Spatially resolved GHz magnetization dynamics of a magnetite nano-particle chain inside a magnetotactic bacterium

Understanding magnonic properties of nonperiodic magnetic nanostructures requires real-space imaging ferromagnetic resonance modes with spatial resolution well below the optical diffraction limit and sampling rates in 5--100 GHz range. Here, we demonstrate element-specific scanning transmission x-ray microscopy-detected (STXM-FMR) applied to a chain dipolarly coupled ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ nano-particles (40--50 nm particle size) inside single cell magnetotactic bacterium Magnetospirillum magnetotacticum. The mode nano-particle driven at 6.748 probed 50 focus size was found have uniform phase response but non-uniform amplitude along segments due superposition dipolar individual particles, agreement micromagnetic simulations.