Composition induced metal-insulator quantum phase transition in the Heusler type Fe₂VAl

We report the magnetism and transport properties of the Heusler compound Fe_2+x V_1−x Al at  −0.10  ≤  x  ≤  0.20 under pressure and a magnetic field. A metal–insulator quantum phase transition occurred at x  ≈  −0.05. Application of pressure or a magnetic field facilitated the emergence of finite zero-temperature conductivity σ ₀ around the critical point, which scaled approximately according to the power law (P  −  P _c ) ^γ . At x  ≤  −0.05, a localized paramagnetic spin appeared, whereas above the ferromagnetic quantum critical point at x  ≈  0.05, itinerant ferromagnetism was established. At the quantum critical points at x  =  −0.05 and 0.05, the resistivity and specific heat exhibited singularities characteristic of a Griffiths phase appearing as an inhomogeneous electronic state.