【摘要】 利用等离子体-气体冷凝方法制备了具有核-壳结构的Co纳米颗粒,并对其结构和磁性进行了研究。结果表明纳米颗粒的尺寸均匀,平均直径约为20 nm,表面包覆着CoO壳层。在CoO壳层和Co核间存在着交换偏置效应。经过磁场冷却,在低温测量的纳米颗粒的磁滞回线不只在横轴方向,在纵轴方向也存在着明显的偏移,并且在横向偏移量和纵向偏移量间存在着线性关系。交换偏置效应和磁滞回线的纵向偏移应该起源于CoO壳层中未被补偿的冻结自旋。根据交换偏置效应的未补偿自旋模型,对Co纳米颗粒的磁场冷却磁滞回线的横向偏移量和纵向偏移量间的线性关系进行了解释。更多还原

【Abstract】 Core-shell-structured cobalt nanoparticles were synthesized by plasma-gas-condensation method.All particles are covered with a CoO shell,and have a narrow size distribution with an average diameter of about 20 nm.Exchange bias effect is found between the CoO shell and Co core.After field cooling,the magnetic hysteresis loops of the particles measured at low temperature show clear shifts in both horizontal and vertical directions.And the horizontal shifts and vertical shifts have a linear relationship.The exchange bias effect and the vertical shifts should arise from these frozen uncompensated spins in CoO shell.And the linear relationship between the horizontal shifts and vertical shifts is interpreted according to the interfacial uncompensated-spin model of exchange bias effect.更多还原