A synergistic approach consisting of Stern-Gerlach magnetic deflection experiments and first principles calculations provides the first conclusive evidence of ferrimagnetism in Mn clusters containing as few as seven atoms. The calculated magnetic moment of 0.71 mu(B)/atom of a Mn-7 cluster is in perfect agreement with the experimental value of 0.72 +/- 0.42 mu(B)/atom. This low value, which is a factor of seven smaller than its free atom value, is shown to result not from the reduction of the individual atomic moments, but from their ferrimagnetic coupling. The large uncertainty in the experimental measurement is explained by the existence of nearly degenerate isomers. (C) 2003 Elsevier B.V. All rights reserved.