The deadline for our postdoc positions has now passed. We received close to 30 applications which are currently being evaluated. We expect to have a short list of candidates available before the end of July and we will start to contact candidates from this list ASAP. We are very grateful for the high interest in these positions and we want to thank all candidates for your time in preparing your applications.
Theory predicts that a strongly injection-locked spin-torque oscillator (STO) should show a characteristic ringing frequency both on its approach to the locked state and under the influence of thermal noise. While experiments have so far failed to detect such ringing, we here show numerically and analytically how current modulation of injection-locked STOs can excite the ringing frequency in a resonant manner, and hence increase the experimental sensitivity. The complexity of such dynamics leads to a nonlinear resonance, which can even unlock the STO as a function of the modulation strength. The results presented here offer a plausible method for experimentally measuring the ringing frequency of STOs. Moreover, the onset of unlocking also provides a measure for the maximum modulation strength that can be applied to phase-locked STOs.
Ezio Iacocca and Johan Åkerman, Resonant excitation of injection-locked spin-torque oscillators, PRB 87, 214428 (2013).
It has been argued that if multiple spin wave modes are competing for the same centrally located energy source, as in a nanocontact spin torque oscillator, that only one mode should survive in the steady state. Here, the experimental conditions necessary for mode coexistence are explored. Mode coexistence is facilitated by the local field asymmetries induced by the spatially inhomogeneous Oersted field, which leads to a physical separation of the modes, and is further promoted by spin wave localization at reduced applied field angles. Finally, both simulation and experiment reveal a low frequency signal consistent with the intermodulation of two coexistent modes.
Randy K. Dumas, E. Iacocca, S. Bonetti, S. R. Sani, S. M. Mohseni, A. Eklund, J. Persson, O. Heinonen, and Johan Åkerman, Spin-Wave-Mode Coexistence on the Nanoscale: A Consequence of the Oersted-Field-Induced Asymmetric Energy Landscape, PRL 110, 257202 (2013).
A truly unique experience! It was a great honor and pleasure to be invited to EINC 2013 and speak about our recent results on Magnetic Droplet Solitons. The Ester Island is a fascinating place with a dramatic and exciting history which can be highly recommended. Although it's essentially on the opposite side of the planet, the travel is surprisingly manageable, with e.g. Air France flying directly from Paris to Santiago and then Lan flying to Easter Island. I want to particular highlight the evening plenary talks given by Nobel Laureates Dan Shechtman (Nobel Prize 2011) and Claude Cohen-Tannoudji (Nobel Prize 1997), who gave very inspiring presentations on “Quasi- Periodic Materials – Crystal Redifined”, and “Manipulating Atoms with Photons and Photons with Atoms”.