Shell Antiferromagnetism in the Mixed Spin-(3/2,2) Mn12-ac Single Molecule Magnet

Shell antiferromagnetism effects on the magnetic properties of the mixed spin-(3/2,2) core/shell Mn ₁₂ -ac Single Molecule Magnet (SMM) are modeled and investigated by using Ising model within the effective field theory developed by Kaneyoshi. We find that the compensation (Tcomp) and Curie temperature (Tc) are obtained at 0.809 and 1.517, respectively. Magnetization of the spin-2 shell Mn atoms (Mns) is negative whereas the magnetization of the spin-3/2 core Mn atoms (Mnc) is positive versus temperature. The hysteresis loops of total Mn ₁₂ -ac exhibit steps indicative of quantum tunneling of magnetization (QTM). Since the magnetization of total Mn ₁₂ -ac exhibits compensation and QTM behavior, we suggest that there is a strong relationship between the compensation and QTM behavior resulting from the shell antiferromagnetism (spins of Mns are down and the spins of the Os are up) in the mixed spin-(3/2,2) core/shell Mn ₁₂ -ac SMM.