纤锌矿CoO纳米团簇的磁性
The magnetism of wurtzite CoO nanoclusters
摘要：
采用密度泛函理论和蒙特卡罗模拟相结合的方法，研究了纤锌矿型CoO纳米团簇表面未补偿自旋导致的Co掺杂ZnO的室温铁磁性的可能性.我们发现，从比热中提取的临界温度随着团簇尺寸的减小而系统地下降，而与特定的团簇形状无关。此外，以缺失磁性位点的形式存在的缺陷进一步降低了$T_\mathrm{C}$。这表明，即使是亚稳分解相也不可能维持ZnO：Co中的室温铁磁性。
英文摘要：
The possibility that the apparent room temperature ferromagnetism, often measured in Co-doped ZnO, is due to uncompensated spins at the surface of wurtzite CoO nanoclusters is investigated by means of a combination of density functional theory and Monte Carlo simulations. We find that the critical temperature extracted from the specific heat systematically drops as the cluster size is reduced, regardless of the particular cluster shape. Furthermore the presence of defects, in the form of missing magnetic sites, further reduces $T_\mathrm{C}$. This suggests that even a spinodal decomposed phase is unlikely to sustain room temperature ferromagnetism in ZnO:Co.
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