Transport and magnetic properties of the Heusler-typeFe2−xV1+xAlsystem(−0.01⩽x⩽0.08)

Abstract

We report on the temperature dependence of magnetization, electrical resistivity, and specific heat for the Heusler-type ${\mathrm{Fe}}_{2\ensuremath{-}x}{\mathrm{V}}_{1+x}\mathrm{Al}$ alloys with compositions $\ensuremath{-}0.01\ensuremath{\leqslant}x\ensuremath{\leqslant}0.08$. The resistivity for a slightly $\mathrm{Fe}$-rich sample with $x=\ensuremath{-}0.01$ reaches $3000\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\ensuremath{\Omega}\phantom{\rule{0.3em}{0ex}}\mathrm{cm}$ at $4.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, showing a semiconductorlike temperature dependence over the wide temperature range up to $1300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. In contrast, a slightly $\mathrm{V}$-rich sample with $x=0.02$ possesses a residual resistivity of only $300\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\ensuremath{\Omega}\phantom{\rule{0.3em}{0ex}}\mathrm{cm}$ with a positive temperature slope below $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The magnetization and specific-heat data on the $x=\ensuremath{-}0.01$ 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 $\mathrm{V}$-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 $\mathrm{Fe}$ antisite defects, whose concentration is evaluated to be about 0.5% for the slightly $\mathrm{Fe}$-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 $400\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ is attributed to the possession of a deep pseudogap at the Fermi level.