Anisotropic exchange interactions in [Ln^{3 +} s(-) Fe_LS^{3 +}] dinuclear systems (Ln³⁺ = Dy, Tm, Yb): Magnetometry and Dual Mode X-band Electron Paramagnetic Resonance spectroscopic study

A recently developed experimental and theoretical procedure is used in order to calculate the magnitude and anisotropy of interaction between a lanthanide and a 3d-metal ion. The general formula of the molecular compounds is [Ln(H₂O)₃(dmf)₄(μ-CN)Fe-(CN)₅] · nH₂O where 1 ≤ n ≤ 1,5 and dmf = N,N′-dimethylformamide, abbreviated as [LnFe] from now on. The main parts of this procedure are (a) the evaluation of the effective g-parameters of the lanthanide ion with the help of EPR measurements. (b) The use of dual mode EPR spectroscopy to define the anisotropic exchange interactions with the help of an anisotropic Hamiltonian model. (c) Use of the same magnetic model to fit magnetization and susceptibility data in order to verify the EPR findings. It was possible to define some trends concerning the exchange components of the [DyFe] dimer according to which the antiferromagnetic isotropic exchange constant is smaller than 4 cm^-1 and the anisotropic components are [D_exc, E_exc] = [≥6(1), 0.0] cm^-1. Also for the case of [TmFe] and [YbFe] dimers the antiferromagnetic isotropic exchange constant is smaller than 0.3 cm^-1 while the anisotropic components are [D_exc, E_exc] = [≥12.0, 0.0] cm^-1 and [D_exc, E_exc] = [0.4(1), 0.0] cm^-1, respectively.