Code: ThOG	Time Slot/Poster Number: 2:00 - 2:20 pm	Session: Solid-State, Semiconductors and Nanoparticles II
Doubly Resonant Raman-EPR Spectrum of Ruby(Al2O3:Cr3+)
X. Lu1; S. Venugopalan2; Hyunjung Kim3; M. Grimsditch4; S. Rodriguez1; A. K. Ramdas1
1Purdue University, West Lafayette, IN; 2SUNY-Binghamton, Binghamton, New York; 3Sogang University, Seoul, Korea; 4Argonne National Laboratory, Argonne, Illinois
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Summary
Raman-electron paramagnetic transitions in ruby, investigated with a dye laser tuned across the Zeeman components of its R1 emission line, reveal the anisotropic splitting of the 4A2 (ground ) state multiplet, and the Ē (excited) state of Cr3+ ions, as the orientation of the magnetic field B is changed with respect to the optic axis c. The spectra show striking and simultaneous “in-resonance” and “out resonance”, consistent with pronounced level mixing effects , non-linearity of the B dependence of the 4A2 multiplet , and the anisotropic g-factor of the Ē (excited) state.

Code: ThOG	Time Slot/Poster Number: 2:20 - 2:40 pm	Session: Solid-State, Semiconductors and Nanoparticles II
Determination of Raman Efficiency in SiGe Alloys
Andrea Picco1; Emiliano Bonera1; Emanuele Grilli1; Marco Giarola2; Gino Mariotto2; Danny Chrastina3; Mario Guzzi1
1Università degli Studi di Milano - Bicocca, Milano, Italy; 2Università di Verona, Verona, Italy; 3LNESS - Politecnico di Milano, Como, Italy
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Summary
A complete measurement of the Raman efficiency in SiGe alloy depending on excitation wavelength and alloy composition, fundamental for the interpretation of spectra from inhomogeneous samples such as self-assembled nanostructures, is still missing. In this work, the SiGe Raman cross section has been obtained as a function of the composition with steps of 0.02 for several commonly used excitation wavelengths. A strong modulation of the efficiency, with resonances in correspondence to the direct electronic transitions in the alloy, is observed. These data can be used to design resonant experiments for the selective characterization of different regions in inhomogeneous samples.

Code: ThOG	Time Slot/Poster Number: 2:40 - 3:00 pm	Session: Solid-State, Semiconductors and Nanoparticles II
A High-pressure Raman Spectroscopic Study of the Negative Thermal Expansion (NTE) Behaviour of Some Cadmium(II) Cyanide Materials
Carl Romao; Mirela M. Barsan; Denis F. R. Gilson; Ian S. Butler
McGill University, Montreal, Canada
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Summary
The negative thermal expansion (NTE) properties of some solid cadmium(II) cyanide materials have been examined as a function of pressure up to about 5.0 GPa by Raman microprobe spectroscopy using a commercial diamond-anvil cell. Each of the cadmium(II) compounds exhibits at least one phase transition above 1.0 GPa, which is associated with distortion of the tetrahedral geometry around the Cd atoms in the solid state. The vibrational modes responsible for the NTE properties are enhanced considerably by the phase transitions.

Code: ThOG	Time Slot/Poster Number: 3:00 - 3:20 pm	Session: Solid-State, Semiconductors and Nanoparticles II
2-Magnon Raman Behavior of NiO Nanoparticles
Farrakh Shazad; Peter Knoll
Inst. of Physics University of Graz, Graz, Austria
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Summary
The 2-Magnon Raman response has been measured for NiO nanoparticles with sizes from 85nm to 4nm. For the first time the magnetic Raman signal has been compared with SQUID magnetization measurements on the same samples. A drastic decrease of antiferromagnetic spin pairs with decreasing particle size has been determined by Raman scattering. The magnetization measurements suggest that this loss of antiferromagnetism can be interpreted as a transition to spin glass ordering competing with super-paramagnetism. At temperatures below 50K the strong increase in magnetization is accompanied by a sudden reduction of antiferromagnetic spin pairs which indicates a maybe new magnetic phase.

Code: ThOG	Time Slot/Poster Number: 3:20 - 3:40 pm	Session: Solid-State, Semiconductors and Nanoparticles II
Low-Frequency Excitations in 20Nb2O5-80NaPO3 Glass for Raman Gain Applications
Alfons Schulte1; Yu Guo1; Walter Schirmacher3; Bernhard Schmid4; Thierry Cardinal2; Tobias Unruh3
1University of Central Florida, Orlando, FL; 2ICMCB, CNRS, University of Bordeaux, Bordeaux, France; 3TU Munich, Garching, Germany; 4U Mainz, Mainz, Germany
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Summary
Niobium-phophate glasses glasses show a low-frequency enhancement of the vibrational density of states (‘Boson peak’) suggesting a significant gain profile for application in Raman amplifiers. We present results of combined Raman and inelastic neutron scattering experiments in a 20Nb2O5 - 80NaPO3 glass to separate the effects of density of states from the light-vibration coupling. Using a recent theory based on the concept that light couples to the elastic strains via spatially fluctuating elasto-optic (Pockels) constants we show that the measured Raman and neutron intensities can be treated on the same footing without resorting to an empirical coupling function.

Code: ThOG	Time Slot/Poster Number: 3:40 - 4:00 pm	Session: Solid-State, Semiconductors and Nanoparticles II
Low-frequency Raman Scattering by Acoustic Vibrations of Anisotropic Nanoparticles
Lucien Saviot1; Daniel B. Murray2
1Laboratoire Interdisciplinaire Carnot de Bourgogne, Dijon, France; 2University of British Columbia, Okanagan, British Columbia, Canada
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Summary
The acoustic vibrational properties of nanoscale objects can be dramatically affected when their size is a few nanometers or less. If the medium surrounding a nanoparticle has a sufficiently different density, the vibrations within the nanoparticle can be confined. This results in the appearance of discrete vibrational modes whose frequency is inversely proportional to the nanoparticle size. This work presents an overview of some recent experimental results together with calculations required to understand the nature of the Raman peaks due to the confined acoustic vibrations of nanoparticles.