论文标题
探索最大的单分子磁铁的磁性
Exploring the magnetic properties of the largest single molecule magnets
论文作者
论文摘要
巨型$ \ {\ Mathrm {Mn} _ {70} \} $和$ \ {\ Mathrm {\ Mathrm {Mn} _ {84} \} $ WHEELS是最大的核心单核分子磁铁，并构成了他们的磁性属性，并理解其磁性属性对理论提出了质疑。从第一原理计算开始，我们使用有效的自旋汉密尔顿人探索这些车轮中的磁性和激发。我们发现，superexchange途径的异常几何形状导致弱耦合$ \ {\ Mathrm {Mn} _ {7} \} $ subunits携带有效$ s = 2 $ spin。该频谱表现出能量尺度和大量归化性的层次结构，最低的能量激发是由于海森贝格 - 环形的刺激刺激的$ \ {\ mathrm {\ mathrm {mn} _ {7} \} \} \} \} \} $ ununits周围围绕的能量，并且在能源周围具有一致的能量，并且在观察到的温度依赖性依赖性依赖性依赖性。我们进一步提出了弱的长距离耦合在选择$ \ mathrm {mn} $ wheels的精确旋转地面中的重要作用。
The giant $\{ \mathrm{Mn}_{70} \}$ and $\{ \mathrm{Mn}_{84} \}$ wheels are the largest nuclearity single-molecule magnets synthesized to date and understanding their magnetic properties poses a challenge to theory. Starting from first principles calculations, we explore the magnetic properties and excitations in these wheels using effective spin Hamiltonians. We find that the unusual geometry of the superexchange pathways leads to weakly coupled $\{ \mathrm{Mn}_{7} \}$ subunits carrying an effective $S=2$ spin. The spectrum exhibits a hierarchy of energy scales and massive degeneracies, with the lowest energy excitations arising from Heisenberg-ring-like excitations of the $\{ \mathrm{Mn}_{7} \}$ subunits around the wheel, at energies consistent with the observed temperature dependence of the magnetic susceptibility. We further suggest an important role for weak longer-range couplings in selecting the precise spin ground-state of the $\mathrm{Mn}$ wheels out of the nearly degenerate ground-state band.
