612 research outputs found
Overcoming device unreliability with continuous learning in a population coding based computing system
The brain, which uses redundancy and continuous learning to overcome the
unreliability of its components, provides a promising path to building
computing systems that are robust to the unreliability of their constituent
nanodevices. In this work, we illustrate this path by a computing system based
on population coding with magnetic tunnel junctions that implement both neurons
and synaptic weights. We show that equipping such a system with continuous
learning enables it to recover from the loss of neurons and makes it possible
to use unreliable synaptic weights (i.e. low energy barrier magnetic memories).
There is a tradeoff between power consumption and precision because low energy
barrier memories consume less energy than high barrier ones. For a given
precision, there is an optimal number of neurons and an optimal energy barrier
for the weights that leads to minimum power consumption
Magnetization reversal by injection and transfer of spin: experiments and theory
Reversing the magnetization of a ferromagnet by spin transfer from a current,
rather than by applying a magnetic field, is the central idea of an extensive
current research. After a review of our experiments of current-induced
magnetization reversal in Co/Cu/Co trilayered pillars, we present the model we
have worked out for the calculation of the current-induced torque and the
interpretation of the experiments
Vortex oscillations induced by a spin-polarized current in a magnetic nanopillar: Evidence for a failure of the Thiele approach
We investigate the vortex excitations induced by a spin-polarized current in
a magnetic nanopillar by means of micromagnetic simulations and analytical
calculations. Damped motion, stationary vortex rotation and the switching of
the vortex core are successively observed for increasing values of the current.
We demonstrate that even for small amplitude of the vortex motion, the
analytical description based the classical Thiele approach can yield
quantitatively and qualitatively unsound results. We suggest and validate a new
analytical technique based on the calculation of the energy dissipation
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