Local spin anisotropy effects upon the magnetization of dimer single molecule magnets

We present an exactly soluble model of equal spin s(1) dimer single molecule magnets. The dimer spins interact via the Heisenberg, Zeeman, and the most general quadratic local and global anisotropic exchange interactions. We derive the Hamiltonian matrix for the general case with each type of anisotropy. For antiferromagnetic couplings and s(1) > 1/2, the low temperature T magnetization exhibits a strong influence of single-ion anisotropy. Our results suggest a substantial presence of axial single-ion anisotropy in the s(1) = 5/2 Fe-2 dimer, [Fe(salen)Cl](2).