Condensed-Matter Physics & Materials Science Seminar
"Synchrotron radiation-based Muller matrix spectroscopic ellipsometry for studies of magnetoelectric materials"
Presented by A Sirenko, NJIT
Monday, April 1, 2013, 1:30 pm
Small Seminar Room, Bldg. 510
Hosted by: Adrian Gozar
Optical spectra of complex materials, such as magneto-electric (ME) and multiferroic (MF) crystals, materials with chirality, and metamaterials, are in the focus of modern experimental and theoretical studies. The complex materials can reveal a so-called bi-anisotropic optical behavior in a form of the fascinating effects, such as nonreciprocal light propagation, negative index of refraction, and polarization plane rotation. These exotic optical phenomena are not limited, but are usually expected to occur in the far-IR part of the optical spectrum, which is dominated by elementary excitations, such as optical phonons, magnons, electromagnons, and crystal field transitions. For the light propagation analysis in bi-anisotropic crystals, dielectric susceptibility , magnetic permeability , and ME tensors should be included into consideration. A combination of an adequate theoretical description with advanced experimental spectroscopic techniques is also required. As we demonstrate in this talk, the theoretical representation of bi-anisotropic phenomena can be done using Mueller matrices (MM). Correspondingly, one of the most efficient experimental techniques for studies of elementary excitations in bi-anisotropic materials is Mueller matrix spectroscopic ellipsometry (MM-SE). To support extensive research efforts for studies of complex materials, a multiuser facility for MM-SE has been designed, developed, and installed at U4-IR beamline at the National Synchrotron Light Source, Brookhaven National Laboratory (NSLS-BNL). The new ellipsometer covers the spectral range between 20 and 4000 cm-1. Several sets of rotating retarders enable a full Muller matrix analysis of anisotropic and bi-anisotropic samples. The typical spot-size of about 3Ã–3 mm2 at the sample position for the slowly focused synchrotron radiation with allows studying relatively small samples. The experimental spectra have been simulated and fitted using Berreman'