Grain-Size-Dependent Low-Temperature Electrical Resistivity of Polycrystalline Co₂MnAl Heusler Alloy Thin Films

Low-temperature electrical resistivity of Co₂MnAl Heusler alloy thin films prepared by DC magnetron sputtering technique has been investigated. After deposition of Co₂MnAl thin films, they were annealed at 200–400 ^∘C to control the crystal structure and the atomic order between Co, Mn, and Al sites. The ratio of intensity of (200) and (220) XRD peaks increases with increasing annealing temperature. The low-temperature dependence of electrical resistivity demonstrated that the film structure and magnetic ordering effected to the resistivity of Co₂MnAl. The temperature dependence of resistivity for all samples has demonstrated the exponential decrease when temperature increases. However, 1000 ^∗(1 /T) dependence of the logarithmic resistivity variation has not demonstrated the linear characteristic for all samples, and also, the temperature dependency of the deposited and annealed films has not been agreed with logarithmic, ρ(T) ∝ ln T, behaviors. The temperature dependence of conductivity of samples has a relation with the square root of temperature. These kinds of behaviors have been attributed to grains/clusters and disordering of samples.