Strongly enhanced Curie temperature in carbon-doped Mn5Ge3 films

Abstract The structural and magnetic properties of Mn 5 Ge 3 C x films prepared at elevated substrate temperatures T S are investigated. In particular, films with x ⩾0.5 and T S =680 K exhibit a strongly enhanced Curie temperature T C =445 K compared to bulk Mn 5 Ge 3 with T C =304 K while at the same time the average Mn moment decreases from 2.6 to 1 μ B . Structural analysis of these films suggests that the carbon is interstitially incorporated into the voids of Mn octahedra of the hexagonal Mn 5 Si 3 -type structure giving rise to a lattice compression. The enhanced ferromagnetic stability in connection with the lattice compression is interpreted in terms of an Mn–Mn interaction mediated by C based on a change in the electronic structure.