The current figure of merit to evaluate Single Molecule Magnet (SMM) performance is the blocking temperature (T_B). The best SMMs show T_B values close to liquid nitrogen boiling point (77 K) while their Orbach effective demagnetization barriers (U_eff) are significantly larger, exceeding 2000 K in some cases. As current high performance SMMs approach the axial limit, new strategies to suppress demagnetization by vibrational tuning have been suggested. In this article, we analyse a set of 17 current high performance SMMs to identify which demagnetization mechanism is limiting the blocking temperature. For the best systems (T_B > 50 K), the limiting mechanism is thermally assisted tunneling and the blocking temperature will depend on the exponential parameters U_eff and τ₀. Strategies focusing on Raman (vibrational) suppression are expected to have a limited effect for this group. In contrast, systems with lower blocking temperatures (T_B < 50 K) would benefit from such strategies, although they are not expected to surpass current record T_B values. The Orbach limit for the blocking temperature can be conveniently estimated using ab initio CASSCF methods. Finally, a recent proposal for a hypothetical high performance SMM is analysed under the presented framework, showing its potential to improve record blocking temperatures.

中文翻译：

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高性能单分子磁体，可抑制Orbach或拉曼弛豫？

评估单分子磁体（SMM）性能的当前优点是阻塞温度（T _B）。最好的SMM的T _B值接近液氮沸点（77 K），而它们的Orbach有效退磁势垒（U _eff）则更大，在某些情况下超过2000K。随着当前的高性能SMM接近轴向极限，已提出了通过振动调谐来抑制退磁的新策略。在本文中，我们分析了一组17种当前的高性能SMM，以确定哪种退磁机制限制了阻塞温度。为了获得最佳的系统（Ť_乙> 50 K），该限制机构被热辅助隧穿和阻挡温度将取决于指数参数ù _EFF和τ ₀。预期针对拉曼（振动）抑制的策略对该小组的影响有限。相反，用较低的阻挡温度（系统Ť_乙<50 K）将受益于这样的策略，虽然他们预计不会超过当前记录Ť_乙值。可以使用从头算起方便地估算阻塞温度的奥巴赫极限CASSCF方法。最后，在提出的框架下分析了一个假设的高性能SMM的最新建议，显示了其改善记录阻塞温度的潜力。