To have a qualitative understanding of the mechanism of magnetic relaxation, we have plotted ab-initio blocking barriers computed from SINGLE_ANISO approach as implemented in Orca as shown in Figure . The relaxation of magnetization can occur through three probable mechanistic pathways namely a) quantum tunneling of magnetization (QTM) within the ground KDs b) Orbach/Raman relaxation process where Raman relaxation process takes place through virtual transitions c) thermally assisted quantum tunneling of magnetization (TA-QTM) within excited KDs. In the computed relaxation mechanism, the KDs are presented according to their magnetic moments. The numbers at each arrow connecting any two energy levels represent the matrix elements of transition-magnetic-moments between the connecting energy levels.