Search results for "Kerr effect"
showing 10 items of 107 documents
Magnetic domain structure of La0.7Sr0.3MnO 3 thin-films probed at variable temperature with scanning electron microscopy with polarization analysis
2013
The domain configuration of 50 nm thick La0.7Sr0.3MnO3 films has been directly investigated using scanning electron microscopy with polarization analysis (SEMPA), with magnetic contrast obtained without the requirement for prior surface preparation. The large scale domain structure reflects a primarily four-fold anisotropy, with a small uniaxial component, consistent with magneto-optic Kerr effect measurements. We also determine the domain transition profile and find it to be in agreement with previous estimates of the domain wall width in this material. The temperature dependence of the image contrast is investigated and compared to superconducting-quantum interference device magnetometry …
45° sign switching of effective exchange bias due to competing anisotropies in fully epitaxial Co3FeN/MnN bilayers
2017
We report an unusual angular-dependent exchange bias effect in ferromagnet/antiferromagnet bilayers, where both ferromagnet and antiferromagnet are epitaxially grown. Numerical model calculations predict an approximately 45° period for the sign switching of the exchange-bias field, depending on the ratio between magnetocrystalline anisotropy and exchange-coupling constant. The switching of the sign is indicative of a competition between a fourfold magnetocrystalline anisotropy of the ferromagnet and a unidirectional anisotropy field of the exchange coupling. This predicted unusual angular-dependent exchange bias and its magnetization switching process are confirmed by measurements on fully …
Magneto-optical properties of two-layer film systems based on Fe and Cr
2020
The results of the investigation of two-layer Fe/Cr systems using the magneto-optical Kerr effect (MOKE) are presented in this paper. The samples were obtained by thermal evaporation in a vacuum with a thickness of individual layers from 2 nm to 50 nm. It was found that the presence of the Cr layer significantly affects the values of the coercivity and the Kerr angle. At a substrate temperature of 450 K, the value of the coercivity is almost half that of the same sample obtained at room temperature of the substrate. In addition, the influence of the order of deposition of layers, as well as the effect of a thin gold protective layer on the parameters measured by the Kerr method, is shown. …
Many-body perturbation theory calculations using the yambo code
2019
Abstract yambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as Quantum ESPRESSO and Abinit. yambo’s capabilities include the calculation of linear response quantities (both independent-particle and including electron–hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron–phonon i…
Er:Cr:YSGG laser with electrooptic PLZT ceramics Q-switching Fabry-Perot interferometer output mirror
2001
Summary form only given. Q-switching of Er:Cr:YSGG laser with transparent PLZT ceramics electro-optic modulators was reported previously. The extremely large quadratic EO effect in PLZT allows to build small size moderate control voltages. The high induced birefringence in PLZT results from an essential contribution to polarization (and consequently to the birefringence) of processes with longer relaxation times up to seconds, corresponding to the Er:Cr:YSGG laser operating rate. PLZT ceramics have also a high value of the refractive index (n /spl ap/ 2.2-2.3 for /spl lambda/ = 3 /spl mu/m, slightly depending on PLZT composition and temperature) and thus considerable Fresnel reflections R/s…
Experimental demonstration of phase bistability in a broad-area optical oscillator with injected signal
2015
We demonstrate experimentally that a broad-area laserlike optical oscillator (a nondegenerate photorefractive oscillator) with structured injected signal displays two-phase patterns. The technique [de Valc\'arcel and Staliunas, Phys. Rev. Lett. 105, 054101 (2010)] consists in spatially modulating the injection, so that its phase alternates periodically between two opposite values, i.e., differing by $\ensuremath{\pi}$.
Surface hysteresis curves of Fe(110) and Fe(100) crystals in ultrahigh vacuum — evidence of adsorbate influences
1992
Abstract We have investigated hysteresis curves of silicon-stabilized Fe(100) and Fe(110) crystals using Polarized Secondary Electron Emission (PSEE) for surface magnetization processes and Magneto-Optical Kerr Effect (MOKE) for bulk hysteresis curves. In particular, the influence of adsorbates (oxygen and sulphur) and surface roughness on the magnetization reversal has been studied. For surface hysteresis curves we found adsorbate-induced reductions of coercive force of up to 50%; the bulk hysteresis curves showed significantly smaller deviations. Similar changes were caused by surface disorder on an atomic scale induced by ion bombardment. The results agree qualitatively with a previous e…
All-optical signal processing at ultra-low powers in bottle microresonators using the Kerr effect.
2010
We present experimental results on nonlinear, ultra-low power photonics applications based on a silica whispering-gallery-mode microresonator. Our bottle microresonator combines an ultrahigh quality factor of Q10(8) with a small mode volume V. The resulting Q(2)/V-ratio is among the highest realized for optical microresonators and allows us to observe bistable behavior at very low powers. We report single-wavelength all-optical switching via the Kerr effect at a record-low threshold of 50 microW. Moreover, an advantageous mode geometry enables the coupling of two tapered fiber waveguides to a bottle mode in an add-drop configuration. This allows us to route a CW optical signal between both …
Nonintrusive monitoring and quantitative analysis of strong laser-field-induced impulsive alignment
2004
We report the observation of impulsive alignment of $\mathrm{C}{\mathrm{O}}_{2}$ molecules produced through their interaction with a nonresonant, strong laser pulse. The periodic alignment is monitored using a polarization technique generally employed in optical Kerr effect experiments; the birefringence produced by alignment of the molecular sample is measured with a weak pulse, time-delayed with respect to the alignment pulse. The technique provides a signal proportional to $⟨{\mathrm{cos}}^{2}\phantom{\rule{0.2em}{0ex}}\ensuremath{\theta}⟩\ensuremath{-}\frac{1}{3}$, where $\ensuremath{\theta}$ is the polar angle between the molecular axis and the strong-field polarization axis. Experimen…
Nonlinear Characterisation of an AsSe Chalcogenide Holey Fiber
2009
oral session TuA " Highly Nonlinear Fibers " [TuA1]; International audience; We report the nonlinear characterization of a chalcogenide holey fiber, based on the AsSe glass composition. A nonlinear coefficient as high as 15 000 W-1 km-1 has been measured.