NUCLEAR-SPIN HEAT-CAPACITY OF SUBMONOLAYER SOLID HE-3 FILMS

The heat capaicty of submonolayer solid He3 films adsorbed on graphite has been measured for temperatures between 2 and 200 mK. Over a very narrow range of coverages an anomalously large nuclear-spin exchange is observed. This peak is analogous to the more dramatic anomaly previously observed for the second-layer system when compressed by a few overlying fluid layers. The implication is that the proposed indirect exchange involving the fluid atoms cannot be the responsible mechanism. © 1990 The American Physical Society.