Stern-Gerlach deflections of cold iron clusters in a molecular beam, with from 15 to 650 atoms per cluster, have been measured. It is found that the clusters deflect uniquely in the direction of the increasing field, indicating spin relaxation within the isolated clusters. The measured average magnetic moments increase with increasing cluster temperature and with increasing field, and in all cases they are found to be below the bulk value.

• Received 16 April 1990

DOI:https://doi.org/10.1103/PhysRevLett.65.488