Structure and magnetic properties of MnSi epitaxial thin films

We report on the correlation between the magnetic and structural properties of epitaxial MnSi (111) thin films grown by solid-phase epitaxy on Si (111) substrates. The Si (111) substrate, with a surface unit cell that is 3.0% larger than that of MnSi, causes an in-plane tensile strain in the film that is partially relaxed due to the presence of misfit dislocations located at the interface. However, the out-of-plane strain has a nonmonotonic dependence on thickness that is attributed to changes in the elastic constants of the film. The thickness dependence of the Curie temperature correlates strongly with strain and reaches a maximum of T-C=43 K, a value that is 46% greater than the bulk value of T-C=29.5 K. Although the films have a strong epitaxial relationship, [1 (1) over bar0]MnSi parallel to[11 (2) over bar ]Si, there are inversion domains in the film due to the noncentrosymmetric crystal structure of MnSi. The presence of these domains implies that there are two magnetic chiralities, which likely contribute to the observed glassy magnetic response of the films.