Structure and magnetic properties of the single-molecule magnet [Mn11CrO12(O2CCH3)(16)(H2O)(4)]center dot 2CH(3)COOH center dot 4H(2)O: magnetization manipulation and dipolar-biased tunneling in a Mn11Cr/Mn-12 mixed crystal
Structure and magnetic properties of the single-molecule magnet [Mn11CrO12(O2CCH3)(16)(H2O)(4)]center dot 2CH(3)COOH center dot 4H(2)O: magnetization manipulation and dipolar-biased tunneling in a Mn11Cr/Mn-12 mixed crystal
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DOI：
10.1103/physrevb.70.104427
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发表时间：
2004-09
影响因子：
3.7
通讯作者：
H. Hachisuka;K. Awaga;T. Yokoyama;T. Kubo;T. Goto;H. Nojiri
中科院分区：
文献类型：
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作者：
H. Hachisuka;K. Awaga;T. Yokoyama;T. Kubo;T. Goto;H. Nojiri
通过对[Mn_（11）Cr/Mn_（12）O_（12）（O_2CCH_3）（16）（H_2O）（4）]·2CH（3）COOH·4 H（2）O（Mn_（11）Cr）混晶的分析，研究了单分子磁体[Mn_（11）CrO_（12）（O_2CCH_3）（16）（H_2O）（4）]·2CH（3）COOH·4 H（2）O（Mn_（11）Cr）的结构和磁性. X射线吸收光谱表明，Mn 11 Cr中的Cr离子处于+3价态，并占据Mn-12骨架中特定的Mn 3+位置。高频电子顺磁共振（EPR）谱很好地解释了假设Mn 11 Cr是在一个基本的自旋状态S=19/2与几乎相同的EPR参数设置为Mn-12。与Mn-12相比，较低的自旋量子数导致较低的势垒高度（56.8K）。磁化曲线表明，在1.8 K的Mn 11 Cr的矫顽磁场为0.95 T，几乎一半的Mn-12。在Mn 11 Cr中观察到的量子隧穿磁化（QTM）低于阻断温度T-B，与Mn-12相同的场间隔。Mn-12和Mn-11 Cr的磁化强度可以通过利用它们的矫顽场的差异来独立控制。Mn-12的磁化方向对Mn-11 Cr中QTM的共振场有显著影响，表明存在偶极偏置隧穿效应。
The structural and magnetic properties of the single-molecule magnet [Mn11CrO12(O2CCH3)(16)(H2O)(4)].2CH(3)COOH.4H(2)O (Mn11Cr) are studied through the analysis of a Mn11Cr/Mn-12 (approximate to1:1) mixed crystal, where Mn-12 is [Mn12O12(O2CCH3)(16)(H2O)(4)].2CH(3)COOH.4H(2)O. X-ray absorption spectra reveal that the Cr ion in Mn11Cr is in the +3 valence state and occupies a specific Mn3+ site in the Mn-12 skeleton. High-frequency electron paramagnetic resonance (EPR) spectra are well explained by assuming that Mn11Cr is in a ground spin-state of S=19/2 with nearly the same EPR parameter set as for Mn-12. The lower spin quantum number results in lower barrier height (56.8 K) compared to Mn-12. The magnetization curves indicate a coercive field of 0.95 T for Mn11Cr at 1.8 K, nearly half that for Mn-12. Quantum tunneling of magnetization (QTM) in Mn11Cr is observed below the blocking temperature T-B, with the same field interval as for Mn-12. The magnetization of Mn11Cr and Mn-12 in the mixed crystal can be independently manipulated by utilizing the difference between their coercive fields. The resonance fields of QTM in Mn11Cr are significantly affected by the magnetization direction of Mn-12, suggesting the effect of dipolar-biased tunneling.