Anisotropy and magnetization reversal with chains of submicron-sized Co hollow spheres
Anisotropy and magnetization reversal with chains of submicron-sized Co hollow spheres
复制标题
亚微米级 Co 空心球链的各向异性和磁化反转
DOI：
10.1103/physrevb.75.214418
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发表时间：
2007-06-01
影响因子：
3.7
通讯作者：
Guo, Lin
中科院分区：
文献类型：
--
作者：
He, Lin;Chen, Chinping;Guo, Lin
研究了具有链状结构的hcp Co空心球的磁性。球的直径范围为500至800 nm，典型的壳厚度为约60 nm。壳是多晶的，平均晶粒尺寸为20至35 nm。在H = 90 Oe时，零场冷却MZFC（T）测量的阻塞温度约为325 K。相应的有效各向异性被确定为Keff = 4.6*10^4 J/m^3。此外，通过对HC（T）的分析确定的阻塞温度和有效各向异性分别为395 K和5.7*10^4 J/m^3。实验测定的各向异性比体相六方晶系钴的磁晶各向异性小一个数量级，约为3 ~ 5*10^5 J/m^3。对HC（T）的进一步分析表明，磁化反转遵循成核旋转模式，其有效转换体积为V* = 2.3*10^3 nm^3。相应的有效直径计算为16.4 nm。它略大于Co的相干长度，约为15 nm。磁各向异性大大降低的可能原因进行了简要的讨论。
Magnetic properties with chains of hcp Co hollow spheres have been studied. The diameter of the spheres ranges from 500 to 800 nm, with a typical shell thickness of about 60 nm. The shell is polycrystalline with an average crystallite size of 20 to 35 nm. The blocking temperature determined by the zero-field-cooling MZFC(T) measurement at H = 90 Oe is about 325 K. The corresponding effective anisotropy is determined as, Keff = 4.6*10^4 J/m^3. In addition, the blocking temperature and the effective anisotropy determined by the analysis on HC(T) are 395 K and 5.7*10^4 J/m^3, respectively. The experimentally determined anisotropy is smaller by one order of magnitude than the magnetocrystalline anisotropy of the bulk hcp Co, which is about 3 to 5*10^5 J/m^3. A further analysis on HC(T) shows that the magnetization reversal follows a nucleation rotational mode with an effective switching volume, V* = 2.3*10^3 nm^3. The corresponding effective diameter is calculated as 16.4 nm. It is slightly larger than the coherence length of Co, about 15 nm. The possible reason for the much reduced magnetic anisotropy is discussed briefly.