Giant Faraday Rotation in Metal-Fluoride Nanogranular Films

Liquid Crystalline Magneto-Optically Active Peralkylated Azacoronene

Organic Faraday rotators have gained significant attention in recent years as a promising alternative to traditional inorganic magneto-optical (MO) materials as a result of their lower cost, superior mechanical properties, and potential for large-scale deployment. This interest is peaked by the fact that a number of high symmetry, rigid, strongly optically absorbing organic chromophores display Verdet constants an order of magnitude higher than commercial inorganic Faraday rotators. Critical to the development of new generations of organic materials is the ability to organize them in optimal structures for optical coupling/measurements. We report herein the synthesis of a dodecyl-substituted hexapyrrolohexaazacoronene (C₁₂-HPHAC) displaying discotic liquid crystalline (LC) properties and large Faraday rotation. Thin films with a redox mixed C₁₂-HPHAC/C₁₂-HPHAC⁺² composition display a discotic columnar LC phase, are stable to air and moisture in the solid and solution states, and achieve a maximum Verdet constant of 3.36 × 10⁵ deg T^-1 m^-1 at 700 nm. This result is consistent with Serber's model of magnetic circular birefringence and displays one of the largest reported Verdet constants for organic materials in the UV-Vis range. The LC phase aligns the molecules and leads to gains in Verdet constants of up to 105% through the favorable orientation of the molecules' magnetic and electric transition dipole moments with respect to the applied magnetic field.

Temperature-variable apparatus for measuring Barnett field

We have developed experimental equipment for observing the Barnett effect, in which mechanical rotation magnetizes an object, at low temperatures. A sample in a rotor is rotated bidirectionally using a temperature-controlled high-pressure gas. The stray field generated from the sample due to the Barnett effect was detected using a fluxgate magnetic sensor with a sensitivity on the order of several picoteslas, even at low temperatures. By replacing the rotor with a solenoid coil, the magnetic susceptibility of the sample was estimated from the stray field to be of the same order of magnitude as that due to the Barnett effect. The Barnett field was estimated using the dipole model. To assess the performance of the setup at low temperatures, measurements were performed on commercial magnetite (Fe3O4) nanogranules. We confirmed the accordance of the g' factor between the experimental results using the present setup and those of our previous study performed at room temperature.

Silver Nanoparticles for Fluorescent Nanocomposites by High-Pressure Magnetron Sputtering

We report on the formation of silver nanoparticles by gas aggregation in a reaction chamber at room temperature. The size distribution of nanoparticles deposited on a silicon substrate for various lengths of an aggregation (high-pressure) chamber was investigated by atomic force microscopy. Nanoparticles were characterized by scanning and transmission electron microscopy and spectral ellipsometry. The physical shape of the nanoparticles and its distribution was correlated with their optical properties. Metal-dielectric nanocomposites were deposited employing simultaneous deposition of Ag NPs via high-pressure magnetron sputtering and the dielectric matrix was deposited via thermal evaporation. Pure and Eu-, Er-, and Yb-doped lithium fluoride was used as the dielectric host matrix. Optical transmittance of lithium fluoride containing silver nanoparticles was measured and their theoretical absorption cross-section calculated. The nanoparticles were also embedded in Eu³⁺-doped downshifting and Er³⁺- and Y^b3+-doped up-conversion materials to study their influence on emission spectra. Spectra of identical layers with and without nanoparticles were compared. Their transmittance at various annealing temperatures is also presented.

Strong Excitonic Magneto-Optic Effects in Two-Dimensional Organic-Inorganic Hybrid Perovskites

This work demonstrates the strong excitonic magneto-optic (MO) effects of magnetic circular dichroism (MCD) and Faraday rotation (FR) in nonmagnetic two-dimensional (2D) organic-inorganic hybrid Ruddlesden-Popper perovskites (RPPs) at room temperature. Due to their strong and sharp excitonic absorption as a result of unique quantum well structures of 2D RPPs, sizeable linear excitonic MO effects of MCD and FR can be observed at room temperature under a low magnetic field (<1 T) compared with their three-dimensional counterpart. In addition, since the band gaps of 2D organic-inorganic hybrid perovskites can be manipulated either by changing the number n of inorganic octahedral slabs per unit cell or through halide engineering, linear excitonic MO effects of 2D-RPPs can be observed through the broadband spectral ranges of visible light. Our result may pave the way for the promising research field of MO and magneto-optoelectronic applications based on 2D organic-inorganic hybrid perovskites with facile solution processes.

Tunable optical and magneto-optical Faraday and Kerr rotations in a dielectric slab doped with double-V type atoms

We theoretically investigate the optical and magneto-optical Faraday and Kerr rotations of a probe field that propagates through a nonmagnetic dielectric slab doped with double-V type atoms. Both rotations and corresponding ellipticities, as well as the intensities of transmitted and reflected beams, are modified by quantum coherence induced in the atomic system. We show that applying a control laser field makes the system optically active and simultaneously, transparent to one component of the probe field. We demonstrate that the response of the slab can be modified both electrically and magnetically. Applying the second control laser field with different Rabi frequencies improves the optical properties of the slab due to the induced coherent effects. We present analytical expressions for facilitating the detailed study of the system behaviors. Magneto-optical Faraday rotation 45° with transmission close to [Formula: see text] and large Kerr rotation with high reflection are significant results from the influence of both the control and magnetic fields on such a small structure. By prevailing over the tradeoff between reflection and rotation, the proposed model could be considered as a special candidate for rotating the polarization plane of the transmitted and reflected beams, simultaneously.