Hirofumi Nema

Cw-NMR study of liquid 3He in nanometer-sized porous alumina

Continuous-wave NMR measurements were performed for liquid 3He in porous alumina discs, which have many small pores of 200 nm in nominal diameter regularly aligned in the same direction. The experimental cell is composed of a stack of 85 anopore discs with C-shaped disc spacers between them. The spacers make the sample space well defined and make it easier to discriminate between liquid NMR signals from different spaces. To eliminate solid 3He layer adsorbed on the aluminas surface, 4 atomic layers of 4He were pre-coated on the surface in the experimental cell. Experiments were made at pressure of 17.9 bar and temperatures down to about 0.5 mK. The obtained NMR signals are composed of two contributions below superfluid transition temperatures. One seems to come from the liquid inside pores and the other between each anopore discs.

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.