In the last decade it has been recognized that magnetic relaxation process taking place in magnetic molecules show a rich phenomenology. The renewed interest in this subject stems from the possibility of using these molecules as quantum qbits, in quantum computation, or finding new physical processes in artificial structures as model systems. In this presentation the Single Ion Magnet (SIM) behavior of several rare earth furoate [1] and cyanoacetate [2] polymers are reported. Special emphasis is given to the competition between the SIM fast relaxation time properties, inherently caused by the ligand field interactions, on one hand, and the intermolecular interactions of exchange or dipolar origin, on the other, that tend to slow down those relaxations. These phenomena are observable at very low temperature, below 1K. The application of an external magnetic field may compete with intramolecular interactions and cause magnetic reorientation of the submolecular magnetic moments in rare earth-transition metal clusters. By a combination of x-ray circular magnetic circular dichroism and conventional vibrating sample magnetometry it has been possible to determine the effect of the Rare earth-Fe3 interaction on the reorientation of the Fe3 moments in “butterfly” carboxylates as a function of Rare earth substitution, ranging from isotropic and anisotropic Kramers ions (Gd and Dy) [3], or anisotropic non-Kramers ions (Tb and Ho) [4] . The different thermo-magnetic relaxational behavior at very low temperatures of these molecules is described.