  Magnetic tunnel junctions are nanoscale devices which have recently attracted
interested in the context of frequency multiplexed spintronic neural networks,
due to their interesting dynamical properties, which are defined during the
fabrication process, and depend on the material parameters and geometry. This
paper proposes an approach to extending the functionality of a standard
magnetic tunnel junction (MTJ) by introducing an additional
ferromagnet/antiferromagnet (FM/AFM) storage layer (SL) vertically integrated
with the standard Vortex MTJ stack into the nanopillar. The magnetostatic field
created by this storage layer acts on the free layer and can be used to change
its static and dynamic properties. To tune the magnitude and direction of this
magnetostatic field, magnetic reconfiguration is carried out through a
thermally assisted switching mechanism using a voltage pulse that heats the AFM
layer in the SL above the Neel temperature in the presence of an external
field. It is experimentally shown that using an MTJ based on a 600 nm diameter
nanopillar with a vortex in the free layer, reconfiguration of the SL allows to
continuously change the core precession frequency in the 15 MHz range. The
reconfigurable analogue storage layer locally affects both the static and
dynamic properties of the MTJ free layer, demonstrating vertical 3D integration
of additional functionalities into a single MTJ nanopillar.
