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首页> 外文期刊>Chemistry: A European journal >Magnetic Anisotropy of the Antiferromagnetic Ring [Cr_8F_8Piv_(16)]
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Magnetic Anisotropy of the Antiferromagnetic Ring [Cr_8F_8Piv_(16)]

机译：反铁磁环的磁各向异性[Cr_8F_8Piv_（16）]

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摘要

A new tetragonal (P42_12) crystalline form of [Cr_8F_8Piv_(16)] (HPiv = pivalic acid, trimethyl acetic acid) is reported. The ring-shaped molecules, which are aligned in a parallel fashion in the unit cell, form almost perfectly planar, regular octagons. The interaction between the Cr~(III) ions is antiferromagnetic (J = 12 cm~(-1)) which results in a S = 0 spin ground state. The low-lying spin excited states were investigated by cantilever torque magnetometry (CTM) and high-frequency EPR (HFEPR). The compound shows hard-axis anisotropy. The axial zero-field splitting (ZFS) parameters of the first two spin excited states (S = 1 and S = 2, respectively) are D_1 = 1.59(3) cm~(-1) or 1.63 cm~(-1) (from CTM and HFEPR, respectively) and D_2 = 0.37 cm~(-1) (from HFEPR). The dipolar contributions to the ZFS of the S = 1 and S == 2 spin states were calculated with the point dipolar approximation. These contributions proved to be less than the combined single-ion contributions. Angular overlap model calculations that used parameters obtained form the electronic absorption spectrum, showed that the unique axis of the single-ion ZFS is at an angle of 19.3(1) deg with respect to the ring axis. The excellent agreement between the experimental and the theoretical results show the validity of the used methods for the analysis of the magnetic anisotropy in antiferromagnetic Dr~(III) rings.
机译：报道了一种新的[Cr_8F_8Piv_（16）]的四方（P42_12）晶体形式（HPiv =新戊酸，三甲基乙酸）。在晶胞中以平行方式排列的环状分子形成几乎完美的平面规则八边形。 Cr〜（III）离子之间的相互作用是反铁磁的（J = 12 cm〜（-1）），这导致S = 0的自旋基态。通过悬臂扭矩磁力法（CTM）和高频EPR（HFEPR）研究了低层自旋激发态。该化合物显示出硬轴各向异性。前两个自旋激发态（分别为S = 1和S = 2）的轴向零场分裂（ZFS）参数为D_1 = 1.59（3）cm〜（-1）或1.63 cm〜（-1）（分别来自CTM和HFEPR）和D_2 = 0.37 cm〜（-1）（来自HFEPR）。用点偶极近似计算了S = 1和S == 2自旋态对ZFS的偶极贡献。事实证明，这些贡献少于单离子组合贡献。使用从电子吸收光谱获得的参数进行的角重叠模型计算表明，单离子ZFS的唯一轴相对于环轴成19.3（1）度角。实验结果与理论结果吻合良好，证明了所用方法对反铁磁Dr〜（III）环的磁各向异性进行分析的有效性。

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