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

We have commissioned a polarized low-energy 8Li ion beam line, which together with a high-field β-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 β-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 8Li beam in a thin overlayer of Ag. Since the 8Li adopts a site with cubic symmetry in Ag there is no quadrupolar splitting of the resonance, and the 8Li acts as a purely magnetic sensor.