Quantitative analysis of magnetic spin and orbital moments from an oxidized iron (1 1 0) surface using electron magnetic circular dichroism

Abstract

Understanding the ramifications of reduced crystalline symmetry on magnetic behavior is a critical step in improving our understanding of nanoscale and interfacial magnetism. However, investigations of such effects are often controversial largely due to the challenges inherent in directly correlating nanoscale stoichiometry and structure to magnetic behavior. Here, we describe how to use Transmission Electron Microscope (TEM) to obtain Electron Magnetic Circular Dichroism (EMCD) signals as a function of scattering angle to locally probe the magnetic behavior of thin oxide layers grown on an Fe (1 1 0) surface. Experiments and simulations both reveal a strong dependence of the magnetic orbital to spin ratio on its scattering vector in reciprocal space. We exploit this variation to extract the magnetic properties of the oxide cladding layer, showing that it locally may exhibit an enhanced orbital to spin moment ratio. This finding is supported here by both spatially and angularly resolved EMCD measurements, opening up the way for compelling investigations into how magnetic properties are affected by nanoscale features.

Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface

“…With electrons as a radiation source, the probed volumes can be on the order of tens of cubic nanometers21. Additionally, existing STEM infrastructure can be exploited to deploy the technique in scanning microdiffraciton mode18212223. This allows for the acquisition of multiple complimentary hyperspectral datacubes from the same sample region but with different electron scattering momenta, in a technique we call STEM-EMCD.…”

“…3. While similar chiral datasets have previously been used to qualitatively infer spatially-resolved magnetic behavior in nanoparticles18 as well as quantitatively extract with high precision from the entire scanned region22, the low signal to noise ratio in individual spectra has precluded the completion of both goals simultaneously. To accomplish this, we exploit spectral redundancy of the datacube to approximate the raw data by using the principal spectral components of highest variance.…”

“…Centering the aperture on the Thales circle allows for a significantly higher intensity in the collected EELS spectra and, thus, faster scan rate. However, is known to be influenced by the presence of cladding oxide layers22 in this aperture position, raising the values over the entire dataset. Critically, both of these systematic errors act to translate all of the values up or down in concert.…”

“…A detailed assessment of the structural quality of this sample can be found in the supplementary information of Thersleff et al 22…”

Magnetic properties of single nanomagnets: Electron energy-loss magnetic chiral dichroism on FePt nanoparticles

“…The simulated diffraction pattern and EMCD map of a L1 0 FePt crystal that is tilted out of the zone axis by 10 • are displayed in Figure 3. Tilting of the sample results in a three beam case, with the first diffraction orders (2 0 0) and 2 0 0 carrying a higher intensity than [18], the EMCD effect is found to be most pronounced in wider areas next to the 1 st order diffraction spots rather than at symmetric positions between O and ± G (cf. the simulated diffraction pattern on the left panel in Fig.…”