Magnetic Properties of Free Metal Clusters

In this dissertation, results of Stern-Gerlach type magnetic deflection experiments on Chromium, Iron, and Aluminum clusters consisting of ∼20-200 atoms are reported. These metal clusters were produced using a laser vaporization technique in helium, and their beams were formed using supersonic expansion into vacuum. Measurements of their magnetic deflections were conducted at temperature ranging from 50K to 250K and at various magnetic field strengths. Both Chromium and Iron clusters are found to behave in accordance with a superparamagnetic model and to have enhanced magnetism compared to their bulks. For Chromium clusters with N≥34, each cluster has at least two isomers with distinguishable magnetic moments at low temperatures. For Iron clusters with T vib =55K, some deviations from the superparamagnetic model were observed. Aluminum clusters with odd numbers of atoms exhibit paramagnetic properties at low temperatures, which are believed to be related to superconductivity. At temperatures as low as 55K, the predicted large diamagnetism of Al 56 due to superconductivity was not observed, within our system's resolution.

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