I believe that our article is highly cited because it deals with the hot topic of spintronics. This new field of research aims at combining the charge and spin of carriers to add new functionalities to existing microelectronic devices. For this purpose, one has to introduce and manipulate spins in semiconductor thin films and nanostructures. In this context, ferromagnetic semiconductors (FMS) are very promising materials for two reasons: (i) they can be used as spin injectors in non-magnetic semiconductors and (ii) since ferromagnetic order is mediated by carriers, their magnetic properties can be manipulated by the application of a gate voltage.

Enlarge “We have found a new material that could be used as a spin injector in silicon or germanium at room temperature. Moreover, its magnetic properties may be electrically tunable.”

The most important requirements are a compatibility with silicon mainstream technology and room temperature operation. The new material we have synthesized: germanium films doped with manganese atoms—although made of Mn-rich nanocolumns—may fulfill all the requirements listed above, hence our work has been extensively cited.

Our paper describes a new method to grow germanium thin films, doped with manganese atoms, to provide ferromagnetic properties. This is a new discovery and a real breakthrough in the sense that these films exhibit ferromagnetism up to room temperature and we have experimental evidence that carriers may be spin-polarized by their interaction with the ferromagnetic nanocolumns.

We have found a new material that could be used as a spin injector in silicon or germanium at room temperature. Moreover, its magnetic properties may be electrically tunable.

This work is the result of a close collaboration between two labs of our institution (Commissariat à l’Energie Atomique, France): one lab working on the growth of SiGe-based nanostructures (DRFMC/SP2M/SiNAPS) and the other working on magnetic and transport properties of thin films and nanostructures (DRFMC/SP2M/NM). This collaboration started in 2004. We actually gathered our competencies to find the best material to be synthesized in the field of spintronics: a group-IV ferromagnetic semiconductor and room temperature ferromagnetism.

In our paper, samples were grown using low-temperature molecular beam epitaxy. This growth technique allows the stabilization of metastable states in the form of Mn-rich nanocolumns embedded in a germanium matrix. That means that isolating the best metastable state remaining ferromagnetic at room temperature by controlling growth parameters is still a challenge nowadays. However, we expect that better control of these parameters would lead to the potential use of this material.

We do not expect strong political implications for our research. However, future applications of this research in the field of microelectronics may have very strong social implications.