Specific heat and Curie temperature evaluation on triangular lattice: Exchange frequencies for³He adsorbed on grafoil, evaluated by path integral techniques

We compute, using path integrals, the cyclic-exchange frequencies of a monolayer of 3 He adsorbed on graphite in the incommensurate solid phase. Interactions between helium atoms are treated with the Aziz potential; between an helium atom and the plan of graphite we use an interaction potential which depends only on the distance above the surface. The specific heat (C_V) and the magnetic susceptibility (χ) are evaluated from the calculated multiple-exchange hamiltonian. The C_V value converges with the 2-, 3- and 4-body exchange cycles while larger cycles are needed for the convergence of the χ value. For the density 0.0785 atom/Ų, we find that the variations of C_V is antiferromagnetic, whereas the variations of χ is ferromagnetic.