ConAl (n=1—8)合金团簇结构和磁性质研究
Structural, electronic and magnetic properties of ConAl (n=1—8) clusters?
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摘要: 采用密度泛函理论中的广义梯度近似(DFT-GGA)对ConAl (n=1—8)合金团簇进行了系统的几何、电子结构和磁性质研究.研究结果表明Al原子倾向于与Co原子形成最大的成键数,即Al原子均处在团簇原子拥有最大配位数的位置上. Al掺杂后ConAl团簇的稳定性减弱,磁性降低.磁性降低的幅度与实验上对较大CoNAlM团簇的磁性检测结果获得了很好地符合.在所有ConAl团簇的最稳定结构中,除Co4Al外, Al与近邻Co原子均呈现反铁磁性耦合.相对于纯Co团簇,非磁性Al元素的掺入以及Al掺杂后Co原子整体自旋极化的减弱是导致ConAl团簇磁性的降低主要原因.Abstract: Based on DFT-GGA calculations, we systematically investigate the structures, electronic and magnetic properties of ConAl (n=1—8) clusters. The results indicate that the aluminum prefers to maximize the number of Co-Al bonds by selecting the site which increases the coordination of cobalt atoms with Al. The doped Al makes the stability of ConAl clusters weakened and the magnetism decreased as compared with that of Con+1 clusters. The reduction magnitude of magnetism of the doping Al accords well with recent Stern-Gerlach experimental result for larger CoNAlMclusters. In all of the ConAl alloy clusters, the Al atom is found to be aligned antiferromagnetically with its neighbor Co atoms except for Co4Al. As compared with the magnetism of pure Co cluster, the magnetism of ConAl cluster is reduced, which is attributed mainly to nor-magnetism Al element embeding and the weakening of spin polarization of the Co atoms.
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