EELS image simulations of Inelastic spin-scattering of confined magnons in magnetic structures

Session

Poster Session Two

Authors

Mr Julio do Nascimento (1), Prof. Vlado Lazarov (1)

Affiliations

1. University of York

Keywords

EELS, magnons, spintronics, STEM

Abstract text

Current advances in Magnon and antiferromagnetic spintronics utilise magnon/spin to charge conversion, and vice versa via SHE and ISHE. Experimental setups consist of nanometer-sized layers and usually abrupt interfaces across which this conversion is happening. Hence the ability to probe magnons on small scales i.e. nm scale is of importance for the further development of spin-based devices. Neutrons and light beams have been used extensively to study magnons on a large scale, however, the need of studying spin excitations on small scale requires sub-nm probes. Advances in electron beam monochromators in STEM have opened possibilities of using electron beams for studying magnons with nm and sub-nm resolution. Collecting signals of scattered electrons via electron energy loss spectroscopy (EELS) by collective excitations such as phonons has been already demonstrated(1), and a number of experiments are ongoing to demonstrate the detection of magnons by EELS. Phonon mode's energy range, up to a few hundred of meV in solid state materials is qualitatively in the same energy range as magnons. 

Although it is well known that, compared to the Coulomb interaction, the magnon's interaction with the electrons is 3 or 4 orders of magnitude weaker, it has been shown experimentally that magnetic ordering can be detected by Brag reflections of electrons (2). In addition, a recent theoretical prediction of EELS signal from thermal magnons in bulk specimens has been reported. This confirms that one can further utilise the STEM/EELS for measuring magnons in confined geometries including interfaces and surfaces. (2,3)

In our work, we calculate the dynamics of magnon modes in finite systems using the second quantisation of the Heisenberg Hamiltonian for thin film and interfaces, as well as hetero-structure between FM and AFM layers and domain walls, taking into account surface and interface anisotropies. We have calculated, magnon dispersion, spin-spin scattering function and the EELS signal for Fe/NiO heterostructure as a prototype AFM/FM interface. The effect of inelastic scattering of the electrons in STEM experiments where modelled using the multislice method. The multislice calculations provide momentum-resolved energy dependence of the inelastic scattering, which can be directly correlated to the EELS signal.

References

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