Thermal and magnetic study of exchange in the quasi-1-D molecular compound, TTF⋅PtS4C4(CF3)4

Abstract

Single crystal magnetic susceptibility results from 2.5 K to 270 K and specific heat results from 3 K to 16 K are reported for TTF⋅PtS₄C₄(CF₃)₄, (TTF=tetrathiafulvalene). The combined results are analyzed using a simple model which ignores differences between the two types of S=1/2 spin carriers and involves a system of ferromagnetic chains treated ’’exactly’’, with interchain antiferromagnetic interaction evaluated in a mean field approximation. Above an apparent ordering transition at 8 K, the susceptibility is well described by the model irrespective of whether the ferromagnetic exchange is Heisenberg, Ising or intermediate to these. The magnetic contribution to the specific heat is obtained using earlier results for the isostructural Au compound. Comparison with specific heat calculations for the Heisenberg, Ising and intermediate cases successfully narrows the ambiguity to an intermediate anisotropic exchange close to the Heisenberg limit.