Tailoring of the magneto-transport properties, half-metallicity and vacancy-induced structural disorder in Co2ZrSn for spintronics

In spintronics, the ability of half-metallic ferromagnets (HMF) to achieve 100 % spin-polarization is essential to develop next-generation magnetic tunnel-junctions. In this work, the effect of Co-vacancy point-defects on the half metallicity and magneto-transport properties of the promising Co 2 ZrSn Heusler alloy are studied. The alloy is synthesized via several processing routes, involving different cooling rates and degrees of metastability. Polycrystalline samples are analyzed by synchrotron X-ray diffraction. The occupancy and the disorder of Co-sites in the crystal structure, evaluated by Rietveld refinement, are responsible for significant changes in such properties, such as the shrinking of the half-metallic band-gap, reduction of saturation magnetization and electrical conductivity. The electrical resistivity, R , measured at low temperature (below 300 K) show a change of regime from a T 2 to a T x dependency, which is interpreted as a change of electron scattering mechanisms due to a crossover from a half-metallic to an itinerant ferromagnetic state. The thermoelectric figure of merit zT is here experimentally determined for the first time. Ab-initio calculated properties, both on pristine and defective structures, are in quantitative agreement with experiments and linearly scale with the Co-site occupancy, which does not affect the half-metallic ground state. Lastly, phonon and thermal properties are discussed in the framework of Slack’s model.. • Processing route affects Co-site occupancy, leading to various vacancy concentration. • Crossover from collective spin wave excitation to spin-flip electron diffusion. • Density of state from DFT shows that half metallicity is resistant to vacancy defects.