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

We report the magnetism and transport properties of the Heusler compound Fe2+xV1-xAl at -0.10 <= x <= 0.20 under pressure and a magnetic field. A metal-insulator quantum phase transition occurred at x approximate to -0.05. Application of pressure or a magnetic field facilitated the emergence of finite zero-temperature conductivity sigma(0) around the critical point, which scaled approximately according to the power law (P-P-c)(gamma). At x <= -0.05, a localized paramagnetic spin appeared, whereas above the ferromagnetic quantum critical point at x approximate to 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.