The influence of a Pb surfactant on the magnetism of dilute Si1-xMnx films

We investigated the effect of Pb surfactant on the growth mode and magnetism of dilute Si1-xMnx thin films grown by molecular beam epitaxy. We find that the nanocolumns that form in Pb-free samples are paramagnetic with a small saturation moment that drops with increasing Mn concentration. On the contrary, samples grown with 2 monolayers of Pb contain MnSi1.7 nanorods that lie in the plane of the films. Although the saturation moment of these samples also drops rapidly with increasing Mn concentration, it is as high as 0.65 mu(B)/Mn. At the lowest Mn concentration (x = 0.5%), the samples grown with a Pb surfactant exhibit two ferromagnetic transitions at the Curie temperatures T-C1 approximate to 40K and T-C2 > 400 K. While the transition at T-C1 is consistent with the Curie temperature of bulk MnSi1.7 crystals, T-C2 is possibly due to a second phase resulting from Mn in the Si matrix. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792219]