Electric-field control of spin-orbit torque memory and oscillator

Abstract

With the advent of the era of data explosion, interest in multifunctional device, which can operate memory, communication, and logic function in one device, is increasing. Spintronics is a technology suitable for realizing a multifunctional device, because the magnetization, which is the core of a spintronic device, has basic physical characteristics of directionality and gyration motion corresponding to memory and oscillator. This dissertation focuses on the methods for each of the spin-orbit torque memory device and the spin-orbit torque oscillator device to add a data processing function. First, two gate electrodes capable of inducing lateral asymmetry were introduced into the memory device. The device whose switching type is reconfigurable according to an asymmetric gate voltage application has a potential to perform a logic function by using a combination of current and voltage, or according to a combination between a plurality of devices. Second, by introducing perpendicular magnetic anisotropy and voltage controlled magnetic anisotropy technology, the frequency tuning range of the spin-orbit torque oscillator in the MHz range was extended to the GHz range. This technology can greatly contribute to the improvement of the neuromorphic computing capacity based on frequency shift keying method. In addition, it was confirmed that the synaptic properties can be mimicked by cumulative frequency tuning with respect to the repeated voltage due to the non-volatile characteristic.