New Insights into Magnetic Nanoparticles from Experiments with Single Particle Sensitivity
The last few years have seen a rapidly growing interest in magnetic nanoparticles which can find application in many fields ranging from medicine to data storage . Magnetic nanoparticles can show a variety of unusual magnetic phenomena when compared to the bulk materials, such as enhanced magnetic moments and magnetic anisotropies, mostly due to the large role played by surface/interface and finite-size effects.
A detailed understanding of these properties is however not a trivial task, since even mono-disperse nanomagnet ensembles can show considerable particle-to-particle variations in their properties either due to size and shape effects or inter-particle interactions. We have used X-ray photoemission electron microscopy (PEEM) to investigate the properties of individual Fe nanoparticles in large mono-disperse ensembles. Surprisingly, we found that Fe nanoparticles with similar size can have significantly different and even metastable magnetic properties .
Recording X-ray absorption spectra of individual nanoparticles we performed further an in situ study on the oxidation behaviour of these particles and found reversible formation and reduction upon annealing of an oxide shell in the Fe nanoparticles, which could be of interest for application in ox-redox catalytic applications.
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