Quantum phase transition and non-Fermi liquid behavior in Fe1-xCoxSi (x >= 0.7)

We report on the nature of electron correlations in Fe1-xCoxSi (0.7 <= x < 1) using combined results of magnetization, specific heat and transport properties. Doping driven quantum critical point is observed to occur at x similar to 0.75. The magnetically unstable regime is identified to be centered around x is an element of [0.75, 0.95]. The emergence of non-Fermi liquid behaviors in x = 0.8 (near to ferromagnetic quantum critical point) and x = 0.9 (disorder-induced) compositions are discussed on the basis of the power-law dependence of susceptibility chi similar to T-g (g similar to 1.07 for x = 0.8 and 0.55 for x = 0.9), specific heat C/T similar to T-1+lambda (lambda similar to 1.52 for x = 0.8 and 0.9) and resistivity Delta rho similar to T-d (d similar to 1.56 for x = 0.8 and 1.38 for x = 0.9). Further, a comprehensive classification of doping dependent physical properties of Fe1-xCoxSi is presented in the revisited temperature-composition (T-x) phase diagram