An exhaustive study of the structural stability, electronic, and magnetic properties of the ternary X2MnZ Heusler alloys, in cubic and tetragonal lattice cells, is presented. We performed density-functional-theory (DFT) calculations, as implemented in the SIESTA code, for X = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Pt, and Au, and Z = Al, Si, Ga, Ge, In, and Sn. To optimize the crystal structure and the lattice constants a local relaxation by means of the conjugate algorithm is used. The spin polarized local electronic density of states for the different chemical components in the various alloys are calculated and some particular examples are discussed. From those results we observe that the alloys that show half-metallic behaviour are Fe2MnSi, Co2MnSi, and Co2MnGe. A general feature is that Mn donates of the order of one electron to the other components. We calculated the magnetic moment per unit cell and the individual contributions coming from all the components, and observe the change as a function of X and Z. The largest moment per unit cell corresponds to Fe2MnIn (7.86 μB) and the smallest to Ru2MnIn (2.15 μB). We compared our results with the existing experimental data for the lattice constants and the magnetic moments per unit cell and found a fair agreement.
