Investigation of enhancement of SOT-MRAM switching characteristic using FM/NM/FM trilayer structure

Abstract

SOT-MRAM can operate at high speed and has different read and write current paths with the three-terminal device, so it is possible to adjust the thickness of the tunnel barrier and improve the magnetoresistance without degradation by current. However, SOT-MRAM has a high critical current compared to the conventional STT-MRAM, which requires improved power consumption and characteristics that enable magnetization switching without external magnetic fields. Applying a current in the ferromagnetic magnetization direction to the FM/NM interface generates an z-spin, which enables field-free switching. Theoretically, as the z-spin increases, the critical switching current also decrease. In this study, to increase the z-spin that enables low-power switching, we used the principle of generating z-spin by precession around the spin-orbit field. The in-plane spin generated by applying current to heavy metal was changed to z-spin, and the results of the interaction with the FM according to the spin direction were confirmed using a material with an opposite spin Hall angle. Through this study, another way to generate z-spin was confirmed, and a structure capable of field-free switching and low-power operation is possible is proposed.