The coefficient of magnetic viscosity. II. The time dependence of the magnetisation of interacting fine-particle magnetic materials
The coefficient of magnetic viscosity. II. The time dependence of the magnetisation of interacting fine-particle magnetic materials
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磁粘系数。
DOI：
10.1088/0305-4608/16/7/006
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
E. Wohlfarth
中科院分区：
文献类型：
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作者：
R. Chantrell;A. Lyberatos;E. Wohlfarth
关于pt，我见同上，第14卷，L.155(1984)。用适当的蒙特卡罗算法计算了偶极相互作用中球形细小钴粒子体系的磁化强度与时间的关系。对于弱相互作用，当体积填充因子p达到约10%时，时间依赖关系遵循指数规律，但相应的粒子体积v超过实际体积v的量与p成正比。对于强相互作用(p高达约50%)，由于相互作用引起的驰豫时间分布，时间依赖关系被发现是对数的。在高温下，磁化到其原始值的一半之前经过的相应时间t1/2大约遵循伏格尔-富勒定律(lnt1/2)-1(T-T0)，具有特征温度T0，但在低温下偏离该定律，因此系统永远不会经历任何相变。温度T_0与体积填充因子呈线性关系，从而证实了伏格尔-富勒定律源于短程合作现象。
For pt.I see ibid., vol.14, L.155 (1984). The time dependence of the magnetisation of a system of fine spherical cobalt particles in dipole interaction is computed by using an appropriate Monte Carlo algorithm. For weak interactions, with volume packing factor p up to about 10%, the time dependence follows an exponential law but with a corresponding particle volume veff which exceeds the actual volume v by an amount proportional to p. For strong interactions (p up to about 50%), the time dependence was found to be logarithmic due to the interaction-induced distribution of relaxation times. The corresponding time t1/2 which elapses before the magnetisation falls to half its original value follows a Vogel-Fulcher law (ln t1/2)-1 approximately (T-T0) with a characteristic temperature T0, at high temperatures but deviates from this law at low temperatures so that the system never experiences any phase transitions. The temperature T0 depends linearly on the volume packing factor, thus confirming that the Vogel-Fulcher law arises from short-range cooperative phenomena.