This is a past event.

Thursday, January 28 @ 4pm – Zoom

Sushree Dash [Advisor: Dr. Miguel Levy] will present: 

Boosting Optical Nonreciprocity: Surface Reconstruction in Iron Garnets

Bi-substituted Iron garnet films are a big contributor in non-reciprocal
devices used in optical telecommunications. The recent evidence of large
near-surface enhancement in magneto-optic response is a huge milestone
in the above-mentioned direction. However, its mechanism at the
electronic and atomic levels is yet to be explored. In this presentation, I will
talk about the significant difference in electronic and atomic structure
between surface and bulk in Bi-substituted iron garnets. To observe the
difference in electronic structure we will be looking into the X-ray- Magnetic
Circular Dichroism Spectra (XMCD) and X-ray Absorption Spectra (XAS) at
L2 and L3 edges of 3d Fe 3+ states at the bulk of the material (by Total
Fluorescence Yield) and surface of the material (by Total Electron Yield). To
observe the atomic structure difference, we will be looking into the HAADF
images by the Scanning- Tunneling Electron Microscope (STEM). Together
with the surface reconstruction underlying these effects reported here, they
provide a useful tool for the further development of improved materials
technologies to advance the integration of nonreciprocal devices in
optical circuits.

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Lisa Eggart [Co-Advisors: Dr. Ravi Pandey, Dr. Brandon Wood] will present: 

First Steps Toward Growth of Aluminum Oxide Passivation Layer Protection

Pitting corrosion is a spontaneous, irreversible process due to localized
electrochemical processes. Some metals form a protective layer of metal
oxide which can inhibit corrosion, and salts such as chlorine can interfere
with this passivation protection. An accurate model of pitting initiation relies
on an understanding of this passivation layer and its formation. This talk will
highlight some of my recent work looking at aluminum oxide nanoparticles
as they grow and become surface-like. Because pitting initiation is an
emerging area of research, this initial work focuses on aluminum oxide
clusters in vacuum and gaining an understanding of their properties and a
comparison to those of a surface. First principles analyses of aluminum
oxide clusters were performed using density functional theory in the
Quantum Espresso suite of tools to establish a reliable model and to
calculate basic properties such as binding and formation energies. Current
work begins to account for the presence of a salt and explores options for
solvent models, and a metal substrate will be incorporated at a later stage.