C. Ulysse

Dynamics of two coupled vortices in a spin valve nanopillar excited by spin transfer torque

We investigate the dynamics of two coupled vortices driven by spin transfer. We are able to independently control with current and perpendicular field and to detect the respective chiralities and polarities of the two vortices. For current densities above J=5.7×107 A/cm2, a highly coherent signal (linewidth down to 46 kHz) can be observed, with a strong dependence on the relative polarities of the vortices. It demonstrates the interest of using coupled dynamics in order to increase the coherence of the microwave signal. Emissions exhibit a linear frequency evolution with perpendicular field, with coherence conserved even at zero magnetic field.

Spectra, thresholds, and modal fields of a kite-shaped microcavity laser

We investigate the lasing spectra, threshold gain values, and emission directionalities for a two-dimensional microcavity laser with a “kite” contour. The cavity modes are considered accurately using the linear electromagnetic formalism of the lasing eigenvalue problem with exact boundary and radiation conditions. We develop a numerical algorithm based on the Muller boundary integral equations discretized using the Nystrom technique, which has theoretically justified and fast convergence. The influence of the deviation from the circular shape on the modal characteristics is studied numerically for the modes polarized in the cavity plane, demonstrating opportunities of directionality improvement together with preservation of a low threshold. These advantageous features are shown for the perturbed whispering-gallery modes of high-enough azimuth orders. Other modes can display improved directivities while suffering from drastically higher threshold levels. Experiments based on planar organic microcavity lasers confirm the coexistence of Fabry–Perot-like and whispering-gallery-like modes in kite-shaped cavities and show good agreement with the predicted far-field angular diagrams.

Current-induced domain wall motion in Co/Pt nanowires: Separating spin torque and Oersted-field effects

We report on low temperature current induced domain wall depinning experiments on (Co/Pt) multilayer nanowires with perpendicular magnetization. Using a special experimental scheme, we are able to extract the different contributions of the Oersted field and spin torque from the dependence of the depinning field on the injected current for selected magnetization configurations. The spin torque contribution is found to be dominant with a small contribution of the Oersted field leading to a nonadiabaticity factor beta in line with previous measurements

Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar

We report on a spectroscopic study of the spin-wave eigen-modes inside an individual normally magnetized two layers circular nano-pillar (Permalloy

High-Tc superconducting Josephson mixers for terahertz heterodyne detection

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Trace formula for dielectric cavities. II. Regular, pseudointegrable, and chaotic examples.

Copper

Wigner and Kondo physics in quantum point contacts revealed by scanning gate microscopy.

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High Domain Wall Velocity at Zero Magnetic Field Induced by Low Current Densities in Spin Valve Nanostripes

Permalloy) by means of a Magnetic Resonance Force Microscope (MRFM). We demonstrate that the observed spin-wave spectrum critically depends on the method of excitation. While the spatially uniform radio-frequency (RF) magnetic field excites only the axially symmetric modes having azimuthal index

Unusual magneto-transport of YBa2Cu3O7−δ films due to the interplay of anisotropy, random disorder and nanoscale periodic pinning

\ell=0

Transport in a Single Self-Doped Nanocrystal

, the RF current flowing through the nano-pillar, creating a circular RF Oersted field, excites only the modes having azimuthal index