Through the use of a new homemade probe, the angular dependences of the dc and ac susceptibilities of single crystals of [Tb3+(ZnL)2]­CF3SO3 (H3L denotes a tripodal hexadentate Schiff base ligand) were investigated for the purpose of resolving the anisotropic magnetic relaxation at low temperatures (down to 2 K). The dc magnetic measurements and crystal field calculations have confirmed a strong uniaxial anisotropy with an easy axis along the C 3 axis, which passes through the Zn-Tb-Zn array. The ac data demonstrate that the magnetic relaxations crucially depend on the angle between the easy axis and the direction of applied magnetic field, and this type of definitive identification is not possible in works using randomly arranged microcrystals or powder. The theoretical analysis shows that the anisotropy of the dynamical properties is a manifestation of a quantum structure, in particular, the angle dependence of the distribution of electronic levels. More specifically, the angle dependences of the energies of the two lowest levels of the Tb3+ ion in 1 kOe were obtained.

Trinuclear M(II)-Gd(III)-M(II) complexes 1 (M = Zn), 2 (M = Mg), and the magnetically dilute sample 1′ were synthesized and the slow magnetization relaxation originating from Gd(III) ions was investigated in detail. These complexes are crystallographically isostructural and belong to D 3 point group symmetry, with M-Gd-M arrayed on the crystallographic 3-fold axis. From the angular-resolved magnetization of a single crystal of 1, an easyaxis-type magnetic anisotropy of Gd(III) with an anisotropy parameter D of −0.21(3) K were revealed. All the complexes underwent slow relaxation under the application of an external magnetic field. The temperature dependence of the relaxation rate τ −1 differed considerably between 1′ and 1, 2 such that: for 1′,τ −1 ∝ T 1.1 over the entire temperature range, whereas for 1 and 2, τ −1 ∝ T 1.56 and τ −1 ∝ T 1.49 above 3 K, respectively. The discrepancy can be attributed to the presence of competing multiple relaxation processes, such as direct and Raman processes, and at dilution, the direct process becomes faster, leading to its predominance in 1′. For 1 and 2, the larger power number (∼1.5) was attributed to the significantly greater contribution from the Raman process, which may be originated from intramolecular atomic vibrations.