Low-energy spin-polarized radioactive beams as a nano-scale probe of matter

We have commissioned a polarized low-energy Li-8 ion beam line, which together with a high-field beta-NMR spectrometer, can act as sensitive new probe of thin films and interfaces. The implantation energy can be continuously adjusted from 1 to 90 keV and the maximum polarization achieved thus far is 80%. This instrument opens up new applications for beta-NMR which parallel and complement efforts with low-energy muons. For example, it is possible to probe the magnetic field distribution near the surface of a material by stopping a polarized Li-8 beam in a thin overlayer of Ag. Since the Li-8 adopts a site with cubic symmetry in Ag there is no quadrupolar splitting of the resonance, and the Li-8 acts as a purely magnetic sensor. (C) 2002 Elsevier Science B.V. All rights reserved.