Recent advances with Dy3+ metallocene complexes in particular have led to some truly exceptional systems and the highest relaxation barrier to date, in excess of 1200 cm−1.
It is found that a small enthalpy decrease (about 0.8 kJ/mol) in initial state causes an extremely large increase (about 100 kJ/mol) in relaxation barrier, which is attributed to the enhanced cooperative atomic motion.
2a, 5a In such cases, the dynamics of the magnetization are governed by both magnetic correlations and the relaxation barrier experienced by individual magnetic units.
The Mn-UO2-Mn coordination polymer exhibits a slow relaxation of magnetization with a high relaxation barrier and shows an open hysteresis, thus providing the first example of an actinide-based SCM.
This infinite chain displays a high relaxation barrier of 134±0.8 K, probably as a result of strong intra-chain magnetic interactions combined with the high Ising anisotropy of the uranyl(V) dioxo group.
Its thermal relaxation barrier of 134 K (93 cm−1) is slightly smaller than that of the previously reported U12Mn6 SMM (Δ E= ca. 142 K (99 cm−1)), 9c but significantly larger than those reported for lanthanide-based single-chain magnets.
The infinite UMn chain displays a high relaxation barrier of 134±0.8 K (93±0.5 cm−1), probably as a result of strong intra-chain magnetic interactions combined with the high Ising anisotropy of the uranyl(V) dioxo group.
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It is shown that the dielectric relaxation in barrier coatings may be interpreted in terms of a 'two-step' continuous time random walk in one dimension.
2, 6 Lower values of the relaxation energy barrier were reported for SMMs based on mononuclear UIII and UV (highest value: 30 K (21 cm−1)).
