Synthesis, structural and electrical-transport characterization, and first-principles investigations of the quaternary Heusler compound NiCrMnAl

We report experimental and first-principles studies of bulk NiCrMnAl alloy. X-ray diffraction of annealed, arc-melted sample shows a cubic Heusler phase. The (111) and (200) superlattice peaks are absent, indicating site disorder. Annealing restores the (400) peak and improves crystallinity but does not yield full long-range order. Calculated elastic and mechanical properties indicate mechanical stability, brittle behavior, and mainly covalent bonding. Phonon calculations show no imaginary modes, confirming dynamical stability. Electronic structure calculations using hybrid-functional (HSE06) method suggest half metallic behavior. Measured resistivity of NiCrMnAl increases with temperature. From 6 to 50 K resistivity follows a power law close to temperature to the 2.63 power. Low temperature fits prefer a disorder dependent model with square root of temperature plus a quadratic term. From 50 to 300 K transport is mainly linear in temperature with a smaller higher-order correction. Chemical disorder likely suppresses the intrinsic half metallic nature.