Direct evidence of a graded magnetic interface in bi-magnetic core/shell nanoparticles using electron magnetic circular dichroism (EMCD)

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Resolving the microscopic magnetic structure of bi-magnetic core/shell nanoparticles is rather complex. Here the Laboratory of Electron Nanoscopies (LENS)- Micro and Nanotechnology and nanoscopies for Electronic and Electrophotonic devices (MIND) group, investigates the local magnetization of antiferromagnetic/ferrimagnetic FeO/Fe3O4 core/shell nanocubes by electron magnetic circular dichroism (EMCD). The electron energy-loss spectroscopy (EELS) compositional analysis of the samples shows the presence of an oxidation gradient at the interface between the FeO core and the Fe3O4 shell. The EMCD measurements evidence that the nanoparticles are composed of four different zones with distinct magnetic moment in a concentric, onion-type, structure. These magnetic areas correlate spatially with the oxidation and composition gradient, with the magnetic moment being largest at the surface and decreasing towards the core. The results show that the combination of EELS compositional mapping and EMCD can provide very valuable information of the inner magnetic structure and its correlation to the microstructure of magnetic nanoparticles.

Direct Evidence of a Graded Magnetic Interface in Bimagnetic Core/Shell Nanoparticles Using Electron Magnetic Circular Dichroism (EMCD)D. del-Pozo-Bueno, M. Varela, M. Estrader, A. López-Ortega, A. G. Roca, J. Nogués, F. Peiró, and S. Estradé. Nano Lett. 2021, 21, 16, 6923–693.