Title:	Vibrational and magnetic spectrum imaging at atomic resolution
DNr:	SNIC 2019/32-22
Project Type:	SNIC Small Storage
Principal Investigator:	Jan Rusz <jan.rusz@physics.uu.se>
Affiliation:	Uppsala universitet
Duration:	2020-01-01 – 2021-01-01
Classification:	10304
Keywords:

Abstract

Rapid developments in nanoengineering calls for characterization methods capable to reach high spatial resolution. In this domain, scanning transmission electron microscope (STEM) provides a broad scale of measurement techniques ranging from Z-contrast or electron energy- loss elemental mapping, differential phase contrast, via local electronic structure studies of single atoms to counting individual atoms in nanoparticles. We will address two particular cases of atomic spatial resolution spectroscopies. A specific case of electron energy-loss spectroscopy, an electron magnetic circular dichroism (EMCD) method has been introduced (Schattschneider et al., Nature 441, 486, 2006) as an analogue to x-ray magnetic circular dichroism, which is a well established quantitative method of measuring spin and orbital magnetic moments in an element-selective manner. The method recently reached atomic plane spatial resolution (Rusz et al., Nat. Comm. 7, 12672, 2016 & Wang et al., Nat. Mater. 17, 221, 2018). Requested CPU-time allocation will enable us to perform large-scale first-principles simulations of the elastic and inelastic scattering of electrons on magnetic materials. In the experiments the magnetic signal observed so far is typically rather weak and obtaining sufficient signal to noise ratios is an issue. Therefore we aim to computationally optimize the measurement conditions for detection of as strong magnetic signal as possible. Development of new measurement setups, for examp! le utilizing phase distribution in electron beams, are planned. Finally, we will perform simulations to provide interpretation to measurements. The primary outcome of this project will be a progress in development of the atomic resolution EMCD technique, which is expected to have a significant impact in the area of nano-magnetism and all its applications. The second technique is based on a development of vibrational spectroscopy in transmission electron microscopy (Krivanek et al., Nature 514, 209, 2014), which recently has reached atomic resolution (Hage et al., Phys. Rev. Lett. 122, 016103, 2019). We will computationally explore the limits of the spatial and angular resolution of the method by means of molecular dynamics simulations combined with colored thermostats and multislice propagation calculations, to describe electron scattering on vibrating lattices.