Assessment of magnetic properties of iron oxide core/shell nanocubes through Electron Magnetic Circular Dichroism

Abstract

Electron magnetic circular dichroism (EMCD) is a novel technique used for the magnetic characterization at the nanoscale using the electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM). The EMCD is analogous to the X-ray magnetic circular dichroism technique (XMCD). However, this technique offers some bene ts in comparison with XMCD, such as the high spatial resolution at which the magnetic information of the sample is obtained, and magnetic depth sensitivity of the whole sample. In this master thesis, the EMCD technique was used to study magnetic nanocubes with a core/shell structure, formed by an iron II oxide core (FeO) covered by a magnetite shell (Fe3O4). The EMCD experiments were carried out using an intrinsic two-beam conditions as a scattering configuration to perform the experiment. In these Fe3O4/FeO nanocubes, it is imperative to probe the dichroic signal from the core and shell regions separately, in order to characterize the magnetic properties of the magnetite shell. For this purpose, EEL spectra were classified using data mining algorithms. Once both contributions were separated, the dichroic signal from both core and shell were obtained. Also, the spin magnetic moment ratio mL/mS is calculated for the magnetic shell. The difference in the dichroic signal between EMCD experiments carried out at room and low temperature are discussed