L. Lagae

Current-driven vortex oscillations in metallic nanocontacts.

We present experimental evidence of subgigahertz spin-transfer oscillations in metallic nanocontacts that are due to the translational motion of a magnetic vortex. The vortex is shown to execute large-amplitude orbital motion outside the contact region. Good agreement with analytical theory and micromagnetics simulations is found.

Technology and materials issues in semiconductor-based magnetoelectronics

There has been an increased interest in the introduction of magnetic thin films into semiconductors. This interest is motivated by the benefit found in using the magnetic thin-film properties (giant or tunnelling magnetoresistance and hysteresis) in magnetic memory (MRAM) products. Furthermore, the use of the electron spin in electronic, spintronic devices requires intimate ferromagnetic/semiconductor combinations. We review the technology and materials aspects of both the MRAM and spintronics fields that highlight the challenges that must be overcome in order to make magnetic (multilayer) films a standard ingredient in future electronics.

Plasmon filters and resonators in metal-insulator-metal waveguides

We present the numerical and experimental demonstration of plasmonic Bragg filters and resonators inside metal-insulator-metal (MIM) waveguides. The presented filters and resonators are fabricated using standard top down lithography methods. The optical bandgap of the integrated Bragg filters is experimentally observed and its optical properties are investigated as a function of the grating pitch and the number of grating periods. Transmission filters based on a nanocavity resonance were measured, obtaining Q-factors above 30. Tuning of the cavity wavelength was experimentally achieved by varying the cavity length.

Agility of vortex-based nanocontact spin torque oscillators

We study the agility of current-tunable oscillators based on a magnetic vortex orbiting around a point contact in spin valves. The theory predicts that frequency tuning by currents occurs at constant orbital radius so an exceptional agility is anticipated. To test this, we have inserted an oscillator in a microwave interferometer to apply abrupt current variations while time resolving its emission. Using frequency shift keying, we show that the oscillator can switch between two stabilized frequencies differing by 25% in less than ten periods. With a wide frequency tunability and a good agility, such oscillators possess desirable figures of merit for modulation-based rf applications.

Time-resolved zero field vortex oscillations in point contacts

We study vortex spin torque oscillators based on magnetic point contacts that operate in zero applied magnetic field. Static and dynamic vortex modes are shown to exist and have distinct electrical signatures. For the oscillatory mode, a spectrally pure slightly asymmetric voltage waveform is observed. It is subject to phase noise as sole fluctuations. The waveforms observed indicate that the vortex orbits outside the point contact region, with a pinned layer magnetization that is static but spatially nonuniform as a result of the current. This nonuniformity results in a reduction in the dc to rf power transduction yield.

Quantized spin-wave modes in magnetic tunnel junction nanopillars

We present an experimental and theoretical study of the magnetic field dependence of the mode frequency of thermally excited spin waves in rectangular-shaped nanopillars of lateral sizes

Direct experimental measurement of phase-amplitude coupling in spin torque oscillators

60\ifmmode\times\else\texttimes\fi{}100

Auto-oscillation and narrow spectral lines in spin-torque oscillators based on MgO magnetic tunnel junctions

,

Frequency shift keying in vortex-based spin torque oscillators

75\ifmmode\times\else\texttimes\fi{}150

Vortex nucleation in spin-torque nanocontact oscillators

, and