Ferromagnetic resonance and magnetic characteristics of intact magnetosome chains in Magnetospirillum gryphiswaldense
Ferromagnetic resonance and magnetic characteristics of intact magnetosome chains in Magnetospirillum gryphiswaldense
复制标题
DOI：
10.1016/j.epsl.2008.03.022
复制
发表时间：
2008-06-30
影响因子：
5.3
通讯作者：
Gehring, Andreas U.
中科院分区：
文献类型：
--
作者：
Fischer, Hakon;Mastrogiacomo, Giovanni;Gehring, Andreas U.
采用静态、动态磁分析和铁磁共振波谱分析方法研究了Gryphiswaldense磁小体细菌完整磁小体链的磁性特征。纳米磁小体一般处于稳定的单畴状态，但也发现了小于30 nm的超顺磁性磁铁矿颗粒特征的磁小体，交流磁化率表明所有磁小体在150 K以下被阻断。在室温下，M. gryphiswaldense由磁小体链的形状决定。低温铁磁共振（FMR）谱表明，这种占主导地位的形状各向异性可以影响在100 K的Verwey转变的检测。静态和动态的磁性分析表明，Verwey转变是模糊的，我们的趋磁细菌失败的Moskowitz测试。这种失败是由非化学计量的磁小体的生物矿化。这种解释是基于高场磁化率的增加和在50 K以下的交流磁化率的异相分量中的明显峰值。这些结果归因于与纳米尺寸磁小体的核心和表面处的缺陷结构相关联的自旋的冻结。从M. GryphisWaldense证明了纳米尺寸磁小体的固有性质受到非化学计量和由它们在细菌中的排列激发的各向异性的显著影响。(c)2008 Elsevier B.V.保留所有权利。
The magnetic characteristics of intact magnetosome chains in Magnetospirillum gryphiswaldense bacteria were investigated by means of static and dynamic magnetic analyses and ferromagnetic resonance spectroscopy. The nano-sized magnetosomes are generally in a stable single-domain state, but magnetosomes smaller than 30 nm characteristic of superparamagnetic magnetite particles were also found. Alternating current (AC) susceptibility indicates that all magnetosomes are blocked below 150 K. At room temperature the anisotropy of M. gryphiswaldense is dominated by the shape of the magnetosome chains. Low-temperature ferromagnetic resonance (FMR) spectroscopy indicates that this dominant shape anisotropy can affect the detection of the Verwey transition at 100 K. The static and dynamic magnetic analyses show that the Verwey transition is smeared and that our magnetotactic bacteria fail the Moskowitz test. This failure is explained by the biomineralization of non-stoichiometric magnetosomes. This interpretation is based on the increase in high-field susceptibility and the distinct peak in the out-of-phase component of the AC susceptibility below 50 K. These results are attributed to freezing of spins associated with defect structures in the core and at the surface of nano-sized magnetosomes. The results obtained from M. gryphiswaldense demonstrate that intrinsic properties of nano-sized magnetosomes are significantly influenced by non-stoichiometry and by the anisotropy excited from their arrangement in the bacteria. (c) 2008 Elsevier B.V. All rights reserved.