Experimental Correlation between Nonlinear Optical and Magnetotransport Properties Observed in Au-Co Thin Films

Magnetic materials where at least one dimension is in the nanometer scale typically exhibit different magnetic, magnetotransport, and magnetooptical properties compared to bulk materials. Composite magnetic thin films where the matrix composition, magnetic cluster size, and overall composite film thickness can be experimentally tailored via adequate processing or growth parameters offer a viable nanoscale platform to investigate possible correlations between nonlinear magnetooptical and magnetotransport properties, since both types of properties are sensitive to the local magnetization landscape. It has been shown that the local magnetization contrast affects the nonlinear magnetooptical properties as well as the magnetotransport properties in magnetic-metal/nonmagnetic metal multilayers; thus, nanocomposite films showcase another path to investigate possible correlations between these distinct properties which may prove useful for sensing applications

Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films

The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films to exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB2 thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature T-C, the authors are the first to report on the correlation between stoichiometry and the lower critical field H-C1. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

Study of Plasmons & Polaritons in Oxide Thin Films

In this presentation we will discuss the role of free electron lasers in the investigation of quasi-particles such as radiative polaritons, bulk plasmons and surface Plasmon polaritons in a variety of oxide thin films including insulating, conducting and highly correlated simple oxides. The first part of the presentation will discuss the case of radiative polaritons. Under broadband and continuous infrared radiation illumination in the 450 – 1100 cm-1 range, these quasi-particles have shown the ability to absorb radiation and transform it into electricity through the heat recovery mechanism. Results acquired with variable incidence angle and polarization will be illustrated. It will then be discussed how a free electron laser such as the one at Thomas Jefferson National Accelerator Facility (TJNAF) could probe more precisely this property of the radiative polaritons by exciting them exactly at their resonance frequency and for the duration of their lifetime (about 10-12 s). The second part of the presentation will involve our recent studies on bulk plasmons and surface Plasmon polariton excitations on conducting oxides such as RuO2. We will discuss our latest results on the metal-insulator transition on VO2 thin films in the ultra-fast time domain and our recent results using THz radiation at the FEL at TJNAF followed by our proposed future FEL-based experiments to investigate relaxation mechanisms in this interesting and important highly correlated oxide system