| Description: | [DPS Seminar] Dr. Ashim Chakravarty (Department of Physics, Michigan Technological University) -- GEOMETRY INDUCED MAGNETO-OPTIC EFFECTS IN LPE GROWN MAGNETIC GARNET FILMS |
| Date: | Wednesday, Oct 28, 2015 |
| Time: | 11:30 a.m. - 12:45 p.m. |
| Venue: | G02, Lecture Hall Complex |
| Details: | This research work addresses dimensionality-induced magneto-optic effects in liquid-phase-epitaxy magnetic garnet thin films. It is found that the Faraday rotation (FR) per unit length evinces a marked and steady enhancement as the film thickness is reduced below ~100 nm in Bi0.8Gd0.2Lu2Fe5O12, although it remains constant in the micron- and most of the sub-micron-regime. The reported specific FR change in such reduced dimensions is due to size-dependent modifications in diamagnetic transition processes in the garnet film. These processes correspond to the electronic transitions from the singlet 6S ground state to spin-orbit split excited states of the Fe3+ ions in the garnet. A measurable reduction in the corresponding ferrimagnetic resonance linewidths is found, thus pointing to an increase in electronic relaxation times and longer lived excitations at reduced thicknesses than in the bulk. These changes together with a shift in vibrational frequency of the Bi-O bonds in the garnet at reduced thicknesses result in magneto-optical enhancement in ultra-thin garnet films. This research work also studies optical transmittance control through multimode elliptically birefringent waveguides achieved by one-dimensional magneto-photonic crystals (MPCs) and the tuning of longitudinal magnetic bias in such waveguides, together with the tuning of the helicity of the input elliptical beam. Magnetization reversal is found to strongly reconfigure the stop band spectrum, through hybridization of the elliptically-polarized states due to normal mode symmetry breaking. |
| Calendar: | Seminar Calendar (entered by ritesh.singh) |