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Your search keyword '"Ferran Macià"' showing total 2 results
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2 results on '"Ferran Macià"'

1. Generation and annihilation time of magnetic droplet solitons

Author

Jinting Hang, Christian Hahn, Nahuel Statuto, Ferran Macià, and Andrew D. Kent

Subjects
Medicine, Science
Abstract

Abstract Magnetic droplet solitons were first predicted to occur in materials with uniaxial magnetic anisotropy due to a long-range attractive interaction between elementary magnetic excitations, magnons. A non-equilibrium magnon population provided by a spin-polarized current in nanocontacts enables their creation and there is now clear experimental evidence for their formation, including direct images obtained with scanning x-ray transmission microscopy. Interest in magnetic droplets is associated with their unique magnetic dynamics that can lead to new types of high frequency nanometer scale oscillators of interest for information processing, including in neuromorphic computing. However, there are no direct measurements of the time required to nucleate droplet solitons or their lifetime–experiments to date only probe their steady-state characteristics, their response to dc spin-currents. Here we determine the timescales for droplet annihilation and generation using current pulses. Annihilation occurs in a few nanoseconds while generation can take several nanoseconds to a microsecond depending on the pulse amplitude. Micromagnetic simulations show that there is an incubation time for droplet generation that depends sensitively on the initial magnetic state of the nanocontact. An understanding of these processes is essential to utilizing the unique characteristics of magnetic droplet solitons oscillators, including their high frequency, tunable and hysteretic response.

Published
2018
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2. Describing synchronization and topological excitations in arrays of magnetic spin torque oscillators through the Kuramoto model

Author

Erik Wahlström, Ferran Macià, Vegard Flovik, Research Council of Norway, and Ministerio de Economía y Competitividad (España)

Subjects
Field (physics), Thin films, FOS: Physical sciences, 02 engineering and technology, Materials ferromagnètics, 01 natural sciences, Article, Spin magnetic moment, Topological defect, 0103 physical sciences, Synchronization (computer science), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical physics, 010306 general physics, Physics, Pel·lícules fines, Multidisciplinary, Spintronics, Condensed Matter - Mesoscale and Nanoscale Physics, Kuramoto model, Nonlinear phenomena, Disordered Systems and Neural Networks (cond-mat.dis-nn), Condensed Matter - Disordered Systems and Neural Networks, 021001 nanoscience & nanotechnology, Classical XY model, Nonlinear Sciences - Adaptation and Self-Organizing Systems, Ferromagnetic materials, 0210 nano-technology, Adaptation and Self-Organizing Systems (nlin.AO), Magnetic dipole–dipole interaction
Abstract

The collective dynamics in populations of magnetic spin torque oscillators (STO) is an intensely studied topic in modern magnetism. Here, we show that arrays of STO coupled via dipolar fields can be modeled using a variant of the Kuramoto model, a well-known mathematical model in non-linear dynamics. By investigating the collective dynamics in arrays of STO we find that the synchronization in such systems is a finite size effect and show that the critical coupling—for a complete synchronized state—scales with the number of oscillators. Using realistic values of the dipolar coupling strength between STO we show that this imposes an upper limit for the maximum number of oscillators that can be synchronized. Further, we show that the lack of long range order is associated with the formation of topological defects in the phase field similar to the two-dimensional XY model of ferromagnetism. Our results shed new light on the synchronization of STO, where controlling the mutual synchronization of several oscillators is considered crucial for applications., This work was supported by the Norwegian Research Council (NFR), project number 216700. V.F. acknowledge partial funding obtained from the Norwegian PhD Network on Nanotechnology for Microsystems, which is sponsored by the Research Council of Norway, Division for Science, under contract no. 221860/F40. F.M. acknowledges financial support from the Ramón y Cajal program through RYC-2014-16515 and from the MINECO through the Severo Ochoa Program for Centers of Excellence in R&D (SEV- 2015-0496).

Published
2016
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