Transport and magnetic properties of the Heusler-type Fe 2-xV1+xAl system (-0.01?x?0.08)

We report on the temperature dependence of magnetization, electrical resistivity, and specific heat for the Heusler-type Fe2-xV 1+xAl alloys with compositions -0.01?x?0.08. The resistivity for a slightly Fe-rich sample with x=-0.01 reaches 3000 μΩ cm at 4.2 K, showing a semiconductorlike temperature dependence over the wide temperature range up to 1300 K. In contrast, a slightly V-rich sample with x=0.02 possesses a residual resistivity of only 300 μΩ cm with a positive temperature slope below 300 K. The magnetization and specific-heat data on the x=-0.01 sample provide ample evidence for the possession of local magnetic moments, whereas the annealed x=0.02 sample can be regarded as a nearly nonmagnetic semimetal. When quenched from high temperatures, even the slightly V-rich sample exhibited a steep rise of resistivity at low temperatures in parallel with an enhancement in the magnetization and the electronic specific heat. The low-temperature resistivity substantially enhances with increasing magnetic moment associated with Fe antisite defects, whose concentration is evaluated to be about 0.5% for the slightly Fe-rich annealed sample. The cause for the large resistivity at low temperatures is attributed to strong spin fluctuations of magnetic antisite defects, while the negative resistivity slope at temperatures above 400 K is attributed to the possession of a deep pseudogap at the Fermi level