Enhancing magnetic properties in Mn 3 Ge thin films by doping

The ferrimagnetic ${\mathrm{Mn}}_{3}\mathrm{Ge}$ compound has appealing properties for spintronic applications, e.g., a low saturation magnetization, and often a large coercive field is found. Here, we report on a combined experimental and theoretical approach to both reduce the magnetization and increase the coercivity of ${\mathrm{Mn}}_{3}\mathrm{Ge}$ by doping. By calculating defect formation energies, we predict several dopants that are expected to specifically occupy only one lattice site of the crystal structure. For Ni as a dopant, we predict a reduction in the magnetization, which we verify by preparing thin film samples by magnetron co-sputtering. We confirm the predicted reduction in magnetization as well as a greatly enhanced coercivity of more than 5 T. To improve the understanding of the sublattice magnetization in the doped ferrimagnetic material, we performed magnetic spectroscopy experiments on selected samples and compared the results with calculated data. An important finding from a detailed analysis of the spectroscopic data is that a frequently observed soft contribution in the magnetization loop arises from impurities in the film.