Magnetic studies on mass-selected iron particles

We have investigated the magnetic properties of mass-selected iron clusters using the Magneto Optical Kerr effect (MOKE) in longitudinal geometry. For the production of these clusters, a newly developed continuous are cluster ion source (ACIS) was applied. The source is based on cathodic arc erosion in inert gas environment and subsequent expansion into high vacuum. Its intensity and stability allows mass selection within a wide size range. The source efficiency is demonstrated in deposition experiments and transmission electron microscopy. For mass-selected iron particles deposited into a silver matrix we could observe a change in the magnetic behaviour from ferromagnetism to superparamagnetism around a size of 10 nm at room temperature.