The geometrical structures, relative electronic and magnetic properties of small Al„Co (1 < n < 9) clusters are systematically investigated within the framework of density functional theory at the BPW91 level. The single Co doping can dramatically affect the ground state geometries of the Al~tl clusters. At the same time, the resulting geometries show that the lowest
energy Al„Co~ clusters prefer to be three dimensional structures. Here, the relative stabilities are investigated in terms of the calculated average binding energies, fragmentation energies, and second-order energy differences. Moreover, the result of the highest occupied-lowest unoccupied molecular orbital energy gaps indicates that AI(,Co~ clusters have the highest chemical stability for Al„Co (1 < n < 9) clusters. Furthermore, the natural population analysis reveals that the charges in Al„Co clusters transfer from the Al frames to the Co atom. Additionally, the analyses of the local and total magnetic moments of the Al„Co clusters show that the magnetic effect mainly comes from the Co atom.