Atomic scale imaging of magnetic circular dichroism by achromatic electron microscopy

Abstract

In order to obtain a fundamental understanding of the interplay between charge, spin, orbital and lattice degrees of freedom in magnetic materials and to predict and control their physical properties, experimental techniques are required that are capable of accessing local magnetic information with atomic-scale spatial resolution. Here, we show that a combination of electron energy-loss magnetic chiral dichroism and chromatic-aberration-corrected transmission electron microscopy, which reduces the focal spread of inelastically scattered electrons by orders of magnitude when compared with the use of spherical aberration correction alone, can achieve atomic-scale imaging of magnetic circular dichroism and provide element-selective orbital and spin magnetic moments atomic plane by atomic plane. This unique capability, which we demonstrate for SrFeMoO, opens the door to local atomic-level studies of spin configurations in a multitude of materials that exhibit different types of magnetic coupling, thereby contributing to a detailed understanding of the physical origins of magnetic properties of materials at the highest spatial resolution.

General nature of the step-induced frustration at ferromagnetic/antiferromagnetic interfaces: topological origin and quantitative understanding

“…Despite its immediate relevance, a comprehensive picture of its emergence and strength remains debatable and is very much a work in progress [3,[13][14][15][16]. This is due without a doubt to the complex geometrical and physical nature of the interfaces as well as to the great difficulty of extracting direct experimental information from the buried interfaces and their defects [17,18]. In particular, magnetic frustration was successfully observed in the Mn/Fe(001) system via spin-polarized scanning tunnelling microscopy (SP-STM) by Schlickum et al [4][5][6].…”

Single-pass STEM-EMCD on a zone axis using a patterned aperture: progress in experimental and data treatment methods

“…In the domain of high spatial resolution, EMCD has been detected using convergent beams of atomic size in a classical three-beam geometry 13 , utilizing phase ramps introduced by beam shift 14 , in zone axis orientation 15,16 , and using atomic size beams distorted by four-fold astigmatism 17,18 . Recent experiments with a weakly convergent electron beam, using both geometric and chromatic aberration correction, led to a detection of EMCD from individual atomic planes 19 . Despite some impressive achievements, the EMCD technique is still under development, primarily due to the struggle with low magnetic signal strength and its sensitivity to dynamical diffraction effects and experimental artifacts.…”

Electron energy-loss magnetic chiral dichroism of magnetic iron film affected by an underlayer in a double-layer structure

“…1 Since EMCD was first demonstrated by Schattschneider et al, 1 much effort has been made to develop it into a routine magnetic characterization technique in the transmission electron microscope (TEM). [4][5][6][7][8][9][10][11][12][13][14] Various EMCD experimental setups, for instance the energy spectrum imaging, 4,5 double aperture q À E mode, 6 spatially resolved EELS mode, 7 and scanning TEM, 8,9 have been proposed to improve the signal to noise ratio and the spatial resolution. In addition, the signal interpretation regarding the magnetic moment quantification has been widely concerned.…”

“…Some EMCD experiments in the literature are actually in accordance with the assumed condition. For instance, experiments were performed on a single crystal in polycrystalline materials of Fe, 9 Co, 16 Ni, 16 or their oxides 7,17 or on epitaxially grown thin layers of single-crystalline Fe, Mn, and their compounds observed from the cross-sectional view. 10,14,18,19 However, the assumption may fail if the EMCD technique is applied to other widely used systems such as core-shell structures, embedded nanoparticles, and multilayers observed along the out-of-plane direction.…”