Kerr Effect Spectroscopy Research Articles

Optical and magneto‐optical properties of pulsed laser‐deposited thulium iron garnet thin films

AbstractThis work presents a combined optical and magneto‐optical spectroscopic study of thulium iron garnet (Tm3Fe5O12, TmIG) films on substituted gadolinium gallium garnet (Gd2.6Ca0.4Ga4.1Mg0.25Zr0.65O12, sGGG) substrates. Spectroscopic ellipsometry, transmission spectroscopy, magneto‐optical Kerr effect spectroscopy and Raman spectroscopy results are presented for TmIG films with a thickness in the range from 20 to 300 nm grown on sGGG by pulsed laser deposition. The complex dielectric functions of TmIG and sGGG are determined and compared with previously published results for bulk yttrium iron garnet and GGG, respectively. The magneto‐optical spectroscopy corroborated with Raman spectroscopy sheds light on strain‐induced changes as a function of TmIG film thickness.

Optical N-invariant of graphene\u2019s topological viscous Hall fluid

Over the past three decades, graphene has become the prototypical platform for discovering topological phases of matter. Both the Chern Cin {mathbb{Z}} and quantum spin Hall upsilon in {{mathbb{Z}}}_{2} insulators were first predicted in graphene, which led to a veritable explosion of research in topological materials. We introduce a new topological classification of two-dimensional matter – the optical N-phases Nin {mathbb{Z}}. This topological quantum number is connected to polarization transport and captured solely by the spatiotemporal dispersion of the susceptibility tensor χ. We verify N ≠ 0 in graphene with the underlying physical mechanism being repulsive Hall viscosity. An experimental probe, evanescent magneto-optic Kerr effect (e-MOKE) spectroscopy, is proposed to explore the N-invariant. We also develop topological circulators by exploiting gapless edge plasmons that are immune to back-scattering and navigate sharp defects with impunity. Our work indicates that graphene with repulsive Hall viscosity is the first candidate material for a topological electromagnetic phase of matter.

Effects of HPO42− and SCN− on the hydrogen bond network of water: femtosecond OHD‐RIKES and FTIR measurements

The influence of an ion on the hydrogen bond (HB) structure of water is of potential interest in various aspects. Herein, we studied the effects of HPO42− and SCN− on the HB network of water in their aqueous solutions by using both femtosecond optical heterodyne‐detected Raman‐induced Kerr effect spectroscopy (fs OHD‐RIKES) and Fourier transform infrared spectroscopy (FTIR) spectroscopy. We found that both the amplitude of the 180 cm−1 HB stretching band of water in the fs OHD‐RIKES fast Fourier‐transformed spectrum and the amplitude of the 3290 cm−1 HB‐related stretching band of water in the FTIR spectrum are obviously enhanced in the high‐concentrated K2HPO4 solution, suggesting that HPO42− has the ability to make the HB of water in its aqueous solution. On the contrary, SCN− has the ability to break the HB of water in its aqueous solution. Copyright © 2016 John Wiley & Sons, Ltd.

Comparative study of optical and magneto‐optical properties of normal, disordered, and inverse spinel‐type oxides

Abstract, , , , and thin films were fabricated by pulsed laser deposition at high and low temperatures resulting in crystalline single‐phase normal, inverse, as well as disordered spinel oxide thin films with smooth surface morphology. The dielectric function, determined by spectroscopic ellipsometry in a wide spectral range from 0.5 to 8.5 eV, is compared with the magneto‐optical response of the dielectric tensor, investigated by magneto‐optical Kerr effect spectroscopy in the spectral range from 1.7 to 5.5 eV with an applied magnetic field of 1.7 T. Crystal field, inter‐valence, and inter‐sublattice charge transfer transitions, and transitions from to metal cation 3d or 4s bands are identified in both the principal diagonal elements and the magneto‐optically active off‐diagonal elements of the dielectric tensor. Depending on the degree of cation disorder, resulting in local symmetry distortion, the magneto‐optical response is found to be strongest for high crystal quality inverse spinels and for disordered normal spinel structure, contrary to the first principle studies of and . The results presented provide a basis for deeper understanding of light–matter interaction in this material system that is of vital importance for device‐related phenomena and engineering.

Change in the sign of the Kerr effect in ion-beam-synthesized Fe3Si films

Ion-beam-synthesized Fe3Si thin films are studied using the magneto-optical Kerr effect, ferromagnetic resonance, electron diffraction, and Auger spectroscopy. A change in the direction of rotation of the plane-polarized light as a function of film-synthesis conditions is discovered when the meridional Kerr effect is recorded. It is shown that the observed effect is related to the presence of thin interference films with different thicknesses on the surfaces of the magnetic layers.

ChemInform Abstract: Atom Substitution Effects in Ionic Liquids: A Microscopic View by Femtosecond Raman‐Induced Kerr Effect Spectroscopy

AbstractReview: 78 refs.

Mechanisms of molecular polarization of bithiophenesilane dendrimers in solutions

A number of consecutive generations of bithiophenesilane dendrimers and their precursors are studied by the methods of the equilibrium electro-optical Kerr effect, dielectric polarization, and absorption spectroscopy in dilute toluene solutions. It is shown that the molecules of hybrid dendrimers containing bithiophene fragments covalently linked via silicon atoms are not kinetically rigid and feature the small-scale mechanism of interaction with external electric fields. A tris(bithiophene)methylsilane fragment is found to be the subunit responsible for the electro-optical and optical spectral properties of the above hybrid dendrimers. It is revealed that the polarization of bithiophensilane dendrimers predominantly shows the deformation pattern.

Electronic Structure of Ferromagnetic SemiconductorGa1−xMnxAsProbed by Subgap Magneto-optical Spectroscopy

We employ Faraday and Kerr effect spectroscopy in the infrared range to investigate the electronic structure of Ga_{1-x}Mn_{x}As near the Fermi energy. The band structure of this archetypical dilute-moment ferromagnetic semiconductor has been a matter of controversy, fueled partly by previous measurements of the unpolarized infrared absorption and their phenomenological impurity-band interpretation. Unlike the unpolarized absorption, the infrared magneto-optical effects we study are intimately related to ferromagnetism, and their interpretation is much more microscopically constrained in terms of the orbital character of the relevant band states. We show that the conventional theory of the disordered valence band with an antiferromatnetic exchange term accounts semiquantitatively for the overall characteristics of the measured infrared magneto-optical spectra.

Studies of Ni and Co Doped Amorphous AlN for Magneto-optical Applications

AbstractMagneto-optical properties of Ni- and Co-doped amorphous AlN thin films were investigated as a function of post grown annealing temperature using magneto-optical Kerr effect (MOKE) spectroscopy. The x-ray diffraction spectra confirmed that the as-grown material is amorphous and retained its morphology after thermal treatment; however the sample morphology strongly depends on the concentration of incorporated transition metals. We observed with help of transmission electron microscopy and atomic force microscopy that the films surface containing TMs with concentrations larger than ∼10 at.% undergo morphological changes suggesting possible Ni and Co atom clustering. Significant enhancement of the polar Kerr rotation signal was observed for Ni- and Co-doped a-AlN materials annealed above 300 °C in nitrogen. The studied materials have shown strong magnetic isotropy in polar geometry whereas the MOKE measurements in longitudinal geometry did not show an explicit signal for the transition metals doped a-AlN studied.

Femtosecond Raman‐induced Kerr effect spectroscopy

AbstractWe report the development of a new vibrational technique called Femtosecond Raman‐Induced Kerr Effect Spectroscopy (FRIKES). This technique combines a narrow‐bandwidth picosecond Raman pump pulse with a broadband femtosecond probe pulse to produce high‐resolution Raman‐induced Kerr effect spectra spanning a large vibrational range. Because it is a polarization detection technique, FRIKES produces background‐free Raman spectra with high signal‐to‐noise and rapid acquisition times. The practicality of FRIKES is demonstrated by obtaining Raman spectra of common solvents, revealing that its performance is comparable to femtosecond stimulated Raman spectroscopy (FSRS). The capabilities of FRIKES will make it a valuable new vibrational spectroscopic tool for studies of chemical and biological systems, especially once it is extended to time‐resolved studies. Copyright © 2008 John Wiley & Sons, Ltd.

Evaluation of the quality of Permalloy gratings by diffracted magneto-optical spectroscopy

Magneto-optical Kerr effect (MOKE) spectroscopy in the -1st diffraction order with p-polarized incidence is applied to study arrays of submicron Permalloy wires at polar magnetization. A theoretical approach combining two methods, the local modes method neglecting the edge effects of wires and the rigorous coupled wave analysis, is derived to evaluate the diffraction losses due to irregularities of the wire edges. A new parameter describing the quality of the edges is defined according to their contribution in the diffracted MOKE. The quality factor, evaluated for two different samples, is successfully compared with irregularities visible on atomic force microscopy pictures.

Non-Markovian nature of relaxational mode in liquids studied by femtosecond OKE spectroscopy

We investigate the time responses of liquids, which change from phonon-like oscillations to an exponential decay, by means of optical Kerr effect (OKE) spectroscopy. We find that the time when the exponential decay becomes dominant and its decay time are on the same order, meaning that the dynamics is non-Markovian for various liquids and temperatures. In addition, these times show a strong correlation with each other, suggesting that the fast response of low-frequency phonon modes plays an essential role for the slow dynamics of the relaxational mode.

Molecular dynamics of poly(ethylene glycol)s studied by optical Kerr effect and Brillouin spectroscopy

The optical Kerr effect and Brillouin scattering study of a series of poly(ethylene glycol)s (PEGs) in the function of temperature and molecular weight (MW) have been performed. The obtained results enabled us to determine some macroscopic and microscopic parameters (such as molecular Kerr constant, hypersonic velocity, adiabatic compressibility), of the compounds investigated. The values of these parameters were found to depend strongly on both temperature and PEG's MW. Analysis of the results indicates on the presence of molecular interactions leading to formation of molecular aggregates. The increase in the MW leads to folding of PEG chains and to formation of statistical coils.

Probing the effects of electrolytes on intermolecular interactions in solution by optical‐heterodyne detected Raman‐induced kerr effect spectroscopy (OHD‐RIKESH)

AbstractTime‐domain experimental femtosecond OHD‐RIKES results for electrolyte solutions (NaI and LiCIO4 in acetonitrile and ethyl acetate) are presented and discussed within the context of the molecular polarizability ellipsoid of the solvent. It is concluded that the anisotropic part of the liquid intermolecular potential is not significatly influenced by the addition of electrolytes, even at concentrations up to the saturation limit.