In-Memory Mathematical Operations with Spin-Orbit Torque Devices.

Analog arithmetic operations are the most fundamental mathematical operations used in image and signal processing as well as artificial intelligence (AI).  In-memory computing (IMC) offers a high performance and energy-efficient computing paradigm. To date, in-memory analog arithmetic operations with emerging nonvolatile devices are usually implemented using discrete components, which limits the scalability and blocks large scale integration. Here, a prototypical implementation of in-memory analog arithmetic operations (summation, subtraction and multiplication) is experimentally demonstrated, based on in-memory electrical current sensing units using spin-orbit torque (SOT) devices. The proposed structures for analog arithmetic operations are smaller than the state-of-the-art complementary metal oxide semiconductor (CMOS) counterparts by several orders of magnitude. Moreover, data to be processed and computing results can be locally stored, or the analog computing can be done in the nonvolatile SOT devices, which are exploited to experimentally implement the image edge detection and signal amplitude modulation with a simple structure. Furthermore, an artificial neural network (ANN) with SOT devices based synapses is constructed to realize pattern recognition with high accuracy of ≈95%.