Magnetic anisotropy in carbon encapsulated Co/CoO “lines” with large exchange bias
- 作者：Bi ; Hong ; Li ; Shandong ; Jiang ; Xiqun ; Du ; Youwei ; Yang ; Changzheng
- 关键词：75.30.Gw ; 75.50.Tt ; 75.30.Et ; Magnetic anisotropy ; Co/CoO ; Exchange coupling ; Coercivity ; Alignment
- 刊名：Physics Letters A
- 出版年：2003
- 期刊代码：57_03759601
- 类别：ph
- 出版时间：January 20, 2003
- 卷：307
- 期：1
- 页码：69-75
- 文件大小：254 K
摘要
Carbon encapsulated cobalt nanoparticles were prepared by Co(II) reduction and post-annealing in inert argon gas. Cobalt nanoparticles form parallel “lines” with approximately equal space of 35 μm on the single-crystal silica substrate in the presence of a magnetic field of 3 kGs. Magnetic measurement results indicate that this system exhibits a strong magnetic anisotropy. Along the line direction, it was ferromagnetic with coercive force of 85 Oe, while perpendicular to the substrate plane, only a narrow hysteresis loop was observed. The samples were oxidized at 573 K for various times under air atmosphere. Coercivity was enhanced due to the exchange coupling between ferromagnetic Co and antiferromagnetic CoO. Compared with the random dispersed Co/CoO nanoparticles that was prepared under the same annealing and oxidation condition, a larger exchange bias was obtained in the magnetic aligned specimen. The mechanism of coercivity enhancement and larger exchange bias was discussed.