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The influence of pseudo-tetrahedral coordination environment of Co2+ ion in polymeric dimethylmalonates on the magnetic anisotropy and slow magnetic relaxation
The interaction of Co(NO3)2⋅6H2O and MI2CO3 (MI = Rb or Cs) with dimethylmalonic acid (H2Me2mal) leads to
the formation of 3D polymeric compounds: {[Co4Rb8(Me2mal)8(H2O)8]⋅5H2O}n (1) and {[CoCs2(Me2mal)2
(H2O)4]⋅H2O}n (2), respectively. The structures of 1 and 2 were characterized using X-ray diffraction analysis
and IR spectroscopy. Each complex contains CoII atoms arranged in four vertex polyhedra. Both compounds
exhibit field-induced slow magnetic relaxation. The dc-magnetic measurements and ab initio calculation results
show that 1 has “easy plane” type of magnetization, where the axial parameter D of both crystallographicaly
independent Co2+ ions is positive. In contrast, parameter D of 2 is negative, which corresponds to “easy axis”
type. For 2 the relaxation process includes the Orbach mechanism, which corresponds to the quantum chemical
calculation.