温度相关的形状各向异性对定向Stoner-Wohlfarth软磁材料磁性的影响
Effect of temperature-dependent shape anisotropy on coercivity with aligned Stoner-Wohlfarth soft ferromagnets
摘要：
在Neel-Brown（N-B）分析的框架下，研究了形状各向异性对定向Stoner-Wohlfarth（SW）软磁合金（fcc Ni，fcc Co和bcc Fe）矫顽力HC（T）的温度效应.通过引入单一的无量纲修正函数，提出了一个扩展的N-B方程：m（\tao）= MS（T）/MS（0），其中\tao = T/TC为约化温度，MS（T）为饱和磁化强度，TC为居里温度。因子m（\tao）说明形状各向异性的温度依赖效应。常数H 0和E0分别用于零温度下的开关场和零场下的势垒。根据这个新推导出的方程，当阻断温度高于这个温度时，超顺磁性就显现出来，这个温度可以用表达式TB = E0 m^2（\tao）/[kBln（t/t0）]来描述，并加上额外的修正因子m^2（\tao）。还讨论了有限尺寸效应导致TC下移对HC（T）和阻塞温度TB的可能影响。
英文摘要：
The temperature variation effect of shape anisotropy on the coercivity, HC(T), for the aligned Stoner-Wohlfarth (SW) soft ferromagnets, such as fcc Ni, fcc Co and bcc Fe, are investigated within the framework of Neel-Brown (N-B) analysis. An extended N-B equation is thus proposed,by introducing a single dimensionless correction function, the reduced magnetization, m(\tao) = MS(T)/MS(0), in which \tao = T/TC is the reduced temperature, MS(T) is the saturation magnetization, and TC is the Curie temperature. The factor, m(\tao), accounts for the temperature-dependent effect of the shape anisotropy. The constants, H0 and E0, are for the switching field at zero temperature and the potential barrier at zero field, respectively. According to this newly derived equation, the blocking temperature above which the properties of superparamagnetism show up is described by the expression, TB = E0m^2(\tao)/[kBln(t/t0)], with the extra correction factor m^2(\tao). The possible effect on HC(T) and the blocking temperature, TB, attributed to the downshift of TC resulting from the finite size effect has been discussed also.
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