Magnetic behavior of free-iron and iron oxide clusters

We report the first measurement of the magnetic properties of isolated iron-atom clusters ranging in size from 2 to 17 atoms as well as the magnetic behavior of the monoxides and dioxides of (2-7)-atom iron clusters. Production of metal clusters is initiated by laser vaporization of an iron rod inside the throat of a high-pressure pulsed nozzle. The neutral metal cluster beam passes through a Stern-Gerlach magnet and the deflected beam is detected by spatially resolved time-of-flight photoionization mass spectrometry. From our analysis we conclude that the spin per atom of iron clusters is at least that of bulk iron, suggesting these small clusters are the precursors to bulk ferromagnetic iron.