Laboratoire de Physique des Solides, CNRS, Université Paris Sud, UMR 8502, Bâtiment 510, F-91405 Orsay Cedex, France.
Phys Rev Lett. 2010 Apr 2;104(13):137202. doi: 10.1103/PhysRevLett.104.137202. Epub 2010 Mar 30.
The magnetic susceptibility of self-organized two-dimensional Co nanodots on Au(111) has been measured as a function of their size in the 2-7 nm diameter range. We show that the activation energy for the thermal reversal displays a power law behavior with the dot volume. Atomic scale simulations based on the Heisenberg Hamiltonian show that this behavior is due to a deviation from the macrospin model for dot size as small as 3 nm in diameter. This discrepancy is attributed to finite temperature effects through the thermal excitation of spin-wave modes inside the particles.
我们测量了自组织二维 Co 纳米点在 Au(111)上的磁化率随其直径在 2-7nm 范围内的变化。结果表明，热反转的激活能与点的体积呈幂律关系。基于海森堡哈密顿量的原子尺度模拟表明，这种行为是由于对于直径小至 3nm 的点，偏离了宏观磁模型所致。这种差异归因于粒子内部自旋波模式的热激发导致的有限温度效应。
