We report on the synthesis and magnetic properties of Mn 12 -based single molecular magnets (SMMs) with benzene and pentafluorobenzene carboxylate ligands. The changes in ligand structure are shown to have a decisive effect on magnetic properties of produced complexes. The compound with benzene demonstrates unusual magnetic behaviour, namely, temperature dependencies of magnetization taken under the zero field cooled and field cooled conditions are split below 10 K and furthermore remnant magnetization and coercive force remain nonzero in this temperature range. In contrast, compound with pentafluorobenzene displays the customary signatures of a blocking temperature at 3K. The effect of ligand substitution was theoretically studied within local density approximation taking into account onsite Coloumb repulsion. Calculation results confirm that the electronic structure and the magnetic exchange interactions between different Mn atoms strongly depend on the type of ligands.
Fullerene-containing complexes of Mn 12 -based single molecular magnets have been studied. It is confirmed that fullerenes have strong influence on the relaxation processes inside single molecular magnets. Notably, the hysteresis curves are found not to return to the initial point after 1 T to À1 T to1 T measurement cycle, but the magnetization progressively increases with each cycle. The effect is reproducible, and we call it ''magnetization training'' drawing an analogy with the ''magnetic training'' in exchange-biased multilayers, but emphasizing that magnetization rather than coercivity is trained in our system. The effect is presumably due to magnetic ordering linked to orientational ordering of incorporated C 60 molecules in magnetic field.
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