Area-Delay-Energy Tradeoffs of Strain-Mediated Multiferroic Devices

Multiferroic devices hold profound promise for ultralow 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 subnanosecond switching delay while spending a miniscule amount of energy of ~1 attojoule at room temperature. Here, we analyze the area-delay-energy tradeoffs of these multiferroic devices by solving the 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 consequences, since it helps to some extent prevent 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 for decreasing the switching delay while still reducing the energy dissipation are discussed.