Competition of multiple spin exchanges in submonolayer solid 3He

We have made NMR measurements of the first layer of solid He-3 adsorbed on graphite down to 120 mu K. Magnetization varies from antiferro- to ferromagnetic on increasing the coverage except for the region around the root 3 x root 3 commensurate phase. This behavior is very similar to that of the second layer and is understood as due to the competition among various multiple spin exchanges. The root 3 x root 3 phase exhibits a ferromagnetic behavior which is not expected from a simple coverage dependence of the multiple exchange energies. [S0031-9007(98)07102-6].