A study on spin-orbit torques in heterostructures with perpendicular magnetic anisotropy

Abstract

In Spintronics, manipulation of spin is a crucial issue in application. Conventionally, Method of field-induced magnetization switching was used to control the spin in magnetic memory device, called MRAM. In order to overcome the problem which conventional MRAM have, concept of spin-transfer torque (STT) was applied as the new generation device. Recently, control of magnetization in heterostructure with perpendicular magnetic anisotropy (PMA) by in-plane current was reported. Moreover, it has been observed in those structures that the domain wall moves along the current direction, opposite to conventional spin transfer torque, and whose velocity can be as fast as a few hundred meters per second. The mechanism involves the coupling of electron`s spin and its orbital motion, resulting in non-equilibrium spin accumulation which ultimately gives rise to a torque on the magnetization, so it is called spin-orbit torques (SOTs). Here, we examined PMA in CoFeB/MgO structure measured by vibration magnetometer (VSM). Also, SOTs in Pt/Co/AlOx heterostructure was obtained by using the lock-in system. By varying the Pt thickness, we demonstrate the origin of SOTs in this system.