【摘要】 本文报道了镍超细微颗粒的磁性,比饱和磁化强度随颗粒尺寸减小而降低,当颗粒尺寸小于15nm时将会呈现剧烈地下降,此时矫顽力H_c亦将趋近于零,有效磁各向异性常数估算为K=-5.8×10~5erg/cm~3,远大于块状镍的数值,反磁化机制可用球键模型描述,对平均直径为9nm的样品,居里温度T_c值明显地低于块状镍的数值,这可能与点阵收缩有关。更多还原

【Abstract】 In this paper we report the magnetic properties of ultrafine Ni particles. The specific magnetic moment drastically decreases with reducing the diameter d of particles when d≤15 nm. The coercivity Hc also approaches zero when d is about 15nm. The value of effective magnetic anisotropy constant is determined as K=-5.8×105 (erg/c.c.). It is found to be larger than the bulk one. The mechanism of reversal magnetization can be understood by sphere chain model. Curie temperature Te is obviously lower for 9nm average diameter particles as compared with the bulk, this may result from the lattice contraction.更多还原