Smogunov A, Dal Corso A, Delin A, Weht R, Tosatti E
Nat Nanotechnol. 2008 Jan;3(1):22-5. doi: 10.1038/nnano.2007.419. Epub 2007 Dec 23.
Whenever a nanosystem such as an adatom, a cluster or a nanowire spontaneously magnetizes, a crucial parameter is its magnetic anisotropy, the intrinsic preference of magnetization to lie along an easy axis. Anisotropy is important in nanosystems because it helps reduce the magnitude of thermal (superparamagnetic) fluctuations, it can modify the flow of current, and it can induce new phenomena, such as the quantum tunnelling of magnetization. We discuss here, on the basis of density functional calculations, the novel and unconventional feature of colossal magnetic anisotropy--the strict impossibility of magnetization to rotate from the parallel to the orthogonal direction--which, owing to a quantum mechanical selection rule, the recently predicted Pt nanowire magnetism should exhibit. Model calculations suggest that the colossal magnetic anisotropy of a Pt chain should persist after weak adsorption on an inert substrate or surface step.
每当诸如吸附原子、团簇或纳米线之类的纳米系统自发磁化时，一个关键参数就是其磁各向异性，即磁化沿着易轴方向的固有偏好。各向异性在纳米系统中很重要，因为它有助于减小热（超顺磁性）涨落的幅度，能够改变电流流动，还能引发新现象，比如磁化的量子隧穿。在此，我们基于密度泛函计算，讨论巨磁各向异性的新奇和非常规特征——磁化从平行方向旋转到正交方向严格不可能——由于量子力学选择规则，最近预测的铂纳米线磁性应该会展现出这一特征。模型计算表明，铂链的巨磁各向异性在弱吸附于惰性衬底或表面台阶后应该依然存在。
