Yin Bing, Li Chao-Chao
Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an, 710127, P. R. China.
Phys Chem Chem Phys. 2020 May 13;22(18):9923-9933. doi: 10.1039/d0cp00933d.
In this work, a theoretical method for the prediction of both the relaxation time of quantum tunneling of magnetization (τQTM) and the effective barrier of magnetic reversal (Ueff) is proposed for single-ion magnet (SIM) systems of Kramers type. The reliability of theoretical τQTM is tested within a large series of 18 lanthanide SIMs. Compared to the experimental results, the deviations of theoretical τQTM are within one order of magnitude for 11 tested SIMs and the largest order-of-magnitude deviation is only 1.86. In the aspect of Ueff, for 5 typical high-performance Dy-SIMs of the local coordination mode of a pentagonal bipyramid, the relative deviations of theoretical values lie within the range of 1.4-7.2%. Thus this method possesses good reliability, at least in the aspect of the order of magnitude. Besides an empirical estimate of the local magnetic field experienced by the central ion, for a given SIM, one ab initio calculation, providing accurate g-factors of both ground and excited Kramers doublets (KDs), is the only computational cost. Therefore this method has a high degree of both reliability and efficiency. Based on the temperature dependence of theoretically predicted Ueff and its contributions from various KDs, some mechanistic information on the magnetic relaxation could be given by this method too. Therefore it is reasonable to expect the bright prospect of this method in the aspects of both the interpretation of the existing experimental results and rational design of future high-performance SIMs.
在这项工作中，针对克莱默斯型单离子磁体（SIM）系统，提出了一种预测磁化量子隧穿弛豫时间（τQTM）和磁反转有效势垒（Ueff）的理论方法。在一系列18种镧系SIM中测试了理论τQTM的可靠性。与实验结果相比，11种测试的SIM的理论τQTM偏差在一个数量级以内，最大数量级偏差仅为1.86。在Ueff方面，对于5种典型的五角双锥局域配位模式的高性能Dy-SIM，理论值的相对偏差在1.4 - 7.2%范围内。因此，该方法至少在数量级方面具有良好的可靠性。除了对中心离子所经历的局部磁场进行经验估计外，对于给定的SIM，一次从头算计算，提供基态和激发态克莱默斯双态（KDs）的精确g因子，是唯一的计算成本。因此，该方法具有高度的可靠性和效率。基于理论预测的Ueff的温度依赖性及其来自各种KDs的贡献，该方法也可以给出一些关于磁弛豫的机理信息。因此，有理由期待该方法在解释现有实验结果和合理设计未来高性能SIM方面都有光明的前景。
