Magnetization Measurements of 3He Monolayer Film on Graphite

A newly developed Faraday-type magnetometer is demonstrated through measurement of the nuclear magnetization of 3He monolayer films adsorbed on Grafoil at temperatures down to 1.1 mK and in magnetic fields of up to 7 T. The magnetic force is measured capacitively by monitoring the displacement of a wire-suspended copper plate holding a stack of diffusion-bonded copper foils interleaved with Grafoil. The strong background signal due to the Grafoil and copper is suppressed by a double gradient coil system that produces opposite field gradients in two regions equidistant from the field center. The upper region contains Grafoil and copper, and the lower region contains non-exfoliated graphite sheets and copper. Preliminary results of magnetization measurements are reported for the first 3He monolaver in the paramagnetic phase below 10 mK.