fe in diamagnetic mother compound FeGa₃, accompanying with a semiconducting to metallic transition. With the substitution of Co, the magnetization of Fe_1−xCo_xGa₃ increases first, and then decreases and finally it becomes diamagnetic. The magnetic properties of Fe_1−xCo_xGa₃ were analyzed in terms of self-consistent renormalization (SCR) theory and Takahashi's theory. The spin-fluctuation parameters, fourth order expansion coefficients of magnetic free energy (${\bar{F}}_{1}$), the magnetic susceptibility in the ground state X(0), the spectral widths of the spin fluctuation spectrum T₀ and T_a in the frequency and wave-number spaces, respectively, were estimated from the parameters derived from magnetic measurements. The magnetic properties of Fe_1−xCo_xGa₃ can be understood almost quantitatively by the SCR theory and Takahashi's theory of spin fluctuations.