Ferromagnetic resonance, ac susceptibility and Mossbauer measurements
on ordered Fe3-XMnXSi (X = 0.75, 0.9, 1.0 and 1.2) alloys reveal that
a well-defined paramagnetic-ferromagnetic (FM) phase transition is fol
lowed at a lower temperature by another transition from FM to the reen
trant state, in which FM order coexists with the cluster spin glass or
der.