This work has primarily focused on the study of the properties of tetragonal Mn3Ge Heusler thin films for spin-transfer torque magnetic random access memory (STT-MRAM) applications. A method to develop highly textured, polycrystalline and (001)-oriented Mn3Ge Heusler films on amorphous substrates was shown. These filmsdisplayed low magnetic moment and giant perpendicular magnetic anisotropy, with coercive fields up to 6 T,at room temperature, making them technologically relevant. However, the small and negative tunneling magnetoresistance (TMR)found in perpendicular magnetic tunnel junctions (p-MTJs) is attributed toa delicate balance of two competing effects: the negative spin polarization of Mn3Ge, that favors a negative TMR, and the Brillouin zone filtering effect at the Mn3Ge/MgO interface, that favors a positive TMR. It is shown from theoretical calculationsthat the latter effect could be eliminated by doping Mn3Ge with a small amount of Co, while maintaining the tetragonal structure and low magnetic moment, i.e. key requirements for STT-MRAM.