ECE Seminar - Spintronic devices for microwave technology and unconventional computing
 

In this talk, I will present recent advances achieved in the development of spintronic microwave technology based on magnetic tunnel junctions (MTJs) from microwave detectors to electromagnetic energy harvesting. I will review the main applications of those devices for computing including the realization of Ising machines based on probabilistic computing with p-bits and oscillatory dynamics.

Spintronic technology takes advantage of the manipulation of the electron spin together with its charge. This technology potentially combines important characteristics such as ultralow power needs, compactness (nanoscale size) and it is CMOS-compatible. Spintronics has different success stories such as the head read for magnetic hard drive and the recent spin-transfer-torque magnetic random access memories. The latter are realized with MTJs which are devices composed of two ferromagnets separated by a ultrathin isolating material. The resistance of this device depends on the relative orientation of the magnetization of the two ferromagnets and in particular the configuration where the magnetization are parallel or antiparallel can code the binary information. Together with memory developments, which are already in the market and integrated within the CMOS processes by main foundries (INTEL, SAMSUNG, GlobalFoundries), MTJs can be used for the development of auto-oscillators and very high efficient detectors. In detail, I will show the applications of spintronic diodes based on MTJs for energy harvesting, sensors and RF detectors and what it is expected to achieve in the next three years for integration with CMOS-technology.

The latter part of the talk will focus on probabilistic computing which is one direction to implement Ising Machines. Probabilistic computing is a computational paradigm using probabilistic bits (p-bits), unit in the middle between standard bit and q-bits. I will show how to map hard combinatorial optimization problems (Max-Sat, Max-Cut, etc) into Ising machine and how to implement those in spintronic technology. I will present new direction in this field considering the concept of extended probabilistic variable such as p-dit and p-int.

This work was supported under the project number 101070287 — SWAN-on-chip — HORIZON-CL4- 2021-DIGITAL-EMERGING-01, the project PRIN 2020LWPKH7 funded by the Italian Ministry of University and Research and by the PETASPIN association (www.petaspin.com) and it has been also funded by European Union (NextGeneration EU), through the MUR-PNRR project SAMOTHRACE (ECS00000022).