Spatially-resolved dynamic sampling of different phasic magnetic resonances of nanoparticle ensembles in a magnetotactic bacterium Magnetospirillum magnetotacticum

Abstract

Nanoscaled magnetic particle ensembles are promising building blocks for realising magnon based binary logic. Element-specific real-space monitoring of magnetic resonance modes with sampling rates in the GHz regime is imperative for the experimental verification of future complex magnonic devices. Here we present the observation of different phasic magnetic resonance modes using the element-specific technique of Time-Resolved Scanning Transmission X-ray Microscopy (TR-STXM) within a chain of dipolarly coupled Fe3O4 nanoparticles (40-50 nm particle size) inside a single cell of a magnetotactic bacterium \textit{Magnetospirillum Magnetotacticum}. The particles are probed with 25~nm resolution at the Fe L3 X-ray absorption edge in response to a microwave excitation of 4.07 GHz. A plethora of resonance modes is observed within multiple particle segments oscillating in- and out-of-phase, well resembled by micromagnetic simulations.

Single-Particle Photothermal Circular Dichroism and Photothermal Magnetic Circular Dichroism Microscopy

“…For example, one may study the properties of chains in magnetotactic bacteria given their potential for magnetic hyperthermia, 43 inspect the biomineralization pathways of Fe in magnetotactic bacteria and chitons (monitoring the process of conversion of antiferromagnetic ferritin into ferrimagnetic magnetite) as well as the alteration of Fe metabolism in the human brain leading to various neurodegenerative disorders including Alzheimer's disease. If the combination of PT MCD with the ferromagnetic resonance (FMR) modality is possible (as discussed below), monitoring magnetic resonance modes within chains of particles in magnetotactic bacteria for biologically encoded magnonic devices 44 may be one of the appealing perspectives. Last but not least, a PT MCD setup can be assembled in a "standard" optical lab and does not require synchrotron radiation facilities.…”