Magnetic clusters in molecular beams, metals, and semiconductors

The evolution of magnetic order from the microscopic to the macroscopic regime may be studied with the use of nanometer-scale clusters. A variety of new techniques can be employed to control the size of the magnetic clusters from the atomic level. Molecular beams are used to construct and measure the magnetic properties of isolated metallic clusters. Superparamagnetic metallic particles embedded in a metal exhibit dramatic field-dependent changes in electrical conduction, providing a measure of spin-dependent scattering. Related efforts in semiconductor hosts with the use of ion implantation have generated room-temperature ferromagnetic clusters that can be directly imaged by magnetic force microscopy.