Magnetospirillum gryphiswaldense biosynthesize high-quality magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass. Here we perform magnetometry and polarized small-angle neutron scattering (SANS) experiments on a powder of freeze-dried and immobilized M. gryphiswaldense. We confirm that the individual magnetosomes are single-domain nanoparticles and that an alignment of the particle moments along the magnetic field direction occurs exclusively by an internal, coherent rotation. Our magnetometry results of the bacteria powder indicate an absence of dipolar interactions between the particle chains and a dominant uniaxial magnetic anisotropy. Finally, we can verify by SANS that the chain structure within the immobilized, freeze-dried bacteria is preserved also after application of large magnetic fields up to 1 T.

中文翻译：

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冻干趋磁细菌中磁小体链的稳定性和磁性研究

Magnetospirillum gryphiswaldense生物合成高质量的磁铁矿纳米粒子，称为磁小体，并将它们排列成一条链，其行为就像一个磁罗盘。在这里，我们对冷冻干燥和固定的M. gryphiswaldense粉末进行磁力测量和极化小角中子散射 (SANS) 实验. 我们确认单个磁小体是单畴纳米粒子，并且粒子矩沿磁场方向的排列仅通过内部相干旋转发生。我们对细菌粉末的磁力测量结果表明，粒子链之间不存在偶极相互作用，并且存在主要的单轴磁各向异性。最后，我们可以通过 SANS 验证，在施加高达 1 T 的大磁场后，固定化、冻干细菌内的链结构也得以保留。