Electron diffraction study of a high-temperature diamond-like silicon ferromagnet with the self-organized superlattice distribution of manganese impurity

New data on the structure of the diluted magnetic semiconductor Si:Mn with the Curie point to $500$ K synthesized by the laser method have been presented. High-resolution electron microscopy and diffraction in the directions $\langle110\rangle$ and $\langle100\rangle$ of epitaxial layers of the diluted magnetic semiconductor Si:$15\,\%$ Mn with the elimination of the contribution from the GaAs substrate and interface have been applied. It has been established that the diluted magnetic semiconductor Si:Mn is a previously unknown compound with the variable composition Si$_{3-x}$Mn$_x$ ($0 < x < 1$), single-phase diamond-like structure, high crystal perfection, and self-organized formation of the superlattice structure with the period of the triple distance between the nearest (110) atomic layers and the interval between the (110) layers doped with Mn atoms and oriented along the growth direction of the Si:Mn film. The layers Si:$15\,\%$ Mn (or Si$_{2.5}$Mn$_{0.5}$) consist of $15$- to $50$-nm blocks with the mutually perpendicular orientations of the superlattice modulations. Manganese atoms in the (110) layers doped with this impurity are located in the form of single-atom stripes, which alternate with the silicon single-atom stripes in agreement with the X-ray spectral analysis and ferromagnetic resonance data. The ferromagnetism of Si$_{3-x}$Mn$_x$ is associated with a specific feature of the impurity band.