Effect of pressure on single-chain magnets with repeating units of the MnIII-NiII-MnIII trimer -: art. no. 144421

The single-chain magnet (SCM) system [Mn-2(saltmen)(2)Ni(pao)(2)(L)(2)](A)(2) (L: intrachain attaching ligand of Ni-II ion; A(-1): interchain counteranion) is a ferromagnetic one-dimensional network system with repeating units of the Mn-III-Ni-II-Mn-III trimer which itself behaves as a single-molecule magnet with an S=3 spin ground state and negative uniaxial single-ion anisotropy (D) parallel to the bridging direction. The slow relaxation of the magnetic moment in this SCM system originates in an energy barrier for spin reversal (Delta E), which is closely related to the ferromagnetic interaction between the trimers (J(trimer)) as well as to the D of the trimer. We have investigated the effects of pressure on three compounds representative of the above SCM family through ac susceptibility measurements under hydrostatic pressures up to P=13.5 kbar and crystal structural analysis experiments up to P=20.0 kbar, and have observed a pronounced enlargement of Delta E when J was artificially increased. The application of hydrostatic pressure brought about the systematic enhancement of Delta E (a maximum increase of 10% within the pressure region of the experiments). The pressure dependence of Delta E varied according to the kind of attaching ligand L involved and the intrachain structure, and we have experimentally found that isotropic lattice shrinkage is desirable if a continuous increase of Delta E in this system is aimed at.