Dong Hui-Ming, Li Hai-Yan, Zhang Yi-Quan, Yang En-Cui, Zhao Xiao-Jun
Department of Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Nankai University , Tianjin 300071, People's Republic of China.
College of Chemistry, Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry, Ministry of Education, Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Tianjin Normal University , Tianjin 300387, People's Republic of China.
Inorg Chem. 2017 May 15;56(10):5611-5622. doi: 10.1021/acs.inorgchem.6b03089. Epub 2017 Apr 28.
A centrosymmetric Dy single-molecule magnet (SMM) and its doped diamagnetic yttrium analogues, DyY and DyY, were solvothermally synthesized to investigate the effects of intramolecular exchange coupling and quantum tunneling of magnetization (QTM) on the magnetic relaxation dynamics. Constructed from two hula-hoop-like Dy ions and a pair of phenoxido groups, the antiferromagnetically coupled Dy exhibits a thermal-activated zero-field effective energy barrier (U) of 277.7 K and negligible hysteresis loop at 2.0 K. The doping of a diamagnetic Y matrix with 90.5% and 95.0% molar ratios reveals the single-ion origin of the Orbach channel, increases the relaxation time by partially quenching the QTM process, and induces an open hysteresis loop until 5.0 K. In contrast, an optimal dc field of 1.0 kOe improves the barrier height up to 290.1 K through complete elimination of the QTM and delays the relaxation time of the direct relaxation pathway. More interestingly, the collaborative dual effects of magnetic-site dilution and external magnetic field make the effective energy barrier and relaxation time increase 8.1% and 49 times, respectively. Thus, the overall magnetization dynamics of the Dy system systematically elaborate the inherent interplay of the QTM and Orbach processes on the effective energy barrier, highlighting the vital role of the relaxation time on the coercive hysteresis loop.
通过溶剂热法合成了一种中心对称的镝单分子磁体（SMM）及其掺杂的抗磁性钇类似物DyY和DyY，以研究分子内交换耦合和磁化量子隧穿（QTM）对磁弛豫动力学的影响。由两个呼啦圈状的镝离子和一对苯氧基基团构成，反铁磁耦合的镝在2.0 K时表现出277.7 K的热激活零场有效能垒（U）和可忽略不计的磁滞回线。用摩尔比为90.5%和95.0%的抗磁性钇基质进行掺杂，揭示了奥巴赫通道的单离子起源，通过部分淬灭QTM过程增加了弛豫时间，并在5.0 K之前诱导出开放的磁滞回线。相比之下，1.0 kOe的最佳直流场通过完全消除QTM将能垒高度提高到290.1 K，并延迟了直接弛豫途径的弛豫时间。更有趣的是，磁位点稀释和外部磁场的协同双重效应使有效能垒和弛豫时间分别增加了8.1%和49倍。因此，镝体系的整体磁化动力学系统地阐述了QTM和奥巴赫过程在有效能垒上的内在相互作用，突出了弛豫时间对矫顽磁滞回线的重要作用。
