Abstract Based on Monte Carlo method, the oscillatory behaviour of the average magnetic moment as a function of the cluster sizes and the temperature dependences of magnetic moment with different sizes have been studied. It is found that the oscillations superimposed on the decreasing moment are associated with not only the geometrical structure effects but also the thermal fluctuation. The hystereses and thermal coercivities for free clusters with zero and finite uniaxial anisotropies have been calculated. The simulated thermal dependence of the coercivity is consistent with the experimental result, but does not fit the $T^{\alpha}$ law in the whole temperature range. It is evident that an easy magnetization direction and an anisotropy resulting from the spin configurations exist in the free clusters with the pure exchange interaction, which is also proved by the natural angle and energy distribution of clusters. A systematic theoretical analysis is also made to establish the relationship between natural angle and coercivity.
Received: 29 December 2005
Revised: 04 April 2006
Accepted manuscript online:
PACS:
75.60.Ej
(Magnetization curves, hysteresis, Barkhausen and related effects)
Fund: Project supported by the State Key Program of Basic Research of China (Grant No 2005CB623605), the Natural Science Foundation of Fujian Province, China (Grant Nos E0320002 and 2005K020), the National
Natural Science Foundation of China (Grant No 10474037)
Cite this article:
Huang Zhi-Gao (黄志高), Chen Zhi-Gao (陈志高), Jiang Li-Qin (蒋丽钦), Ye Qing-Ying (叶晴莹), Wu Qing-Yun (吴青云) Monte carlo simulation of magnetization and coercivity of free magnetic clusters 2006 Chinese Physics 15 1602
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