Assemblies of Aligned Magnetotactic Bacteria and Extracted Magnetosomes: What Is the Main Factor Responsible for

nderstanding the origin of the magnetic anisotropy in an assem-bly of aligned magnetic nanocrys-tals is an important challenge in the field of nanotechnology. It has implications both at a fundamental and applied level. On the one hand, it provides a deeper knowledge of the properties of organized magnetic nanocrystals. On the other hand, it helps with designing new structures useful for magnetic recording.1,2 It has long been known that aligning nanoparticles gives rise to magnetic anisot-ropy, that is, a squarer hysteresis loop for a magnetic field applied parallel to the direc