An international cooperation between the groups of Costantini in Warwick, Kratzer in Duisburg-Essen (Germany), Kern in Stuttgart (Germany) and Suzuki in Fukuoka (Japan) managed to unravel the atomic scale structure of thin films of MnSi grown by reactive epitaxy on Si(111). A combination of scanning tunnelling microscopy (STM) experiments and density functional theory (DFT) calculations allowed to address the formation energy of the MnSi films as well as the relationship between their structural and electronic properties. The results showed that the stacking sequence of Mn and Si lattice planes significantly depends on the growth protocol. In particular, a detailed comparison using simulated STM images obtained from DFT calculations lead the team to conclude that their films differ in the stacking sequence of the Mn and Si layers from samples grown previously using co-deposition of Mn and Si. Since the magnetic properties of MnSi films are closely related to their atomic structure, the occurrence of two possible stacking sequences implies that strict control of the growth conditions is required to reproducibly fabricate MnSi thin layers with specified properties. MnSi thin films might have interesting future applications in spintronics, where researchers are seeking for magnetic materials with well-defined atomically sharp interfaces with the Si substrate to attain an efficient spin injection.
The paper has been published in Physical Review B and can be found here.