Al_2O_3/NiO包裹Ni纳米颗粒的结构和磁性

Structure and magnetic properties of Al_2O_3/NiO coated Ni nanoparticles

用电弧法蒸发Ni-Al合金(4%-5%Al,质量分数),制备了Al2O3/NiO包裹Ni及Ni-Al合金纳米颗粒.高分辨电镜显示该纳米颗粒具有壳核结构,核为纳米Ni及Ni-Al合金,壳为Al2O3/NiO复合氧化物.壳的厚度为2-4nm,颗粒的尺寸为5-60nm.壳核结构防止纳米Ni颗粒的进一步氧化和团聚.饱和磁化强度为29.6Am2/kg,矫顽力为4.13kA/m.由于铁磁和反铁磁性相界面处存在交换耦合作用,磁滞曲线出现小的偏置.

Al2O3/NiO composite-coated Ni nanoparticles are prepared by arc-discharging a bulk Ni-Al (4%-5% Al, mass fraction) alloy. The HRTEM shows the nanoparticles form in a core-shell structure, with the size of the particles in range of 5-60 nm and the thickness of the shell 2-4 nm. The core consists of particles of Ni and few Ni-AI alloy, while the shell consists of Al2O3/NiO composites. The core-shell structure can prevent Ni nanoparticles from oxidation and agglomeration. A saturation magnetization of Ms=29.6 Am2/kg and a coercive force of Hc=4.13 kA/m are achieved for the nanoparticles. The loop shift in the hysteresis loop shows the existence of the exchange anisotropy at the ferromagnetic-antiferromagnetic interfaces of the nanoparticles.