This paper investigates the single-molecule magnets of pure and Cr/Fe-doped Mn 12 -Ac. The components of the mixed crystals are identified by AC susceptibility technique. The ground-state spin and anisotropy parameters of doped Mn 12 -Ac are obtained: (i) Mn 11 Cr-Ac (S=19/2, D=0.62 K, B=0.0009 K, =63 K), and (ii) Mn 11 Fe-Ac (S=21/2, D=0.39 K, B=0.001 K, =55 K). The single-ion origin of the magnetic anisotropy is discussed.
