Non-perturbative Methods in Phenomenological Simulations of Ring-Shape Molecular NanomagnetsParallel Processing and Applied Mathematics

Two non-perturbative numerically exact methods: exact diagonalization and quantum transfer matrix are applied to computationally complex Heisenberg-like spin models of ring shaped molecular nanomagnets and implemented in the high performance computing environment. These methods are applicable to the wide class of ring-shaped nanomagnets. For the hypothetical antiferromagnetic nanomagnet Ni12 the influence of single-ion anisotropy on the ground states is investigated. For Cr8 it is demonstrated that the alternation of the nearest-neighbor bilinear exchange couplings leads to small changes in the magnetic torque with respect to the uniformly coupled system. Specific heat and entropy for Cr8 are showed to be good indicators of crossing fields. The applicability of the Lande rule to both systems is checked.