A Manganise Ions Ground State in Mn_xSi_{1-x} : Negative - U Properties   Centre?
  The properties of magnetic deluted and strong correlated systems of MnxSi1-x systems are discussed. In frame work of the model of the double defects including manganese ion and silicon vacancy are considered properties of these systems. The role of the Jahn -Teller distortions of different symmetry types in MnSi system magnetic-properties formation is discussed. It has been established that defect {Mns+1 - Vsio} is the center with negative-U properties and Jahn-Teller's full symmetric vibration mode initiates change of a crystal-field value from intermediate (a configuration - {Mns+1 - Vsio}) to strong (a configuration -{Mns-1 - Vsi+2}). 
S. M. Yakubenya
cond-mat.str-el