  Multiferroic devices hold profound promise for ultra-low energy computing in
beyond Moore's law era. The magnetization of a magnetostrictive
shape-anisotropic single-domain nanomagnet strain-coupled with a piezoelectric
layer in a multiferroic composite structure can be switched between its two
stable states (separated by an energy barrier) with a tiny amount of voltage
via converse magnetoelectric effect. With appropriate choice of materials, the
magnetization can be switched with a few tens of millivolts of voltages in
sub-nanosecond switching delay while spending a miniscule amount of energy of
~1 attojoule at room-temperature. Here, we analyze the area-delay-energy
trade-offs of these multiferroic devices by solving stochastic
Landau-Lifshitz-Gilbert equation in the presence of room-temperature thermal
fluctuations. We particularly put attention on scaling down the lateral area of
the magnetostrictive nanomagnet that can increase the device density on a chip.
We show that the vertical thickness of the nanomagnet can be increased while
scaling down the lateral area and keeping the assumption of single-domain limit
valid. This has important consequence since it helps to some extent preventing
the deterioration of the induced stress-anisotropy energy in the
magnetostrictive nanomagnet, which is proportional to the nanomagnet's volume.
The results show that if we scale down the lateral area, the switching delay
increases while energy dissipation decreases. Avenues available to decrease the
switching delay while still reducing the energy dissipation are discussed.
