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Kerr Effect (kerr + effect)

Distribution by Scientific Domains
Physics and Astronomy75%
Chemistry16%

Kinds of Kerr Effect

  • magneto-optical kerr effect
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  • optical kerr effect
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    Selected Abstracts

    Plasmon induced modification of the transverse magneto-optical response in Fe antidot arrays

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 10 2010
    J. F. Torrado
    Abstract In this Letter we present the effects that the excitation of plasmon-like modes in periodically perforated Fe films have over the Transverse Magneto-Optical Kerr Effect (TMOKE). The excitation of the modes gives rise to clear signatures in the TMOKE spectra. We analyze the spectral position of the structures as a function of both the polar and azimuth angle. Schematic representation of the system, and TMOKE signal for a Fe membrane along , = 0°. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Pinning energy of domain walls in MnZn ferrite films

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007
    V. H. Calle
    Abstract Mn Zn ferrite films deposited on (100) MgO substrates by rf sputtering technique with different thicknesses , in the range of 30-450 nm were studied. AFM images show grain size increase as film thickness increases. Grains with diameters between L , 70 and 700 nm were observed. The mono and multidomain regime in MnZn ferrite films and their effect on the pinning energy of domain walls are observed via Magneto-optical Kerr Effect, MOKE. At , , 300 nm, the coercive field, Hc, reaches a maximum value of 80 Oe. This result indicates the existence of a multidomain regime associated to a critical grain size, Lc. We used the Jiles-Atherton model (JAM) to discuss the experimental hysteresis loops. The k pinning parameter obtained from JAM shows a maximum value of k /,o = 67 Am2 for grains with Lc , 529 nm. The total energy per unit area E was correlated with k and D. We found a simple phenomenological relationship given by E , kD; where D is the magnetic domain width. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    The Quest for Nanoscale Magnets: The example of [Mn12] Single Molecule Magnets

    ADVANCED MATERIALS, Issue 43 2009
    Guillaume Rogez
    Abstract Recent advances on the organization and characterization of [Mn12] single molecule magnets (SMMs) on a surface or in 3D are reviewed. By using nonconventional techniques such as X-ray magnetic circular dichroism (XMCD) and scanning tunneling microscopy (STM), it is shown that [Mn12]-based SMMs deposited on a surface lose their SMM behavior, even though the molecules seem to be structurally undamaged. A new approach is reported to get high-density information-storage devices, based on the 3D assembling of SMMs in a liquid crystalline phase. The 3D nanostructure exhibits the anisotropic character of the SMMs, thus opening the way to address micrometric volumes by two photon absorption using the pump-probe technique. We present recent developments such as µ-SQUID, magneto-optical Kerr effect (MOKE), or magneto-optical circular dichroism (MOCD), which enable the characterization of SMM nanostructures with exceptional sensitivity. Further, the spin-polarized version of the STM under ultrahigh vacuum is shown to be the key tool for addressing not only single molecule magnets, but also magnetic nano-objects. [source]

    Effects of uniaxial stress on the magnetic properties of thin films and GMR sensors prepared on polyimide substrates

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008
    Berkem Özkaya
    Abstract The effects of externally applied uniaxial stress on the magnetic properties of Co thin films and pseudo-spin-valve (PSV) structures on flexible polyimide substrates were investigated. The advantage of the polyimide substrate is its flexibility and high elasticity (,1%), which cannot be achieved using conventional crystalline substrates. The Co layers exhibit a macroscopic easy axis induced by the preparation process. When the stress is applied perpendicular to the induced in-plane easy axis, the magnetic domains in the film rotate towards the applied stress direction, which was confirmed using Kerr microscopy and magneto-optical Kerr effect (MOKE) magnetometer measurements. A Co/Cu/Ni PSV system was prepared on polyimide substrate with dc magnetron sputtering. Applying uniaxial stress leads to opposite rotation of the magnetisation directions in both layers to each other due to different signs of the magnetostriction coefficients of Co and Ni. The magnetisation and giant magnetoresistance (GMR) curves under applied stress were recorded using in situ MOKE and current in-plane four-point probe techniques, respectively. When the stress is applied perpendicular to the external magnetic field (Hext), the operating range of the GMR sensor increases, whereas the sensitivity decreases. Anisotropy energies and saturation magnetostriction values of the Co and Ni layer were determined by fitting the GMR and magnetisation curves using a micromagnetic model. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Time-resolved photoinduced Kerr rotation in semiconductor microcavity

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009
    Y. Mitsumori
    Abstract We studied photoinduced Kerr effect in cavity polaritons in a semiconductor microcavity by carefully measuring the time-resolved Kerr rotation and ellipticity spectra. The Kerr rotation angle of the microcavity polaritons is a hundred times larger than a conventional single quantum well. A spectral shape analysis of the observed spectra suggests that the photoindeced Kerr effect mainly results from a line broadening of the polarions due to spin-polarized polariton-polariton scattering. Enhancement in oscillator strength also contributes to the large rotation angle. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Photoinduced spin waves in Fe/AlGaAs (001) heterostructure

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2008
    H. B. Zhao
    Abstract Photoinduced spin waves are investigated for Fe films on AlGaAs (001) using the time resolved magneto-optical Kerr effect. We observe first and second order standing spin waves as well as uniform magnetization precession. The anisotropy fields and exchange stiffness constant are obtained from the field and azimuthal dependence of the spin wave frequencies using the Landau-Lifshitz-Gilbert equation. A comparison with spin wave resonance measurements reveals a more pronounced interface effect on the low order standing spin waves in thin films. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Ultrafast optical Kerr effect of excitons weakly confined in GaAs thin films

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008
    Atsushi Kanno
    Abstract We investigate ultrafast response of optical Kerr effect (OKE) induced by excitons weakly confined in GaAs thin films. The observed decay time of optical response agrees approximately with incident pulse duration. At 100-fs pulse irradiation the response time is estimated to be 170 fs, though the exciton lifetime is about 10 ns. It is considered that the ultrafast response of OKE is caused by not population relaxation but orientation relaxation of excitons. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Influence of film thickness on the electrical and magnetic properties of Co,Fe,Al,O films

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2007
    M. H. Phan
    Abstract Influence of film thickness (t) on the electrical and magnetic properties of Co,Fe,Al,O films has been systematically investigated via means of vibrating sample magnetometry (VSM), permeability spectra and magneto-optical Kerr effect (MOKE). It is found that the electrical resistivity (,) decreases as the film thickness increases; , = 412.5 µ,cm for the t = 600 nm sample decreases to , = 368.2 µ,cm for the t = 1200 nm sample. The coercive force, measured along the easy-axis direction, decreases as the film thickness increases. Interestingly, along the hard-axis magnetization direction, the magnetic hysteresis loop is reversed and the coercive force is negative for the t = 600 and 800 nm samples. However, this peculiar feature disappears as t reaches 1200 nm, which is probably attributed to the microstructural change with respect to changes of film thickness. At a frequency of 1GHz, the hard-axis effective permeability decreases from 1252 to 1000 as the film thickness increases from 600 to 1200 nm, respectively. The VSM and MOKE results reveal an increase in magnetic anisotropy in the near-surface region of the film. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    On the role of the soft layer in exchange-spring hard/soft magnetic bilayers

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004
    D. Bisero
    Abstract Bilayers of SmCo/NiFe and SmCo/Co with well-defined in-plane uniaxial anisotropy were grown by dc magnetron sputtering on glass substrates. The magnetization reversal process was investigated by magneto-optic Kerr effect from both sides of the samples, obtaining the hard and soft response separately. The NiFe layers turn out to be exchange coupled to the SmCo films and, for soft layer thicknesses above 30 nm, display reversible demagnetization loops expected from exchange-spring magnets. The experimental NiFe magnetization curve is in good agreement with the theoretical curve obtained by minimizing the magnetic energy in the soft film for an ideal hard/soft bilayer. The soft layer critical thickness above which the exchange spring behavior sets up and its presumed independence on soft layer characteristics are discussed, by comparing the two systems under investigation. We find that SmCo/Co does not fulfil the predictions of the currently accepted theories and that the magnetization reversal of the bilayer is dominated by the Co layer. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Synthesis, Structure, and Nonlinear Optical Properties of Cross-Conjugated Perphenylated iso -Polydiacetylenes

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2005
    Yuming Zhao Prof.
    Abstract Monodisperse, cross-conjugated perphenylated iso- polydiacetylene (iso- PDA) oligomers, ranging from monomer 15 to pentadecamer 25, have been synthesized by using a palladium-catalyzed cross-coupling protocol. Structural characteristics elucidated by X-ray crystallographic analysis demonstrate a non-planar backbone conformation for the oligomers due to the steric interactions between alkylidene phenyl groups. The electronic absorption spectra of the oligomers show a slight red-shift of the maximum absorption wavelength as the chain length increases from dimer 17,b to pentadecamer 25, a trend that has saturated by the stage of nonamer 22. Fluorescence spectroscopy confirms that the pendent phenyl groups present on the oligomer framework enhance emission, and the relative emission intensity consistently increases as a function of chain length n. The molecular third-order nonlinearities, ,, for this oligomer series have been measured via differential optical Kerr effect (DOKE) detection and show a superlinear increase as a function of the oligomer chain length n. Molecular modeling and spectroscopic studies suggest that iso- PDA oligomers (n>7) adopt a coiled, helical conformation in solution. [source]

    Nonlinear Optical Properties of Ferrocene- and Porphyrin,[60]Fullerene Dyads

    CHEMPHYSCHEM, Issue 7 2007
    Evangelia Xenogiannopoulou Dr.
    Abstract A series of novel [60]fullerene,ferrocene and [60]fullerene,porphyrin dyads, in which a fullerene and an electron donating moiety are attached through a flexible triethylene glycol linker are synthesized and their nonlinear optical (NLO) response studied. Specifically, the third-order susceptibility ,(3) of all fullerene derivatives are measured in toluene solutions by the optical Kerr effect (OKE) technique using 532 nm, 35 ps laser pulses and their second hyperpolarizability , are determined. All fullerene dyads studied exhibit enhancement of their NLO response compared to pristine fullerenes which has been attributed to the formation of a charge separated state. All experimentally measured hyperpolarizability , values are also calculated by the semiempirical methods AM1 and PM3. A good correlation is found between the theoretical and experimental values, suggesting that simple semiempirical methods can be employed for the designing and optimization of the fullerene-containing dyads displaying improved nonlinear responses. [source]