Tunable properties and potential half-metallicity in (Co2-xTix)FeGe Heusler alloys: An experimental and theoretical investigation

A Co2-xTixFeGe(0≤x≤1) Heusler alloy series has been synthesized and investigated in steps of x=0.125. While the parent Co2FeGe composition was previously reported to exhibit multi-phase structures, the novel substitution of Ti for Co is successful in stabilizing single-phase microstructures for compositions from x=0.125 to 0.625. The single-phase compositions crystallized in a face-centered cubic crystal structure. Soft-ferromagnetic behavior and a very high Curie temperature, as high as 881 K, is obtained for alloys with the lowest Ti concentration. Magnetic and electrical properties of these alloys suggest the possibility of half-metallic behavior in them. Both experimental findings and theoretical calculations support that the substitution of Ti atoms displaces Fe atoms towards vacated Co sites. The theoretical calculations also predict half-metallic character in the alloys after Ti substitution. The alloys are found to be unusually hard, with Vicker's hardness approaching 12 GPa for the most Ti-rich material.