Quantitative experimental determination of site-specific magnetic structures by transmitted electrons

Abstract

Understanding the magnetic structure of materials on a nanometre scale provides fundamental information in the development of novel applications. Here we show a site-specific electron energy-loss magnetic chiral dichroism method, first experimentally demonstrating that the use of transmitted electrons allows us to quantitatively determine atomic sitespecific magnetic structure information on a nanometre scale. From one NiFe 2 O 4 nanograin in composite films, we extract its atomic site-specific magnetic circular dichroism spectra and achieve the quantitative magnetic structure information, such as site-specific total magnetic moments and orbital to spin magnetic moment ratios, by constructively selecting the specific dynamical diffraction conditions in electron energy-loss magnetic chiral dichroism experiments. The site-specific electron energy-loss magnetic chiral dichroism method shows its unique ability for solving the site-specific magnetic structure at nanoscale resolution, compared with X-ray magnetic circular dichroism and neutron diffraction. This work opens a door to meet the challenge of exploring the magnetic structures of magnetic materials at the nanoscale using transmitted electrons.

E-beam-induced in situ structural transformation in one-dimensional nanomaterials

“…Electron microscopy is an effective method to provide morphological and structural characterization of nanomaterials. Additionally, the chemical, electronic, and magnetic properties of nanomaterials can also be obtained with the recent developments in electron microscopy [9][10][11]. In particular, the high energy electron beam (e-beam) within the electron microscope is able to be used for the modification and fabrication of nanostructures.…”

An in-plane magnetic chiral dichroism approach for measurement of intrinsic magnetic signals using transmitted electrons

“…Approximately, q = k out – k in + h – g and similarly for . k out and k in are the incident and outgoing wave vectors, while g , h are the indices of the plane-wave components (see refs 10, 13 for more details).…”

“…in 2006 that electron magnetic circular dichroism (EMCD) signal can be detected using high-energy electrons in the transmission electron microscope (TEM), theoretical and experimental progress have led to improvements in spatial resolution and signal-to-noise ratio2345, an improved fundamental understanding of the technique678910 and quantitative measurements of spin and orbital magnetic moments with both element and site specificity11121314. In Lorentz mode, with the conventional TEM objective lens (which would normally impart a strong out-of-plane magnetic field to the sample in the electron beam direction) switched off, EMCD in principle allows the intrinsic (remanent) magnetic states of materials to be studied in magnetic-field-free conditions15.…”

Magnetic measurements with atomic-plane resolution

“…The technique attracted a lot of interest due to its analogy to X-ray magnetic circular dichroism3, as well as for its potential of reaching atomic resolution routinely available in probe-corrected scanning transmission electron microscopy (STEM). Since the inception of EMCD, a rapid development has followed, deepening the theoretical understanding456, initiating development of new experimental set-ups and improving the spatial resolution and quantitativeness7891011121314. However, the goal of achieving atomic resolution remains unaccomplished.…”