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Nonlinear Optical Materials
We are interested in nonlinear optical (NLO) materials in the deep-UV, UV, as well as the IR. A specific area of NLO materials are compounds that are non-centrosymmetric (NCS), i.e. lacking a crystallographic inversion center (see figure right). These acentric materials exhibit second-harmonic generation (SHG). A major research area involves the synthesis and characterization of SHG materials.
We are able to perform powder SHG measurements at 1064nm, and are in the process of acquiring a 2.09um IR laser. Once installed, we will be able to perform SHG measurements from the deep-UV through the IR.
Crystal Growth
Crystal Growth
The Halasyamani laboratory has a variety of crystal growth equipment. These include two four-circle floating zone furnaces, a Bridgman furnace, 18 top-seeded solution growth systems, and will soon have a Czochralski puller. In addition, the lab has the capability to cut, polish, and index the grown crystals.
MFF
Multi-ferroic Fluorides
An additional area of research we are involved with concerns multi-ferroic fluorides. For our purposes, multi-ferroic materials exhibit ferroelectricity, i.e. reversible polarization, and some sort of magnetic ordering (ferro-, anti-ferro, ferrimagnetism). The interest with multi-ferroic materials stems from their applications in information storage. Suggestions have been made that on a single multi-ferroic bit, information could be independently encoded by both polarization and magnetization. We are investigating magnetic ordering in materials that undergo a ‘non-classic’ ferroelectric mechanism, e.g., BaNiF4 (see Figure). As seen in the Figure, the green octahedra and yellow spheres represent the structure of the ‘up’ polarization of BaNiF4, whereas the gray octahedral and spheres represent the structure of the ‘down’ polarization. The structural re-orientation through the NiF6 octahedral rotations and Ba2+ displacements result in the polarization reversal, switching between ‘up’ and ‘down’, i.e. the ferroelectric behavior. We are investigating a host of mixed-metal fluorides that could undergo this non-classic ferroelectric mechanism and exhibit magnetic ordering.
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